Section 5-1 Grading and Drainage 2026.pdf
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CHAPTER 5: STORMWATER MANAGEMENT SECTION 1: GRADING AND DRAINAGE Engineering Design Standards City of Buckeye, Arizona January 2026 5-1 Grading and Drainage City of Buckeye 2026 Summary of 2026 Section 5-1 Updates The following list summarizes notable updates to Section 5-1, however not all changes may be documented in this summary. Applicants are encouraged to familiarize themselves with the document in its entirety. General • Applied new formatting changes throughout document • Updated language in up front section summary 5-1.000 General Information 5-1.002 Definition and Abbreviations • Added definition for “Regional Stormwater Facilities” 5-1.003 Grading and Draining Policies • Revised subsection H by adding additional finish floor design criteria 5-1.004 Drainage Easements • Created this new section covering public, private, and temporary drainage easements. 5-1.200 Hydrology 5-1.211 Downtown Buckeye Area • Clarified retention requirements for parcels less than an acre 5-1.400 Street Drainage 5-1.407 Pipe Inlets and Outlets • Revised subsection A to include the requirement for brass benchmarks in headwalls (when directed by the City) • Revised subsection B to create an exception for trash racks 5-1 Grading and Drainage City of Buckeye 2026 5-1.900 Stormwater Disposal 5-1.901 General Requirements • Revised subsection B to specify a different drywell option for underground retention • Revised subsection K by eliminating the Underground Injection Control application for grading and drainage plan approval 5-1.904 Drywells Post-Construction • Removed prior subsections C and D dealing with drywell drilling logs and Underground Injection Control registration. These requirements will be moved to a different EDS Section 1-2. 5-1.1100 Drainage Reports • Add a Mass Grading Memo section and provided context for when such a memo would be needed 5-1.1200 Plan Preparation 5-1.1203 Additional Requirements by Plan Type • Created subsection E for plans with underground retention 5-1.1300 Materials 5-1.1301 Approved Products List • Created this new section referencing the Approved Products List Appendix A – Standard Details COB Standard Detail 51403A • Revised General Note 6 cover requirements for traffic applications COB Standard Detail 51403B • Revised Table 2 cover requirements for 12”-48” pipes with H-25 loads COB Standard Detail 51404 • Updated City logo on manhole cover 5-1 Grading and Drainage City of Buckeye 2026 COB Standard Detail 51407A • Revised Detail Title to note it applies to pipes starting at 18” • Eliminated 15” pipe option from the dimension table • Add a benchmark to the headwall when directed by the City • Added General Note 6 dealing with the added benchmark COB Standard Detail 51407C • Revised dimensions of railing spacing • Revised steel tubing specifications 5-1 Grading and Drainage City of Buckeye 2026 Table of Contents 5-1.000 General Information ........................................................................................... 2 5-1.001 Drainage Design Criteria .............................................................................................................. 2 5-1.002 Definitions and Abbreviations ................................................................................................... 3 5-1.003 Grading and Draining Policies .................................................................................................. 5 5-1.004 Drainage Easements ........................................................................................................................ 7 5-1.005 Diligence ................................................................................................................................................... 8 5-1.100 General Floodplain Management Requirements ......................................... 8 5-1.101 General Requirements ................................................................................................................... 8 5-1.102 Special Flood Hazard Areas ........................................................................................................ 9 5-1.103 Section 404 Permits .......................................................................................................................... 9 5-1.200 Hydrology ........................................................................................................... 10 5-1.201 General Requirements .................................................................................................................. 10 5-1.202 Storm System Sizing ........................................................................................................................ 10 5-1.203 Rainfall ........................................................................................................................................................ 11 5-1.204 Rational Method .................................................................................................................................. 11 5-1.205 Runoff Coefficients ........................................................................................................................... 13 5-1.206 HEC-1 Model........................................................................................................................................... 14 5-1.207 Methods for Estimating Peak Discharge Alluvial Fans ........................................... 15 5-1.208 Pre vs Post ............................................................................................................................................... 15 5-1.209 Runoff Volume Calculation – Retention ........................................................................... 16 5-1.210 Runoff Volume Calculation – Detention ........................................................................... 17 5-1.211 Downtown Buckeye Area ............................................................................................................. 18 5-1.300 Hydraulics .......................................................................................................... 19 5-1.301 General Requirements .................................................................................................................. 19 5-1.302 HEC-RAS ................................................................................................................................................... 19 5-1.400 Street Drainage.................................................................................................. 19 5-1 Grading and Drainage City of Buckeye 2026 5-1.401 Design Criteria for Streets and Gutters ............................................................................. 19 5-1.402 Valley Gutters ....................................................................................................................................... 21 5-1.403 Storm Drains and Culverts ........................................................................................................ 22 5-1.404 Manholes ............................................................................................................................................... 24 5-1.405 Catch Basins ....................................................................................................................................... 24 5-1.406 Scuppers ................................................................................................................................................ 25 5-1.407 Pipe Inlets and Outlets ................................................................................................................. 25 5-1.408 Grouted Riprap.................................................................................................................................. 25 5-1.500 Open Channel Flow .......................................................................................... 26 5-1.501 General Requirements ................................................................................................................ 26 5-1.502 Open Channels .................................................................................................................................. 27 5-1.600 Retaining Walls .................................................................................................. 27 5-1.601 General Requirements ................................................................................................................. 27 5-1.700 Residential Lot Grading ................................................................................... 28 5-1.701 General Requirements ................................................................................................................ 28 5-1.800 Stormwater Storage Facilities ....................................................................... 28 5-1.801 General Requirements ................................................................................................................ 28 5-1.802 Stormwater Storage Facilities – Surface Retention Basins............................... 29 5-1.803 Stormwater Storage Facilities – Underground Retention Systems ............ 29 5-1.804 Underground Retention with CMP ......................................................................................... 31 5-1.805 Underground Retention with Perforated Pipes/Chambers ............................... 32 5-1.806 Stormwater Storage Facilities – On-Lot Residential Retention ....................... 32 5-1.807 Stormwater Storage Facilities – Detention Basins ................................................... 33 5-1.900 Stormwater Disposal ....................................................................................... 34 5-1.901 General Requirements ................................................................................................................ 34 5-1.902 Drywells – Locations ...................................................................................................................... 35 5-1.903 Drywells – Design / Pre-Construction .............................................................................. 35 5-1.904 Drywells Post-Construction ..................................................................................................... 36 5-1 Grading and Drainage City of Buckeye 2026 5-1.905 Ground Percolation Post-Construction........................................................................... 36 5-1.1000 Regional Drainage ........................................................................................... 36 5-1.1001 Retention Basins ............................................................................................................................... 36 5-1.1002 Channels: ............................................................................................................................................... 37 5-1.1100 Drainage Reports .............................................................................................. 37 5-1.1101 General Requirements ................................................................................................................. 37 5-1.1102 Master Drainage Report Submittal..................................................................................... 39 5-1.1103 Preliminary Drainage Report Submittal .......................................................................... 46 5-1.1104 Mass Grading Memo Submittal ............................................................................................ 52 5-1.1105 Final Drainage Report Submittal ........................................................................................... 57 5-1.1200 Plan Preparation ............................................................................................... 69 5-1.1201 General Requirements ................................................................................................................ 69 5-1.1202 Grading and Drainage Plan Requirements .................................................................. 69 5-1.1203 Additional Requirements By Plan Type ............................................................................ 72 5-1.1300 Materials ............................................................................................................. 73 5-1.1301 Approved Products List ................................................................................................................ 73 5-1.1302 Storm Drain Requirements ........................................................................................................ 73 Table of Tables Table 1 – Runoff Coefficients for Rational Formula ................................................................................... 13 Table 2 – Street Drainage Design Criteria ...................................................................................................... 21 Table of Figures Figure 1 – Downtown Drainage Area ................................................................................................................... 18 Figure 2 – City Engineer Signature/Approval Block ............................................................................... 59 Appendices Appendix A – Standard Details 5-1 Grading and Drainage City of Buckeye 2026 1 5-1 – Grading and Drainage This section provides policy and standards establishing the drainage design criteria within the incorporated boundaries of the City of Buckeye (City). General guidance is provided for complying with the various federal, state, county, and City regulations applicable to land development activities associated with floodplain management, water quality issues, and stormwater management. Examples of these regulations include the National Flood Insurance Act, the federal Clean Water Act (CWA), state and county statutes and the City of Buckeye Municipal Code, specifically Chapter 14, otherwise known as the Floodplain Management Code. Specific guidance is presented for preparing drainage reports and grading and drainage plans using design standards and methodologies developed by the City of Buckeye and the Flood Control District of Maricopa County (FCDMC). The FCDMC manages floodplains for the City of Buckeye. Any lots or parcels located within a floodplain will need to obtain a Floodplain Use Permit or Floodplain Clearance through the FCDMC to grade, fill, build, install any wall or fencing, or perform any other changes to the property. The City Engineer is required, pursuant to Chapter 23, Article 23-2, of the City Code, to develop standards and details regarding improvements to be constructed within the city. The standards, design criteria, and policy set forth in this section were developed and recommended by the City Engineer pursuant to Chapter 23, Article 23-2, and adopted by the City Council in Resolution No. 04-26 on 1/20/2026. Implementation: The requirements of this section shall become effective in accordance with City Code. The standards and requirements of this section shall apply to all new plans, including plans seeking a new City Engineer’s signature or a re-approval from the City Engineer, submitted to the City following the effective date of the City Council’s adoption of the resolution approving the standards and requirements of this section. Modification Authority: The City Engineer or designee may approve variances to the requirements of this section. A Variance Process Guide and Variance Application can be found on the City website. 5-1 Grading and Drainage City of Buckeye 2026 2 5-1 Grading and Drainage 5-1.000 General Information 5-1.001 Drainage Design Criteria A. This section has been created for the design of drainage systems which are to be installed and located within the City of Buckeye (City) and provides basic engineering requirements for development and comprehensive stormwater management programs within the City. B. In the preparation of construction documents for public and private developments located within the City, this section will provide the drainage design criteria. C. The following current editions of Flood Control District of Maricopa County (FCDMC) publications are used as a basis for design guidance and criteria, except as amended herein: 1. Drainage Policies and Standards Manual 2. Volume I – Hydrology Manual 3. Volume II – Hydraulics Manual 4. Volume III – Erosion Control Manual D. The City shall require for review / approval a grading and drainage plan and drainage report be submitted wherever development and/or grading is proposed within the City limits. E. Construction documents for grading and drainage submitted to the City for approval must be sealed by an Arizona Registered Professional Civil Engineer. F. All drainage plans, drainage reports, and construction drawings shall meet City and FCDMC regulations. The policies and standards in this section are intended to be an implementation guide for preparing drainage plans and drainage designs that are in conformance with the regulations. Sometimes additional documentation may be required for submittal and review by the City or FCDMC to prove conformance with the regulations. G. The City has developed COB EDS Section 5-3 Low Impact Development Manual and encourages the use of these applications for all areas, but in particular, the area west of the White Tanks Mountains. 5-1 Grading and Drainage City of Buckeye 2026 3 5-1.002 Definitions and Abbreviations • ADA - Americans with Disabilities Act • ADEQ – Arizona Department of Environmental Quality • ADOT – Arizona Department of Transportation • Base Flood Elevation (BFE) – 100-year water surface elevation of floodplain. • City - City of Buckeye • City Engineer - City of Buckeye City Engineer or designee. • CLOMR – Conditional Letter of Map Revision • CMP – Corrugated Metal Pipe • COB - City of Buckeye • Council - City Council of the City of Buckeye, Arizona. • CWA – Clean Water Act • Detention System - A stormwater collection system which captures runoff by means of a temporary storage facility and releases the runoff in a controlled manner to an approved point of discharge. • Developer - Shall also be interpreted to mean Landowner or Contractor; including development companies authorized to act on behalf of the Developer/Landowner. • Development - Shall mean any man-made change to improved or unimproved real property, public or private, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation, drilling, blasting and where the manmade alteration could possibly affect the surrounding real property, or the general public. • EDS – Engineering Design Standards • Emergency Outfall Elevation (EOE) – The elevation of a drainage area’s overland spill over point. • Engineer - An engineer registered professionally in the State of Arizona to do engineering within the purview of his or her practice area. • EPA – Environmental Protection Agency • FCDMC – Flood Control District of Maricopa County • FEMA – Federal Emergency Management Agency 5-1 Grading and Drainage City of Buckeye 2026 4 • FHWA – Federal Highway Administration • Flood Insurance Rate Maps (FIRMs) - Produced by FEMA delineating flood prone areas (floodplains & floodways). • Floodplain Use Permit – A permit required for development in a floodplain. • HW – High Water elevation for a retention or detention basin. • Landowner - Shall also be interpreted to mean Developer or Contractor; including development companies authorized to act on behalf of the Developer/Landowner. • Law - Any federal, state or local law, statute, common law, code, rule, regulation, order or ordinance. • LOMR – Letter of Map Revision, the FEMA process to revise the FIRMs. • MAG - Maricopa Association of Governments Uniform Standard Specifications and Details for Public Works Construction current edition. • MCDOT – Maricopa County Department of Transportation • NAVD88 – North American Vertical Datum 1988 • NFIP – National Flood Insurance Program • Offsite Flows - Stormwater flows reaching the development or site from outside the area of development, including but not limited to washes, rivers, streams, sheet flows from adjacent lands and roadways, or overflow from canals and retention or detention basins. • One Hundred-Year Storm (100-Year Storm) - A rainstorm of intensity and duration that has a one percent statistical probability of being equaled or exceeded during any given year. • One Hundred-Year Two-Hour Storm (100-Year 2-Hour Storm) - 100-year storm event with a duration/intensity of two hours. • PUE – Public Utility Easement • Regional Stormwater Facilities - Drainage and flood control improvements designed to serve multiple properties or an entire drainage basin, providing stormwater quantity and/or quality management beyond the limits of a single development. • Retention System - A stormwater collection system which captures, contains, and disposes of runoff by means of storage and disposal facilities (i.e. infiltration). 5-1 Grading and Drainage City of Buckeye 2026 5 • ROW - Right-of-Way • Stormwater Facilities - Stormwater drainage system physical components that include but are not limited to retention/detention basins, headwalls, catch basins, storm drainpipe, culverts, channels, manholes, drywells, trench drains, scuppers, etc. • Ten-Year Storm (10-Year Storm) - A rainstorm of intensity and duration that has a ten percent statistical probability of being equaled or exceeded during any given year. • TSDN – Technical Support Data Notebook • Ultimate Outfall Elevation - Elevation within the development or improvement where runoff ‘ultimately’ leaves the development, for a storm greater than the 100-year event, or a failure of the drainage system. There may be more than one ultimate outfall elevation associated with a development. • USACE – United States Army Corps of Engineers • Volume Provided (VP) - Calculated capacity of a stormwater storage facility (i.e. surface basins or underground storage). • Volume Required (VR) - Calculated amount of stormwater runoff required to retain/detain from the respective tributary area. • WS100 - Water surface elevation of the 100-year storm. 5-1.003 Grading and Draining Policies A. All developments within the City of Buckeye including residential developments, parcels or fractional interests in improved or unimproved land, lots or parcels of any size (subdivision), all types of commercial developments shall provide sufficient stormwater facilities to ensure: 1. Regional drainage solutions in accordance with stormwater management programs set forth by the City. 2. The protection of the health, safety, and welfare of its citizens, their property, the environment, and shall not jeopardize the quality of groundwater resources. 3. Avoidance of adverse impacts of development to surrounding properties. 4. That all proposed structures will be protected from 100-year flooding and that there is reasonable access for emergency and public service 5-1 Grading and Drainage City of Buckeye 2026 6 vehicles. Adverse impacts to existing structures located adjacent to the development will not be permitted. 5. Such facilities shall include separate and distinct parcels within the development and shall be planned for accordingly (i.e. retention). B. All stormwater from the 100-year, 2-hour storm which falls within a development, including the respective one-half of all adjacent streets, shall be retained within the boundaries of said development. Greater storm events may be required by the Master Drainage Report or special circumstances. The 100-year 6-hour storm is required if using underground retention. C. Predevelopment runoff versus post development runoff retention is not acceptable – except for a “first flush” facility or discharge to an approved designated drainage outfall, and only when approved by the City Engineer. 1. The typically approved designated drainage outfall would be a river or wash that connects unrestricted to a river, or facilities owned and operated by the FCDMC, with necessary approval from the FCDMC. D. No drainage system shall be approved if the effect may cause an increase in peak discharge, volume, or velocity of runoff or change the point of entry of drainage onto another property during the runoff event. E. Changes or additions to sites which require a site plan approval will be required to address drainage alterations and/or additions on the entire site with approval of the City and meet current drainage requirements as set forth in this section. F. Retention or detention basins shall not be located within City of Buckeye’s ROW, except in the case of regional public retention or detention basins, or otherwise approved by the City Engineer. G. Lowest building finished floor elevations within the City of Buckeye are to comply with the Maricopa County Floodplain Regulations. H. Finished floor elevations not located within a delineated floodplain shall be a minimum of: 1. Eighteen inches above the lowest drainage outfall for the residential lot. 2. Eighteen inches above the ultimate outfall for commercial and industrial developments. 3. Minimum of six inches above the highest adjacent top of curb elevation on the outfall side of the lot. 5-1 Grading and Drainage City of Buckeye 2026 7 4. One foot above the adjacent WS100. 5. One foot above the EOE for the drainage area. 5-1.004 Drainage Easements A. A drainage easement is an easement over an area designed and used for conveyance and/or retention of storm water runoff where no improvements or alterations can be made which will impede, divert, or cause the storm water runoff to have an adverse effect on adjoining, upstream, or downstream properties. 1. Drainage easements should be recorded on a plat or minor subdivision. 2. For those projects that do not require a plat or minor subdivision, the easements shall be recorded by separate instrument or document. The applicant shall provide the following documents for preparation of the easement: a. A legal description of the easement area, sealed by a registered land surveyor. b. A graphic exhibit of the easement area, sealed by a registered land surveyor. c. Proof of ownership (Current title report). B. Public Drainage Easement: 1. A Public Drainage Easement is required if storm water from a regional storm water facility or public right-of-way is conveyed onto or through private property. C. Private Drainage Easement: 1. A private drainage easement is required when storm water runoff from private land is conveyed across property lines in non-historic fashion or when storm water runoff from private land is stored in a common retention area on another parcel. D. Temporary Drainage Easement: 1. A temporary drainage easement is required where storm water is conveyed or retained in an area subject to future development, and it is anticipated that the drainage area will be ultimately modified or extinguished. These easements can only be modified or extinguished 5-1 Grading and Drainage City of Buckeye 2026 8 through the City approval of submitted improvement plans for the subject area. 5-1.005 Diligence A. The applicant’s Registered Professional Civil Engineer shall be held solely responsible for the correctness and adequacy of all data, drawings, calculations, and reports submitted to the City for review and approval. In addition, the Engineer shall comply with all local, state, and federal floodplain regulations in the design of the development. Approval by the City does not necessarily imply that the design is appropriate, or that the development is in strict compliance with all applicable regulations and standards. Review and approval of drainage submittals shall not create liability on the part of the City, or its employees, for any flood damages that may result from reliance upon any administrative decision made by the City or its employees. 5-1.100 General Floodplain Management Requirements 5-1.101 General Requirements A. The City of Buckeye participates in the NFIP administered by FEMA. The FCDMC manages floodplains for the City of Buckeye. The following is required: 1. Development must follow and be in compliance with the Floodplain Regulations of Maricopa County. 2. Any work (building, grading, filling, extraction of sand and gravel or other material, installing wall or fence, or other improvements or man-made changes) within a delineated FEMA floodplain or locally administered floodplain shall obtain an approved Floodplain Use Permit or Clearance issued by FCDMC prior to approval by the City. 3. After obtaining a Floodplain Use Permit and prior to Final Inspection, a complete, correct, and current Finished Construction FEMA Elevation Certificate shall be submitted to the Community Floodplain Administrator and approved prior to occupancy or use of any building within a Special Flood Hazard Area designated on the Flood Management Maps, except those uses exempted by applicable law. 4. A complete, correct, and current Finished Construction FEMA Floodproofing Certificate shall be submitted to the Community Floodplain Administrator and approved prior to occupancy or use of any non-residential building within a Special Flood Hazard Area designated 5-1 Grading and Drainage City of Buckeye 2026 9 on the Flood Management Maps, for any non-residential development where the lowest floor has not been elevated to or above the Regulatory Flood Elevation. 5-1.102 Special Flood Hazard Areas A. Portions of the City of Buckeye fall within areas that have been designated Special Flood Hazard Areas (SFHAs) by FEMA. These areas are subject to inundation by the 1-percent annual chance flood. There are also locally administered floodplains located within the City of Buckeye. These delineated floodplains are not shown on the FIRMs. They are shown as pending floodplains on the FCDMC’s floodplain viewer located at http://gis.maricopa.gov/floodplainviewer/. 5-1.103 Section 404 Permits A. The City of Buckeye requires development to comply with Section 404 of the CWA. B. The USACE and EPA jointly administer Section 404 of the CWA. The CWA regulates the discharge of dredged or fill material into washes, rivers, streams, lakes, certain man-made canals and other waters of the United States including wetlands. These regulatory areas are designated as “Waters of the U.S.” or jurisdictional waters. Examples of activities that might be regulated under this program include: 1. Stream crossings 2. Dam construction and flow regulation 3. Water diversion for canals, irrigation systems, and stock tanks 4. Streambed modification and stabilization, and 5. Building subdivisions, master planned communities, highways and airports. C. In order to allow time for permit processing and coordination, applicants are encouraged to contact the Corps early in the project planning stage for information about permits, and submittal and notification requirements. D. The City of Buckeye does not have the jurisdiction to designate or authorize any alteration, modification, or encroachment to designated 404 areas. E. Projects with minimal environmental impacts that meet specific requirements can be permitted with nationwide permits. Projects with 5-1 Grading and Drainage City of Buckeye 2026 10 potentially significant impacts may require individual permits with public notice. F. Section 404 permit activities may not jeopardize the continued existence of a threatened or endangered species or its critical habitat. Consult with the USACE or the U.S. Fish and Wildlife Service for guidance concerning threatened and endangered species within the City of Buckeye. G. While the Corps issues the Section 404 permit, Section 401 of the CWA requires ADEQ to certify (possibly with additional conditions) that the draft permit complies with state water quality standards and appropriate requirements of state law. The goal of the program is that no discharge of dredged or fill material be permitted if either a practicable alternative exists that is less damaging to the aquatic environment, or if the nation's waters would be significantly degraded. 5-1.200 Hydrology 5-1.201 General Requirements A. Standards contained in this section are in accordance with the Maricopa County Drainage Policies and Drainage Design Manual for Maricopa County, Arizona, Volume I Hydrology, and is to be followed to provide design criteria necessary for engineers relating to hydrology, except where amended herein. 5-1.202 Storm System Sizing A. Storm systems within the City shall be developed within two classifications: 1. The 10-Year Storm Event – The runoff generated from the 10-year storm shall be contained within the roadway’s curb section. This will consist of stormwater facilities necessary to collect and convey stormwater runoff for more frequent rainfalls. The primary purpose is to remove nuisance flows from pavement during frequent return period storms to maintain safe and efficient traffic movement. 2. The 100-Year Storm Event – The runoff generated from the 100-year storm shall be contained within the roadway’s right-of-way. This will consist of stormwater facilities necessary to collect, convey, retain, and/or detain stormwater runoff for less frequent rainfalls. The design is to include analysis of the overall drainage system ensuring that there will always be positive drainage of the one-hundred-year flows, and that all structures are above the HW or WS100 elevation. The primary 5-1 Grading and Drainage City of Buckeye 2026 11 purpose is to protect adjacent properties from damage caused by large, infrequent storms. 3. Private developments need to contain the 100-year runoff within the site. 5-1.203 Rainfall A. The design rainfall is NOAA Atlas 14, Volume 1, Semi-arid Southwest study or as updated by the Flood Control District of Maricopa County, relating to rainfall depths and intensities within the City of Buckeye boundaries for hydrology calculations. 5-1.204 Rational Method A. The Rational Method is applicable to estimate runoff for drainage area up to 160 acres with uniform land use and no channel routing. A City approved rainfall runoff model is required for drainage areas in excess of 160 acres, varied land use, or channel routing. 1. Rational Method Runoff Equation: Q = C*I*A Q = the peak discharge (cubic feet per second) from a given area C = coefficient relating the runoff to rainfall (Table 1) I = average rainfall intensity (inches/hour), lasting for a TC TC = the time of concentration (hours) A = drainage area (acres) 2. Time of Concentration: iterative process that calculates the interval of time from the beginning of the rainfall event of a specific drainage area; from the most hydraulically remote point to reach the point of concentration. Time of Concentration (TC) is calculated by utilizing the formula developed by Papadakis & Kazan (1987): TC = 11.4L0.5Kb0.52S-0.31I-0.38 TC = time of concentration in hours L = length of the longest flow path in miles Kb = watershed resistance coefficient S = watercourse slope in feet/mile I = rainfall intensity in inches/hour 5-1 Grading and Drainage City of Buckeye 2026 12 B. Engineers shall utilize the Drainage Design Manual for Maricopa County, Volume I - Hydrology to estimate the resistance coefficient (Kb) and the adjusted Intensity for the TC equation. 1. Time of concentration shall not be less than: a. Ten minutes for Residential developments. b. Five minutes for Commercial, Multi-Family, Build for Rent, and Industrial development. 5-1 Grading and Drainage City of Buckeye 2026 13 5-1.205 Runoff Coefficients A. The City uses the following Runoff Coefficients for the Rational Method: Table 1 – Runoff Coefficients for Rational Formula Land Use Description 10-Year 100-Year Agricultural 0.20 0.25 Commercial 0.85 0.95 Concrete, Asphalt, Roofs 0.85 0.95 Desert Landscaping 0.40 0.50 Golf Courses 0.25 0.31 Grass 0.25 0.31 Gravel Roadways 0.70 0.88 Industrial 0.80 0.95 Parks 0.25 0.31 Residential < 1 du per acre 0.42 0.53 Single Family Residential (1-2 units per gross acre) 0.48 0.60 Single Family Residential (2-4 units gross per acre) 0.65 0.80 Single Family Residential (4-6 units gross per acre) 0.68 0.84 Single Family Residential (> 6 units per gross acre) 0.75 0.94 Multi-Family Residential 0.75 0.94 Undeveloped Lots, Unimproved Areas (Bare Ground) 0.40 0.50 Undeveloped Desert < 5% 0.40 0.50 Undeveloped Desert 5% - 10% 0.55 0.69 Undeveloped Desert, Mountain Terrain > 10% 0.80 0.95 B. Where portions of a drainage area are composed of different runoff characteristics, a calculated weighted coefficient for the total drainage area 5-1 Grading and Drainage City of Buckeye 2026 14 may be determined using values from Table 1 or the Drainage Design Manual for Maricopa County, Volume I - Hydrology. Therefore, C values are to be used in the calculation by dividing the summation of the products of the area of the parts and their coefficients by the total area: CW = Σ (Ci*Ai) AT Ci = subarea runoff coefficient Ai = size of subarea AT = size of the watershed or modeling subbasin 5-1.206 HEC-1 Model A. The U.S. Army Corps of Engineer’s HEC-1 Computer Model procedures are applicable for any watershed area over 160 acres in size. HEC-1 is required for analyzing drainage areas over 160 acres in size. Please note FEMA no longer accepts HEC-1 models so HEC-HMS would need to be used for FEMA submittals. Minimum required submittals when using HEC-1 are: 1. Provide assumptions used in developing the model. 2. A printout of the input data. 3. A schematic (routing) diagram of the stream network. 4. The runoff summary output table which includes drainage basin name, area, and 100-year flow values. 5. Electronic model input file(s). 6. Supporting Documentation and Source Material for parameter selection. 7. Adjustments to the modeling parameters made to address warnings and error messages will have a narrative section to detail the impact of the adjustments on the output. B. Precipitation values for HEC-1 modeling shall be determined using the Drainage Design Manual for Maricopa County, Hydrology. Precipitation values are to be obtained from the Isopluvial maps for the specific frequency desired. Both 100-year 6-hour and 100-year 24-hour rainfall should be modeled and the storm resulting in the larger flows should be used for design. 5-1 Grading and Drainage City of Buckeye 2026 15 5-1.207 Methods for Estimating Peak Discharge Alluvial Fans A. Alluvial Fan Conditions – Split-flow channel conditions exist within parts of the City of Buckeye and must be taken into consideration. These splits in the alluvial channels usually include highly erosive soils and are generally unstable and therefore unpredictable. In setting finished floor elevations relative to upstream splits, it should be assumed that 100% of the flow could go either direction in any given flood event. The report should include a description of all assumptions made regarding watershed conditions used to calculate the peak flow rates. 5-1.208 Pre vs Post A. Site improvements increase the runoff volume and peak discharge and reduce the time of concentration. Pre vs. Post stores the difference between the post-development condition and the pre-development condition. 1. Pre vs. Post is only acceptable with prior City approval. 2. When this method is suitable to the City (typically for projects adjacent to major drainage ways that discharge directly to a river, or facilities owned and operated by the FCDMC) the applicant’s engineer will provide a detailed analysis of the existing or pre-development condition. 3. That runoff volume will be deducted from the anticipated post- development condition to determine the project’s retention / detention volume. 4. First Flush is required at a minimum when using Pre vs Post. First Flush requires one hundred percent retention of the first one half inch of rainfall. B. The following HEC-1 analysis procedures must be used when it is necessary to establish a comparison of pre-development to post-development discharge (runoff) conditions. 1. The HEC-1 modeling procedures must be followed. 2. Reflect fully developed conditions by: a. Increasing the percent impervious to reflect the amount of impervious surfaces that will exist under fully developed conditions. b. Recalculate the time of concentration (Tc) based on the proposed drainage system, after full development. Normally there should be a reduction in Tc after development. 5-1 Grading and Drainage City of Buckeye 2026 16 c. The existing condition model must be sub-divided, as necessary, to create concentration points which will match the sub-watershed areas above each proposed storage facility under fully developed conditions. d. Each separate storage facility proposed must be modeled as it will physically exist under fully developed conditions with appropriate routing and combining operations through each basin and through the entire watershed. The modeling of storage capacity provided, as one hypothetical reservoir at the outlet with all the upstream storage arbitrarily combined at this one location, is not acceptable. e. As a minimum, the 10, 25, 50, and 100-year frequency events shall be analyzed. The flow will be compared for watercourses and flow and volume will be compared for downstream regional storage facilities such as basins or flood retarding structures. f. Comparison of discharge values for existing and post development conditions must be made at concentration points just downstream from each proposed storage facility; other critical locations such as road crossings; and at points where flows exit the proposed development. 5-1.209 Runoff Volume Calculation – Retention A. The only accepted method for determining the required stormwater storage volume is the standard formula described below. 1. City requires on-site storage of runoff from the 100-year, 2-hour frequency event. 2. The HEC-1 model or similar computer program is not to be used to determine the city required 100-year, 2-hour stormwater storage runoff volumes. B. Standard Formula for Runoff Volumes Vr = (P/12) AC Vr = Required storage volume in cubic feet. P = Precipitation amount = The depth of the 100-year 2-hour rainfall in inches. A = Area in square feet; the developed portion of the entire site, to the centerline of adjacent streets, on which any man-made change is 5-1 Grading and Drainage City of Buckeye 2026 17 planned, including, but not limited to construction, excavation, filling, grading, paving, or mining. C = Runoff coefficient; Rational Method values from Section 5-1.205. 5-1.210 Runoff Volume Calculation – Detention A. HEC-1 modeling can be used for storage basin design and analysis, or if a pre- versus post volume difference is needed. Use Modified Puls level pool routing option in HEC-1 for hydrograph routing through storage basins and lakes. For permanent lakes assume no available storage below the normal water surface elevation. 5-1 Grading and Drainage City of Buckeye 2026 18 5-1.211 Downtown Buckeye Area A. In the downtown area of the City of Buckeye, identified in Figure 1, are areas of the City that have reduced or no retention requirements. Parcels larger than one acre require the retention of Pre vs Post runoff or first flush, whichever is greater. Parcels less than one acre are not required to have retention, however developments cannot create an adverse impact to adjacent properties. Figure 1 – Downtown Drainage Area 5-1 Grading and Drainage City of Buckeye 2026 19 5-1.300 Hydraulics 5-1.301 General Requirements A. Engineering design requirements contained in this section are in accordance with the FCDMC Drainage Policies & Standards Manual; Drainage Design Manual for Maricopa County, Arizona, Volume II Hydraulics, which are to be followed to provide design criteria necessary for engineers relating to hydraulics, except where amended herein. 5-1.302 HEC-RAS A. The U.S. Army Corps of Engineer’s HEC-RAS Computer Models – Minimum required submittals when using HEC-RAS are: 1. A printout of the input data 2. A plan of the stream network with cross section locations and stationing. Include flow obstructions, ineffective flow areas modeled and other appropriate parameters at a sufficient scale to support the modeling. Overlay the cross sections on the topographic work map. 3. A detailed output summary table that includes flow rates, velocities, water surface elevations, bank stations, n-values, ineffective flow stations, flow obstruction stations, and other relevant parameters. 4. Cross section profiles. 5. Electronic model input file(s). 6. Supporting Documentation and Source Material for parameter selection 7. Models should be submitted without warnings or error messages unless prior approval is obtained to allow warnings messages. A detailed narrative is required to validate warning messages. 8. Adjustments to the modeling parameters made to address warnings and error messages will have a narrative section to detail the impact of the adjustments on the output. 5-1.400 Street Drainage 5-1.401 Design Criteria for Streets and Gutters A. All properties as a condition of development, must be accessible during the 100-year storm event. 5-1 Grading and Drainage City of Buckeye 2026 20 B. Street drainage design shall not increase runoff onto adjacent properties. C. Lower classifications of roadway shall not direct runoff to higher classifications of roadways. For example, local roadways shall not direct surface runoff onto Parkway, Arterial, and Collector streets. D. Commercial, industrial, or multifamily developments shall not direct runoff onto adjacent public ROW. E. An inverted crown within public streets and roads is not allowed. F. Curb openings or depressed curb with flows over sidewalks are not permitted. G. Bubble up structures are not permitted for right-of-way drainage. H. Storm drain systems are required to hydraulically capture any runoff in excess of the street drainage capacity design criteria relating to water depth requirements and flow rates in Table 2 (i.e. piping, catch basins, and street capacity). I. Drainage structures in a sump condition are required to show by calculation that routing of flows in excess of the 10-year event to a retention / detention basin without exceeding the roadway’s ponding depth / limits. J. Street Drainage Calculations shall calculate street/gutter flow and velocity by using the modified Manning’s equation in Section 3 of the Drainage Manual for Maricopa County, Volume II Hydraulics. K. All roadway stormwater drainage capacities shall be designed for the 10-year and 100-year peak storms according to Table 2: 5-1 Grading and Drainage City of Buckeye 2026 21 Table 2 – Street Drainage Design Criteria Design Storm Event Street Type Required Dry Lanes Maximum Depth of Water 10-Year Local Streets Minor Collector None Top of Curb* Major Collector Minor Arterials Minimum One Dry Lane in Each Traffic Direction. No Conveyance Through Intersections. Top of Curb or as Required by Dry Lane Criteria Major Arterials Parkways Minimum Two Dry Lanes in Each Traffic Direction. No Conveyance Through Intersections. Top of Curb or as Required by Dry Lane Criteria 100-Year Local Streets Minor Collector None Flow Must Be Contained Within The Right-of-Way* Major Collector Minor Arterials None Flow Must Be Contained Within The Right-of-Way or Eight Inches Maximum Depth From Gutter Flow Line Major Arterials Parkways Minimum One Dry Lane in Each Traffic Direction. No Conveyance Through Intersections. Flow Must Be Contained Within The Right-of-Way or Eight Inches Maximum Depth From Gutter Flow Line or as Required by Dry Lane Criteria * Analysis for local streets shall account for both roll curb and gutter and vertical curb and gutter scenarios as needed. ➢ Maximum Velocity = 10 ft/sec ➢ Maximum Flow Rate = 100 ft3/sec 5-1.402 Valley Gutters A. Cross street valley gutters are only permitted on local streets for the purpose of transporting runoff when a storm drain system is not required. 5-1 Grading and Drainage City of Buckeye 2026 22 B. Cross street valley gutters are not acceptable for use on Parkways, Arterials, or Collectors due to impact on traffic. C. See COB EDS Section 6-3 for additional valley gutter requirements. 5-1.403 Storm Drains and Culverts A. Design Storm: Culverts under public streets or commercial/industrial access points must convey the 100-year flow with no overtopping of the street or driveway. B. Material: 1. The acceptable standard material for storm drains within the right-of- way or within a Public Drainage Easement is to be rubber gasket reinforced concrete pipe (RGRCP) Class III, Class IV, or Class V or polypropylene pipe (PP). Polypropylene pipe shall utilize COB Standard Details 51403A and 51403B for trenching, and COB Standard Details 51403C and 51403D for manhole connections. Class V RGRCP pipe is to be specified any time there is less than two feet of cover over the proposed storm drain or whenever H-20 wheel loading calculations require it. C. Minimum Size: 1. Minimum storm drain pipe size within public storm drainage systems or within the public right-of-way and private streets for storm drain lines shall be 18 inches. 2. Minimum storm drain pipe size for equalization of retention or detention basins shall be 18 inches. If a basin is short more than 1/3 of the basin volume required, the engineer shall provide calculations for sizing the equalizer pipe. 3. Box culverts constructed to ADOT Highways Division Structures “SD” Standard Details. Minimum box height is four feet. D. Minimum horizontal separation of storm drains between sewer lines and water lines shall be six feet edge of pipe to edge of pipe. E. Minimum vertical separation of storm drains between sewer lines and water lines shall be two feet edge of pipe to edge of pipe. F. Design Velocity: 1. Minimum design velocity for storm drainpipe during 10-year storm shall be 2.0 feet per second. 5-1 Grading and Drainage City of Buckeye 2026 23 2. Maximum design velocity for storm drainpipe shall be 15.0 feet per second. G. Stormwater pipes discharging into retention or detention basins are required to be one half foot above the bottom elevation of the basin with the appropriately sized riprap and/or concrete aprons for control of scour. H. Calculations for the hydraulic capacity of storm drainpipes, Manning’s Equation shall be used. Q = 1.486 ∗ A ∗ R 2/3 ∗ Sf 1/2 n Q = Discharge, cubic feet per second A = Flow Area, square feet R = Hydraulic Radius, ft n = Manning's Roughness coefficient, 0.013 Sf = Friction Slope, assumed equal to pipe slope, ft/ft See Table 4.1 of the FCDMC Drainage Design Manual Volume II Hydraulics for Manning’s “n” values. I. Hydraulic Grade Line: 1. Regardless of full flow or partial flow conditions, calculations for establishing the hydraulic grade line (HGL) for storm drainage catch basins, pipes, and other drainage structures are to be included on the Grading and Drainage improvement plans. 2. The HGL matching the design storm shall be shown on storm drain piping profile drawings and in the Final Drainage Report on a small- scale profile. 3. Storm drainage facilities within or in connection to the public right-of- way require the Hydraulic Grade Line (HGL) for the design storm be at least one foot below finished grade, flow line of gutter, top of grate elevation, or manhole cover. 4. Hydraulic Grade Line calculations shall be based on the basin being a quarter full for the 10-year design and half full for the 100-year design. J. Once public storm drains leave the right-of-way maintain an eight-foot buffer on each side for all landscape materials other than decomposed granite, turf, ground cover plants. 5-1 Grading and Drainage City of Buckeye 2026 24 5-1.404 Manholes A. Manholes are required at all junctions of two or more pipes and at all changes of grade, pipe size, pipe material or alignment for storm drains within the right-of-way or public storm drain easement. 1. The elevation of pipe crowns, not inverts, are to be matched at manholes and structures where pipe sizes change. 2. Directional changes of storm drains requiring a manhole shall have a minimum 0.10 feet drop in elevation between storm drain inverts. 3. Deflection angle of storm drains at a manhole should not exceed 90 degrees. B. Required manhole spacing: 1. Storm drain diameter less than or equal to 48 inches, maximum manhole spacing is 400 feet. 2. Storm drain diameter greater than 48 inches and less than or equal to 84 inches, maximum manhole spacing is 600 feet. 3. Storm drain diameter greater than 84 inches, maximum manhole spacing is 1,300 feet. C. Storm drain manhole materials and construction shall follow MAG Uniform Standard Details and Specifications for Public Works Construction. D. Storm drain manhole, frame, or cover shall not be located in the curb, gutter, sidewalk, or driveways. E. Public storm drain manhole frame and cover shall be constructed per MAG Standard Detail 423. The label on the cover shall read “Buckeye Storm Sewer” as shown in COB Standard Detail 51404. 5-1.405 Catch Basins A. Catch basins shall be the curb opening type constructed to MAG Standard Details 542-1 and 542-2. B. Grated inlets and combination curb opening-grated inlet type are generally not allowed within City of Buckeye right-of-way unless approved by the City for unique low points such as within a major median. C. Slotted drains are not allowed within the City of Buckeye right-of-way and City owned properties. 5-1 Grading and Drainage City of Buckeye 2026 25 D. Calculations for sizing catch basins and inlets, including friction losses and clogging factors, shall comply with Section 3 of the Drainage Design Manual for Maricopa County, Arizona, Volume II Hydraulics and Table 6.8 of the Drainage Polices and Standards Manual for Maricopa County. 5-1.406 Scuppers A. Scuppers are not permitted on collector or higher street classifications. B. Scuppers are not permitted with curb separated sidewalks. C. Under sidewalk scupper constructed to MAG Standard Detail 206 modified to use handrail per COB Standard Detail 51407C. Metal cover types are not acceptable. D. Calculations of scupper sizes shall be according to Section 3 of the Drainage Manual for Maricopa County, Volume II Hydraulics, or FHWA HEC-12 and HEC- 22. Clogging factors shall be from Table 6.8 of the Drainage Policies and Standards Manual for Maricopa County. E. Scuppers must convey a minimum of the 10-year flow. Spillway width shall match scupper width or shall taper at 3:1 maximum. Concrete spillways shall extend to basin or channel bottom. 5-1.407 Pipe Inlets and Outlets A. Headwalls are required for pipe outlets per COB Standard Detail 51407A. Special considerations will be given for alternative outlet design for golf courses, natural washes, and channels. When directed by the City, a brass benchmark shall be installed in the center of the headwall. Frequency of benchmark installation will typically be one per PLSS section of land. B. Access barriers / trash racks are required on the exposed ends of all storm drains 18 inches in diameter and greater per COB Standard Detail 51407B. If storm drain is 36” inches or greater in diameter and has a straight run of less than 200’ the trash racks can be omitted. C. Headwalls greater than 30 inches in height, and any headwalls adjacent to sidewalks require handrails per COB Standard Detail 51407C. 5-1.408 Grouted Riprap A. Grouted riprap is required in residential areas, parks and usable open space. Concrete base shall be a minimum of four inches thick with hand placed rock averaging six inches in diameter that are embedded approximately three 5-1 Grading and Drainage City of Buckeye 2026 26 inches into the concrete. The rock shall be free of concrete on the exposed surface and shall be spaced an average of two inches apart. Grouted riprap shall extend a minimum of six feet from the concrete apron. 5-1.500 Open Channel Flow 5-1.501 General Requirements A. Calculations required in the design of open channel flow shall comply with FCDMC Drainage Policies & Standards Manual and the Drainage Design Manual for Maricopa County, Arizona, Volume II Hydraulics, Section 6. B. Conveyance of the historic flows shall be maintained. C. Offsite historical flow characteristics (location, flowrate, velocities, etc.) entering and exiting the development shall be maintained. Channel routing within the development may be altered. D. If offsite flow terminates within the development, increased amounts of retention or detention will be required. E. Routing of offsite flows within City of Buckeye right-of-way or PUEs are not allowed, except where crossings (culverts, bridges) are permitted. F. Culverts are required to convey the channel flow capacity. No low water crossings are allowed. G. Where man-made channels are required, the emphasis should be placed on non-erosive velocities or appropriate erosion protection per the Drainage Policies and Standards for Maricopa County, Arizona. Concrete or shotcrete lined channels are prohibited in residential or recreational areas. H. All engineered channels shall have a minimum of one foot of freeboard for subcritical flow and two feet for supercritical flow. The design engineer will consider greater amounts of freeboard due to velocity, transitions, etc. where applicable. I. For channel drop structures, the maximum vertical drop height from invert crest to invert toe for any single step shall be two- and one-half feet. A six- foot wide (minimum) horizontal apron shall be provided for every two- and one-half feet of vertical drop in a "stair step" fashion. Drop structures constructed of concrete or shotcrete shall have a roughened surface to discourage inappropriate recreational use. 5-1 Grading and Drainage City of Buckeye 2026 27 J. Total scour depth protection is required. Engineer shall submit calculations for adequately sized erosion control measures. Launchable rip rap is not allowed. K. Adequate safety measures must be taken (i.e. safety railings, safety fence, warning signs etc.) where accessible to the public. 5-1.502 Open Channels A. The channels shall comply with the following: 1. Channels that are located adjacent to the right-of-way have the following requirements: a. Channels accessible to the public or in residential areas shall be limited to three feet in normal flow depth and channel side slopes shall not exceed 4:1. b. Channels are not allowed within the right-of-way. c. Channels are not allowed within a PUE. 2. Channels within private commercial and industrial developments without public access are allowed greater depths with the following requirements but not limited to: a. Vertical side slopes when using structural walls, otherwise maximum side slope of 3:1 (h:v). b. A six-foot-tall viewable fence around the channel. 5-1.600 Retaining Walls 5-1.601 General Requirements A. Retaining walls are required for elevation differences greater than one foot between lots in subdivisions, or between a development and adjacent properties. B. The height of retaining walls cannot exceed six feet. C. Terraced retaining walls are encouraged in areas where over six feet is required to be retained. D. When terraced retaining walls are used, the top of the footing of the upper retaining wall shall be a minimum of one foot below the top of the lower retaining wall. The slope between the retaining walls shall not exceed 4:1 and 5-1 Grading and Drainage City of Buckeye 2026 28 the toe of the slope shall be a minimum of four inches below the top of the lower retaining wall. E. When a retaining wall is used adjacent to a side slope of a retention basin, a minimum two-foot-wide bench shall be provided adjacent to the retaining wall prior to the slope beginning. F. All retaining walls require structural details and calculations. G. Retaining walls require separate review and permitting by the City of Buckeye Building Department. 5-1.700 Residential Lot Grading 5-1.701 General Requirements A. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall a minimum of six inches within the first ten feet. B. For residential lots, where conditions prohibit six inches of fall within ten feet, the grade shall slope away from the foundation at a minimum slope of 5%, and the water shall be directed to drains or swales. Impervious surfaces shall have a minimum slope of 2% when located within ten feet of the building foundation. C. Minimum residential side yard slopes shall be 0.5%, or steeper if required by soils report, and shall typically drain to the street, unless otherwise approved in a community Master Drainage Report. 5-1.800 Stormwater Storage Facilities 5-1.801 General Requirements A. All retention / detention facilities must be drained within 36 hours. B. All retention and detention basins shall have a minimum of one foot of freeboard above the HW. C. All basins’ emergency outfall elevation shall be at least one foot below any adjacent finished floor building elevation. D. Recreational facilities are not allowed within retention/detention basins (pickleball courts, basketball courts, playgrounds, etc.). E. Flow removed from the street shall not be allowed to return to surface street flow. Basins sized for less than the design storm must convey the excess flow 5-1 Grading and Drainage City of Buckeye 2026 29 to the next downstream basin by storm drain or by private landscape tracts not within the right-of-way. 5-1.802 Stormwater Storage Facilities – Surface Retention Basins A. The most common method of stormwater storage is surface retention or detention basins. Where surface storage of the required retention is planned and provided, the basin shall comply with the following: 1. Basins that are located adjacent to the right-of-way have the following requirements: a. Basins must be landscaped in accordance with the City of Buckeye Development Code. b. Maximum HW of three feet in depth. c. Retention / detention is not allowed within the right-of-way. d. Retention / detention is not allowed within a PUE. e. Side slopes shall not exceed 8:1 within eight feet of a public right-of- way or back of sidewalk, whichever is greater. Side slopes shall not exceed 4:1 in other perimeter areas. 2. Basins within private commercial and industrial developments without public access are allowed greater HW depths with the following requirements but not limited to: a. Vertical side slopes when using structural walls, otherwise maximum side slope of 3:1 (h:v). b. A six-foot-tall viewable fence around the retention basin. c. A drivable access for maintenance to the bottom of the basin. 3. Retention or detention is not allowed in paved parking lot areas. 5-1.803 Stormwater Storage Facilities – Underground Retention Systems A. Underground storage is an acceptable method for certain applications to store stormwater runoff. Underground stormwater storage utilizes storage tanks, vaults, chambers, etc. to place the required stormwater retention or detention volume underground within the development site. The engineer shall consider the following during the design process for any project involving underground storage: 1. 100-year 6-hour volume provided. 5-1 Grading and Drainage City of Buckeye 2026 30 2. Soil conditions. 3. Access to the underground structure for routine maintenance. 4. Structural loads including H-20 traffic loads. 5. Buoyancy of the structure. 6. Drainage of the underground structure within the required 36-hour period. B. Underground stormwater storage is allowed for: 1. Commercial developments. 2. Industrial developments. 3. Multifamily developments such as condominiums and apartments. C. Underground storage is not allowed: 1. Within Single Family Residential developments. 2. Within City of Buckeye right-of-way. 3. Beneath surface retention or detention basins unless an anchor system is used, and buoyancy calculations are provided. 4. Where a high groundwater table encroaches onto the storage tank. D. All stormwater entering an underground retention system shall first pass through a cleaning mechanism (retention basin or sand and debris separator) capable of treating the first flush flow. Flow greater than the first flush flow may bypass the cleaning mechanism. An alternative to the cleaning mechanism is to provide a sediment isolation chamber. E. A geotechnical report is required by an Arizona Registered Professional Engineer detailing the following: 1. Ground water table elevation with respect to the bottom elevation of underground storage structure. 2. Soil pH. 3. Soil resistivity in ohm-cm. 4. Chloride and sulfate concentration in ppm. F. A minimum 75-year service life of any underground stormwater storage is required. 5-1 Grading and Drainage City of Buckeye 2026 31 G. Underground stormwater storage structures minimum cover shall be three feet in depth, or three feet below the pavement section. H. Underground stormwater storage structures must drain within 36 hours by percolation or drywells. When utilizing drywells: 1. Provide drywell detail relating to the connection of the underground stormwater storage structure. 2. The system shall be inspected to ensure it is properly installed per these requirements. 5-1.804 Underground Retention with CMP A. Installation of CMP underground stormwater storage must be in accordance with MAG Specification Section 621 and manufacturers specifications. B. Metal type, corrugation sizes, and lining must be designed to the National Corrugated Steel Pipe Association (NCSPA), unless otherwise approved by the City Engineer. C. Refer to the American Iron and Steel Institute Estimated Material Service Life Table for additional guidance. 1. Aluminized Type 2 – the bedding, haunching, and initial backfill shall have pH between 5-9 and resistivity ≥ 1,500 ohm-cm or pH between 4.5- 9 and resistivity ≥ 5,000 ohm-cm. 2. Polymer Coated – the bedding, haunching, and initial backfill shall have pH between 4-9 and resistivity ≥ 750 ohm-cm. D. Underground stormwater storage structures must provide a minimum of two access points: 1. Access manholes shall be 48 inches in diameter with a 30-inch bolted manhole frame and cover (solid or grated). The cover shall be labeled “Retention Tank.” 2. Access manholes must include a fixed ladder. 3. Concrete collars are required per MAG Standard Detail 422. 4. Engineer must provide construction details and specifications for CMP underground stormwater storage including but not limited to: a. End walls. b. Access risers. 5-1 Grading and Drainage City of Buckeye 2026 32 c. Excavation, bedding, and backfill according to MAG Standard Specifications 601 and 760 with material and installation requirements. d. Watertight joints. 5-1.805 Underground Retention with Perforated Pipes/Chambers A. Aggregate void volume for retention calculations shall not exceed 50% of the aggregates certified void volume. B. Aggregate void volume for retention calculations shall be limited to the height between the bottom of the pipe/chamber and the top of the pipe/chamber. C. Aggregate material gradation and void volume testing shall be submitted prior to construction. Approved aggregate material shall be supplied by only the approved supplier. D. The aggregate envelope utilized for retention shall have an approved filter fabric on the bottom, side, and top of the aggregate. 5-1.806 Stormwater Storage Facilities – On-Lot Residential Retention A. Individual single family residential developments (one dwelling unit per lot) with lots greater than or equal to one acre (43,560 SF) are allowed to fulfill retention requirements with on-lot retention. The following are requirements of on-lot retention: 1. Calculations and design criteria of on-lot retention shall comply with Section 5-1.700 of this section. 2. Where on-lot retention is allowed, the engineer has an option to submit either a drainage report or provide calculations on the grading and drainage improvement plans. 3. Calculations provided by the engineer are to include onsite and the respective half street runoff. 4. Finish floor elevations shall be set at a minimum of one foot above the basin and lot outfall. 5. On-lot retention shall not be located within ROW or a PUE. 6. Side slopes: Maximum 4:1. 7. Basin water depth is limited to one foot deep. 5-1 Grading and Drainage City of Buckeye 2026 33 8. Runoff coefficients used in calculating runoff shall comply with Section 5-1.205 of this section. 9. Parcels with on-lot retention shall be identified on the final plat. 10. Copy of recorded covenant requiring the 100-year 2-hour retention including adjacent half street runoff in perpetuity on parcel deed shall be submitted with building permit applications where lots are subject to on-lot retention. 11. As Built grading and drainage plan shall be submitted to the City prior to the obtaining a Certificate of Occupancy. 12. Any modifications to the configuration of the basin requires submittal of a grading and drainage plan to the City. 13. Individual single family residential developments with on-lot retention that receives flood irrigation shall include a minimum of 75% of the gross lot area of the lot multiplied by 0.50 feet in additional volume required by irrigation. 5-1.807 Stormwater Storage Facilities – Detention Basins A. Detention basins capture runoff by means of a storage facility and release the runoff in a controlled manner. Detention basins have the following additional requirements: 1. Post-development peak discharges may not exceed pre-development peak discharges for the 2-, 10-, 50-, and 100-year storm events. First flush requirements must be met. 2. Controlled releases into existing rivers, washes, and public stormwater storage facilities must be discussed in the drainage report. 3. Detention basins shall have a free outlet with a minimum outlet pipe of 18 inches in diameter with or without orifice plates. The design engineer shall provide calculations that confirm the appropriate outlet to drain the required volume within the 36-hour time period. 4. Detention basins with a piped outlet shall require the invert be a minimum of one-half foot above the bottom of basin or at such a depth to retain the first flush volume. 5. The controlled outflow from the detention basin shall be a point of discharge such as a river, wash, or regional facility approved by the City, FCDMC, or the Corps of Engineers. To be approved: watershed timing 5-1 Grading and Drainage City of Buckeye 2026 34 issues must be studied and determined to not be an issue for downstream properties, system sediment balance must not be significantly affected, and cumulative impacts of applying such a policy throughout the watershed must not be detrimental to public safety or property. 5-1.900 Stormwater Disposal 5-1.901 General Requirements A. Retention basins greater than one foot of ponding depth or underground retention with closed bottoms, require a minimum of one drywell for stormwater disposal. B. Underground retention with pretreatment or isolation chambers shall utilize Maxwell IV drywells or approved equal. All other retention applications shall utilize Maxwell Plus drywells or approved equal. C. Drywells must penetrate a minimum of ten feet into a permeable stratum and a constant head percolation test must be carried out on the completed drywell before acceptance. Certified percolation test results are to be filed with the City. D. Direct connections of storm drain piping to drywells will not be permitted. E. Drywells are to be equipped with a secured grate to prevent unauthorized removal. F. Top of the drywell grates shall be set 0.3 feet above the bottom finished grade elevation of retention basins. G. Drywell usage in areas with high groundwater may not be feasible or allowed. The Engineer shall evaluate alternative options such as a trench drain per COB Standard Detail 51900 to dispose of storm runoff. Geotechnical evaluations will be required to determine the presence of groundwater. H. All commercial and industrial developments that have fueling areas, bulk fuel storage, or bulk oil storage shall have a separate drainage area and drain to a storage facility that includes an Envibro petrochemical drywell system or approved equal. I. Property owners of record shall be responsible for the design, performance, operation, and maintenance of all drywells in the development. Whenever it is determined that the drywell system cannot drain the basin(s) within 36- 5-1 Grading and Drainage City of Buckeye 2026 35 hours, the owner is obligated to replace deteriorated drywells or add drywells to comply with the 36-hour drain requirement. J. All drywells shall be registered in accordance with the Safe Drinking Water Act’s Underground Injection Control program and constructed by a licensed contractor. K. Drywells shall comply with the ADEQ publication Guidance for Design, Installation, Operation, Maintenance, and Inspection of Drywells and the additional requirements described herein. 5-1.902 Drywells – Locations A. Drywells shall be located as far as practical (minimum 20 feet) from a basin inlet. B. When multiple drywell installations are required, each drywell shall be located a minimum of 100-feet apart. C. Drywells shall be located a minimum of 20 feet from permanent foundations and structures. D. Drywells shall be located a minimum of 25 feet from stormwater underground storage structures. E. Drywells shall be located a minimum of 100 feet away from water wells and septic systems. F. Drywells are not allowed within public street ROW, PUE, nor private street roadway tracts. G. Drywells shall never be placed within basin side slopes. H. Drywells shall be a minimum of 10 feet from toe of side slope. I. Drywells installed in asphalt parking lots shall have concrete adjustment rings placed around the grate per MAG Standard Detail 422. 5-1.903 Drywells – Design / Pre-Construction A. Drywell infiltration or volume cannot be considered in retention calculations in efforts to reduce the size of the retention area. B. A maximum disposal rate of 0.20 cubic feet per second may be used for estimating the number of drywells required for preliminary plat/site plan. In other words, one drywell for every 25,920 cubic feet of required retention will be required for design. When the requirement for drywells is triggered the 5-1 Grading and Drainage City of Buckeye 2026 36 entire basin required volume must be assumed to be drained via drywells only. C. Calculations are required in the final drainage report showing the minimum number of drywells required to drain retention facilities in 36 hours. D. If localized depressions are allowed within a basin, a Maxwell Plus drywell shall be placed within the depression, but as far as practicable from a basin inlet. 5-1.904 Drywells Post-Construction A. Each drywell shall be tested after installation and constant head percolation test is required. Fifty percent of the tested percolation rate shall be used in calculations for drywell stormwater disposal, up to but not exceeding 0.50 cubic feet per second, compensating for deterioration of percolation rates over time. If the post construction percolation testing results in the stormwater storage facilities disposal time is greater than 36 hours, additional drywells are required to be installed. B. Certification of post-construction drywell percolation rates, revised disposal rates, and quantity of drywells, are required by the Engineer on the as-Built Plans. See COB EDS Section 1-2 for additional information on drywell as-built requirements. 5-1.905 Ground Percolation Post-Construction A. Ground percolation can be included in post-construction basin disposal calculations as outlined in the Percolation Test Requirement for Retention Basins in the Maricopa County Drainage Policies and Standards, with the exception that an average of the percolation rates measured can be used for Equation 6.7 instead of the lowest measured rate. 5-1.1000 Regional Drainage 5-1.1001 Retention Basins A. Regional detention/retention facilities are large storage facilities located at strategic sites within a watershed to provide control of runoff. The advantage of this type of facility is that the siting and design of regional storage facilities is normally incorporated as part of an overall drainage master plan. B. Regional retention basins are typically deeper in depth. Greater water depths will require flatter side slopes and approval of the City. The following depth/side slope criteria shall be used: 5-1 Grading and Drainage City of Buckeye 2026 37 1. Basins 0’ to 3’ in ponding depth ----------- 4:1 side slopes 2. Basins 3’ to 6’ in ponding depth ----------- 6:1 side slopes 3. Basins 6’ to 9’ in ponding depth ----------- 10:1 side slopes 4. Basins greater than 9’ in ponding depth ----12:1 side slopes C. Regional detention/retention facilities to be designed with active recreation amenities are to provide a minimum of one maintenance access that is not to exceed a 10:1 rate of slope (match basin side slope where basins are greater than nine feet in depth) with a minimum unobstructed width of 20 feet. 5-1.1002 Channels: A. For engineered channels with flow depths greater than three feet the following shall be required: 1. Access ramps shall meet the FCDMC ramp requirements. 2. Paved access ramps shall be required for the portions that will be inundated by the 100-year peak event and shall be properly "toed in" to protect the ramp from erosion during storm events. 3. Access ways or ramps may be combined with portions of multi-use trails, subject to approval by the City. 4. Safety barriers or fencing. 5-1.1100 Drainage Reports 5-1.1101 General Requirements A. A detailed drainage study is required of the applicant to evaluate the total contributing flow impacting the proposed development. All developments within the City shall provide such storm drainage facilities as are necessary to ensure that all improvements, structures and properties, both within the subject development and those located upstream and downstream of the development, shall be protected from the adverse impact of stormwater up to the 100-year storm due to the proposed development. B. The “Master”, “Preliminary”, “Mass Grading Memo” and “Final” Drainage Report(s) must be sealed and signed by a registered Civil Engineer in the state of Arizona. 5-1 Grading and Drainage City of Buckeye 2026 38 C. A Master Drainage Report shall be submitted in support of PADs, Community Master Plans, and Rezones. D. A Preliminary Drainage Report shall be submitted in support of Preliminary Plats, Site Plans, and Conditional Use Permits. E. A Mass Grading Memo shall be submitted in support of Mass Grading plans, when those plans precede the final improvement package and Final Drainage report. F. A Final Drainage Report shall be submitted in support of all civil plans and final plats. G. All Drainage Reports shall adhere to the City of Buckeye Preliminary and Final Drainage Report Guidelines as published in the following sections. H. Purpose of the Drainage Report Guidelines: 1. This document was prepared as a tool for developers and engineers seeking construction permits for any proposed improvements within the city limits that require the preparation and submittal of accompanying “master”, “preliminary”, “mass grading” and “final” drainage reports. 2. This Drainage Report Guideline will serve as a reference document that defines the city’s minimum standards and requirements for master, preliminary, mass grading, and final drainage design. Adherence to these minimum drainage requirements by the development and engineering community is imperative to mitigate the hazards associated with the potential for increased runoff due to new development. 3. Additional information may be required for approval as deemed necessary by the City. I. Intent of the Drainage Report Guidelines: 1. The intent of this document is to convey to the user the minimum topics that a master, preliminary, mass grading, and final drainage report submitted to the City of Buckeye should address. 2. The intent of this document is not to provide a comprehensive drainage design section. 3. This document assumes that the user is familiar with the basic concepts and industry standard practice for hydrologic and hydraulic analysis 5-1 Grading and Drainage City of Buckeye 2026 39 and computations. Further, it is assumed that the user has a good understanding of the theory and science behind those subjects. 4. This document should not be expected to address all situations that may be relevant on specific project sites. It will merely provide a guide that will aid developers and engineers in the goal of meeting the basic minimum criteria for any drainage design conducted within the City of Buckeye. 5. Every project is different and may be associated with a set of drainage design challenges unique to its specific location not common to other projects. Although these issues may not be specifically addressed by this guideline, they must be identified and addressed by the master, preliminary, and final drainage report(s) for that project. 6. Each basic design guideline element does need to be addressed within the drainage report(s) to assure that the element was considered and evaluated. For example, regardless of the existence of offsite flow impacts to a particular project site, offsite flow should always be addressed and explained in the master or preliminary drainage report and then in detail for the final drainage report. 7. It is the responsibility of the engineer to provide a complete and thorough drainage evaluation that meets the industry standard of care for each project. 5-1.1102 Master Drainage Report Submittal A. Minimum Elements Required: 1. This section will briefly summarize the basic elements that should be addressed by all master drainage reports submitted to the City of Buckeye for review and approval. 2. A general discussion of items listed below is required for master drainage report submittals. At the master drainage report submittal, the discussion of the required items may be brief and general with the understanding that these items will be addressed in greater detail with the subsequent submittal of individual preliminary and final drainage reports. 3. It is important that the items below are addressed at the master plan stage for the proposed development to minimize the number of 5-1 Grading and Drainage City of Buckeye 2026 40 drainage issues that may otherwise not be identified until the project is much further along. 4. For a summary of the basic elements that should be addressed by all final drainage reports submitted to the City of Buckeye for review and approval refer to Section 5-1.1104. Several additional items that are not usually required for inclusion with the master drainage report must be discussed in the final drainage report. In certain cases, it may be appropriate to include some of those items in the master drainage report submittal. It is up to the developer/engineer to use his or her judgment when determining the appropriate contents of a master drainage report. B. Master Drainage Report Format / Minimum Design Elements / Description of Design Elements: Cover Sheet Table of Contents 1. Introduction 1.1. Project Description 1.2. Project Name & Address if known 1.3. Location & Topography 1.4. Existing/On-Going Studies 1.5. Regional Drainage Plan 1.6. FEMA Flood Hazard Zones 2. Offsite Hydrology 2.1. Methodology and Criteria 2.2. Existing Land Use 3. Onsite Hydrology 3.1. Methodology and Criteria 4. Proposed Drainage Infrastructure 4.1. Conveyance of Runoff Through Project Site 4.2. Onsite Retention Requirements 4.2.1. Required Retention Volume 5-1 Grading and Drainage City of Buckeye 2026 41 4.2.2. Provided Retention Volume 4.2.3. Ultimate Site Outfall 5. Special Issues or Considerations 5.1. 401/404 Permit 5.2. Floodplain Use Permit with FCDMC 6. Summary and Conclusions 7. References APPENDICES EXHIBITS Each element listed above is briefly described below. Each element should include a brief discussion and may include some preliminary analysis if required to support/document any data shown within the text or on tables. If any of the elements listed above and described below are not applicable to a particular project site, the developer/engineer should still include the element heading within the master drainage report. A single sentence explaining why the element is not applicable to the specific project site must be provided. This is important since it indicates that the developer/engineer is aware of such elements and has addressed them. If an element is simply missing from the report, it is unclear whether it was considered and/or the reason or reasons it was deemed ‘not applicable’. If required, the appendix provided for the master drainage report will contain detailed calculations and data sheets necessary to develop the summary tables. Cover Sheet – The Cover Sheet should include the project name and location, submittal date and submittal number, a list of all prior submittal dates and corresponding submittal numbers, prepared for including contact name, company name, address, telephone number, and email; prepared by including: contact name, company name, address, telephone number, and email; Engineer’s seal and date. Table of Contents – List all sections, figures, tables, exhibits, appendices, and Engineer’s seal. Introduction – Every master drainage report must include a short introductory section that describes the general area within which the project site is located, some ‘context’ for the project site and a summary of the overall area. 5-1 Grading and Drainage City of Buckeye 2026 42 Project Description – This will include the specific project site location, a simple vicinity map (showing the project site relative to the overall region), hydrologic character of the area, the purpose of the report; any existing regional drainage facilities, features such as irrigation canal, CAP, or Railroad. At the preliminary level, the above items may be explained in general/broad terms. These and other elements will be described in much more detail in the final drainage report. Project Name and Address if Known – Briefly state the name of the project and the address if known. Location and Topography – A very brief description of the hydrologic character within which the project site is located (natural desert, mountain, alluvial fan, valley, foothills, etc.) as well as the major existing land uses (Industrial, Commercial, Lot Split & Subdivision). This section should also include a description of the topography in terms of overall direction of flow. Any other major features such as existing washes or flood control channels should be noted as well. Existing/On-going Studies – This is a list of any past/on-going studies available within the vicinity of the project site that may have an impact on the site. These are usually relevant to offsite discharges impacting proposed project sites. These may include, but are not limited to, Floodplain Delineation Studies (FDS), Area Drainage Master Studies (ADMS), and Area Drainage Master Plans (ADMP). At the preliminary level, the report can list relevant studies as a ‘bullet’ list. The preliminary and final drainage reports will contain a more detailed description and summary of each study listed. Regional Drainage Plan – This should be a general description of regional drainage features and/or the existence of a regional drainage plan. At the master report level, these features need only be acknowledged with a full discussion following in the preliminary and final drainage reports. FEMA Flood Hazard Zones – It is important to establish any known flood hazards that may exist around or on the project site. This information will be used as a basis for determining the need for the mitigation of known hazards through site improvements that could require a CLOMR/LOMR process. Regardless of the existence of a known flood hazard zone, a figure must be provided illustrating the overall project site superimposed onto the effective FIRM. The panel number and effective date of the FIRM must be visible on the 5-1 Grading and Drainage City of Buckeye 2026 43 figure. This information is important at the master level as it can have a significant impact on the project master plan. Offsite Hydrology – This section will contain a brief description of the existing condition hydrology, as well as the proposed condition hydrology. It will briefly describe the detailed methodology, criteria and assumptions that will be used to develop the hydrology. There will be a general description of the offsite discharges impacting the project site. This section of the report must contain a summary table of offsite subbasin area discharges and a corresponding concentration point that can be quickly and easily referenced on a figure (minimum 11”x17”) within the report. Finally, the appendix will contain documentation for any calculations and computations used to develop the data contained within the summary table. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any offsite peak flow rates necessary to support the preliminary plat. This section must reference the methods and criteria required by the City of Buckeye. Existing Land Use – This section is contained within the Offsite Hydrology section of the report. It will provide a general overview of the existing offsite land uses. Onsite Hydrology – This section of the report will describe the nature of the onsite proposed land use, and an approximation of the weighted roughness coefficient (“C” value) based on City of Buckeye criteria within Section 5-1.204 and the FCDMC’s Drainage Design Manual, Hydrology. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any onsite peak flow rates necessary to support the master plan. This section must reference the methods and criteria required by the City of Buckeye. This section should explain in general terms the more detailed approach that will be used in the preliminary and final drainage reports. Proposed Drainage Infrastructure – This is a general discussion of the proposed drainage system that will be used within the project site to safely collect and dispose of runoff generated during 10-year and 100-year peak storm events. The detailed description and accompanying analysis will be presented in the final drainage report. Conveyance of Offsite Runoff Through Project Site – As a sub-section of ‘Proposed Drainage 5-1 Grading and Drainage City of Buckeye 2026 44 Infrastructure’, this section will provide a general description of the proposed conveyances that will be detailed in the final drainage report. This section will give a summary of those conveyances as well as their expected operation during the 10-year and 100-year peak events per the City of Buckeye requirements. Onsite Retention Requirements – This section will explain the City of Buckeye requirements for onsite retention including, freeboard, side slopes, ponding depths, drain time and means of draining the basin. The equation used to compute the required volume of retention onsite should be shown with all the terms clearly labeled and defined within the text. Required Retention Volume – This section should show the equation used to determine the required retention volume, define the terms and direct the reader to the appendix for detailed calculations and data documenting the computation of the required retention volume for the project site. Provided Retention Volume – This section should show the equation used to determine the provided retention volume, define the terms and direct the reader to the appendix for detailed calculations and data documenting the computation(s). This section should provide the information necessary to show that areas designated for retention on the preliminary plat are sufficient given the basin geometry constraints (per City of Buckeye requirements) and in light of the required volume computed in the previous section. Site Ultimate Outfall – This section should provide a brief description of the site ultimate outfall proposed on the preliminary plat. This section should describe (in concept) the way in which basin surcharges will be conveyed through the site. Such basin surcharge could be due to a non-design storm event that results in more volume intercepted by the basin than is provided by the basin. Special Issues or Considerations – This section of the report should include an overview of any issues or considerations that could become significant during the preparation of the final drainage report and are unique to this project site. Such issues or considerations may include but are not limited to the following: • 401/404 permit requirements • Floodplain use permit Summary and Conclusions – This section will provide a quick summary of the proposed master drainage concept for the project site and make conclusions 5-1 Grading and Drainage City of Buckeye 2026 45 as to its operation and ability to support the proposed project as well as meet the City of Buckeye requirements. References – This section will provide a set of references that will document any and all explanation, calculations, methodology, criteria, past & on-going studies, etc. that were contained within the text of the preliminary report. At a minimum these references should include a title, author, and date. APPENDICES – This portion of the report will contain exhibits, calculations, and other supporting data. Information from previous referenced reports that is important to the design of the proposed project should be included with Cover Sheet with City Approval documented. EXHIBITS – At a minimum, every master drainage report submitted must provide an offsite and onsite drainage exhibit. The offsite drainage exhibit may be at a smaller scale than that used for the onsite exhibit but must be easily readable. Any delineated subbasin areas necessary for the support of the proposed master plan must be at a scale suitable for area verification. This exhibit must show the entire offsite area contributing to the discharge at the project boundary and must include all information necessary for verification of the developed flow rates used in the drainage report. If the offsite discharges were developed under a separate study or provided for use with this project, the source of these discharges must be clearly referenced and specified within the report. In this case, the offsite drainage exhibit may be much less detailed and need only serve as a reference to the reader that will establish the geographic context within which the project site exists. The onsite drainage exhibit should be plotted at a size and scale appropriate for verification of any master drainage subbasin areas, concentration points, proposed retention/detention basin volumes, etc. At a minimum, this exhibit must show project property boundaries, all existing structures, existing drainage patterns/features, existing contours and/or spot elevations, phase labels in the appropriate phase, proposed retention/detention basin locations, expected onsite flow patterns and flow arrows. 5-1 Grading and Drainage City of Buckeye 2026 46 5-1.1103 Preliminary Drainage Report Submittal A. Minimum Elements Required: 1. This section will briefly summarize the basic elements that should be addressed by all preliminary drainage reports submitted to the City of Buckeye for review and approval. 2. A general discussion of items listed below is required for the preliminary drainage report submittals. At the preliminary drainage report submittal, the discussion of the required items may be brief and general with the understanding that these items will be addressed in greater detail with the subsequent submittal of the final drainage report. 3. It is important that the items below are addressed at the preliminary plat stage for the proposed development to minimize the number of drainage issues that may otherwise not be identified until the project is much further along. 4. For a summary of the basic elements that should be addressed by all final drainage reports submitted to the City of Buckeye for review and approval refer to Section 5-1.1004. Several additional items (see Section 5-1.1004) that are not usually required for inclusion with the preliminary drainage report must be discussed in the final drainage report. In certain cases, it may be appropriate to include some of those items in the preliminary drainage report submittal. It is up to the developer/engineer to use his or her judgment when determining the appropriate contents of a preliminary drainage report. B. Preliminary Drainage Report Format / Minimum Design Elements / Description of Design Elements: Cover Sheet Table of Contents 1. Introduction 1.1. Project Description 1.2. Project Name & Address if known 1.3. Location & Topography 1.4. Existing/On-Going Studies 1.5. Regional Drainage Plan 5-1 Grading and Drainage City of Buckeye 2026 47 1.6. FEMA Flood Hazard Zones 2. Offsite Hydrology 2.1. Methodology and Criteria 2.2. Existing Land Use 3. Onsite Hydrology 3.1. Methodology and Criteria 4. Proposed Drainage Infrastructure 4.1. Conveyance of Runoff Through Project Site 4.2. Onsite Retention Requirements 4.2.1. Required Retention Volume 4.2.2. Provided Retention Volume 4.2.3. Ultimate Site Outfall 5. Special Issues or Considerations 5.1. 401/404 Permit 5.2. Floodplain Use Permit with FCDMC 6. Summary and Conclusions 7. References APPENCIDES EXHIBITS Each element listed above is briefly described below. Each element should include a brief discussion and may include some preliminary analysis if required to support/document any data shown within the text or on tables. If any of the elements listed above and described below are not applicable to a particular project site, the developer/engineer should still include the element heading within the preliminary drainage report. A single sentence explaining why the element is not applicable to the specific project site must be provided. This is important since it indicates that the developer/engineer is aware of such elements and has addressed them. If an element is simply missing from the report, it is unclear whether it was considered and/or the reason or reasons it was deemed ‘not applicable’. 5-1 Grading and Drainage City of Buckeye 2026 48 If required, the appendix provided for the preliminary drainage report will contain detailed calculations and data sheets necessary to develop the summary tables. Cover Sheet – The Cover Sheet should include the project name and location, submittal date and submittal number, a list of all prior submittal dates and corresponding submittal numbers, prepared for including contact name, company name, address, telephone number, and email; prepared by including: contact name, company name, address, telephone number, and email; Engineer’s seal and date. Table of Contents – List all sections, figures, tables, exhibits, appendices, and Engineer’s seal. Introduction – Every preliminary drainage report must include a short introductory section that describes the general area within which the project site is located, some ‘context’ for the project site and a summary of the overall area. Project Description – This will include the specific project site location, a simple vicinity map (showing the project site relative to the overall region), hydrologic character of the area, the purpose of the report; any existing regional drainage facilities, features such as irrigation canal, CAP, or Railroad. At the preliminary level, the above items may be explained in general/broad terms. These and other elements will be described in much more detail in the final drainage report. Project Name and Address if Known – Briefly state the name of the project and the address if known. Location and Topography – A very brief description of the hydrologic character within which the project site is located (natural desert, mountain, alluvial fan, valley, foothills, etc.) as well as the major existing land uses (Industrial, Commercial, Lot Split & Subdivision). This section should also include a description of the topography in terms of overall direction of flow. Any other major features such as existing washes or flood control channels should be noted as well. Existing/On-going Studies – This is a list of any past/on-going studies available within the vicinity of the project site that may have an impact on the site. These are usually relevant to offsite discharges impacting proposed project sites. These may include, but are not limited to, Floodplain Delineation 5-1 Grading and Drainage City of Buckeye 2026 49 Studies (FDS), Area Drainage Master Studies (ADMS), and Area Drainage Master Plans (ADMP). At the preliminary level, the report can list relevant studies as a ‘bullet’ list. The final drainage report will contain a more detailed description and summary of each study listed. Regional Drainage Plan – This should be a general description of regional drainage features and/or the existence of a regional drainage plan. At the preliminary report level, these features need only be acknowledged with a full discussion following in the final drainage report. FEMA Flood Hazard Zones – It is important to establish any known flood hazards that may exist around or on the project site. This information will be used as a basis for determining the need for the mitigation of known hazards through site improvements that could require a CLOMR/LOMR process. Regardless of the existence of a known flood hazard zone, a figure must be provided illustrating the overall project site superimposed onto the effective FIRM. The panel number and effective date of the FIRM must be visible on the figure. This information is important at the preliminary level as it can have a significant impact on the proposed preliminary plat. Offsite Hydrology – This section will contain a brief description of the existing condition hydrology, as well as the proposed condition hydrology. It will briefly describe the detailed methodology, criteria and assumptions that will be used to develop the hydrology. There will be a general description of the offsite discharges impacting the project site. This section of the report must contain a summary table of offsite subbasin area discharges and a corresponding concentration point that can be quickly and easily referenced on a figure (minimum 11”x17”) within the report. Finally, the appendix will contain documentation for any calculations and computations used to develop the data contained within the summary table. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any offsite peak flow rates necessary to support the preliminary plat. This section must reference the methods and criteria required by the City of Buckeye. Existing Land Use – This section is contained within the Offsite Hydrology section of the report. It will provide a general overview of the existing offsite land uses. Onsite Hydrology – This section of the report will describe the nature of the onsite proposed land use, and an approximation of the weighted roughness 5-1 Grading and Drainage City of Buckeye 2026 50 coefficient (“C” value) based on City of Buckeye criteria within Section 5-1.205 and the FCDMC’s Drainage Design Manual, Hydrology. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any onsite peak flow rates necessary to support the preliminary plat. This section must reference the methods and criteria required by the City of Buckeye. This section should explain in general terms the more detailed approach that will be used in the final drainage report. Proposed Drainage Infrastructure – This is a general discussion of the proposed drainage system that will be used within the project site to safely collect and dispose of runoff generated during 10-year and 100-year peak storm events. The detailed description and accompanying analysis will be presented in the final drainage report. Conveyance of Offsite Runoff Through Project Site – As a sub-section of ‘Proposed Drainage Infrastructure’, this section will provide a general description of the proposed conveyances that will be detailed in the final drainage report. This section will give a summary of those conveyances as well as their expected operation during the 10-year and 100-year peak events per the City of Buckeye requirements. Onsite Retention Requirements – This section will explain the City of Buckeye requirements for onsite retention including, freeboard, side slopes, ponding depths, drain time and means of draining the basin. The equation used to compute the required volume of retention onsite should be shown with all the terms clearly labeled and defined within the text. Required Retention Volume – This section should show the equation used to determine the required retention volume, define the terms and direct the reader to the appendix for detailed calculations and data documenting the computation of the required retention volume for the project site. Provided Retention Volume – This section should show the equation used to determine the provided retention volume, define the terms and direct the reader to the appendix for detailed calculations and data documenting the computation(s). This section should provide the information necessary to show that areas designated for retention on the preliminary plat are sufficient given the basin geometry constraints (per City of Buckeye requirements) and in light of the required volume computed in the previous section. Site Ultimate Outfall – This section should provide a brief description of the site ultimate outfall proposed on the preliminary plat. This section should 5-1 Grading and Drainage City of Buckeye 2026 51 describe (in concept) the way in which basin surcharges will be conveyed through the site. Such basin surcharge could be due to a non-design storm event that results in more volume intercepted by the basin than is provided by the basin. Special Issues or Considerations – This section of the report should include an overview of any issues or considerations that could become significant during the preparation of the final drainage report and are unique to this project site. Such issues or considerations may include but are not limited to the following: • 401/404 permit requirements • Floodplain use permit Summary and Conclusions – This section will provide a quick summary of the proposed preliminary drainage concept for the project site and make conclusions as to its operation and ability to support the proposed preliminary plat as well as meet the City of Buckeye requirements. References – This section will provide a set of references that will document any and all explanation, calculations, methodology, criteria, past & on-going studies, etc. that were contained within the text of the preliminary report. At a minimum these references should include a title, author, and date. APPENDICES – This portion of the table of contents will list all appendices provided in the preliminary report and a brief description of their contents. EXHIBITS – At a minimum, every preliminary drainage report submitted must provide an offsite and onsite drainage exhibit. The offsite drainage exhibit may be at a smaller scale than that used for the onsite exhibit but must be easily readable. Any delineated subbasin areas necessary for the support of the proposed preliminary plat must be at a scale suitable for area verification. This exhibit must show the entire offsite area contributing to the discharge at the project boundary and must include all information necessary for verification of the developed flow rates used in the drainage report. If the offsite discharges were developed under a separate study or provided for use with this project, the source of these discharges must be clearly referenced and specified within the report. In this case, the offsite drainage exhibit may be much less detailed and need only serve as a reference to the reader that will establish the geographic context within which the project site exists. 5-1 Grading and Drainage City of Buckeye 2026 52 The onsite drainage exhibit should be plotted at a size and scale appropriate for verification of any preliminary drainage subbasin areas, concentration points, proposed retention/detention basin volumes, etc. At a minimum, this exhibit must show project property boundaries, all existing structures, existing drainage patterns/features, existing contours and/or spot elevations, phase labels in the appropriate phase, proposed retention/detention basin locations, expected onsite flow patterns and flow arrows. 5-1.1104 Mass Grading Memo Submittal A. Minimum Elements Required: 1. This section will briefly summarize the basic elements that should be addressed by all mass grading memos submitted to the City of Buckeye for review and approval. A table of contents is required. However, a similar report format that addresses each element listed below will be the minimum expectation of the applicant or his/her representative by the city for mass grading memo submittals. B. Mass Grading Memo Format / Minimum Design Elements / Description of Design Elements: Cover Sheet Table of Contents 1. Introduction 1.2. Project Description 1.2. Project Name & Address 1.3. Location & Topography 1.7. Existing/On-Going Studies 1.8. Regional Drainage Plan 1.9. FEMA Flood Hazard Zones 2. Offsite Hydrology 2.1. Methodology and Criteria 2.2. Existing Land Use 3. Onsite Hydrology 3.1. Methodology and Criteria 5-1 Grading and Drainage City of Buckeye 2026 53 4. Conveyance of Runoff Through Project Site 4.1. Ultimate Site Outfall 5. Special Issues or Considerations 5.1. 401/404 Permit 5.2. Floodplain Use Permit with FCDMC 6. Summary and Conclusions 7. References APPENCIDES EXHIBITS Each element listed above is briefly described below. Each element should include a brief discussion and may include some preliminary analysis if required to support/document any data shown within the text or on tables. If any of the elements listed above and described below are not applicable to a particular project site, the developer/engineer should still include the element heading within the Mass Grading Memo. A single sentence explaining why the element is not applicable to the specific project site must be provided. This is important since it indicates that the developer/engineer is aware of such elements and has addressed them. If an element is simply missing from the memo, it is unclear whether it was considered and/or the reason or reasons it was deemed ‘not applicable’. If required, the appendix provided for the Mass Grading Memo will contain detailed calculations and data sheets necessary to develop the summary tables. Cover Sheet – The Cover Sheet should include the project name and location, submittal date and submittal number, a list of all prior submittal dates and corresponding submittal numbers, prepared for including contact name, company name, address, telephone number, and email; prepared by including: contact name, company name, address, telephone number, and email; Engineer’s seal and date. Table of Contents – List all sections, figures, tables, exhibits, appendices, and Engineer’s seal. Introduction – Include a short introductory section that describes the general area within which the project site is located, some ‘context’ for the project site and a summary of the overall area. 5-1 Grading and Drainage City of Buckeye 2026 54 Project Description – This will include the specific project site location, a simple vicinity map (showing the project site relative to the overall region), hydrologic character of the area, the purpose of the report; any existing regional drainage facilities, features such as irrigation canal, CAP, or Railroad. At the Mass Grading level, the above items may be explained in general/broad terms. These and other elements will be described in much more detail in the final drainage report. Project Name and Address if Known – Briefly state the name of the project and the address if known. Location and Topography – A very brief description of the hydrologic character within which the project site is located (natural desert, mountain, alluvial fan, valley, foothills, etc.) as well as the major existing land uses (Industrial, Commercial, Lot Split & Subdivision). This section should also include a description of the topography in terms of overall direction of flow. Any other major features such as existing washes or flood control channels should be noted as well. Existing/On-going Studies – This is a list of any past/on-going studies available within the vicinity of the project site that may have an impact on the site. These are usually relevant to offsite discharges impacting proposed project sites. These may include, but are not limited to, Floodplain Delineation Studies (FDS), Area Drainage Master Studies (ADMS), and Area Drainage Master Plans (ADMP). At the Mass Grading Memo level, the memo can list relevant studies as a ‘bullet’ list. The final drainage report will contain a more detailed description and summary of each study listed. Regional Drainage Plan – This should be a general description of regional drainage features and/or the existence of a regional drainage plan. At the Mass Grading Memo level, these features need only be acknowledged with a full discussion following in the final drainage report. FEMA Flood Hazard Zones – It is important to establish any known flood hazards that may exist around or on the project site. This information will be used as a basis for determining the need for the mitigation of known hazards through site improvements that could require a CLOMR/LOMR process. Regardless of the existence of a known flood hazard zone, a figure must be provided illustrating the overall project site superimposed onto the effective 5-1 Grading and Drainage City of Buckeye 2026 55 FIRM. The panel number and effective date of the FIRM must be visible on the figure. Offsite Hydrology – This section will contain a brief description of the existing condition hydrology, as well as the proposed condition hydrology. It will briefly describe the detailed methodology, criteria and assumptions that will be used to develop the hydrology. There will be a general description of the offsite discharges impacting the project site. This section of the memo must contain a summary table of offsite subbasin area discharges and a corresponding concentration point that can be quickly and easily referenced on a figure (minimum 11”x17”) within the report. Finally, the appendix will contain documentation for any calculations and computations used to develop the data contained within the summary table. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any offsite peak flow rates necessary to support the Mass Grading Memo. This section must reference the methods and criteria required by the City of Buckeye. Existing Land Use – This section is contained within the Offsite Hydrology section of the memo. It will provide a general overview of the existing offsite land uses. Onsite Hydrology – This section of the memo will describe the nature of the onsite proposed land use, and an approximation of the weighted roughness coefficient (“C” value) based on City of Buckeye criteria within Section 5-1.205 and the FCDMC’s Drainage Design Manual, Hydrology. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any onsite peak flow rates necessary to support the mass grading plans. This section must reference the methods and criteria required by the City of Buckeye. This section should explain in general terms the more detailed approach that will be used in the final drainage report. Conveyance of Offsite Runoff Through Project Site – This section will provide a general description of the proposed conveyances that will be detailed in the final drainage report. This section will give a summary of those conveyances as well as their expected operation during the 10-year and 100- year peak events per the City of Buckeye requirements. Site Ultimate Outfall – This section should provide a brief description of the site ultimate outfall proposed on the Mass Grading plans. 5-1 Grading and Drainage City of Buckeye 2026 56 Special Issues or Considerations – This section of the memo should include an overview of any issues or considerations that could become significant during the preparation of the final drainage report and are unique to this project site. Such issues or considerations may include but are not limited to the following: • 401/404 permit requirements • Floodplain use permit C. Summary and Conclusions – This section will provide a quick summary of the proposed Mass Grading concept for the project site. Confirmation should be provided that runoff exiting the subject parcel is not being increased, historic discharge points are being kept, and no adverse impact will be created to adjacent parcels or the public ROW. References – This section will provide a set of references that will document any and all explanation, calculations, methodology, criteria, past & on-going studies, etc. that were contained within the text of the Mass Grading Memo. At a minimum these references should include a title, author, and date. APPENDICES – This portion of the table of contents will list all appendices provided in the Mass Grading Memo and a brief description of their contents. EXHIBITS – At a minimum, every Mass Grading Memo submitted must provide an offsite and onsite drainage exhibit. The offsite drainage exhibit may be at a smaller scale than that used for the onsite exhibit but must be easily readable. Any delineated subbasin areas necessary for the support of the mass grading plan must be at a scale suitable for area verification. This exhibit must show the entire offsite area contributing to the discharge at the project boundary and must include all information necessary for verification of the developed flow rates used in the memo. If the offsite discharges were developed under a separate study or provided for use with this project, the source of these discharges must be clearly referenced and specified within the memo. In this case, the offsite drainage exhibit may be much less detailed and need only serve as a reference to the reader that will establish the geographic context within which the project site exists. The onsite drainage exhibit should be plotted at a size and scale appropriate for verification of any preliminary drainage subbasin areas, concentration points, etc. At a minimum, this exhibit must show project property boundaries, 5-1 Grading and Drainage City of Buckeye 2026 57 all existing structures, existing drainage patterns/features, existing contours, phase labels in the appropriate phase, proposed retention/detention basin locations, expected onsite flow patterns and flow arrows, and ultimate outfall elevation. 5-1.1105 Final Drainage Report Submittal A. Minimum Elements Required: 1. This section will briefly summarize the basic elements that should be addressed by all final drainage reports submitted to the City of Buckeye for review and approval. A table of contents is required. However, a similar report format that addresses each element listed below will be the minimum expectation of the applicant or his/her representative by the city for final drainage report submittals. 2. Many of the elements listed below were included in the preliminary drainage report guidelines. Unlike the general/broad element discussions contained within the preliminary drainage report, those items addressed by the final drainage report must be presented in greater detail and will usually include extensive analysis with supporting data and calculations provided in an appendix and summarized in tables. B. Final Drainage Report Format / Minimum Design Elements / Description of Design Elements: Cover Sheet Table of Contents 1. Introduction 1.1. Project Description 1.1.1. Project Name & Address if known 1.1.2. Location & Topography 1.1.3. Existing/On-Going Studies 1.1.4. Regional Drainage Plan/Characteristics 1.1.5. FEMA Flood Hazard Zones 1.1.6. Reference to established Benchmark, address location of any proposed On-site Temporary Benchmarks 2. Offsite Hydrology 5-1 Grading and Drainage City of Buckeye 2026 58 2.1.1. Methodology and Criteria 2.1.2. Development of Offsite Peak Discharges 2.1.3. Conveyance of Offsite Discharge 2.1.4. Discharge at the entrance and exit points 2.1.5. Existing Land Use 3. Onsite Hydrology 3.1.1. Methodology and Criteria 3.1.2. Existing Condition Discharges 3.1.3. Proposed Condition Discharges 3.1.4. Future Land Use 4. Proposed Drainage Infrastructure 4.1. Conveyance of Runoff Through Project Site 4.1.1. Street Conveyance 4.1.2. Inlet Sizing 4.1.3. Proposed Storm Drain Conveyance 4.1.4. Proposed Channel Conveyance 4.2. Onsite Retention Requirements 4.2.1. Proposed Basin Geometry and Freeboard 4.2.2. Required Retention Volume 4.2.3. Provided Retention Volume 4.2.4. Dissipation of Stored Runoff 4.2.5. Onsite Retention Summary 4.2.6. Ultimate Site Outfall 5. Interim Condition Drainage Concept 6. Special Issues or Considerations 6.1. 401/404 Permit 6.2. AZPDES 6.2.1. SWPPP 6.2.2. First Flush 5-1 Grading and Drainage City of Buckeye 2026 59 6.3. Downstream Impacts of Proposed Improvements 6.4. Upstream Impacts of Proposed Improvements 6.5. Floodplain Use Permit with FCDMC 7. Summary and Conclusions 8. References APPENDICES EXHIBITS Each of the elements listed above is briefly described below. Note that although these descriptions may be brief, the actual element may require an extensive discussion and supporting analysis with calculations provided within the final drainage report. Some of the elements listed above and described below may not be applicable to a particular project site. In this case, the developer/engineer should provide the element heading within the report and then a sentence explaining why this is not applicable to the specific project site. This is important since it indicates that the developer/engineer is aware of these elements and has addressed them. If the element is simply missing from the report, it is unclear if it was considered and/or the reason or reasons it was deemed ‘not applicable’. The appendix provided for the final drainage report will contain detailed calculations and data sheets necessary to develop the summary tables. Cover Sheet – The Cover Sheet should include the project name and location, submittal date and submittal number, a list of all prior submittal dates and corresponding submittal numbers, prepared for including contact name, company name, address, telephone number, and email; prepared by including contact name, company name, address, telephone number, and email; Engineer’s seal and date. Include the Signature/Approval Block below. Figure 2 – City Engineer Signature/Approval Block 5-1 Grading and Drainage City of Buckeye 2026 60 Table of Contents – List all sections, figures, tables, exhibits, appendices, and Engineer’s seal. Introduction – Every final drainage report must include an introductory section that describes the general area within which the project site is located, some ‘context’ for the project site and a brief summary of the overall area. Project Description – This will include the specific project site location, vicinity map, aerial photo, features such as irrigation canal, CAP, or Railroad. Project Name and Address if Known – Briefly state the name of the project and the address if known. Location and Topography – A brief description of the hydrologic character within which the project site is located (natural desert, mountain, alluvial fan, valley, foothills, etc.) as well as the major existing land uses (Industrial, Commercial, Lot Split & Subdivision). This section should also include a description of the topography in terms of overall direction of flow and existing approximate percent grade through the project site. Any other major features such as existing washes or flood control channels should be noted as well. A plan view figure should be provided at a scale sufficient for the reader to see the adjacent streets/features that will place the project site in a clear context of the region within which it exists. Existing/On-going Studies – This is a list of any past/on-going studies available within the vicinity of the project site that may have an impact on the site. These are usually relevant to offsite discharges impacting proposed project sites. These may include, but are not limited to, Floodplain Delineation Studies (FDS), Area Drainage Master Studies (ADMS), Area Drainage Master Plans (ADMP), and adjacent or Final Drainage Reports, if available. Regional Drainage Plan/Characteristics – This should be a description of regional drainage features. Such features could be an engineered flood control channel or a major existing wash corridor. FEMA Flood Hazard Zones – This is important to establish any known flood hazards that may exist around or on the project site. This information will be used as a basis for determining the need for the mitigation of known hazards through site improvements that could require a CLOMR/LOMR process. Regardless of the existence of a known flood hazard zone, a figure must be provided illustrating the overall project site superimposed onto the 5-1 Grading and Drainage City of Buckeye 2026 61 appropriate effective FIRM. The panel number and effective date of the FIRM must be visible on the figure. Reference to Established Benchmark – This section will identify an established benchmark and will include description, location, elevation, and datum. This will also include a discussion of any proposed onsite Temporary Benchmarks. Offsite Hydrology – This will be a detailed description of the offsite discharges impacting the project site. This section of the report must contain a summary table of offsite subbasin area discharges and a corresponding concentration point that can be quickly and easily referenced on a drainage exhibit provided in the back of the report. Finally, the appendix will contain all detailed calculations and computations. Methodology and Criteria – A brief description of the methodology and criteria followed to develop any offsite peak flow rates necessary to support the final plat. This section must reference the methods and criteria required by the City of Buckeye. Development of Offsite Peak Discharges – This section will describe the methods, criteria and assumptions used to develop offsite discharges. If offsite discharges were developed by another study, that study should be referenced and documented in the appendix. Conveyance of Offsite Discharge – Explain how offsite discharges impacting the project site will be conveyed through and/or around the site. Discharge of Entrance and Exit Points – This will be a discussion of the existing discharges along the proposed project site boundary. This discussion will establish a basis for the existing condition that a proposed development may not change unless the change is an improvement to the existing condition. Existing Land Use – This section is contained within the ‘Offsite Hydrology’ section of the report. This will provide a description of the existing offsite land use and (if required) an exhibit illustrating the existing ground cover, structures, and discharges. Onsite Hydrology – This section of the final drainage report will describe the nature of the onsite proposed land use, land use dimension and areas, roughness coefficient and weighted “C” value used based on City of Buckeye criteria within Section 5-1.205 and FCDMC’s Drainage Design Manual, Hydrology. 5-1 Grading and Drainage City of Buckeye 2026 62 Methodology and Criteria – A detailed description of the methodology and criteria followed to develop the onsite peak flow rates. This section must reference the methods and criteria required by the City of Buckeye. Proposed Condition Discharges – This section will provide a detailed discussion of the proposed condition discharges. This section of the report must contain a summary table of onsite (proposed condition) discharges and a corresponding concentration point that can be referenced on a drainage exhibit provided in the back of the final drainage report. At a minimum, the summary table should include the following: • Proposed concentration points and the Discharge at the entrance to the site must be labeled. • Contributing subbasin area(s) ID and corresponding area of each and the Discharge at the concentration point must be stated. If there is more than one contributing area at a particular concentration point, provide a total summation of the individual areas. Footnote the table to direct the reader to the detailed calculation and data documenting the proposed condition discharges. • The proposed discharge at the concentration point for the 10-year and 100-year storm events. Finally, the appendix will contain all detailed calculations and computations. At a minimum, the 10-year and 100-year storm events must be analyzed. Proposed/Future Land Use – This section is contained within the ‘Proposed Condition Discharges’ section of the final drainage report. This will provide a description of the proposed/future land use and if required an exhibit illustrating it. A paragraph should be added to explain how this proposed/future land use relates to the most recent version of the City of Buckeye General Plan. Proposed Drainage Infrastructure – This is a detailed discussion of the proposed drainage system that will be constructed within the project site to safely collect and dispose of runoff generated during 10-year and 100-year peak storm events. Such systems may include or be a combination of local street conveyance, catch basins and storm drain, or open channels. Conveyance of Offsite Runoff Through Project Site – As a sub-section of ‘Proposed Drainage Infrastructure’, this section will provide the detailed description of the proposed conveyances within the project site. This section 5-1 Grading and Drainage City of Buckeye 2026 63 explains how these conveyances operate during the 10-year and 100-year peak events and illustrates that the water surface elevations associated with those return periods are at least 1 foot below the proposed adjacent finish floor elevations. Street Conveyance – Should provide a summary table of all proposed streets within the development, the corresponding longitudinal slope, the estimated peak discharge within the street at the appropriate concentration point and the water surface elevation within the street relative to the proposed adjacent finish floor elevation. This section must demonstrate that the City of Buckeye conveyance requirements are met for the 10-year and 100-year peak storm events. The concentration points shown in the summary table must be clearly labeled on a drainage exhibit provided in the back of the final drainage report. The final drainage report must address that each lot has an all-weather access road. Inlet Sizing – This section is a detailed discussion of the methods, criteria, and assumptions used to design the proposed inlets within and around the project site that will convey surface runoff to the proposed drainage facilities. A summary table of all proposed inlets should be included. At a minimum, this table should include the inlet label, the corresponding concentration point, the inlet type and size, the design discharge, the calculated inlet capacity, the ponded water surface elevation at the inlet and the adjacent finish floor elevation(s). Provide calculations for any areas where water overtops the curb using weir calculations. The table should be footnoted with a reference to the appendix for the detailed calculation and data sheets. This section must demonstrate that all the City of Buckeye requirements for inlet design are met. Clogging factors must be considered and addressed. The concentration points shown in the summary table must be clearly labeled on a drainage exhibit provided in the Appendix. Proposed Storm Drain Conveyance – This section will provide a summary table of all proposed storm drainpipe inlet and outlet elevations, within the development. The table will include the corresponding longitudinal pipe slopes, the estimated peak discharge within each pipe, the corresponding concentration point and the computed hydraulic grade line at each node along the proposed storm drain system as well as at each proposed inlet to the system. Provide storm drain model output with storm drain profiles or HGLs in the Appendix. 5-1 Grading and Drainage City of Buckeye 2026 64 This section must explain the need for a storm drain system within the development. If required, spread or depth calculations should be provided to show that the proposed storm drain system is required at a particular location. A detailed discussion of the methods, criteria and assumptions used to design the proposed inlets that will convey surface runoff to the proposed storm drain system should be provided in the ‘Inlet Sizing’ section. The concentration points shown in the summary table must be clearly labeled on a drainage exhibit provided in the Appendix. Proposed Channel Conveyance – Provide a detailed hydraulic analysis using appropriate methodology. Provide a summary table of all proposed channels within the development (if applicable). The table must include the estimated peak discharge within the channel at appropriate cross sections along with the velocity, depth, top width, bottom width, side slopes, Manning’s “n” value, energy grade line, and the water surface elevations along the channel relative to adjacent finish floor elevations. This section must demonstrate that the City of Buckeye conveyance requirements are met for the 100-year peak storm events for proposed channels. Freeboard should be provided within the channels for the 100-year peak storm event and a detailed discussion of the analysis of channel capacity should be documented with supporting calculations in the appendix. This discussion should explain the nature of the flow (subcritical, supercritical), the proposed channel lining, velocities, side slopes bank protection method and any effects due to backwater effect. The concentration points shown in the summary table must be clearly labeled on a drainage exhibit provided in the Appendix. Onsite Retention Requirements – This section will explain the City of Buckeye requirements for onsite retention including, freeboard, side slopes, ponding depths, drain time and means of draining the basin. The equation used to compute the required volume of retention should be shown with all the terms clearly labeled and defined within the text. Proposed Basin Geometry and Freeboard – Describe the proposed basin geometry including side slopes, ponding depths, and freeboard. Required Retention Volume – This section should show the equation used to determine the required retention volume, define the terms and direct the 5-1 Grading and Drainage City of Buckeye 2026 65 reader to the appendix for detailed calculations and data documenting the computation of the required retention volume throughout the project site. Provided Retention Volume – This section should show the equation, or equations used to determine the storage provided by proposed retention basins throughout the project site. The applicability of the equation based on the geometry of the proposed basin should be explained and the reader should be directed to the appendix for detailed calculations and data documenting the computation of the retention volume provided by each proposed retention basin. Refer to the example format required for the volume provided on the following example. If applicable this section will also provide detailed explanation and appropriate references to any relevant calculations used to determine equalizer pipe sizes between two or more basins acting as a single facility. Basin 1 Contour Elevation Area Of Contour (ft2) Integral Volume (ft3) Freeboard 1601 56,983 54,404 HWE 1600 51,825 49,298 1599 46,770 44,292 1598 41,814 39,396 Bottom 1597 36,977 Provided at HWE 132,985 Provided at 1 ft Freeboard 187,389 Required 106,037 Extra Volume 26,948 Dissipation of Stored Runoff – This section will briefly explain the time it should take each proposed retention basin to drain following a storm event. The drain time of all proposed retention basins must be less than or equal to the 36-hour time limit per the City of Buckeye requirements. If drywells are being used, there must be a reference in the text to detailed calculations and data in the appendix of the report showing the number of drywells required in each 5-1 Grading and Drainage City of Buckeye 2026 66 basin. Similarly, if some other method of bleeding the basin volume is used, this must be supported with calculations and data in the appendix and referenced in this section. A summary table should be provided in this section showing the proposed retention basin label, the total volume required within the basin, the total number of drywells proposed to dissipate the required volume and the estimated time to drain. The table should provide a footnote directing the reader to the appendix for the detailed calculations and data used to estimate the number of drywells and the corresponding drain times. The reader should be referred to the drainage exhibit in the report for the drywell locations within the proposed retention basins. Onsite Retention Summary – This section will contain a summary table that clearly labels each proposed retention basin on the project site. The proposed retention basin labels should be clearly shown on the drainage exhibit provided in the final drainage report. The proposed retention basin summary table must include but is not limited to the following: • The proposed retention basin label. • The individual labels of each drainage sub basin area contributing runoff to a proposed retention basin. • The sum total of the individual drainage basin areas contributing runoff to the proposed retention basin. • The computed runoff coefficient (weighted “C” value) for the total contributing area at a proposed retention basin. • The total storage volume required (not including freeboard). • The total storage volume provided by the retention basin (not including freeboard). • Footnotes directing the reader to the appendix for detailed calculations and data documenting all the data summarized within the table. Interim Condition Drainage Concept – If the proposed development is going to be constructed in phases, provide narrative detailing how interim drainage will be managed. This section must address these issues and clearly show that all the City of Buckeye drainage requirements are met. All supporting calculations and data should be included in the final drainage report 5-1 Grading and Drainage City of Buckeye 2026 67 appendix. Any summary tables required to clearly show the results of any calculations necessary to demonstrate that the interim drainage facilities will work must be included in this section of the final drainage report. Avoid retention basins outside of the proposed site. However, if a temporary basin is required outside of the site, a temporary drainage easement is required from the adjacent property owner. The developer will maintain the interim retention basin within the easement. Special Issues or Considerations – This section of the final drainage report should include issues or considerations unique to this project site that have not been adequately covered in the preceding sections of the report. Such issues or considerations may include but are not limited to the following: • 401/404 permit requirements • Arizona Pollutant Discharge Elimination System (AZPDES) permit • Stormwater Pollution Prevention Plan - stormwater runoff and impacts on water quality during construction • First flush considerations with proposed onsite detention • Downstream impacts of proposed improvements • Upstream impacts of proposed improvements • Floodplain Use Permit with FCDMC • Other: ADOT, ADEQ, FCDMC, FEMA, MCDOT, Roosevelt Irrigation District, Buckeye Irrigation District, & Salt River Project Summary and Conclusions – This section will provide a quick summary of the proposed drainage design for the project site and make conclusions as to its operation and ability to meet the City of Buckeye requirements. References – This section will provide a complete set of references that were used within the text of the final drainage report. At a minimum these references should include a title, author, and date. APPENDICES – This portion of the report will contain exhibits, calculations, and other supporting data. Information from previous referenced reports that is important to the design of the proposed project should be included with Cover Sheet with City Approval documented. EXHIBITS – At a minimum, every final drainage report submitted must provide an onsite and offsite drainage exhibit. 5-1 Grading and Drainage City of Buckeye 2026 68 The drainage exhibit should be plotted at a size and scale appropriate for verification of drainage subbasin areas, concentration points, flow path lengths, proposed retention/detention basin volumes, etc. This exhibit should never be smaller than 1-inch equals 100 feet. The preferred scale is a scale that will result in the largest possible plot with the least number of sheets (match lines) required. At a minimum, this exhibit must show: • Project property boundaries • Adjacent property within a minimum of 100 feet of the project boundary • All existing structures • Existing drainage patterns/features • Existing contours and/or spot elevations • Proposed slopes on streets • Proposed curb and gutter lines • Proposed phase lines with phase labels in the appropriate phase • Proposed contours • Proposed lots (numbered) • Proposed grade breaks • Proposed drainage subbasin delineations and labels • Proposed concentration point locations and labels • All proposed drainage infrastructure • Proposed retention/detention basins • Proposed drywells and locations • Water surface elevations for washes and channels • Any other information necessary for verification of the proposed drainage design concept documented within the final drainage report. • Indicate the direction of flow within individual subbasins using flow arrows 5-1 Grading and Drainage City of Buckeye 2026 69 5-1.1200 Plan Preparation 5-1.1201 General Requirements A. Basic plan requirements that apply to all construction plans prepared for submission to the City can be found in COB EDS Section 1-1. 5-1.1202 Grading and Drainage Plan Requirements A. The following requirements apply to all grading and drainage plans prepared for submission to the City of Buckeye: 1. The plan must encompass the entire development or site and a minimum of 50 feet outside. The plan must show and clearly label all existing utilities and improvements, topographic features and show topography within the site and 50 feet outside as discussed above. 2. For most projects, the plan scale should be 1 inch = 40 feet. For projects that will utilize a high level of detail for grading improvements, a scale of 1 inch = 30 feet, 1 inch = 20 feet, or 1 inch = 10 feet may be used. 3. Existing topography shall be in the form of 1-foot contours. The 5-foot contour line shall be darkened and/or utilize a different line type than the remaining 1-foot contour lines for readability of the plan. Contour lines shall have the elevations clearly labeled. 4. Proposed contours with elevation labels shall be shown for retention or detention basins, channels, and matching into existing conditions. 5. For plans where structures are proposed, the outline of the structure should be shown on the grading and drainage plan. 6. For plans where habitable structures are proposed, the lowest finish floor elevation and pad elevation should be provided within the outline of the building. The lowest finish floor elevations for habitable structures should be provided based on NAVD 88 datum for certification purposes. To accomplish this, the lowest finish floor elevations shall be provided to nearest hundredth of a foot in the format FF = X,XXX.XX and pad elevations shall be provided to the nearest tenth of a foot in the format PAD =X,XXX.X. 7. The plans must show the 100-year 6-hour or 100-year 24-hour (whichever is greater) flow rate for all washes, channels, or swales entering and exiting the boundary of the site and provide intermediate values of the 100-year flow rate within the site at least one time per 5-1 Grading and Drainage City of Buckeye 2026 70 sheet as a minimum per wash, at confluences and at points of interest such as culverts, storm drains, utility crossings, channel improvements, etc. The 100-year flow rate should be shown with a directional arrow in the following format: Q100 = xx cfs. 8. All delineated (FEMA and local) floodplains should be shown on the plans. 9. The limits of 100-year floodplains should be delineated and labeled for all plans containing washes with 100-year flow rates of 50 cfs or greater. 100-year water surface elevations should also be labelled. 10. Erosion hazard setbacks should be shown on the plans for all watercourses with 100-year flow rates of 50 cfs or greater. Refer to Arizona Department of Water Resources State Standard 5-96 Guideline 1 for additional information. 11. Cross sections are required adjacent to existing properties and at representative locations throughout the development. Include typical sections of all engineered channels and swales with bottom width and side slopes labeled. 12. For proposed retaining walls, the top and base of wall elevations should be provided on the plans. Elevations should be provided at ends, changes in elevation, property lines, or as needed to provide a reasonable level of definition of the elevations of the walls. All exposed ends of retaining walls should be stepped down to 1-foot or less retaining wall height. 13. For developments with retention / detention basins, the basin should be clearly labeled with a unique name to match the drainage report. Basin side slopes should be labelled, and the following information is to be summarized: • VR = XXX ft3 for volume required, • VP = XXX ft3 for volume provided, • BTM = XXXX.X for basin bottom elevation, • HW = XXXX.X for basin high water elevation, • FE = XXXX.X for basin freeboard elevation, • Basin’s emergency outfall elevation (EOE = XXXX.X) and location noted. 5-1 Grading and Drainage City of Buckeye 2026 71 14. For retention basins with drywells provide the following information: • Number of drywells, • Rim elevations of each drywell • Northings and eastings for each drywell location 15. Typically, storm drain plan and profiles are shown on the paving plans. If culverts and storm drain are to be constructed per the grading plan however, plan view information and profile view information shall be provided on the same sheet and include the following: a. Plan View i. Unique name that matches the drainage report ii. Number of barrels or pipes iii. Size of barrels or pipes iv. Material b. Profile View i. Unique name that matches the drainage report ii. Existing and finished grade over the barrel or pipe iii. Number of barrels or pipes iv. Length and slope of barrels or pipes, including upstream and downstream invert elevation labels. v. Size of barrels or pipes vi. Material vii. HGL Lines for design storm viii. Crossing utilities shown and labelled with vertical separation dimensioned 16. Callouts for catch basins shall include wing lengths, v depth, and a unique name that matches the drainage report. 17. Callouts for scuppers shall include number of barrels and a unique name that matches the drainage report. 18. Callouts for grouted riprap shall include length and width. Callouts for loose riprap shall include length, width, and diameter. 5-1 Grading and Drainage City of Buckeye 2026 72 5-1.1203 Additional Requirements By Plan Type A. General - The following requirements are in addition to the above requirements depending on the type of plan or development. Some requirements may apply to other plan types depending on the nature of the project and improvements. B. Commercial and Multifamily: 1. Provide driveway gutter grades at end of curb returns and longitudinal slopes along curb returns. 2. High and low points for driveway paving should be labeled with elevations. 3. Grade breaks in the parking lot should be labelled. 4. Proposed contours with elevation labels shall be shown for parking lot grading. 5. General flow patterns around the parking lot should be depicted 6. Longitudinal and cross slopes of accessible routes should be labelled C. Residential Subdivisions: 1. Provide lot numbers. 2. Label tract names and street names from the final plat. 3. Dimension and label streets with tracts or rights-of-way and PUE widths and show street centerline with stationing from paving plans. 4. Provide longitudinal and cross slope for streets. 5. For small washes or swales through lots on custom residential subdivisions, the flow path should be shown on the plans. 6. Label high and low points within streets with elevation. 7. Provide top of curb elevations (football grades) at the intersection of lot lines with the tract or rights-of-way lines. For corner lots provide top of curb elevations at the end of the curb returns. D. Mass Grading Plans: 1. Mass grading limits should be clearly delineated and labeled. 2. No grading is allowed within existing ROW for the major offsite roads adjacent to the proposed development. 5-1 Grading and Drainage City of Buckeye 2026 73 3. No specific proposed hard elevations, hard grades, finish floor elevations, or volumes should be shown. 4. No utilities, paving, drainage infrastructure, or hard improvements should be proposed as part of the set. 5. Grading contours must be shown as the predominant line type on the plan set. Contours are at one (1) foot maximum intervals. 6. All grading contours must have an elevation label on every sheet. 7. Drainage arrows indicating general flow direction shall be shown throughout the project area and on adjacent roads and parcels. 8. Site plan/platting information may be referenced on the Mass Grading Plan but should be shaded/screened back in presentation. 9. All relevant shaded/screened back information will need to be included in a Final Grading or Improvement Plan for review and approval. A note shall be added to the plan sheets indicating this. E. Plans with Underground Retention: 1. Provide construction details for underground storage facilities. 2. See other requirements in Section 5-1.800. 5-1.1300 Materials 5-1.1301 Approved Products List A. The Approved Products List can be found on the City website. B. Proposed products for use that are not on the Approved Products List, are required to be submitted to the City for review and approval. 5-1.1302 Storm Drain Requirements C. Rubber gasket reinforced concrete pipe (RGRCP) is to be Class III, Class IV, or Class V and shall meet MAG Standard Specifications 618 and 735. D. Polypropylene pipe (PP) shall meet MAG Specifications 618 and 740. Per City discretion, mandrel testing may be required for polypropylene pipe, with a maximum allowable deflection of 5.0%. [End of Section] 5-1 Grading and Drainage City of Buckeye 2026 74 Appendix A – Standard Details 51403A Polypropylene Trench Installation 51403B Polypropylene Trench Installation 51403C 12”-60” Polypropylene Waterstop Grouted Manhole Connection 51403D 12”-60” Polypropylene Waterstop Grouted Manhole Connection 51404 City of Buckeye Manhole Cover 51407A Headwall 18” to 36” Pipe 51407B Trash Racks 51407C Typical Handrail and Anchor Plate 51900 Trench Drain with Drain Basins POLYPROPYLENE TRENCH INSTALLATION DETAIL NO: REVISED: 51403A 12-19-25 TRENCH INSTALLATION DETAIL MIN. COVER TO RIGID PAVEMENT, H 4" FOR 12"-24" PIPE 6" FOR 30"-60" PIPE SPRINGLINE MIN. COVER TO FLEXIBLE PAVEMENT, H INITIAL BACKFILL HAUNCH BEDDING MIN TRENCH WIDTH (SEE TABLE) SUITABLE FOUNDATION 1. ALL PIPE SYSTEMS SHALL BE INSTALLED IN ACCORDANCE WITH ASTM D2321, "STANDARD PRACTICE FOR UNDERGROUND INSTALLATION OF THERMOPLASTIC PIPE FOR SEWERS AND OTHER GRAVITY FLOW APPLICATIONS", LATEST ADDITION, WITH THE EXCEPTION THAT THE INITIAL BACKFILL MAY EXTEND TO THE CROWN OF THE PIPE. SOIL CLASSIFICATIONS ARE PER THE LATEST VERSION OF ASTM D2321. CLASS IVB MATERIALS (MH, CH) AS DEFINED IN PREVIOUS VERSIONS OF ASTM D2321 ARE NOT APPROPRIATE BACKFILL MATERIALS. 2. MEASURES SHOULD BE TAKEN TO PREVENT MIGRATION OF NATIVE FINES INTO BACKFILL MATERIAL, WHEN REQUIRED. 3. FOUNDATION: WHERE THE TRENCH BOTTOM IS UNSTABLE, THE CONTRACTOR SHALL EXCAVATE TO A DEPTH REQUIRED BY THE ENGINEER AND REPLACE WITH SUITABLE MATERIAL AS SPECIFIED BY THE ENGINEER. AS AN ALTERNATIVE AND AT THE DISCRETION OF THE DESIGN ENGINEER, THE TRENCH BOTTOM MAY BE STABILIZED USING A GEOTEXTILE MATERIAL. 4. BEDDING: SUITABLE MATERIAL SHALL BE CLASS I, II, III, OR IV. THE CONTRACTOR SHALL PROVIDE DOCUMENTATION FOR MATERIAL SPECIFICATION TO ENGINEER. COMPACTION SHALL BE SPECIFIED BY THE ENGINEER IN ACCORDANCE WITH TABLE 3 FOR THE APPLICABLE FILL HEIGHTS LISTED. UNLESS OTHERWISE NOTED BY THE ENGINEER, MINIMUM BEDDING THICKNESS SHALL BE 4" (100mm) FOR 12"-24" (300mm-600mm) DIAMETER PIPE; 6" (150mm) FOR 30"-60" (750mm-1500mm) DIAMETER PIPE. THE MIDDLE 1/3 BENEATH THE PIPE INVERT SHALL BE LOOSELY PLACED. PLEASE NOTE, CLASS IV MATERIAL HAS LIMITED APPLICATION AND CAN BE DIFFICULT TO PLACE AND COMPACT; USE ONLY WITH THE APPROVAL OF A SOIL EXPERT. 5. INITIAL BACKFILL: SUITABLE MATERIAL SHALL BE CLASS I, II, III, OR IV IN THE PIPE ZONE EXTENDING TO THE CROWN OF THE PIPE. THE CONTRACTOR SHALL PROVIDE DOCUMENTATION FOR MATERIAL SPECIFICATION TO ENGINEER. MATERIAL SHALL BE INSTALLED AS REQUIRED IN ASTM D2321, LATEST EDITION. COMPACTION SHALL BE SPECIFIED BY THE ENGINEER IN ACCORDANCE WITH TABLE 3 FOR THE APPLICABLE FILL HEIGHTS LISTED. PLEASE NOTE, CLASS IV MATERIAL HAS LIMITED APPLICATION AND CAN BE DIFFICULT TO PLACE AND COMPACT; USE ONLY WITH THE APPROVAL OF A SOIL EXPERT. 6. MINIMUM COVER: MINIMUM COVER, H, IN NON-TRAFFIC APPLICATIONS (GRASS OR LANDSCAPE AREAS) IS 12" (300mm) FROM THE TOP OF PIPE TO GROUND SURFACE. ADDITIONAL COVER MAY BE REQUIRED TO PREVENT FLOTATION. FOR TRAFFIC APPLICATIONS; CLASS I OR II MATERIAL COMPACTED TO 90% SPD AND CLASS III COMPACTED TO 95% SPD IS REQUIRED. FOR TRAFFIC APPLICATIONS, MINIMUM COVER, H, IS 24" (600mm) UP TO 60" (1500mm) DIAMETER PIPE, MEASURED FROM TOP OF PIPE TO BOTTOM OF FLEXIBLE PAVEMENT OR TO TOP OF RIGID PAVEMENT. TABLE 1, RECOMMENDED MINIMUM TRENCH WIDTHS PIPE DIAM. MIN. TRENCH WIDTH 12" 30" (300mm) (762mm) 15" 34" (375mm) (864mm) 18" 39" (450mm) (991mm) 24" 48" (600mm) (1219mm) 30" 56" (750mm) (1422mm) 36" 64" (900mm) (1626mm) 42" 72" (1050mm) (1829mm) 48" 80" (1200mm) (2032mm) 60" 96" (1500mm) (2438mm) GENERAL NOTES: FINAL BACKFILL POLYPROPYLENE TRENCH INSTALLATION DETAIL NO: REVISED: 51403B 10-10-25 TABLE 2, MINIMUM RECOMMENDED COVER BASED ON VEHICLE LOADING CONDITIONS * VEHICLES IN EXCESS OF 75T MAY REQUIRE ADDITIONAL COVER TABLE 3, MAXIMUM COVER FOR POLYPROPYLENE PIPE, ft FILL HEIGHT TABLE GENERATED USING AASHTO SECTION 12, LOAD RESISTANCE FACTOR DESIGN (LRFD) PROCEDURE WITH THE FOLLOWING ASSUMPTIONS: NO HYDROSTATIC PRESSURE UNIT WEIGHT OF SOIL (үs) = 120 PCF SURFACE LIVE LOADING CONDITION PIPE DIAM. H-25 HEAVY CONSTRUCTION (75T AXLE LOAD) * 12" - 48" 24" 48" (300mm - 1200mm) (610mm) (1219mm) 60" 24" 60" (1500mm) (610mm) (1524mm) CLASS I CLASS II CLASS III CLASS IV PIPE DIA COMPACTED 95% 90% 85% 95% 90% 95% 12" 41 28 21 16 20 16 16 (300mm) (12.5m) (8.5m) (6.4m) (4.9m) (6.1m) (4.9m) (4.9m) 15" 42 29 21 16 21 16 16 (375mm) (12.8m) (8.8m) (6.4m) (4.9m) (6.4m) (4.9m) (4.9m) 18" 44 30 21 16 22 17 16 (450mm) (13.4m) (9.1m) (6.4m) (4.9m) (6.7m) (5.2m) (4.9m) 24" 30 21 15 11 16 11 11 (600mm) (9.1m) (6.4m) (4.6m) (3.4m) (4.9m) (3.4m) (3.4m) 30" 39 27 19 14 19 15 14 (750mm) (11.9m) (8.2m) (5.8m) (4.3m) (5.8m) (4.6m) (4.3m) 36" 28 20 14 10 14 11 10 (900mm) (8.5m) (6.1m) (4.3m) (3.0m) (4.3m) (3.4m) (3.0m) 42" 30 21 14 10 15 11 10 (1050mm) (9.1m) (6.4m) (4.3m) (3.0m) (4.6m) (3.4m) (3.0m) 48" 29 20 14 9 14 10 10 (1200mm) (8.8m) (6.1m) (4.3m) (2.7m) (4.3m) (3.0m) (3.0m) 60" 29 20 14 9 14 10 9 (1500mm) (8.8m) (6.1m) (4.3m) (2.7m) (4.3m) (3.0m) (2.7m) 12"-60" POLYPROPYLENE WATERSTOP GROUTED MANHOLE CONNECTION DETAIL NO: REVISED: 51403C 08-21-25 INSTALLATION VIEW DETAILED CONNECTION VIEW VARIES A B PERFORMANCE HIGHLY DEPENDENT ON INSTALLATION. CONTRACTOR MUST ENSURE MANHOLE GASKET IS UNIFORMLY SEATED AROUND STRUCTURE ADAPTER. EXTRA PRECAUTIONS MUST BE TAKEN TO PREVENT DIFFERENTIAL SETTLEMENT BETWEEN THE PIPE AND MANHOLE. NOTES ENSURE BACKFILL IS PLACED UNDER PIPE AND PROPERLY COMPACTED POLYPROPYLENE DUAL WALL PIPE (12" - 60" Ø) STAINLESS STEEL TAKE-UP CLAMP (2 ~ PLACES) FILL VOID SPACE WITH ACCEPTABLE GROUT MATERIAL STRUCTURE WALL NON-SHRINK PATCHING COMPOUND CAST IRON GRATE AND FRAME STAINLESS STEEL TAKE-UP CLAMP SCREWS WILL BE PLACED 180° FROM EACH OTHER 12"-60" POLYPROPYLENE WATERSTOP GROUTED MANHOLE CONNECTION DETAIL NO: REVISED: 51403D 08-21-25 PIPE SIZE PIPE OD "A" MIN. HOLE Ø "B" MIN. DISTANCE FROM PIPE INVERT TO STRUCTURE INVERT 12" 14.5" 19.50" 3.7" (300mm ) (368mm) (495mm) (94mm) 15" 17.6" 23.00" 4.0" (375mm) (447mm) (584mm) (102mm) 18" 21.2" 26.50" 4.2" (450mm) (538mm) (673mm) (107mm) 21" 24.8" 30.25" 4.5" (525mm) (630mm) (768mm) (114mm) 24" 27.8" 33.25" 4.5" (600mm) (706mm) (845mm) (114mm) 30" 35.1" 40.50" 5.2" (750mm) (892mm) (1029mm) (132mm) 36" 41.1" 47.00" 5.5" (900mm) (1044mm) (1194mm) (140mm) 42" 47.7" 53.00" 5.7" (1050mm) (1212mm) (1346mm) (145mm) 48" 53.6" 59.00" 5.7" (1200mm) (1361mm) (1499mm) (145mm) 60" 66.3" 72.00" 6.4" (1500mm) (1684mm) (1829mm) (163mm) BUCKEYE S T O R M S E W E R S T O R M S E W E R ARIZONA BUCKEYE ARIZONA CITY OF BUCKEYE MANHOLE COVER DETAIL NO: REVISED: 51404 10-14-25 24" 30" 1. COVERS SHALL BE PER MAG STD. DETAIL 423-1 AND 423-2 GENERAL NOTES SYM 3" MAX F 1' 2'-6" * 8" 1-1/2" 6" 8" 6" 12" 6" D/16+6" E D/2 12" ℄ HEADWALL 18" TO 36" PIPE DETAIL NO: REVISED: 51407A 12-19-25 DIMENSION TABLE 4:1 EMBANKMENT SLOPE D[IN] DIMENSIONS TYPE F E 18 INLET 12'-11" 12'-11" OUTLET 12'-11" 4'-9" 24 INLET 15'-0" 15'-0" OUTLET 15'-0" 5'-6" 30 INLET 17'-2" 17'-2" OUTLET 17'-2" 6'-4" 36 INLET 19'-4" 19'-4" OUTLET 19'-4" 7'-1" 1. SEE MAG STANDARD DETAIL 501-3 FOR REMAINING DETAIL INFORMATION. 2. THIS DETAIL MODIFIES PIPE SIZES 18 THROUGH 36 ONLY. ALL OTHER SIZES SHALL BE CONSTRUCTED PER MAG STANDARD DETAIL 501-3. 3. SEE DETAIL 51407C FOR HANDRAIL. 4. ALL CONCRETE SHALL BE CLASS 'A' PER SECTION 505 AND 725. 5. CONCRETE REINFORCING SHALL BE NO. 4 BAR 12" O.C. BOTH DIRECTIONS. 6. BENCHMARK BRONZE CAP IS TO BE PROVIDED BY THE CITY OF BUCKEYE ENGINEERING DIVISION. COORDINATE WITH CIVIL INSPECTOR. CONTRACTOR TO SET BENCHMARK ON THE HEADWALL. PLAN VIEW PROFILE VIEW * FOR PIPES GREATER THAN 36-INCHES AND UP TO 84-INCHES IN DIAMETER CUT OFF WALL TO BE A MINIMUM OF 6 FEET BELOW THE APRON. FOR PIPES GREATER THAN 84-INCHES IN DIAMETER, MINIMUM CUT OFF WALL DEPTH SHALL BE PER ADOT STANDARDS. GENERAL NOTES: F/L OF APRON = 6" BELOW INVERT OF PIPE BEVEL. SEE DETAIL INLET ONLY FINISHED GRADE D HANDRAIL IF REQUIRED CONSTR. JOINT WHEN DESIGNATED ON PLANS, INSTALL BRONZE BENCHMARK WITH STEM AS PROVIDED. SEE NOTE 6. BRONZE BENCHMARK CAP BENCHMARK STEM 45° 45° Z 6-5/8" ON CENTER SPACING ON RACK BARS TRASH RACKS DETAIL NO: REVISED: 51407B 08-21-25 A A BAR RACK DETAIL EYE BOLT DETAIL SECTION A-A PROVIDE PLASTIC SLEEVE 3 4" DIA. LOCK TYPE WASHER AND 5 8" NUT 1'-6" MIN 3" 8" 12" FL 12" X 412" GALV. BOLT IN CONCRETE WITH BRASS NUT 12" X 2" BAR STOCK TOP BANK 6" FOR REINF. CONC. HEADWALL MAX 3.0' W/O STIFFENERS 3" WALL 14" X 2" STEEL BAR PLATE 3-5/8" 5 8" X 3-1/2" Y 3" GALV. PIPE WALL 12" X 2" BAR STOCK 12" X 2" RACK BAR TYPICAL HANDRAIL AND ANCHOR PLATE DETAIL NO: REVISED: 51407C 12-18-25 (VARIES - USE EQUAL SPACES (4'-6" O.C. MAX.) 1'-2" 1'-2" 3'-6" TYP. 3/16" TYP. GRIND SMOOTH GALV. SPRAY 1'-2" ANCHOR PLATE DETAIL 1.5" ROUND STEEL TUBING SCH. 40(ASTM 53) - GRIND WELDS SMOOTH. SHOP PRIME W/RUST INHIBITING PRIMER. FIELD REPAIR PRIMER AS NEEDED. FINISH PAINT TO BE DESERT BEIGE (SUBMITTALS REQUIRED) 1/4" X 5" X 5" MILD STEEL PLATE TOP OF HEADWALL 2-1/2" X 6" ANCHOR BOLTS TRENCH DRAIN WITH DRAIN BASINS DETAIL NO: REVISED: 51900 11-08-25 1. DOME GRATE / SOLID COVER SHALL BE DUCTILE IRON PER ASTM A 536 GRADE 70-50-05. LOCKING MECHANISMS SHALL BE STAINLESS STEEL FOR DOME GRATE. 2. PVC DRAINAGE STRUCTURE TO BE CUSTOM MANUFACTURED ACCORDING TO SITE CONDITIONS. RISER EXTENSIONS ARE NEEDED FOR STRUCTURES OVER 84". 3. DRAINAGE CONNECTIONS STUB JOINT TIGHTNESS SHALL CONFORM TO ASTM D3212 FOR CORRUGATED HDPE. 4. BACKFILL OVER PERF PIPE SHALL BE PER MANUFACTURERS REQUIREMENTS. DRAIN BASINS AND RISERS SHALL BE SURROUNDED BY A MINIMUM OF 6" OF NO. 8 CRUSHED WASHED STONE. 5. FILTER FABRIC SHALL ENCOMPASS THE TRENCH TOP WITH A MINIMUM OF A 1' OVERLAP, AND SHALL EXTEND A MINIMUM OF 5' DOWN THE TRENCH SIDES. 4" HDPE NYLOPLAST SOLID LOCKING COVER (SEE NOTE 1) BASIN PONDING DEPTH (MAX 3' FOR USE OF THIS SYSTEM) NYLOPLAST ENVIROHOOD Ø 30" NYLOPLAST RISER EXTENSION (TYP) FILTER FABRIC (US 80NW) NONWOVEN GEOTEXTILE OR EQUIVALENT. (TYP) DRAIN ROCK (NO. 8 CRUSHED WASHED STONE MATERIAL) Ø 30" NYLOPLAST DRAIN BASIN (TYP) 200' MAX OF 12" HDPE PERF PIPE LEGEND A SECTION A-A 3' 3' SEE NOTE 3 PERFORATED BOTTOMS A 10' 2'-6" 12" HDPE PERF PIPE DRAIN ROCK (NO. 8 CRUSHED WASHED STONE MATERIAL) FILTER FABRIC (US 80NW) NONWOVEN GEOTEXTILE OR EQUIVALENT. SEE NOTE 5. 6" MIN SEE NOTE 4 10' DRAIN ROCK (NO. 8 CRUSHED WASHED STONE MATERIAL) SOIL SEE NOTE 4 FILTER FABRIC 3' 3' TWO BIO-DRIVEN HC-5 LB CUBES BY OILSPONGE SUSPENDED 1' ABOVE DRAIN BASIN BOTTOM (TYP) 5' MIN FILTER FABRIC (US 80NW) NONWOVEN GEOTEXTILE OR EQUIVALENT. SEE NOTE 5. (TYP) BASIN BOTTOM BASIN BOTTOM GENERAL NOTES: 6" MIN SEE NOTE 4 1' TURN UP MIN 6' MIN 6' MIN NYLOPLAST DOME LOCKING GRATE ELEVATED 0.3' ABOVE BASIN BOTTOM (SEE NOTE 1)