Frank Filice
San Francisco Department of Public Works
1 Dr. Carlton B. Goodlett Place
City Hall, Room 348
San Francisco, CA  94103

Dear Mr. Filice:

Thank you for your presentation to the Lake Merced Task Force in early June.  It brought to mind a long standing concern of The Golden Gate Audubon Society about the use of rip-rap for erosion at Lake Merced.  While concurring there may be places rip-rap seems to be an acceptable means of erosion control, such as the shoreline along Skyline Blvd. just north of Harding Rd., there are other sites where we believe other alternatives might be more desirable.

We have several concerns with the use of rip-rap.  First is its negative habitat value.  It eliminates plant growth and provides no positive value to native plants or wildlife. Our next concern is that it appears to do little to solve the flooding problem, and its use so far, except at the Harding Rd. site, has done little to solve the erosion problem.  Finally, it is unsightly.

We also believe the recent use of rip-rap has not been well planned.  It seems to have been used as an expedient and relatively inexpensive erosion control.  Its use so far has been a repeated failure.  

There are several reasons of which we are aware that cause severe erosion at Lake Merced.  Flooding from the streets is certainly the most obvious.  There have been cases of incredible levels of rainfall that have overwhelmed gutters that run into the lake and the sewage system that carries water and sewage from elsewhere in San Francisco and Daly City.  Then there are cases of poor engineering. Such was the case with the recent fairway construction at Harding Golf Course and with the construction of the handicapped access at the picnic area by the Boathouse.  There are cases where the City simply failed to do the work necessary to prevent erosion, such as the recent pier site at the southwest corner of the South Lake.  The permit application to the California Department of Fish and Game stated the site was not subject to flooding.  That project was necessary in the first place because of flood damage to the existing pier that was the result of a flash flood that overwhelmed the existing drainage system, that in turn poured tons of water, mud and debris onto the old pier.  That was an engineering shortfall.  Finally there is the matter of large trees on steep slopes.  Most of these grow on the Harding Park edge of the lake.  When they fail they bring tons of sand and organic material into the lake.

The only real long-term solution to this problem is to develop an erosion control plan for Lake Merced.  It should pinpoint each and every potential erosion site and rate them for potential impact on the lake and the surrounding infrastructure.  That could be done as a component of the proposed Recreation and Park Department Master Plan for Lake Merced that has been stalled because of budget limitations.

For the long term we believe the DPW and PUC should make every effort to use alternatives to rip-rap.  The use of natural plant materials is what we view as the preferred alternative.  In fact, if you consider the last flood at the south end of the lake, the only shoreline that held up was protected by mature willows and by freshly planted vegetation that was held in place by netting.  That seems to have held the soil down and allowed the water to flow over.  There were several points where it was apparent flood waters swept through the willows, but did not take them out.  The only other banks not damaged by the flood were some of those most recently planted.  It seems to us that use of vegetation worked as well or better than the rip-rap that has been dumped along the lake’s shoreline.  We can only wonder how it would have held up if it were several years old and if it were planted according to an engineering plan to reduce the erosive impact of flood waters.  

We think another course of action would be to engineer a means of disbursing the flood waters.  This might include increasing the number of drains into the lake along the most flood prone areas of Lake Merced, connecting more street drainage to the sewage system beneath John Muir Dr., and contouring the perimeter path differently so additional low points could be created to diffuse flood flow into the lake.

Short term solutions should be undertaken immediately to provide for reduction of flash floods.  Plantings of willow and other shrubs and plants that have proven effective in reducing erosion should begin as soon as possible.  The planting plan should be developed by a qualified professional.  Another short term solution that needs to be implemented is to clean-up the drains and streets at Lake Merced.  Starting in October, John Muir Dr. and lower Lake Merced Blvd. should be swept weekly.  Storm drains should be checked monthly and kept open.  When we know major storms are approaching, the DPW or PUC should carry out visual inspections to assure drains in the areas most likely to flood are open.  Any rip-rap that is used should be placed in such a manner that it can be removed if an alternative long term solution is adopted.  When possible, rip-rap that is already in place should be moved and countoured to solve further near term flood damage.  We should set a goal to eventually remove most if not all of it.

The Vista Grande Canal is a particular problem that is the shared responsibility of Daly City and San Francisco.  The PUC has not had trucks cited and removed from a City owned site at the southern end of John Muir Dr.  The result is that the area has turned into an illegal corporate yard and dump.  That refuse flows into the Vista Grande Canal from property owned by the City and County of San Francisco, and therefore does not seem to be the primary responsibility of Daly City.  The site was originally leveled for use as a temporary corporation yard for media vehicles during the most recent U.S. Open held at the Olympic Club.  Following the event, the site was abandoned.  Eventually truckers found it and started using it.  That site needs to be cleaned up, and a berm should be erected to block access.  Until it is, the Vista Grande Canal is more likely to be plugged by debris, and the flow of water from the canal into the ocean and into the lake is more likely to be polluted.  We understand the Olympic Club has complied with a request to remove some vegetation that might fall into or across the canal.  Now is the time for the San Francisco to do the same.  There may be other issues with the canal that are solely the responsibility of Daly City.  Proper management of the Vista Grande Canal is both a near term and long term solution that must be incorporated in any and all planning for erosion control.

Finally we suggest that the DPW and PUC contact soils engineers, hydrologists, or other professionals who might provide additional resources that are necessary to develop both long and short term solutions to this problem. Greg and Rachel Kammen are local professionals who come to mind.  They can be reached by e-mail at  HYPERLINK "mailto:greg@kammanhydrologiy.com"
greg@kammanhydrology.com or  HYPERLINK "mailto:rachel@kammanhydrology.com"
rachel@kammanhydrology.com
By way of background, Rachel is a hydrologist presently consulting on the Bolinas Lagoon Ecosystem Restoration Project.

We hope this letter provides you with some helpful ideas that will enable us to maintain habitat values and aesthetic quality at Lake Merced while effectively reducing the impacts of flood and erosion.

Very truly yours,

Dan Murphy
Conservation Committee
 HYPERLINK "mailto:murphsf@yahoo.com"
murphsf@yahoo.com

Cc:  Greg Bartow
Arthur Feinstein
Elizabeth Murdock
Bob Bennett
Nancy Smith
Mondy Lariz
John Plummer
Yomi Agunbiade