Title
Golf Course Drainage Report by Public Works
Bod
To: Honorable Chair and Members of the Golf Commission
From: Dave Leimsieder, Acting Director, Recreation and Parks
Re: Recommendation to Receive Presentation of “Chuck Corica Golf Course Drainage, Project Technical Memorandum,” December 5, 2022
BACKGROUND
Two slough systems, the East Slough and West Slough, meander through the Golf Course carrying rainfall and irrigation runoff from the Golf Course and stormwater runoff from surrounding roads. The two sloughs eventually discharge into a retention pond near Doolittle Drive, where the water is pumped into the San Leandro Bay. Groundwater beneath the Golf Course is shallow and tidally influenced and also contributes to the volume of water in the sloughs, particularly in the downstream portions of the slough near the pump station.
Stormwater runoff from Harbor Bay Parkway is collected in storm inlets and carried to the East Slough in a City storm line. The West Slough has a much larger tributary area that is generally bounded by Island Drive, Oleander, Magnolia and Fitchburg. Flow enters the city storm system and eventually is discharged, as various points to the West Slough. Incidents of flooding in the residential neighborhoods adjacent to the Golf Course and on Harbor Bay Parkway, causing the road to be closed, prompted City staff to investigate the cause of flooding.
In February 2022, staff entered into agreement with Wood Rodgers, an engineering firm with expertise in hydraulic analysis and familiarity with the City’s storm system, to conduct a detailed investigation of the flooding and prepare their findings and proposed solutions in a technical memorandum.
Wood Rogers reviewed existing documentation, conducted staff interviews, field surveys, and condition assessments. Included as Exhibit 1 is the Technical Memorandum.
DISCUSSION
Flooding in the surrounding neighborhood and Harbor Bay Parkway are likely caused by accumulated sediment in the system. Sedimentation effects the ability of the slough system to drain runoff to the Golf Course pump station in three ways: reducing the slough’s hydraulic capacity, reducing the hydraulic capacity of the slough’s culverts, and blocking the storm outfalls discharging into the sloughs.
Wood Rogers recommends both immediate and next step actions. The immediate actions are listed in order of importance.
Immediate actions:
1. Remove sediment blocking the outfalls discharging into the sloughs.
2. Remove sediment from slough culverts.
3. Lower the Golf Course pump station “pump-on” elevation. Groundwater drains into the sloughs, reducing its hydraulic capacity. Lowering the pump-on elevation will continuously pump the groundwater out of the sloughs, leaving more conveyance and storage for runoff during storm events. This new pump station operation can be seasonally implemented in the winter, or before known rainstorms. During summer months, the pump station can be operated as it is now to keep standing water in the sloughs for aesthetic purposes.
4. Repair structurally compromised culverts. Like sediment-filled culverts, structurally compromised culverts have a reduced hydraulic capacity.
5. Install duck-billed flap gates at outfalls of storm sewers discharging into the sloughs. The flap gates will prevent sediment from collecting inside City-owned storm sewers, reducing the annual maintenance of the asset.
Next step actions:
6. Develop a Hydrologic and Hydraulic model of the Golf Course storm system.
7. Determine the impacts of climate change on system.
FINANCIAL IMPACT
The City’s stormwater fund incurred the cost to prepare the Technical Memorandum. There is no impact to the Golf Fund.
RECOMMENDATION
Receive Presentation of “Chuck Corica Golf Course Drainage, Project Technical Memorandum,” December 5, 2022
Respectfully submitted,
Erin Smith, Public Works Director
Exhibit:
1. Chuck Corica Golf Course Drainage, Project Technical Memorandum, December 5, 2022, prepared by Wood Rogers