City of Nashua, NH
Capacity, Management, Operation and Maintenance (CMOM) and Stormwater Collection System
B8.3
B8.4
B8.5
Investigation and Evaluation Program - Phase II
Scope of Work for Engineering Services
Model Calibration/Verification
Consultant shall utilize the flow and rainfall monitoring data collected to perform dry and wet weather
calibration and verification of the hydraulic model. The monitoring data collected shall be used to
initially calibrate/verify the model. Representative storm events of varying intensities and depths shall
be selected from the rainfall data set to be used for calibration and verification. Three (3) storms shall
be used for calibration and one (1) for verification of the model.
The model shall be calibrated by adjusting hydrologic and hydraulic parameters until reasonable
agreement is reached between observed and predicted flows, volumes and depths. Model calibration
accuracy and quality shall be judged by industry-standard guidelines.
Model Simulations
Consultant shall use the calibrated and verified model to simulate design storm events, and evaluate the
sewer system response to wet weather, including the 1-year, 2-year, and 5-year storm events. Baseline
(current conditions) scenario shall be evaluated. The ability of the sewer system to convey baseline
flows during both dry and wet weather shall be evaluated. Locations of predicted surcharging and
hydraulic deficiencies shall be identified. Tables and figures depicting the performance of the collection
system for each storm event shall be developed. Tables shall show the length of sewers surcharged by
size ranges, and figures shall illustrate sewers that are partially and fully surcharged, including type of
surcharge (i.e., backwater-induced or capacity-related).
Flow Monitoring Evaluation Technical Memorandum
Consultant shall develop and submit a Flow Monitoring Evaluation Technical Memorandum (TM),
incorporating the results of Tasks B8.1 through B8.4. The TM also include a table of contents, sketches,
technical narratives, methodologies, results, and all pertinent information used to develop and calibrate
the model, and conduct model simulations.
Electronic versions (PDF and Word format) of the Draft TM shall be submitted to the City for review and
comment. Following the City’s review of the Draft TM, Consultant shall incorporate the City’s comments,
and submit a Final TM.
Deliverables: Flow meter data and updated model. Flectronic (PDF and editable word) versions of
Draft and Final TM, and five (5) hard copies of Final TM.
C. Stormwater Collection System Investigation and Evaluation (Tasks C1-C4)
Consultant shall perform engineering services for the continuation of the City’s Stormwater Collection System
Investigations. The scope includes the following tasks:
Task C1
Task C2
Task C3
Task C4
Stormwater CCTV and Manhole Inspections
Stormwater GIS Edits and Updates
Headwall Inspections
Green Infrastructure Inventory
AUGUST 2021
