01 13 26 DS - First Amendment to PSA - Dibble and Associates Consulting Engineers

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AMENDMENT NO. 1 TO THE PROFESSIONAL SERVICES AGREEMENT 
BETWEEN 
THE CITY OF TOLLESON 
AND 
DIBBLE & ASSOCIATES CONSULTING ENGINEERS, INC. DBA DIBBLE 
 
THIS AMENDMENT NUMBER NO. 1 TO THE PROFESSIONAL SERVICES AGREEMENT (this 
“Amendment”) between the CITY OF TOLLESON, an Arizona municipal corporation (the “City”) 
and DIBBLE & ASSOCIATES CONSULTING ENGINEERS, INC., an Arizona corporation dba DIBBLE 
(the “Consultant”), (collectively, the “parties”), is hereby entered into and shall be effective on 
the last signature date set forth below.   
Note: Amendment changes are noted with additions in bold font and deletions in strikeout font. 
RECITALS 
A. 
The City and the Consultant entered into a Professional Services Agreement on 
April 3, 2023 (the “Agreement”) for Consultant to provide on-call professional engineering and 
surveying services (“Services”).  The terms of the Agreement are incorporated herein by 
reference. 
 
B. 
The parties desire to amend the Agreement to increase the compensation limit in 
the Agreement. 
AGREEMENT 
NOW, THEREFORE, in consideration of the foregoing introduction and recitals, which are 
incorporated herein by reference, the following mutual covenants and conditions, and other 
good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, 
the City and the Consultant hereby agree as follows: 
 
1. 
The parties agree to amend Paragraph 3 Compensation of the Agreement, as 
follows: 
 
“The City shall pay Consultant a price not to exceed $250,000 for the Services as set forth 
in the Fee Proposal, attached hereto as Exhibit D and incorporated herein by reference.” 
 
2. 
The parties agree to amend Pierce Coleman PLLC notice address in Paragraph 
14.14 of the Agreement as follows:  
 
With copy to: 
 
Pierce Coleman PLLC 
7730 East Scottsdale Road, Suite 105 
17851 N. 85TH STREET, SUITE 175 
Scottsdale, Arizona 8526085255.  
Attn: Justin Pierce, City Attorney

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3. 
Effect of Amendment. In all other respects, the Agreement is affirmed and 
ratified and, except as expressly modified herein, all terms and conditions of the Agreement 
shall remain in full force and effect. 
4. 
Non-Default. By executing this First Amendment, the Consultant affirmatively 
asserts that (i) the City is not currently in default, nor has it been in default at any time prior to 
this First Amendment, under any of the terms or conditions of the Agreement and (ii) any and all 
claims, known and unknown, relating to the Agreement and existing on or before the date of this  
First Amendment are forever waived. 
5. 
Conflict of Interest. This First Amendment and the Agreement may be canceled by 
the City pursuant to A.R.S. § 38-511. 
 
[SIGNATURES ON THE FOLLOWING PAGE(S).] 
[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK.]

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IN WITNESS WHEREOF, the parties hereto have executed this First Amendment as of the 
date and year last set forth below. 
 
“City” 
 
CITY OF TOLLESON,  
an Arizona municipal corporation 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Reyes Medrano, Jr., City Manager 
 
 
 
Date 
 
ATTEST: 
 
 
 
 
 
 
 
 
 
Crystal Zamora, City Clerk 
 
APPROVED AS TO FORM: 
 
 
 
 
 
 
 
 
 
Justin S. Pierce, City Attorney 
 
 
“Consultant” 
 
DIBBLE & ASSOCIATES CONSULTING ENGINEERS, INC.,  
an Arizona corporation dba DIBBLE  
 
 
By:  
 
 
 
 
 
 
 
 
 
 
 
 
Name:  
 
 
 
 
 
 
DATE 
Its:

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EXHIBIT “D” 
TO 
FIRST AMENDMENT OF 
PROFESSIONAL SERVICES AGREEMENT 
BETWEEN 
THE CITY OF TOLLESON 
AND 
DIBBLE & ASSOCIATES CONSULTING ENGINEERS, INC. DBA DIBBLE 
 
[Fee Proposal]

p 602.957.1155 
3020 East Camelback Road, Suite 201 
dibblecorp.com 
f 602.957.2838 
Phoenix, AZ 85016 
 
October 22, 2025 
City of Tolleson 
9055 W Van Buren St. 
Tolleson, AZ 85353 
Attn:  Mr. Chris Hamilton 
 
 
RE: 
NEC 91st Avenue and Van Buren Site Drainage Design 
 
Scope of Work and Fee Proposal 
 
On-Call Engineering and Surveying Services Contract – Task Order 
Dear Mr. Hamilton: 
Thank you for the opportunity to support the City of Tolleson (City) with site drainage design services for 
the property on the northeast corner of 91st Avenue and Van Buren Street. This proposal has been 
prepared based on our understanding of the project as described in the Project Understanding and Scope 
of Services sections. We look forward to partnering with you on this task. 
PROJECT UNDERSTANDING 
This site drainage design will develop site drainage retention facilities for Parcel 102-48-263 on the 
northeast corner of 91st Avenue and Van Buren Street based on the results of Tolleson Drainage Study – 
Phase I – 91st Avenue Retention Basin Conditions Review (Retention Concept Memo), for the subject parcel 
and City provided site design concepts. The design will also evaluate options to collect runoff on Lizanne 
Way and direct it into the site drainage facilities. This scope assumes that a preferred option to collect 
Lizanne Way drainage will be identified and included in the construction documents.  
Exhibit A – Project Location Map

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DESIGN STANDARDS: 
The project will be designed in accordance with the following standards, in order of precedence: 
• 
City of Tolleson Engineering & Planning Department Standards, including Ordinance 507 – 2011 
Supplemental to MAG Standard Specifications and Details 
• 
Maricopa Association of Governments (MAG), Uniform Standard Specifications and Details for 
Public Works Construction, 2025 Edition 
• 
Arizona Department of Transportation (ADOT), Standard Specifications for Road and Bridge 
Construction, 2021 
• 
Federal Highway Administration, Manual on Uniform Traffic Control Devices for Streets and 
Highways, 2009 Edition Revision 2 with Arizona Supplements 
• 
Flood Control District of Maricopa County (FCDMC), Drainage Policies and Standards Manual, 
August 2018 
• 
FCDMC, Drainage Design Manual for Maricopa County, Arizona: Volume I Hydrology, July 2023 
• 
FCDMC, Drainage Design Manual for Maricopa County, Arizona: Volume II Hydraulics, December 
2018 
• 
FCDMC, Drainage Design Manual for Maricopa County: Volume III Erosion Control, July 2018 
• 
Arizona Department of Environmental Quality (ADEQ), Engineering Bulletin No. 10, Guidelines for 
Construction of Water Systems, May 1979 
• 
ADEQ, Engineering Bulletin No. 11, Minimum Requirements for Design, Submission of Plans and 
Specifications of Sewage Works, July 1978 
SCOPE OF SERVICES 
TASK 1: SUPPLEMENTAL SURVEY 
The City has provided survey information for the subject parcel that will be used for design. Dibble will 
provide supplemental survey for the Lizanne Way portion of the design. 
For Lizanne Way, Dibble will perform the following survey services: 
• 
Project control for Lizanne Way tied to the site survey control provided by the City 
• 
Prepare design ready AutoCAD base file including existing utilities and existing site features 
based on available utility as-built and quarter section drawings as well as conventional 
topographic survey.  
• 
Prepare a survey control sheet sealed by an Arizona Registered Land Surveyor (RLS). 
 
TASK 2: CONCEPTUAL DESIGN 
Dibble will develop a conceptual design plan for the site and Lizanne Way drainage retention facilities 
under the following subtasks. A conceptual design technical memo and plan will be provided for review 
and comment. 
TASK 2.1: RETENTION CALCULATION REFINEMENT 
Previous conceptual design of the site storage was based on a volume calculation from the original 
storage basin design. Dibble will re-evaluate the retention requirements for the site through further 
development of the FLO-2D modeling previously completed as part of Phase 2 Tolsun Farms Drainage 
Evaluation Alternatives Analysis.

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• 
Existing underground storm drain facilities will be added to the FLO-2D model using the 
SWMM storm drain component. The result will be an existing condition FLO-2D model. As-
built information of the exiting storm drain system will be collected and will be used for storm 
drain model development. A survey allowance, Section A4: Additional Supplemental Survey, 
has been included for collection of unforeseen missing storm drain data.  
• 
The original stormwater model boundary will not be changed. It is understood that half street 
drainage generated on Van Buren Street east of the model’s eastern boundary at the 
Roosevelt Irrigation District Canal may enter the model area; however, this component of 
runoff was not a component of the original storage basin watershed area. As adjacent 
development occurs, this half-street runoff is expected to be collected into on-site storage. 
Therefore, the FLO-2D model boundary will remain at the Roosevelt Irrigation District Canal, 
which is consistent with the Durango Area Drainage Master Plan subbasin delineation. 
• 
The results of the existing condition FLO-2D modeling will be compared against anecdotal 
data of historical basin storage levels provided by the City. Adjustments to runoff components 
may be necessary at that time.  
 
  TASK 2.2: PERCOLATION TESTING 
• 
The City provided a previous geotechnical report titled “Geotechnical Exploration La Entrada 
Tolleson” completed by Alpha Geotechnical & Materials in 2012 for Job #11-G-1944.  It is 
assumed that this design will utilize the information and results from this report.  This scope 
includes one additional site percolation test that will be completed for the analysis to comply 
with FCDMC standards. 
 
  TASK 2.3: SITE RETENTION & STORM DRAIN LAYOUT 
• 
Based on a site design concept to be provided by the City, Dibble will create a concept layout 
for the retention facilities including up to two underground storage options. Options may vary 
in location of underground storage and selected materials (CMP and additional proprietary 
storage options such as ADS). The concept design will incorporate surface storage as the site 
plan allows. 
• 
The storage layout will incorporate up to two storm drain concepts to collect drainage flow 
currently ponding at the intersection of Van Buren Street and Lizanne Way (as shown in 
Exhibit A) and convey it to the site drainage storage facilities. 
• 
Each storage option will include an estimate of retention facility drain time using geotechnical 
data specific to the site and provided by the City. 
• 
The number of drywells required for each storage option will be calculated based on an 
assumed drywell capacity of 0.1 cfs; the in-situ capacity and final number of drywells required 
to be calculated during construction. 
• 
A concept drawing and conceptual level estimate of construction cost for each option will be 
provided to the City in a technical memo for review and selection of a preferred option. 
 
TASK 3: DESIGN DEVELOPMENT 
Based on comments and feedback on the concept design, Dibble will prepare Design Development 
documents for the selected alternative including: 
• 
On-site plans including site demolition plan, grading & drainage plan, and cross sections 
• 
Site retention facilities plan and profile and details 
• 
Off-site plans including storm drain plan and profile, details, and utility impacts, and details

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• 
Refinement of the storm drain and storage basin design within the FLO-2D model to Design 
Development stage 
• 
Preliminary drainage report 
 
Design Development plans (75% level) will be provided for review and comment. Plan sets will include 
cover, notes, survey control, plan and profiles, grading and drainage, and details (up to 11 total sheets), 
Technical specifications, quantities, engineer’s opinion of probable construction cost, and preliminary 
drainage report will be prepared for this submittal.  
 
TASK 4: CONSTRUCTION DOCUMENTS 
Based on comments and feedback on the design development plans, Dibble will prepare Construction 
Documents including: 
• 
Refinement of the storm drain and storage basin design within the FLO-2D model to final design 
stage 
• 
Final on-site plans including site demolition plan, grading & drainage plan, and cross sections 
• 
Final site retention facilities plan and profile and details 
• 
Final Off-site plans including storm drain plan and profile, details, and utility impacts  
• 
No landscape design plans will be provided; it is assumed final ground surface that is disturbed 
will be compacted ground per MAG standards. 
• 
Final drainage report 
 
Final (100%) construction plans, specifications, quantities and estimate, and final drainage report will be 
submitted for review and comment by the City. Sealed plans will be prepared that incorporate comments 
from the 100% review. 
 
TASK 5: UTILITY COORDINATION 
Dibble will conduct utility coordination efforts including the preparation of utility conflict review letters. 
The letter, along with the Design Development submittal plans will be distributed to each utility provider 
for review. Dibble will conduct coordination meetings with utility companies reporting facilities in conflict 
with the proposed design. It is anticipated that two meetings will be conducted. Prior to the final 
submittal, Dibble will prepare a Utility Clearance Letter summarizing the status of each utility provider 
with respect to the project improvements.  
 
If utility conflicts are unavoidable, Dibble will coordinate with utility companies for their design of 
relocations as required. Dibble will review the relocation/new design for conformance with the proposed 
design and will incorporate the corresponding design into the project construction documents. Upon 
receipt of either no conflict letters or final relocation plans with a letter from each utility provider, Dibble 
will prepare the Utility Clearance Letter.  
 
TASK 6: PROJECT MANAGEMENT AND MEETINGS 
Dibble’s Project Manager will be knowledgeable of the project and have responsible charge of the 
progress of each phase of the project. The Project Manager will be the point of contact for the City. The 
Project Manager will be responsible for administrative issues, technical direction of the work, scheduling, 
and budgetary oversight for the project as well as coordination and reporting with the City’s Project 
Manager.

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Dibble’s Project Manager will be responsible for ensuring that Dibble’s internal Quality Control Program 
is followed for this project, including review and oversight by the QA/QC Reviewer. In addition, senior 
engineering staff, not part of the regular design effort, will independently review the design for 
conformance to design standards, constructability, and quality at each design progress level prior to 
submittal to the City. 
 
Project Meetings 
The following meetings are included in this scope of work. 
• 
One concept development meeting with the City and identified stakeholders to review the 
alternatives developed in the concept task, 
• 
Two comment resolution meetings, 
• 
One virtual miscellaneous coordination meeting with the City and various stakeholders. 
 
ALLOWANCES 
A1: STRUCTURAL DESIGN 
Dibble will provide structural design and CAD details for non-standard junction structures if determined 
necessary in the design development. It is assumed that up to 2 structural design details may be needed. 
A2: POTHOLES 
Dibble shall utilize a qualified subconsultant to perform subsurface utility exploration (SUE) services. A 
utility pothole list will be developed by Dibble and approved by the City prior to authorization of 
exploration activities. The SUE subconsultant shall be responsible for survey layout, pothole excavation, 
backfilling with native material, patching with cold patch, traffic control, and permitting. SUE will be paid 
at the unit rate for all potholes excavated, including dry holes. It is estimated that 5 potholes may be 
required for this project. 
A3: LEGAL DESCRIPTIONS 
New easements (likely drainage and/or temporary construction) may be required for this project 
pending the selected option. Dibble will prepare up to 2 legal descriptions with exhibits for new land 
rights.  
A4: ADDITIONAL SUPPLEMENTAL SURVEY 
If the facility sizes and elevations of the existing storm drain systems serving the retention basin cannot 
be obtained from as-built drawings, field survey will be conducted to collect missing data.  
EXCLUSIONS TO THIS SCOPE OF SERVICES 
The work listed below is specifically excluded from this scope of work, but can be added to the contract 
for an additional fee to be negotiated should the City elect to do so: 
• 
Site civil improvement design including any pavement, curb, sidewalk, lighting, and structures. 
• 
Landscape, irrigation, and SWPPP design 
• 
Floodplain Mapping and FEMA coordination  
• 
Utility relocation design 
• 
Environmental investigations 
• 
401/404 Permitting

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• 
Sediment Transport Analysis 
• 
Geotechnical investigation or analysis 
• 
Traffic control design 
• 
Public Outreach/Public Involvement 
• 
Construction staking/Construction inspection 
• 
As-built survey  
• 
Permitting submittals and fees

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FEES 
Dibble is prepared to complete the services described herein for a fixed, lump sum fee as summarized 
below: 
1.0 
Supplemental Survey 
 
 
 
 
 
$  7,192  
 
 
2.0 
Conceptual Design  
 
 
 
 
 
$ 30,120 
3.0 
Design Development 
 
 
 
 
 
$ 25,380 
4.0 
Construction Documents 
 
 
 
 
 
$ 17,642 
5.0 
Utility Coordination  
 
 
 
 
 
$  2,268 
6.0 
Project Management and Meetings  
 
 
 
$  4,828 
SUBTOTAL 
 
 
 
 
 
 
$ 71,620 
 
    Direct Expense: Percolation Test/Mileage 
 
 
 
 
$   5,300 
 
Total Project Lump Sum Fee (Base Contract) 
 
 
 
 
$ 92,730 
 
 
Allowances 
A1      Structural Design 
 
 
 
 
 
 
$  8,000 
 
A2     Potholes 
 
 
 
 
 
 
 
$  5,000 
A3     Legal Descriptions 
 
 
 
 
 
 
$  2,500 
A4     Additional Supplemental Survey 
 
 
 
 
$  2,500 
 
 
Total Project Lump Sum Fee (with Allowance)  
 
 
 
$ 110,730 
 
 
 
We appreciate this opportunity to serve the City on this project. Please contact us at your convenience 
with any questions regarding the enclosed documents.  
 
Regards,  
 
 
 
 
Jason A Simmers, PE 
Paul Balch, PE 
 
Senior Project Manager 
Vice President/Transportation Group Leader  
Dibble 
Dibble 
 
 
Enclosures

LABOR BREAKDOWN:
   Classification
Hours
Billing Rate
Cost
Sr Project Manager
55
230.00
$             
12,650.00
$             
 
Senior Engineer
58
210.00
$             
12,180.00
$             
Project Engineer
174
172.00
$             
29,928.00
$             
 
Assistant Engineer
150
140.00
$             
21,000.00
$             
Senior Designer
36
150.00
$             
5,400.00
$                
Designer
16
130.00
$             
2,080.00
$                
Senior Technician
16
143.00
$             
2,288.00
$                
Technician
16
119.00
$             
1,904.00
$                
   Total Hours
521
87,430.00
$             
DIRECT EXPENSE
Percolation Test (Subconsultant)
5,000.00
$                
Mileage
300.00
$                   
Direct Subtotal
5,300.00
$                
TOTAL LUMP SUM FEE (BASE CONTRACT):
92,730.00
$             
ALLOWANCES:
A1: Strutural Design
8,000.00
$                
A2: Potholes
5,000.00
$                
A3: Legal Descriptions
2,500.00
$                
A4: Additional Supplemental Survey
2,500.00
$                
SUBTOTAL (ALLOWANCES): 
18,000.00
$             
TOTAL PROPOSED LUMP SUM FEE:
110,730.00
$           
10/22/2025
Signature
Date
Vice President/Transporation Group Leader
Title
CONSULTANT/SUBCONSULTANT FEE PROPOSAL SUMMARY
On-Call Engineering and Surveying Services Contract – Task Order
NEC 91st Ave and Van Buren St Site Drainage Design
City of Tolleson
10/22/2025
Dibble
Page 1 of 1

250.00
$          
230.00
$          
210.00
$          
172.00
$          
140.00
$          
150.00
$          
130.00
$          
143.00
$          
119.00
$          
Total 
Total 
Phase
Task
Description
Staff Hours
Fee
1
91st Avenue & Van Buren Site Drainage
1
Supplemental Survey
4
16
16
16
52
7,192.00
$            
2
Conceptual Design
6
24
70
64
18
182
30,120.00
$          
3
Design Development
12
18
50
56
16
152
25,380.00
$          
4
Construction Documents
13
16
46
22
2
99
17,642.00
$          
5
Utility Coordination
2
4
8
14
2,268.00
$            
6
Project Management and Meetings
18
4
22
4,828.00
$            
TOTAL STAFF HOURS
55
58
174
150
36
16
16
16
521
TOTAL FEE
-
$                 
12,650.00
$     
12,180.00
$     
29,928.00
$     
21,000.00
$     
5,400.00
$       
2,080.00
$       
2,288.00
$       
1,904.00
$       
87,430.00
$          
Technician
City of Tolleson
NEC 91st Ave and Van Buren St Site Drainage Design
On-Call Engineering and Surveying Services Contract – Task Order
DIBBLE STAFF - HOUR MATRIX
Senior 
Designer
Designer
Senior 
Technician
Project 
Principal
Sr Project 
Manager
Senior 
Engineer
Project 
Engineer
Assistant 
Engineer
10/22/2025
Dibble
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