November 28, 1998

Joan Ryan, Engineer
San Francisco Public Utilities Commission
Bureau of System Planning & Regulatory Compliance
1212 Market Street, 2nd & 3rd Floors
San Francisco, California 94102

Dear Joan:

Thank you for sending a copy of the CH2MHILL Technical Memorandum, Feasibility Evaluation of Alternatives to Raise Lake Merced.  I have now had the opportunity to read this report fairly carefully.  It seems to provide a very good evaluation of alternative approaches to augmenting the natural water systems supporting Lake Merced.  I do, however, have a few questions:

1.  How do you know that any of these approaches will work in the long run?

As you know, Lake Merced is a natural lake, not a reservoir.  As such it supported itself for many centuries without human intervention.  However, as the Memorandum points out, “The Lake Merced area has undergone significant changes during the 20th century,” many of which have proven to be detrimental to the lake.  Previous attempts to correct this situation using infusions of surplus water have, again as the Memorandum states, “provided short-term benefits, but no sustained increase in the lake level.”  What is different about the current proposals?

 2.  Won’t the option selected, diverting storm water from Vista Grande Canal to the lake, aggravate rather than offset normal rainfall cycles?

Certainly one of the major changes brought about during the twentieth century has been the substantial reduction in the proportion of rainfall that benefits the lake, and the diversion of that rainfall to the Pacific Ocean through a system of storm sewers.  However, much of the impact on lake level was historically indirect, through the replenishment of the Westside Basin aquifer that supports Lake Merced, and not direct runoff into the lake.

I am not, as you know, a hydrogeologist.  But it seems to make intuitive sense that the aquifer would operate somewhat as a hydrological savings bank, collecting water in wet years and storing it to be used in dry years.  I would be surprised if the fluctuation in the level of the aquifer were as great as year-to-year changes in rainfall.  Again referring to the Memorandum: “The Lake is a part of a complex hydrogeologic system referred to as the Westside Basin. . . Past studies have indicated that the Lake is integrally related to the groundwater levels in the Westside Basin (USGS 1990, GWMPT TM-18).”

Rainwater runoff through the storm sewer system is, however, directly related to annual rainfall.  It would seem that relying on this runoff to support the lake would act as something of an amplifer, magnifying fluctuations in lake level as a response to annual rainfall.  Is this not the case?  And have the ecological implications of increasing the fluctuation in lake level been thoroughly evaluated?

3.  Doesn’t the health of Lake Merced ultimately depend upon maintaining proper levels in the Westside Basin aquifer?

Again, as indicated above, your own Technical Memorandum suggests as much.  And it suggests that this course is being pursued: “In an effort to address Westside Basin groundwater issues, with the additional benefit of considering the lake, the City has entered into a cooperative agreement with the other Westside Basin potable groundwater users to develop an AB 3030 Groundwater Management Plan.”  Yet Workshop notes issued by that consortium state that “the relationship between Lake Merced and the water table is relatively insignificant to the concern of pumping impacts on Lake Merced.”  They base this conclusion on a distinction between “direct” and “indirect” relationships, whatever that means.  However, the operative conclusion is clear: the users of the water drawn from the Westside Basin intend to pump away without concern for Lake Merced!

What is the SF-PUC, a member of this consortium, doing to correct this situation?

4.  Finally, what was the public input to the formulation and evaluation of these alternatives?

I for one was not aware that this study was being conducted, nor that a decision was forthcoming from the PUC that would have such a dramatic impact on the future of Lake Merced.  And while I have been out of the area for the past several weeks, other members of our group report that they had no knowledge of the PUC meeting adopting a plan for Lake Merced before it was reported in the Chronicle (November 25), and that the only public representative at that meeting was the attorney for the golf courses.

Unfortunately, it sounds like ‘business as usual’ at the SF-PUC.

Sincerely,

John Plummer

P.S.:
In the hope that it will spur additional public comment I am posting a copy of this letter to our web site (www.lakemerced.org).  If you will provide a copy of the Technical Memorandum in electronic format, as well as any relevant supporting material such as PUC meeting minutes, I will be happy to post those there as well.
JP

c.c.: Anson Moran, General Manager, SF-PUC
 Michael Carlin, SF-PUC
 Gavin Newsom, SF Board of Supervisors
 Patrick Sweetland, Coordinator, Westside Basin Planning Group