Vista Grande Stormwater Diversion
Project
On February
23 we were invited to present our analysis of the Vista Grande
demonstration project data to the Regional Water Quality Control
Board. Attending on behalf of Friends of Lake Merced were David
Dawdy, Dick Allen, Mona Cereghino, and John Plummer, who made the
presentation.We demonstrated that there was a significant increase in E-coli bacteria levels during storms in which contaminated water was diverted into the lake (ppt slides), and described the errors in the consultant's analysis that led them to the opposite conclusion. David Dawdy has prepared a memorandum summarizing this material.
We also requested that the public notice and water quality monitoring protocols be tightened. Unfortunately, the project team seems not to be influenced by these findings, and is proceeding with their project as originally designed. We have written to Patrick Sweetland, Manager of Water and Wastewater Resources for the City of Daly City, asking that this protocol be reviewed.
The
Regional Water Quality Control Board has approved the Year 3 sampling
plan subject to two conditions. One of those is an agreement to
hold a meeting with community representatives, including Friends of
Lake Merced, to review the statistical analysis and to determine if
adjustments to the sampling plan are called for as a result of this
review.
Greg
Bartow, PUC water engineer, sent an e-mail to Keith Lichten at the RWQCB
confirming his understanding of the conditions under which approval of
the sampling plan was to be issued. (1/24/06) Keith Lichten responded with an
e-mail approving the sampling plan, but noting several additional
areas of concern that need to be addressed by the research team.
(1/26/06) The rainy
season is upon us, so it is time to start planning for the 2005-'06
diversion program. The sponsors of this project issued a "final"
plan on December 12. The program is to get underway this
month. So much for public input. Here are the relevant
documents: Water
Quality Screening Plan and Operational Guidelines, 2005/06 Wet Season, Lake MercedPilot Stormwater Enhancement Project (pdf). This is the proposal prepared by EOA Inc., a firm of consulting engineers. It might be a good proposal. Unfortunately, however, it is based in major parts on errors made analyzing the data collected during the past two years. Unless and until the researchers understand the nature of those errors and their implications we don't think that this demonstration project should be allowed to proceed.
Water Quality Screenng Plan, Comments
from Friends of Lake Merced (doc). We prepared a commentary
on the EOA, Inc. proposal that we sent to Keith Lichten at the Regional
Water Quality Control Board (12/13/2005). We asked Keith for an
independent, objective and professional review of our position on the
issues identified in our commentary. So far we haven't heard from
Keith. EOA, Inc. prepared a brief
response to some of our comments. (doc) Patrick Sweetland, Manager of Water
and Wastewater Resources for the City of Daly City, also wrote to Keith
Lichten, enclosing a copy of the EOA, Inc. response.
Basically Patrick's argument is that he has paid a lot of high-priced
talent to develop this program, that he doesn't need any input from the
community, and that he'd much prefer it if the Regional Board just
approved his plan without any further review. Were I trying to
defend the positions taken in the proposal I'd rather not have any
further review either (or is it too?).
The
Public Utilities Commission and the City of Daly City have issued a
final
report on the pilot study of stormwater diversion from the Vista Grande
Canal into Lake Merced. Unfortunately the researchers have made a
fundamental error, applying statistical methods not appropriate for
risk analysis, that will assure continued safe recreational use of Lake
Merced. We are posting this study here now, together with the
following support documents:
Draft
report from the Vista Grande research team. (pdf file,
9/15/05) Letter
to Patrick Sweetland, Manager of Water and Wastewater Resources, City
of Daly City, from Friends of Lake Merced, commenting on this draft
report. (9/16/05) Response to
this letter from the Vista Grande research team. (pdf file,
10/22/05) Letter
to John West,
Environmental Scientist at the Regional Water Quality Control Board,
from Friends of Lake Merced, commenting on the draft report.
(9/26/05) Response to
this letter from the Vista Grande research team. (pdf file,
10/22/05) Final
report from the Vista Grande reserch team (pdf file, 10/22/05) Comments on
the final report from Friends of Lake Merced. (11/04/05) Letter to Dr. Robert Cooper,
Professor Emeritus, UC Berkeley School of Public Health. Dr. Cooper served as expert advisor to this study. (11/29/05)
A
report claiming to describe the
success of this project (pdf) was presented at the 10th
International Conference on Urban Drainage, Copenhagen/Denmark, 21-26
August 2005. Authors of this paper include M.J. Casteel1, G.
Bartow, and S.R. Taylor of the San Francisco Public Utilities
Commission, and P. Sweetland of the Daly City water department.
We do not agree with the major findings of this report . 100% of
the difference between coliform counts in stormwater runoff and lake
water after diversion of stormwater into the lake is attributed to
riparian filtering, with no recognition of the effects of mixing and/or
coliform die-off. It is probable that these factors dominate the
observed differences in coliform concentration. The
pilot project, demonstrating the
potential for transferring stormwater from the Vista Grande Canal into
Lake Merced continues during the 2004-2005 rain season. Initial
data for four storm events has been collected and is available in an
Excel file here. When
the pilot project is complete we will post the final report here as
well.
The initial demonstration was
conducted February 25, 2004, during the
"100-year storm" that dumped an estimated three inches of rain on Lake
Merced in just one hour. In order to relieve some of the overload
on the Vista Grande stormwater canal a larger than planned amount of
water was diverted into the demonstration area, and into Lake
Merced. Tests taken at the various sampling sites on 2/26/04
demonstrated very high levels of both E-COLI and Enterococcus
bacteria. This necessitated a second sampling that was collected
on 3/3/04. In the intevening week the levels of coliform bacteria
had returned to acceptable levels, within the limit required for
noncontact recreation. An
Excel file containing flow data and coliform test results is available
here.The good news is that the lake is again safe for use by boaters. Unfortunately, while we're happy to report this outcome we are far from understanding the underlying causes. Much more study is needed to assure that this was not a fortuitous, but one-time phenomenon.
The
Regional Water Quality Control Board has approved this Plan,
and authorized the PUC and Daly City to go forward with the demonstration.
We are pleased that we were able to provide support for this project.
and authorized the PUC and Daly City to go forward with the demonstration.
We are pleased that we were able to provide support for this project.
A project is currently being developed
to test the feasibility of diverting stormwater from the Daly City's
Vista Grande Canal into Lake Merced. While we completely support
this
effort to capture fresh rainwater and put it to good use, rather than
sending it into the Ocean, we do have some concerns about this
program. Specifically, coliform contamination has been found in
this
stormwater, indicating a connection at some point between the
stormwater and wastewater systems. The purpose of the current
test is
to see if that coliform can be removed through natural screening
processes.
We want to assure that adequate safeguards are taken to protect public
health and safety.A revised Preliminary Water Quality Screening Plan
An
Addendum to the revised Plan
was submitted to the Regional Water
Quality Control Board February 4. The Regional Board then
approved this Plan, and authorized the PUC and Daly City to go forward
with the demonstration. We are pleased that we were able to
provide support for this project.
We have prepared
a new commentary on this Plan which was sent to Greg Bartow and
Patrick Sweetland (January 29). When they have had time to review
and respond this will then been forwarded to the regulatory
agencies with jurisdiction on this issue. Please let us know if you have
comments you would like to add. We have commented on the
revised and expanded plan in preparation for a meeting with the
RWQCB January 15, 2004. Greg Bartow and Patrick
Sweetland, writing on behalf of the project sponsors, responded to
the RWQCB report on January 12, 2004. The
Regional Water Quality Control Board has issued their report,
mirroring many of the issues and concerns described in our own
memoranda of October 21 and December 16.Information sources regarding Stormwater BMP
For more information about stormwater Best Management Practices (BMP) visit:
Urban Stormwater BMP Performance Monitoring (pdf)
International Storwater BMP Database
Preliminary Data Summary of Urban Stormwater Best Management Practices (EPA)
Stormwater Best Management Practices -- Harvard University
There are of course several web sites that provide useful background information about coliform contamination Here are a few:
Heal the (Santa
Monica) Bay
Vermont Department of Health
Washington Department of Health
CNA Environmental, Inc.
Vermont Department of Health
Washington Department of Health
CNA Environmental, Inc.
Engineering background for the current project
We have been provided monitor data collected from eight storm events last winter. These are available in an Excel file, together with some analysis of that data.
Some engineering information about this project has been made public. Briefly, a connecting pipe will be installed leading from the Vista Grande Canal on the South side of John Muir Drive to the shore of Lake Merced just East of the Pacific Rod & Gun Club. From that point 300 feet of perforated pipe will be laid along the upper edge of the lake bank. A map indicating the rough location and grading of this pipe is provided here (pdf file).
A swath of groundcover approximately 10 feet wide, largely wild blackberry, will be removed to make room for this pipe. The capacity of this pipe will be 10 cubic feet, or 78.1 gallons, per second. This translates into 20 acre-feet of water per day when this system is operating at capacity. This is effectively the same as unleashing 300 feet of rainfall in 24 hours on the cleared area; this is the reason for our concern about further erosion of this lake shore.
Additional engineering drawings indicating construction details have also been provided (drawing 1 and drawing 2). Frankly, we don't know how to interpret these drawings. If you have any questions please contact Patrick Sweetland, Manager of Water and Wastewater Resources for the City of Daly City. We are sure that he will be happy to answer your questions.
