Fremont City Council Meeting: 03/04/25 07:00 PM
3300 Capitol Avenue Div/Dept: Environmental Services
Fremont, CA 94538 Category: Fees & Rates
SCHEDULED
Sponsors:
COUNCIL STAFF REPORT (ID # 5362) DOC ID: 5362 A
Updated: 2/27/2025 11:16 AM by Dina Lewis A Page 1
LAKE ELIZABETH WATER QUALITY IMPROVEMENT PROJECT - Approve $135,000 Budget Appropriation to Pilot Surface Aerators, Floating Islands, and Monitoring Probes for Improvement of Water Quality and Heat Event Resiliency in Lake Elizabeth
Contact Persons:
Name: Kathleen Cote-Guarnieri Dan Schoenholz
Title: Environmental Services Manager Community Development Director Div/Dept: Environmental Services Community Development
Phone: 510-494-4583 510-494-4438
E-Mail: [email protected] [email protected]
Executive Summary: In response to a large scale fish die-off event in July 2024, the City contracted with Applied Marine Science to conduct testing to determine the cause of the die-off and identify potential management actions to prevent or reduce potential reoccurrence.
Water quality testing conducted during and after the event determined the cause to be low dissolved oxygen concentrations and elevated lake water temperatures resulting from an extreme heat event. The testing indicated that a harmful algal bloom was not a factor.
While lake conditions have returned to normal, staff is recommending proactive steps to reduce the likelihood of die-offs during future extreme heat events. After evaluating a menu of potential options identified by Applied Marine Science, staff is recommending a $175,000 pilot program which would include the following elements:
• Three surface aerators for improved oxygenation $20K
• Nine floating islands for shade and temperature regulation $55k • Three continuous monitoring probes $10k
• Installation and labor $40k
• Project Management $40k
• Contingency $10k
The total estimated project cost is $175,000 with $135,000 funded from the Integrated Waste Management Fund Open Space account and $40,000 from PWC8501-501 (Parks Capital Replacement project). This appropriation would increase funding to an existing contract between Applied Marine Science and the City of Fremont, which the City executed in its capacity as Fiscal Agent for the Alameda Countywide Clean Water Program.
BACKGROUND: Completed in 1969, Lake Elizabeth is an 83-acre man-made freshwater lake designed for flood control and stormwater storage during the rainy season. The lake is owned by the Alameda County Flood Control and Water Conservation District (ACFCD) and licensed by the City for recreational purposes. The sections below provide additional background.
July 2024 Fish Die-Off: About 1,000 fish at Lake Elizabeth died during an excessive heat wave occurring July 3-6, 2024. As the heat event began, the City increased supplemental Council Staff Report (ID # 5362) Meeting of March 4, 2025 Updated: 2/27/2025 11:16 AM by Dina Lewis A Page 2
water to mitigate evaporation and rising water temperatures. Applied Marine Science was brought in to evaluate the situation and conduct water quality testing. Results from testing conducted during and after the event determined the cause of the die-off to be low dissolved oxygen concentrations and elevated lake water temperatures, which pushed fish species beyond the ranges they can typically tolerate. A dissolved oxygen level of 5.0 mg/L concentration is the standard target and Lake Elizabeth dropped below 1.0 during the event.
The microcystins analysis was negative, indicating that a harmful algal bloom was not a factor.
Routine Lake Maintenance: Routine lake maintenance activities conducted by the City include maintaining lake levels during the summer months with additional water from the irrigation system at Central Park, testing the water for bacteria monthly, and controlling the bird population which has the potential to present bacterial contamination. Annual bird population mitigation measures include the installation of goose fencing, enhanced clean -up on Duck Island and egg addling. The City also installs and removes the weir boards (controlled by ACFCD) at the connection of Mission Creek which impacts flow of water into the lake.
Lake Depth: Reduced water depth since the lake was last dredged in 2001 appears to have increased the July 2024 heat event impact on lake water temperatures. Lake Elizabeth’s historical maximum depth is 7’ at the deepest location. According to a 2023 bathymetric study and the 2001 construction documents for the dredging project at Lake Elizabeth, due to sediment accumulation the lake depth has decreased two to three feet, depending upon location. The western half of the lake towards the docks was not dredged in 2001, so it is generally shallower than the rest of the lake, especially at the western edges. ACFCD has no plans to dredge in the foreseeable future as ACFCD staff has advised the City that “flood protection is not affected by the current lake bottom elevations and therefore no sediment removal is warranted at this time.”
Regulatory Water Quality Considerations: The San Francisco Regional Water Quality Control Board (Water Board) oversees local municipal compliance with the Municipal Regional Stormwater Permit (MRP) and the San Francisco Bay Basin Water Quality Control Plan (Basin Plan). The Basin Plan identifies beneficial uses of local water bodies which for Lake Elizabeth include cold freshwater habitat, warm freshwater habitat, spawning, wildlife, water contact and non-contact recreation.
Fremont conducts many water quality compliance activities though its participation in the Alameda County Clean Water Program (ACCWP). As a member agency, the City has access to ACCWP contracted resources. The City was able to utilize ACCWP’s contractor Applied Marine Science to respond to this event. Applied Marine Science conducted water quality testing, incident analysis, and identified potential management actions that could mitigate reoccurrence. Action to prevent future die-offs will be necessary to ensure the City remains in compliance with the MRP and Basin Plan.
Integrated Waste Management Open Space Fund: The City negotiated a $500,000 payment for park open space projects as part of a 2006 Altamont Landfill Disposal Contract Amendment with Waste Management. An Open Space account within the Integrated Waste Management Fund (Fund 115) was established and has been used for park enhancement projects at Sabercat Historical Park and in Stivers Lagoon at Central Park. That account has Council Staff Report (ID # 5362) Meeting of March 4, 2025 Updated: 2/27/2025 11:16 AM by Dina Lewis A Page 3
a remaining balance of $135,000 which is available for implementing the recommended actions for Lake Elizabeth.
DISCUSSION/ANALYSIS: Applied Marine Science analyzed potential management actions to improve dissolved oxygen content in Lake Elizabeth and counteract the impact of heat events on lake temperatures, given current lake depth. The analysis focused on three components described below.
Oxygenation: Staff evaluated several types of shore-based oxygenation systems designed to pump oxygen to the bottom of the lake and determined these were not well suited to the site conditions of Lake Elizabeth and would have limited effectiveness. Aerators which mix water to introduce oxygen, reduce stratification, and discourage algae growth, are better suited to the size and depth of the lake. Options evaluated included surface aerators (both solar and shore powered), fountain aerators, and sub surface aspirators. The most effective system to deploy, given current lake depths, would be a Kasco shore powered surface aerator. A solar powered system, though less effective, would be an alternative if shore power cannot be installed.
Temperature: Possible management actions to improve lake temperature include floating islands, increasing freshwater inputs, and shoreline planting. Floating vegetative islands are approximately 5’ x 5’ and would be secured to the lake bottom. They have multiple benefits including temperature regulation from shade, plant roots that keep oxygen in the water column, and cleansing of lake water by nutrient absorption. Staff recommends installation of nine floating islands as part of the pilot program to be supplemented with future shoreline planting. The City would continue to utilize freshwater inputs as needed to respond to significant heat or evaporation events.
Monitoring: In conjunction with the installation of aerators and floating islands, staff recommends installing three continuing monitoring probes to monitor temperature and dissolved oxygen levels. This would enable staff to intervene if parameters are trending negatively. It will also enable the City to evaluate the effectiveness of the installed measures to maintain desired temperature and dissolved oxygen levels. The probes will require periodic downloads and occasional calibration by park staff.
The City would utilize ACCWP’s contract with Applied Marine Science to implement the recommended pilot program. Applied Marine Science has the capability to procure the selected elements and manage the installation. Electrical power installation for the aerators would be coordinated with the Maintenance Department.
FISCAL IMPACT: The proposed project would utilize the remaining $135,00 in the Integrated Waste Management Fund Open Space account and $40,000 from the Park Capital Replacement CIP project (PWC8501-501). Use of the IWM Open Space account would require a budget appropriation. No appropriation is needed for PWC8501 since there is adequate funding in the current year’s approved budget. Ongoing maintenance activities are expected to be minor and would be conducted by existing parks staff.
ENVIRONMENTAL REVIEW: This project is exempt from the California Environmental Quality Act (CEQA) pursuant to CEQA Guideline Section 15333 as small habitat restoration projects are exempt from environmental review. Staff has determined that the proposed project qualifies as a small habitat restoration project because it is under 5 acres, will have Council Staff Report (ID # 5362) Meeting of March 4, 2025 Updated: 2/27/2025 11:16 AM by Dina Lewis A Page 4
no significant adverse impact on endangered, rare or threatened species or their habitat, will not result in significant impacts when viewed in connection with past, present and future projects, and there are no hazardous materials at or around the project site.
ATTACHMENTS: None.
RECOMMENDATION: Appropriate $135,000 from the Integrated Waste Management Fund Open Space account to implement the Lake Elizabeth Water Quality Improvement Project as described in this staff report.