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501 Sycamore Street 319-232-0271 fax
Suite 222
Waterloo, Iowa 50703
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WATERLOO SANITARY SEWER ANALYSIS - HYDRAULIC MODELING
CITY OF WATERLOO, IOWA
SUPPLEMENTAL AGREEMENT NO. 1
WHEREAS, a Protessional Service Agreement was entered mb by the City of Waterloo, lowa,
(Client), 715 Mulberry Street, Waterloo, Iowa, and AECOM Technical Services, Inc. (ATS), 501
Sycamore Street, Suite 222, Waterloo, Iowa, dated May 11, 2015, tor developing a hydrauflc
computer model ot the City's sanitary sewer collection system.
WHEFIEAS, the Client and ATS now desire to enter into Supplemental Agreement No. 1 tor
additional hydraulic computer modeling tasks that are required per Appendix 7 of the Consent
Decree.
NOW THEREFORE, it is mutually agreed to amend the original Protessional Service Agreement as
follows:
A. Project Description
The City ot Waterloo, Iowa, and ATS entered into an agreement to collect data, develop a
model of the sanitary sewer system, calibrate the model to a metered dry and wet weather
conditions, validate the calibrated model, and evaluate the overall performance of the
system based on the results of the calibration. Since the development of the original
agreement, the City 01 Waterloo has entered into a Consent Decree (CD) wTh the
Environmental Protection Agency (EPA). Appendix 7 of the CD detines the expectations
associated with developing the hydraulic model and assessing the overall sanitary sewer
system pertormance, which expands upon the original Scope of Services. Specitically, the
CD further detines the dry and wet weather calibration efforts and also requires the
evaluation 01 three design storm events to assess the performance ot the existing sanitary
sewer system. This amendment presents a Scope 01 Services associated with additional
tasks required to align with bbs CD.
B. Scope of Services
The Scope ot Services will encompass and include detailed work, services, materials,
equipment, personnel and supplies necessary to provide regulatory requirement as outlined
in Appendix 7 ot the CD which is in addition to the scope as listed in the original agreement.
The Scope of Services is further defmned as foliows:
Task 1 - Drv Weather Calibration and Validation. Two distinct dry weather periods during
the tlow monitoring period will be identitied. One period for dry weather calibration and the
second as a validation event will be utilized.
Task 2 - Add Base FIow and Heavy Water User Inputs. ln addition to adjusting per capita
flow rates as part ot the model calibration, base flow and heavy water user inputs will be
added where necessary.
Task 3 - Validation ot Model for Second Dry Weather Period. Validate the calibrated model
using a second dry weather period from the 2015 1 Iow monitoring data.
Task 4 - Wet Weather Calibration. ldentify tour distinct wet weather events during the tlow
monitoring period. Utilize three ot the events for calibration and one event for validation.
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Task 5 - Evaluate Raintall and Gauqe Data. Evaluate rainfall and ram gauge data and
develop appropriate rainfall patterns for each of the four calibration events as input into the
model.
Task 6 - lReview FIow Apportionment. Review flow apportionment based on available flow
data and level of service fiows.
Task 7 - Calibrate Isolated Basmns Based on FIow Meter Data. Calibrate isolated basins
based on 1 Iow meter data for three unique monitored events. It is anticipated that the first,
third, and tourth Iargest events will be used for the calibration process.
Task 8 - Calibrate Downstream Meters. Calibrate downstream meters requiring meter (lIow)
subtraction for each 01 the three identitied calibration events.
Task 9 - Calibrate Model Hvdraulics. Calibrate model hydraulics by adjusting hydraulic
parameters where necessary to account lor sediment, downstream 1 Iow restriotions and other
significant Iosses tor each ot the three identified calibration events.
Task 10 - Validate the Model With Wet Weather Event. Validate the model to one of the
tour identified wet weather events. It is anticipated that the second Iargest event will be
used lor the validation process.
Task 11 - Wet Weather Event Svstem Performance. Utilizing the calibrated model, evaluate
the performance of the sanitary sewer system by analyzing typical 2-, 5-, and 1 0 -year
recurrence interval storm events for a 6 -hour storm based on the rainfall totais of Appendix 7
(referencing the "Rainfall Frequency Atlas of the Midwest" also known as "Bulietin 71").
Task 12 - Technical Memorandum. Provide maps and develop a technical memorandum
documenting model development, calibration and validation process, wet weather system
pertormance, existing deficiencies, identify future model needs and application.
Task 13 - Proiect Administration. This task mncludes project administration and coordination
throughout the project development. This task includes mntra-office meetings, which will be
attended by the project team, as weu as general day-to-day administrative tasks and typing 01
intra -office memoranda.
111. Compensation
Compensation for the above services will be on an hourly basis mn accordance with Part VI
of the original agreement and shall be integrated with the fees in the original agreement.
The estimated fee is One Hundred One Thousand Seven Hundred Dollars ($101 700.00).
IV. In all other respects, the obligations of the Client and the Consultant shall remain as
specified in the Protessional Services Agreement dated May 11, 2015.
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IN WITNESS WHEREOF, the parties hereto have executed this Supplemental Agreement No. 1 as
of the dates shown below:
AECOM TECHNICAL SERVICES, INC.
By Date January 26 2016
Dougla2;4/—E el, P..
Associate Vice President
APPROVED FOR CLIENT:
By: N—vtl� Date �/ I //
O:Wdministration\AGREE\SUPPLE\SAI Wat SS Analysis Hyd Modeling.docx