Lake Merced Task Force
Water Committee Report
January 10, 2001
Major Findings
Lake Merced is a surface manifestation of the underlying Westside Basin Aquifer. Over-pumping of the aquifer is the major reason for the lake’s alarming deterioration and declining water level and quality. There is a hydrologic connection between the lake and aquifer resulting in an ongoing imbalance between the amount of groundwater being removed from the aquifer and the amount of water being recharged or replaced into it. Over-pumping has a measurable and negative impact on the lake’s beneficial uses – natural habitat for fish, birds and wildlife, recreation, scenic values and as an emergency potable water supply. Continued over-pumping of the aquifer will threaten the very sustainability of Lake Merced. The Water Committee strongly believes that sufficient technical data exist to support its Major Findings.The following two recitals in the May 1995 San Francisco Public Utilities Commission Resolution 95-0082 (attached) support the Water Committee’s Major Findings:There is evidence that continued over-pumping of the Westside Basin Aquifer could cause saltwater to intrude into this underground water resource. This too could have potentially dire consequences for peninsula domestic water users because contaminated water in an aquifer does not readily cleanse itself.
To restore these badly degraded resources will require rapid implementation of an integrated water resource program involving conjunctive use of surface water, groundwater, storm water, and reclaimed water, and changes in current water management practices.
“Whereas, Lake Merced is a surface expression of the Merced groundwater aquifer (also know as the Westside aquifer) and the water level in Lake Merced is influenced by the pumping of groundwater from the Merced basin; andWork Conducted"Whereas, the water level in Lake Merced has declined precipitously since 1987, and the best available scientific evidence indicate that the cause of the decline is groundwater pumping by the Olympic Club, the San Francisco Golf and Country Club, the Lake Merced Golf and County Club, the City of Daly City, golf courses and cemeteries in the Colma vicinity, the California Water Service Company in South San Francisco, and the City of San Bruno, among others, coupled with increased urban development which has reduced groundwater recharge, the 1987-92 drought and a lack of inflow to the lake itself.”
The Water Committee reached its Major Finding through the following:
· Reviewing numerous technical reports and memoranda prepared by water experts and local agencies, policy statements, San Francisco Board of Supervisors and Public Utilities Commission resolutions, environmental impact reports, and other technical references (see “Data” at http://www.lakemerced.org, the Friends of Lake Merced web site);The Committee began its work with a review of the 1998 report “Feasibility Evaluation of Alternatives to Raise Lake Merced.” The Committee determined that these alternatives would not fully meet the restoration goals or ensure the long–term viability of the lake and the underlying aquifer. Further investigation drew the Committee to the inescapable conclusion that the health of the lake is directly related to the health of the Westside Basin Aquifer. In fact, this view has been validated repeatedly by numerous technical experts, including State water officials, who generously volunteered their time to our project.· Convening a Peer Review Panel and Technical Advisory Group composed of senior State water officials, consultants, and academics to provide a “reality check” on the numerous technical studies reviewed by the Committee; and
· Holding meetings with the San Francisco Public Utilities Commission and Daly City staff, local golf courses, and members of State water agencies.
It is obvious that, over the years, significant amounts of money and time has been spent by various parties on technical experts who studied Lake Merced and its relationship to the Westside Basin Aquifer. At this point, more studies and collection of data are not nearly as important as taking urgently needed common sense steps.
The Water Committee notes that there has been little discernable movement to implement any of the proposed programs to protect Lake Merced and the Westside Basin Aquifer, especially the programs described in the San Francisco Public Utilities Commission Resolution 95-0082. With exception of a proposed study of the Vista Grande Canal storm water diversion project no other work on the 1998 alternatives has been undertaken.
Nor has there been any to change in the present business-as-usual water management practices that permitted the degradation of these environmentally sensitive and valuable resources. Lastly, the lake and aquifer’s beneficial uses are jeopardized by the failure of various agencies to fulfill their public trust responsibilities.
Status of Lake Merced
Lake Merced is the proverbial “canary in the coal mine” for the Westside Basin Aquifer. It is providing unmistakable warning signs as to the stressed condition of the aquifer and imbalance in the groundwater water budget. Senior State water officials and other water resource professionals we consulted all concur with this view.
Unless water management practices are changed drastically, and soon, we should expect that Lake Merced water levels and water quality to continue an irreversible decline. This will ultimately lead to the disappearance of Lake Merced as a community resource. The evidence for this includes the following:
· The water levels at Lake Merced have not recovered to their historic levels of 25 to 27 feet (as specified in the San Francisco Public Utilities Commission Resolution 95-0082). The water level continues to fall in spite of several years of above-normal rainfall. The lake’s long term water level equilibrium has been disrupted by over-pumping of the aquifer.Lake Merced’s impaired water levels and quality are surface manifestations of the stressed condition of the Westside Basin Aquifer. The lake’s impairment harms its beneficial uses - habitat for fish and wildlife, scenic values, recreation and emergency potable water supply.· The lake’s current water level of 17 to 18 feet has eliminated the temperature gradient necessary to sustain a cold water habit. Measurements confirm water temperature is generally rising, especially at lower depths.
· Significant oxygen depletion at depths greater than 10 feet means that the lake cannot sustain a healthy fish population. Measurements confirm the lake’s dissolved oxygen levels are at unacceptably low levels.
· Rising levels of ammonia runoff into the lake promotes the growth of algae that, in turn, decreases dissolved oxygen, a process called eutrophication. Measurements confirm increasing concentrations of ammonia.
· According to measurements taken by the PUC, Lake Merced is less than half its historic volume. The lake today is approximately 2,991 acre feet, significantly less than the historic volume of 5,375 acre feet. This precipitous
reduction in volume means that the problems of temperature, oxygen and ammonia levels and other lake deterioration factors accelerate.· The PUC also stated that quantity of emergency potable water available for domestic use, or fire fighting has been substantially reduced from nearly a 10-day supply to only 4 days.
Saltwater Intrusion
Wells in the vicinity of Lake Merced and near San Francisco International Airport are showing gradual increases in chloride ion concentrations -- a frequent precursor of saltwater intruding into an aquifer. Aquifer saltwater intrusion is a growing problem in California threatening domestic, industrial and agriculture water supplies. It results from over-drafting a freshwater aquifer that is adjacent to a saltwater body. Saltwater intrusion is very costly to contain and virtually impossible to reverse.
A lack of data collection, including water quality measurements, from existing monitoring wells near Lake Merced and at other locations throughout the region of the Westside Basin Aquifer means that the aquifer’s long-term health cannot be evaluated. Westside Basin Aquifer saltwater intrusion could threaten the quantity and quality of domestic water for users on the peninsula.
Recommendations
It should be noted that certain parties disagree with the conclusions contained within the Major Findings of this report. However, all parties agree on the need for an integrated water resource program that governs surface water, storm water, groundwater, and recycled water use in the Westside Basin. An integrated water resource program should be implemented to protect Lake Merced and the Westside Basin Aquifer. The program should protect the water quality and quantity and enhance beneficial uses, and it may forestall potentially expensive environmental remediation. The program shall govern overall water management and use in the region of the Westside Basin Aquifer.
The goals of a specific, enforceable and expeditiously implemented integrated water resource program shall be:
1. Raising water levels in Lake Merced to 25 to 27 feet (as required by San Francisco Public Utilities Commission Resolution 10.435 dated January 30, 1950) while taking into account impacts on the natural habitat, if any, that might result from raising the lake’s level;The elements of an integrated water resource program should include the following:2. To restore the Westside Basin Aquifer to a level that will eliminate the imbalance between the amount of ground water being removed and the amount of water being recharged to the aquifer; and
3. To implement water management practices that will restore, enhance and sustain the long-term beneficial uses of Lake Merced and the Westside Basin Aquifer.
· A. No later that April 1, 2001 implement the 1996 Memorandum of Understanding between the San Francisco PUC, Daly City, and the Olympic Club, San Francisco Golf and Country Club and the Lake Merced Country Club. Within 18 months of implementation, these irrigators shall complete conversion to a recycled water program that will reduce golf course use of well water by at least 90%;The Water Committee would support legal action by the San Francisco Public Utilities Commission or others to enforce implementation of an integrated water resource program or other actions and programs that will ensure restoration and maintenance of Lake Merced and the Westside Basin Aquifer’s beneficial uses.· B. No later than June 1, 2001, the San Francisco Public Utilities Commission shall implement a conjunctive water use program with other irrigators or other surface, ground and reclaimed water users (e.g., Daly City, City of San Bruno, California Water Service Company, Colma cemeteries and golf courses, San Francisco Recreation and Park, San Francisco Fire Department and Zoo, Golden Gate National Recreation Area) through amendment of existing water contracts and other actions as deemed appropriate. A conjunctive water program is an agreement to manage surface water, groundwater, storm water, and reclaimed water supplies. It will help increase the reliability of local water supplies, particularly during droughts; protect the Westside Basin Aquifer from salt-water intrusion; and restore water quality and levels for Lake Merced.
· C. No later than September 1 2001, the San Francisco Public Utilities Commission, Daly City, along with San Mateo County and as necessary, other jurisdictions shall implement a program to recharge the Westside Basin Aquifer via injection wells using locally available tertiary treated (reclaimed) water that meets all appropriate water quality standards for injection of recycled water into an aquifer.
· D. No later than April 1, 2001, the San Francisco Public Utilities Commission and other water agencies or companies shall regularly assess the condition of the Westside Basin Aquifer through a network of monitoring wells including measurements of water quality, chloride ion concentrations, especially along Ocean Beach and the Bayshore.
· E. Effective immediately, the San Francisco Public Utilities Commission and Recreation and Park Department shall regularly monitor and evaluate impacts to Lake Merced’s water quality posed by issues such as the over-the-lake sewer pipe, surface water run-off,
· F. The integrated water resource program shall affirmatively state that the use of Hetch Hetchy water to raise Lake Merced is poor public policy.
In addition, the San Francisco Public Utilities Commission shall provide the Lake Merced Task Force with information regarding:
1. Diversion of Vista Grande storm water into Lake Merced has been proposed. But the water quality issues surrounding this proposal are not well documented. This will require measurements of turbidity (including total and dissolved suspended solids), bacteria and other water quality parameters. An evaluation should be made whether the diversion of Vista Grande storm water will adversely impact the Lake Merced’s status as an emergency potable water supply.Summary2. The rupture of the over-the-lake sewer pipe, especially a seismic event, could catastrophically impact Lake Merced’s emergency potable water supply and wildlife habitat. An engineering evaluation of the sewer pipe’s integrity shall be made as well as an investigation into its relocation.
To overlook the negative impact of over-pumping of the Westside Basin Aquifer would seriously undermine the goals of the Lake Merced Task Force. Most importantly, ignoring the overdraft of the aquifer will perpetuate environmentally unsound water management practices. The failure to act on the Major Finding and the Water Committee’s recommendations will jeopardize domestic water supplies for future generations as well as ensure that Lake Merced will inexorably continue to deteriorate.
Prepared by:
Lake Merced Task Force - Water CommitteeCo-Chairs
Dick Allen, Golden Gate Heights Neighborhood Association
Tim Colen, Greater West Portal Neighborhood AssociationJohn Plummer, Friends of Lake Merced
Dick Morten, San Francisco Planning and Urban Research Association (SPUR),
Jerry Cadagan, Committee to Save Lake Merced
Carolyn Gates, SPEAK
Bud Wilson, West of Twin Peaks Central Council
Cat Woodmansee, Friends of Lake Merced
Jim Wood, Pacific Rowing Club
Bob Passmore, retired Zoning Administrator, City of San FranciscoDavid Dawdy, retired hydrologist, United States Geologic Survey – technical advisor
Tony Jones, PhD. Oceanographer – technical advisor
