Master Concept Sewer Report
City of Mesa — Planning and Zoning Board - Public Hearing (2026-08-26)
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h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 1 Table of Contents Page 1.0 SCOPE 2 2.0 SITE LOCATION 2 3.0 DESCRIPTION AND PROPOSED DEVELOPMENT 3 4.0 EXISTING INFRASTRUCTURE 3 5.0 PROPOSD DEMAND 4 6.0 PROPOSED DESIGN 5 7.0 REFERENCES 6 EXHIBITS Exhibit A – Vicinity Map Exhibit B – Aerial Map Exhibit C – Master Sewer Plan APPENDICES Appendix A – Water and Sewer Modified Use Rates h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 2 1.0 Scope The objectives of this sewer master report are: 1. To research and identify the current wastewater infrastructure in the vicinity of the project. 2. To determine the wastewater demand flows that are anticipated in this project. 3. To provide guidance on sizing throughout the site and in conjunction with the Gateway Crossing project that needs to be served to the south 2.0 Site Location The project site is located on the northeast corner of Williamsfield Road and Ellsworth Road in the City of Mesa, Arizona (see Exhibit A). More specifically, the project site is located within a portion of the Southwest and Northwest Quarter of Section 27, Township 1 South, Range 7 East of the Gila and Salt River Base and Meridian, Maricopa County, Arizona. h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 3 3.0 Description and Proposed Development The site is currently on an approximately 210-acre parcel that resides at the northeast corner of Williams Field Road and Ellsworth Road. The improvements will consist of multi-family residential, mixed-use development, general office space, and hotel. The site is currently undeveloped desert and slopes from east to west at approximately 0.4% and drains into a set of box culverts at Ellsworth Road that connects to the Ellsworth Channel on the west side of the street. The project is planned to have a core phase that will be built out immediately, and the rest of the site has a general use plan, as identified by the Legacy Park Community Plan, that does not yet have a determined site use and will be built out by separate developers at a later time. For these later developments, the most likely land use, as identified in the Community Plan, will be used for wastewater demand. To the south, the site is bound by the Legacy Sports Complex and future Gateway Crossing. The north and eastern sides of the site are bound by Arizona State Route 24. The west side is bounded by the future Gateway East, a 273-acre development used for manufacturing, industrial, retail, office, and hotel space. 4.0 Existing Infrastructure There currently exists a 15” sewer main at the southwest corner of the parcel that crosses Ellsworth Road to the west and continues along Gateway Boulevard. About 500’ west of this sewer extension, the line upsizes to 18”, then 24”, and continues until it reaches the main 30” trunk at Ray Road. The City of Mesa commented that the capacity in the existing 15” pipe is 1.29 MGD, and the capacity of the 18” pipe is 2.1 MGD. This existing system is anticipated to take flows from both the Legacy Parkway and Gateway Crossing projects. h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 4 5.0 Proposed Demand Due to the nature of the proposed project, the City of Mesa accepted revised demand use values prepared by Optimus Civil Design Group in a report dated 11/06/2025 to be incorporated on both Legacy Parkway and Gateway Crossing. These are shown in the table below: Use Demand Factor Unit Retail 0.10 gpd/sf Restaurant 0.17 gpd/sf Office 0.07 gpd/sf Hotel 134.00 gpd/room Multi-Family 164.25 gpd/unit A peaking factor of 2.13 was accepted. A summary of the peak wastewater flows that are anticipated for the project can be found below. These are broken out into the Core Phase 1, the remainder of the Legacy Park Project (Remainder), and Gateway Crossing, which has been analyzed to get a holistic sense of the infrastructure needs. A detailed breakout of the calculations can be found in the Appendix. Development Peak GPD Legacy Park – Phase 1 542,195.55 Legacy Park – Remainder 1,115,958.83 Subtotal 1,658,154.38 Gateway Crossing 108,839.81 Grand Total 1,766,994.19 h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 5 6.0 Proposed Design The existing 15” sewer pipe that has been stubbed out for use is not sufficient to carry the capacity of the Legacy Park and Gateway Crossing project. Due to this, a new 18” sewer line will be installed under Ellsworth Road and tied into the existing sewer main where the 15” pipe upsizes to an 18” pipe. Due to the shallower sewer depths available on this project, deviations from the City’s minimum slopes shall be allowed per the table below. Where feasible, the development will utilize the current City minimum sewer slopes found in the Engineering & Design Standards 2025, referenced in the table below. Based on Final Engineering Design Plans and in conjunction with the Grading Plans some sewer stubs may get shallow for an adequate depth at the Building/PAD. Therefore, in those instances based on sound engineering judgment, the development will be permitted to utilize the revised minimum slopes listed below. However, and in particular with regards to the 18-inch sewer extension from west of Ellsworth Road, the proposed sewer interceptor will be allowed to use the revised minimum sewer slopes along the entirety of Williams Field Road, through the Gateway Crossing project, until it reaches its termination point at the proposed Legacy Parkway. Diameter (in) Minimum Slope 8 0.40% 10 0.30% 12 0.23% 15 0.17% 18 0.14% The existing 15” pipe that is currently stubbed out to the parcel will be removed from the casing pipe, and a new 18” pipe will be inserted and extended along Williams Field Road east as a part of the Gateway Crossing Project. West of Ellsworth, the 15” pipe is planned to be replaced with an 18” pipe by either removal and replace or pipe bursting. Stubs will be provided to the Legacy Park parcel at the time of the Gateway Crossing project. See Exhibit C for the current proposed design and allocation of flows. h:\251461 - legacy park - mesa\civil\reports\sewer\master plan\legacy park - master sewer plan.doc 6 In conclusion, the existing 15” sewer pipe will not be able to serve the proposed Legacy Park and Gateway Crossing developments. Instead, a new 18” sewer pipe will be installed under Ellsworth Road in the existing 15” pipe’s casing pipe and tied back in at the location of the upsizing to the existing 18”. 7.0 References 1. City of Mesa Engineering & Design Standards, August 2025. 2. ADEQ Bulletin No. 11 EXHIBITS 4650 E. COTTON CENTER BLVD. SUITE 140 PHOENIX, AZ 85040 PH: (602) 286-9300 FAX: (602) 286-9400 4650 E. COTTON CENTER BLVD. SUITE 140 PHOENIX, AZ 85040 PH: (602) 286-9300 FAX: (602) 286-9400 SR-24 E PECOS ROAD PROJECT ELLSWORTH ROAD E RAY ROAD PROPOSED GATEWAY CROSSING (BY OTHERS) ARIZONA ATHLETIC GROUND OF JOB NO.: DRAWN: DESIGNED: CHECKED: DATE: DRAWING NO TJM TJM JDB 07/2026 NO. REVISION DATE 4650 E. COTTON CENTER BLVD. SUITE 140 PHOENIX, AZ 85040 PH: (602) 286-9300 FAX: (602) 286-9400 Contact Arizona 811 at least two full working days before you begin excavation Call 811 or click Arizona811.com 251461 LEGACY PARK SANITARY SEWER APPENDIX A Water and Sewer Modified Use Rates Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Valley Cities Comparison Charts 11/6/2025 Retail (gpd/sf) Restaurant (gpd/sf) Office (gpd/sf) Hotel (gpd/room) MF (gpd/unit) Mesa1 0.2 1.5 0.4 350 154 Phoenix2 0.125 0.125 0.115 200 240 Peoria3 0.03 0.03 0.03 200 200 Buckeye4 0.13 0.5 0.13 200 235 1 Engineering & Design Standards, 2023, City of Mesa - Table 3.1 2 Design Standards Manual for Water and Wastewater, City of Phoenix, 2021 - Table 8 3 City of Peoria Engineering Standads, 2025 - Table 8-3 4 Water Distribution and Transmission, City of Buckeye, 2025 - Table 2 Retail (gpd/sf) Restaurant (gpd/sf) Office (gpd/sf) Hotel (gpd/room) MF (gpd/unit) Mesa1 0.5 1.2 0.4 380 136 Phoenix2 0.075 0.075 0.09 150 180 Peoria3 0.02 0.02 0.02 120 120 Buckeye4 0.5 0.5 0.1 130 200 ADEQ5,6 0.1 1.24 0.1 45 200 1 Engineering & Design Standards, 2023, City of Mesa - Table 4.1 2 Design Standards Manual for Water and Wastewater, City of Phoenix, 2021 - Table 8 3 City of Peoria Engineering Standards, 2025 - Table 9-1 4 Gravity Sewer Engineering Design Standards, City of Buckeye, 2025 - Table 1 5 AAC Title 18, Chapter 9, 2025 - Table 1 6 Estimation of capita per sf from City North/Tempe Marketplace/oast industry experience Retail: 0.0025 person/sf Office: 1 person/200sf Residential: 2.5 persons/unit Hotel: 1.5 persons/unit Restaurant: 0.01 employees/sf; 750 customers/day Demand Factors - Water Demand Factors - Wastewater Page 1 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Valley Cities Comparison Charts 11/6/2025 Peaking Factor Mesa1 2.5 Phoenix2 1.63 Peoria3 3.2 Buckeye4 2 ADEQ5 1.70 1 Engineering & Design Standards, 2023, City of Mesa - Table 4.3 2 Design Standards Manual for Water and Wastewater, City of Phoenix, 2021 - E.3 page19 - based on population 3 City of Peoria Engineering Standards, 2025 - Table 8-2 4 Gravity Sewer Engineering Design Standards, City of Buckeye, 2025 - Table 2 5 AAC Title 18, Chapter 9, 2025 - D.1.b.i, page 70 - based on population Retail Restaurant Office Hotel MF Mesa 250.00% 80.00% 100.00% 108.57% 88.31% Phoenix 60.00% 60.00% 78.26% 75.00% 75.00% Peoria 66.67% 66.67% 66.67% 60.00% 60.00% Buckeye 384.62% 100.00% 76.92% 65.00% 85.11% ADEQ N/A N/A N/A N/A N/A Peaking Factors Water to Wastewater Factor Page 2 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Valley Cities Comparison Analysis 11/6/2025 Min Max Average Min Max Average Retail 0.03 0.2 0.12 Retail 0.03 0.13 0.10 Restaurant 0.03 1.5 0.54 Restaurant 0.03 0.5 0.22 Office 0.03 0.4 0.17 Office 0.03 0.13 0.09 Hotel 200 350 237.50 Hotel 200 200 200.00 MF 154 240 207.25 MF 200 200 225.00 Retail 0.02 0.5 0.24 Retail 0.02 0.5 0.17 Restaurant 0.02 1.24 0.61 Restaurant 0.02 1.24 0.46 Office 0.02 0.4 0.14 Office 0.02 0.1 0.08 Hotel 45 380 165.00 Hotel 45 150 111.25 MF 120 200 167.20 MF 120 200 175.00 Retail 60.00% 384.62% 190.00% Retail 60.00% 384.62% 170.00% Restaurant 60.00% 100.00% 77.00% Restaurant 60.00% 100.00% 76.00% Office 66.67% 100.00% 80.00% Office 66.67% 78.26% 74.00% Hotel 60.00% 108.57% 77.00% Hotel 60.00% 75.00% 67.00% MF 60.00% 88.31% 77.00% MF 60.00% 85.11% 73.00% Peaking Factor Peaking Factor Value 1.63 3.20 2.2 Value 1.63 3.20 2.13 Retail (gpd/sf) Restaurant (gpd/sf) Office (gpd/sf) Hotel (gpd/sf) MF (gpd/sf) Peaking Factor Water 0.10 0.22 0.09 200.00 225.00 - Wastewater 0.10 0.17 0.07 134.00 164.25 2.13 *Values determined from the "Factor Comparison (excluding Mesa)" table for average water flows. Wastewater flows were then reduced by the W to WW Factor % average value. The only exception is retail, which was manually reduced to 100%. 1 These values all contain data from ADEQ for a common average. The W to WW Factor % does not incorporate ADEQ, however, since there are no published water demand numbers. 1 These values all contain data from ADEQ for a common average. The W to WW Factor % does not incorporate ADEQ, however, since there are no published water demand numbers. Factor Comparison (including Mesa) W to WW Factor Wastewater1 Water Factor Comparison (exluding Mesa) Water Wastewater1 W to WW Factor Proposed Water and Wastewater Demand Factors Page 3 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Use by Area 11/6/2025 Legacy Park Parcel Retail (sf) Restaurant (sf) Office (sf) Hotel (rooms) MF (units) Population1 1 721,354 3,607 2 637,283 3,186 3 467,834 2,339 4 271,706 1,359 5 290,763 1,454 6 257,004 1,285 7 276,062 1,380 8 246,114 1,231 9 346,847 1,734 10 4,760 2,040 74 238 11 61,530 26,370 696 2,421 12 151,690 65,010 1,679 13 600 900 14 150 225 15 100,000 250 16 17,500 7,500 337 1,036 17 334 835 18 411 1,028 19 469 1,173 27,360 Gateway Crossing - 75 Acre +/- Commercial Development - SEC Ellsworth Rd and Williams Field Rd Parcel Retail (sf) Restaurant (sf) Office (sf) Hotel (rooms) MF (units) Population1 GC 177,350 29,150 212 1,344 1,344 1 Estimation of capita per sf from City North/Tempe Marketplace/past industry experience Use Factor Unit Retail 0.0025 persons/sf Restaurant 0.02 persons/sf Office 0.005 persons/sf Hotel 1.5 persons/room MF 2.5 persons/unit Use by Area/Units Population Uses Use by Area/Units Page 4 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Potable Water Demands 11/6/2025 Legacy Park - Phase 1 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF ADD (GPD) ADD (Ac-Ft/Yr) 10 4,760 2,040 0 0 74 476.00 448.80 0.00 0.00 16,650.00 17,574.80 19.69 11 61,530 26,370 0 0 696 6,153.00 5,801.40 0.00 0.00 156,600.00 168,554.40 188.82 12 151,690 65,010 0 0 0 15,169.00 14,302.20 0.00 0.00 0.00 29,471.20 33.01 13 0 0 0 600 0 0.00 0.00 0.00 120,000.00 0.00 120,000.00 134.43 15 100,000 0 0 0 0 10,000.00 0.00 0.00 0.00 0.00 10,000.00 11.2 345,600.40 387.15 Legacy Park - Phase 2 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF ADD (GPD) ADD (Ac-Ft/Yr) 1 0 0 721,354 0 0 0.00 0.00 64,921.86 0.00 0.00 64,921.86 72.73 2 0 0 637,283 0 0 0.00 0.00 57,355.47 0.00 0.00 57,355.47 64.25 3 0 0 467,834 0 0 0.00 0.00 42,105.06 0.00 0.00 42,105.06 47.17 4 0 0 271,706 0 0 0.00 0.00 24,453.50 0.00 0.00 24,453.50 27.39 5 0 0 290,763 0 0 0.00 0.00 26,168.67 0.00 0.00 26,168.67 29.31 6 0 0 257,004 0 0 0.00 0.00 23,130.36 0.00 0.00 23,130.36 25.91 7 0 0 276,062 0 0 0.00 0.00 24,845.54 0.00 0.00 24,845.54 27.83 8 0 0 246,114 0 0 0.00 0.00 22,150.26 0.00 0.00 22,150.26 24.81 9 0 0 346,847 0 0 0.00 0.00 31,216.19 0.00 0.00 31,216.19 34.97 14 0 0 0 150 0 0.00 0.00 0.00 30,000.00 0.00 30,000.00 33.61 16 17,500 7,500 0 0 337 1,750.00 1,650.00 0.00 0.00 75,825.00 79,225.00 88.75 17 0 0 0 0 334 0.00 0.00 0.00 0.00 75,150.00 75,150.00 84.18 18 0 0 0 0 411 0.00 0.00 0.00 0.00 92,475.00 92,475.00 103.59 19 0 0 0 0 469 0.00 0.00 0.00 0.00 105,525.00 105,525.00 118.21 698,721.90 782.71 Gateway Crossing (not a part of Legacy Park - retail center by Vestar south of Williams Field Road) Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF ADD (GPD) ADD (Ac-Ft/Yr) GC 177,350 29,150 0 212 0 17,735.00 6,413.00 0.00 42,400.00 0.00 66,548.00 74.55 66,548.00 74.55 Legacy Park Subtotal: 1,169.86 Gateway Crossing Subtotal: 74.55 Grand Total 1,244.41 Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Page 5 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Wastewater Use Analysis 11/6/2025 Legacy Park - Phase 1 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) 10 4,760 2,040 0 0 74 476.00 346.80 0.00 0.00 12,154.50 12,977.30 27,641.65 11 61,530 26,370 0 0 696 6,153.00 4,482.90 0.00 0.00 114,318.00 124,953.90 266,151.81 12 151,690 65,010 0 0 0 15,169.00 11,051.70 0.00 0.00 0.00 26,220.70 55,850.09 13 0 0 0 600 0 0.00 0.00 0.00 80,400.00 0.00 80,400.00 171,252.00 15 100,000 0 0 0 0 10,000.00 0.00 0.00 0.00 0.00 10,000.00 21,300.00 254,551.90 542,195.55 Legacy Park - Phase 2 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) 1 0 0 721,354 0 0 0.00 0.00 50,494.78 0.00 0.00 50,494.78 107,553.88 2 0 0 637,283 0 0 0.00 0.00 44,609.81 0.00 0.00 44,609.81 95,018.90 3 0 0 467,834 0 0 0.00 0.00 32,748.38 0.00 0.00 32,748.38 69,754.05 4 0 0 271,706 0 0 0.00 0.00 19,019.39 0.00 0.00 19,019.39 40,511.29 5 0 0 290,763 0 0 0.00 0.00 20,353.41 0.00 0.00 20,353.41 43,352.76 6 0 0 257,004 0 0 0.00 0.00 17,990.28 0.00 0.00 17,990.28 38,319.30 7 0 0 276,062 0 0 0.00 0.00 19,324.31 0.00 0.00 19,324.31 41,160.77 8 0 0 246,114 0 0 0.00 0.00 17,227.98 0.00 0.00 17,227.98 36,695.60 9 0 0 346,847 0 0 0.00 0.00 24,279.26 0.00 0.00 24,279.26 51,714.81 14 0 0 0 150 0 0.00 0.00 0.00 20,100.00 0.00 20,100.00 42,813.00 16 17,500 7,500 0 0 337 1,750.00 1,275.00 0.00 0.00 55,352.25 58,377.25 124,343.54 17 0 0 0 0 334 0.00 0.00 0.00 0.00 54,859.50 54,859.50 116,850.74 18 0 0 0 0 411 0.00 0.00 0.00 0.00 67,506.75 67,506.75 143,789.38 19 0 0 0 0 469 0.00 0.00 0.00 0.00 77,033.25 77,033.25 164,080.82 523,924.34 1,115,958.83 Gateway Crossing (not a part of Legacy Park - retail center by Vestar south of Williams Field Road) Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) GC 177,350 29,150 0 212 0 17,735.00 4,955.50 0.00 28,408.00 0.00 51,098.50 108,839.81 51,098.50 108,839.81 Legacy Park Subtotal: 1,658,154.38 Gateway Crossing Subtotal: 108,839.81 Grand Total 1,766,994.19 Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Page 6 Legacy Park - 200 +/- Acre Mixed Use Development NEC Ellsworth Rd and Williams Field Rd Wastewater Use Analysis - ADEQ Only 11/6/2025 Legacy Park - Phase 1 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) 10 4,760 2,040 0 0 74 476.00 2,529.60 0.00 0.00 14,800.00 17,805.60 30,258.59 11 61,530 26,370 0 0 696 6,153.00 32,698.80 0.00 0.00 139,200.00 178,051.80 302,578.73 12 151,690 65,010 0 0 0 15,169.00 80,612.40 0.00 0.00 0.00 95,781.40 162,769.56 13 0 0 0 600 0 0.00 0.00 0.00 27,000.00 0.00 27,000.00 45,883.42 15 100,000 0 0 0 0 10,000.00 0.00 0.00 0.00 0.00 10,000.00 16,993.86 328,638.80 558,484.16 Legacy Park - Phase 2 Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) 1 0 0 721,354 0 0 0.00 0.00 72,135.40 0.00 0.00 72,135.40 122,585.88 2 0 0 637,283 0 0 0.00 0.00 63,728.30 0.00 0.00 63,728.30 108,298.98 3 0 0 467,834 0 0 0.00 0.00 46,783.40 0.00 0.00 46,783.40 79,503.05 4 0 0 271,706 0 0 0.00 0.00 27,170.55 0.00 0.00 27,170.55 46,173.25 5 0 0 290,763 0 0 0.00 0.00 29,076.30 0.00 0.00 29,076.30 49,411.86 6 0 0 257,004 0 0 0.00 0.00 25,700.40 0.00 0.00 25,700.40 43,674.90 7 0 0 276,062 0 0 0.00 0.00 27,606.15 0.00 0.00 27,606.15 46,913.50 8 0 0 246,114 0 0 0.00 0.00 24,611.40 0.00 0.00 24,611.40 41,824.27 9 0 0 346,847 0 0 0.00 0.00 34,684.65 0.00 0.00 34,684.65 58,942.61 14 0 0 0 150 0 0.00 0.00 0.00 6,750.00 0.00 6,750.00 11,470.86 16 17,500 7,500 0 0 337 1,750.00 9,300.00 0.00 0.00 67,400.00 78,450.00 133,316.83 17 0 0 0 0 334 0.00 0.00 0.00 0.00 66,800.00 66,800.00 113,518.98 18 0 0 0 0 411 0.00 0.00 0.00 0.00 82,200.00 82,200.00 139,689.52 19 0 0 0 0 469 0.00 0.00 0.00 0.00 93,800.00 93,800.00 159,402.40 679,496.55 1,154,726.89 Gateway Crossing (not a part of Legacy Park - retail center by Vestar south of Williams Field Road) Parcel Retail Restaurant Office Hotel Rms MF Units Retail Restaurant Office Hotel MF Total (GPD) Peak (GPD) GC 177,350 29,150 0 212 0 17,735.00 36,146.00 0.00 9,540.00 0.00 63,421.00 107,776.76 63,421.00 107,776.76 Legacy Park Subtotal: 1,713,211.05 Gateway Crossing Subtotal: 107,776.76 Grand Total 1,820,987.81 Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Uses by square foot / units Flow (GPD) Page 7