March 24, 2022
Elba Mijango
Associate Engineer
City of Manteca
1001 W. Center St.
Manteca, CA 95337
Transmitted via email
Subject: Proposal to Evaluate the Impact of Oakwood Lake Water District on the City of Manteca Water Distribution System
Dear Elba:
Thank you for the opportunity to submit this proposal to provide additional services for the City of Manteca (City) Water Master Plan (Master Plan). This proposal summarizes our understanding of the project, our scope of work, and our proposed schedule and budget.
Project Understanding
The Oakwood Lake Water District (OLWD) supplies drinking water to the Oakwood Shores subdivision (Oakwood Shores) and the adjacent Oakwood Lake Mobile Home Park (MHP) in an unincorporated area of San Joaquin County southwest of the City. The OLWD supplies groundwater from two water supply wells and provides groundwater treatment for arsenic and manganese at a centralized water treatment plant (WTP). The OLWD WTP consists of a coagulation filtration system, 0.5 MG treated water storage tank, distribution system booster pump station, motor control center, and radio telemetry/SCADA.
The City is interested in evaluating the impacts of fully incorporating the OLWD water system into the City’s distribution system and would like to include this assessment in the Master Plan. The recommendations from this evaluation would be incorporated into the Master Plan as a capital project.
Scope of Work
Task 1 – Data Review and Water Demand Analysis: HydroScience will review available information regarding the OLWD water system, water supply, and historical water use provided by the City. Existing reports and information may include, but not be limited to:
• OLWD Water System Master Plan (March 2019)
• Relevant maps and inventory data
• GIS electronic data files
• Water billing records (5 years, if available)
• Groundwater quality data
• Groundwater pumping data
• As-built drawings
• Historical pump test data (if available)
• Identified O&M issues
• Available information regarding system condition
ATTACHMENT 4 Exhibit "A"
HydroScience will review estimates developed in the Water Master Plan for existing and future demands, taking into consideration the buildout potential of the community. HydroScience will review and update as necessary the average day demand (ADD) and maximum day demand (MDD) estimates for existing and future conditions.
Existing and future demand estimates will coincide with the planned timeframes for the City’s Master Plan. Water demand estimates for the OLWD service area have been represented as water use factors by customer type in the current OLWD Water Master Plan. Those will be cross checked and confirmed against the water use factor estimates developed for the City. Resulting water demand estimates will be incorporated into the Master Plan.
Assumptions
• HydroScience will not conduct a separate hydraulic model calibration for the OLWD service area and will instead rely on the calibration of the City’s system • HydroScience will confirm water use factors and demand projections developed in the OLWD Water System Master Plan to the extent that the use factors are reasonable relative to similar customer types.
Task 2 – Model Scenarios: If possible, the OLWD model will be imported into the City model.
Otherwise, HydroScience will build the OLWD infrastructure into the City potable water hydraulic model and develop scenarios to represent ADD and MDD. If necessary, the OLWD portion of the model will be populated with the baseline water demands (i.e., ADD and MDD) on a parcel/meter basis, loading the nearest model node or pipe. Scenarios will be developed for extended period simulations (EPS) for the purpose of evaluating impact to the City system. Unless diurnal water use data is available for OLWD, it is assumed that similar peaking factors and diurnal patterns developed for the City of Manteca will be used to estimate peaking within the OLWD service area.
These scenarios will be run with and without OLWD water supply infrastructure (i.e. wells, storage, and treatment) to mimic fully incorporating the OLWD system into the City’s system and to mimic connection via emergency interties where each utility will operate their respective water supply infrastructure.
Model scenarios will mirror the scenarios developed for the City of Manteca Water Master Plan and will include:
• ADD – serves as baseline scenario
• MDD and PHD – applies peaking factors and diurnal patterns to the ADD to evaluate system operation on a peak summer day. Diurnal patterns applied to MDD will represent peak hour (PHD) during the EPS scenarios.
• MDD plus Fire Flow (FF) – used to evaluate adequacy of system to meet fire flow while maintaining residual pressure and velocities below criteria. Velocity criteria for emergency conditions will differ from MDD conditions to prevent oversizing. • Water Age (Low Seasonal) – used to evaluate water movement and turnover in the system.
Conducted under minimum day or low seasonal demand conditions to capture worst case (longest water age). Dead-ends and oversized mains can increase water age and in turn affect water quality.
ATTACHMENT 4 Exhibit "A"
These scenarios will be designed as standalone alternatives. Each of the scenarios will be evaluated according to the same design criteria as those developed for the Water Master Plan and the City’s water system. The scenarios will be used to evaluate the impacts of absorbing the OLWD service area into the City’s system. A discussion of the impacts of each scenario on the system along with maps identifying pressures and flows throughout the system will be provided.
HydroScience will identify any hydraulic deficiencies resulting from the hydraulic modeling and the improvements needed to address those deficiencies.
Assumptions
• It is assumed that the existing OLWD model is populated with demands and scenarios to represent MDD, MDD plus FF, and PHD but may not include a diurnal curve for modeling EPS scenarios.
• Results of these modeling scenario analyses will be integrated into the network and system design alternatives technical memoranda (TM).
• Alternatives selected by the City for implementation will be presented in the Water Master Plan.
Task 3 – OLWD Facility Assessment: This task is a desktop assessment of the supply, storage, and treatment facilities. HydroScience will review available information for the OLWD system including as-built drawings, pumping records, water quality data, available well pump test data, and any operational or physical deficiencies identified by OLWD operators. This data will form the basis for assessing the feasibility to integrate the existing supply, storage, and treatment facilities into the City’s system from an operational perspective. The assessment will consider the capacity, quality, reliability, and robustness of the existing facilities.
Additionally, HydroScience will identify facilities necessary to connect and integrate the OLWD water system, including tie-in facilities (i.e. pipelines, valves).
The assessment will be summarized in a TM. Recommended improvements will be incorporated into the Master Plan.
Assumptions
• This assessment is not intended to evaluate the condition of the facilities and will not include an onsite condition assessment. It is assumed that existing documentation and operator feedback will be adequate for assessing the feasibility to integrate OLWD facilities.
Deliverables:
• OLWD Facility Assessment TM – Draft and final
ATTACHMENT 4 Exhibit "A"
Project Schedule and Budget
The schedule to complete this work will align with the development of the Water Master Plan. The total not -to-exceed fee to complete this scope of work is $26,000.
We appreciate the opportunity to provide these additional services. Should you have any questions regarding this proposal, contact me at (530) 848-3938 or [email protected].
Sincerely yours,
HYDROSCIENCE ENGINEERS
Curtis Lam
Principal
ATTACHMENT 4 Exhibit "A"