LAKE MERCED: Initiative to Raise and Maintain Lake
Level and Improve Water Quality;
Task 3 Technical Memorandum, Draft for Public Review and Comment
The following constitute the comments of the Golden Gate Audubon Society
regarding the document named above. The Golden Gate Audubon Society
is a grassroots conservation organization with a membership in San Francisco,
Oakland, Berkeley and much of the rest of the Bay Area. Through our
field trips, newsletters, programs and public comments we have educated the
public, advised public agencies and documented the presence of birds and
mammals at the lake for 84 years. The Golden Gate Audubon Society is located
at 2530 San Pablo Ave., Suite G, Berkeley, CA 94702. Our telephone
number is (510) 843-2222.
We find this technical memorandum lacking in a number of ways. There
are numerous errors in identifying graphics that make it very confusing and
difficult to read. Failure to include a glossary for some of the technical
terms and abbreviations is another factor limiting the readability of this
document. For those reasons it should be rewritten and submitted to
the public in a corrected form. We believe there are substantive errors
such as the modeling discussion on page 34. Also, there are errors
of omission such as the failure to discuss treatment of chloramine in recycled
water. We have included a number of recommendations through the text
of our comments which we hope will add to the value of this document.
p. iii. Existing Lake Water Quality: The second sentence is of questionable
accuracy. We concur that the present water conditions result in algae
growth and poor habitat for some aquatic species, but certainly not all.
For example, present conditions seem to favor Clark's Grebe. It would
be best to mention a few aquatic species that are negatively impacted by
present eutrophic conditions.
It would seem appropriate to identify when eutrophic conditions would normally
occur at Lake Merced. When water levels were considerably higher, eutrophic
conditions did occur by late summer and during September and October.
It should be pointed out that increasing water level will only shorten the
period for conditions that result in eutrophic conditions.
The second to last sentence should be amended to mention that South Lake
is also larger than North Lake, and with considerably greater water volume
it has suffered a little less from high nutrient levels. It is likely
the geographic position of South Lake somewhat reduces nutrient levels.
p. iv. Groundwater: In the section discussed from p. iii it is stated,
"the conditions can be accelerated by the introduction of nutrients in stormwater,
groundwater, or other inputs." However in this section it is stated
that "Treatment of groundwater prior to discharge to the lake would not likely
be necessary as ground water in the lake area is assumed of similar quality
to that already discharging to the lake." This seems to be a contradiction.
Any groundwater released into the lake should be tested, monitoring should
be ongoing, and treatment should be made available if necessary.
GGAS RECOMMENDATION: p. v. We need to add an additional element
to thisdocument right here, before we get into the details of the memorandum.
Here should be added a statement regarding adaptive management. Details
of the adaptive management plan should be incorporated into the body of the
document and should focus at least on several indicators including water
quality, marsh healthy, bird life, health of the fishery, studies of specific
insect species and other relevant indicators suggested by others.
p. 2. Once again we must question the reasoning behind the selection
of 26 feet as the optimal level for the lake. This may in fact be the
ideal level for the lake. It may not. This would be a good place to
identify the scientific reasoning used by Geo/Resources in determining this
as the best level for the lake.
p. 4 a) History: The document cited from Archaeological Consultants,
1981 is not cited in the Bibliography. That should be corrected.
p. 6: The "Impound Lake", as it has recently come to be known, was
never planned and it wasn't separated by the constructed of the concrete
bridge. To our knowledge the "berm" was constructed by wind and wave
action that caused drifting sand from the lake bottom to pile up around the
piers for the bridge. The original structure spanned the lake but allowed
water to flow beneath it. South Lake remained complete until the water
level dropped during the 80s. Water was deep enough on both sides of
the bridge to allow people to fish from it. This statement should be
p. 7, paragraph 1: The zoo still pumps water from the aquifer.
They just built new wells a few years ago.
Paragaraph 2, last line: It might
be better to use the term "birding" instead of "bird watching".
p. 9. ii) Topography: It would be helpful if a description of the vegetation
buffer between the perimeter path and the water's edge were included here.
p. 10. Geology: This first paragraph is unclear. Are you saying
the relationship between the Colma and Merced Formations generates interest
but there is no real knowledge about that relationship? It that's so,
it should be stated.
p.12. iii) Geology: The locations of the cross-sections
are not illustrated in Figure 3-1. There is no Figure 3-1. Not
only that, there is no such illustration under any number.
p.16. last paragraph: What does this mean? I take it to
mean the length of time a hypothetical H2O molecule stays in the lake before
evaporation or going into the aquifer.
p. 17. vii) Pathway and Trails: This is understated. A
trial connects the wood foot-bridge below the Sunset Circle to Harding Park
and public use is such that Harding Rd. is a foot trail and is supposed to
be formalized in the new Harding Golf Course project. There are several
formal and informal trails elsewhere around the lake.
viii) Boat Launch:
Actually there is boat launching is available into both North and South Lakes
via docks, ramps and informal access sites elsewhere.
ix) Fishing Piers: This is slightly
misleading. It should say the fishing pier at the southwest end of South
Lake is being replaced. This section too should identify all fishing
piers specifically. For example, the Hass Pier should be named and
the site should be identified simply to identify points of public access
to the lake.
x) Fishing Beaches: How did you
miss this? They exist now and historically at the North Lake below
the Sunset Circle, at the picnic area by the Harding Rd entrance and on the
south lake on both sides of the concrete bridge/sewer. This is critical
to include because like in ix) above, it identifies points of public access
to the lake.
P. 20 Physical Characteristics: The last 4 items at the bottom
of the page appear to be questionable. Our understanding of stratification
is that it is a desirable condition in a cold water lake because wind conditions
do not churn water below about 27 feet. Thus cold water remains deep
in the lake, fish such as trout can take refuge there, different organisms
exist there and it essentially adds to the viability of the lake. Also,
as one who uses the lake several times a week, it seems highly questionable
whether "extended calm conditions" exist at Lake Merced. There is seldom
a day without wind on the South Lake at least.
GGAS RECOMMENDATION: At this point it would be very positive to
discuss the matter of stratification. At what point does stratification
occur? Is it desirable? Without stratification, what are the
benefits of adding water to the lake? This is the point where a scientific
explanation for adding water to a specific range of depths should be made.
It seems the prior statement of 26 feet should be dropped in favor of a range
which can be sustained over an annual cycle. Note here we are not favoring
any specific depth, but a range which might simulate a natural cycle and
reduce the ongoing expense of constantly adding water and creating unnatural
p. 27. v) Trophic Status: Table 2-4 is the wrong table.
I guess it's supposed to be 2-3. Did anybody proof read this document?
The last sentence of that first paragraph is very unclear. "An order
of magnitude" means nothing to me, and I would suggest it means little to
many others. Perhaps a different descriptor could be used.
GGAS RECOMMENDATION: This brings to mind a constant problem with
this document, there is no glossary. If public review is welcomed,
the document should be written in such a way that the general public can
understand it clearly. How many people might understand terms like
"dissolved oxygen", "order of magnitude", "trophic", or "eutrophic" to name
only four. Addition of a glossary would certainly increase the readability
of this document.
p. 29. e) Water Quality of Existing Inflows: Section 4b is not on pg.
43 but it is on pg. 42.
The last paragraph states: "Lake Merced is presumed to be directly connected
with the shallow aquifer system." Presently, at what level of certainty
are we? What would it take to confirm or refute this?
Then the paragraph goes on, "Ground water thus represents a significant nitrogen
source that can exacerbate eutrophication." Doesn't this suggest we
can't use ground water to enhance lake water? If we can it would seem to
require treatment. That contradicts previous statements. We need
p. 34. i) Model Results: The paragraph that begins "Total volumes:"
suggests that water increases will take place over a single year. That
is not part of any plan of which the Golden Gate Audubon Society is aware
and we would like to know the origin of the plan and just how it will be
accomplished in terms of habitat protection. Since the Department of
Fish and Game and GGAS have long stood for a graduated raising of lake levels,
not unlike what has happened in the past year, I must say we are quite stunned
to see reference to a model that adds the maximum amount of water in a single
year. On looking at Tables 4-3 and 4-4 we find we were misled once
again. Tables 4-1 and 4-2 seem the correct tables and they seem to contradict
the whole reason for our concern. Just what is going on here? The text states,
"These figures show that after the first year of water addition less supplemental
water is required to achieve equivalent lake level increases. Less
water is required because the first year included the initial raising of
the lake level and subsequent years require a smaller lake level increase."
That certainly seems to say lake level is going to be raised all at once
and then maintained. Further, it does not seem to be supported by Figure
4-1 and 4-2. Perhaps this is just an error in editing and can be changed
in a subsequent report. Otherwise the model in question will require
major mitigation that should be discussed at this point.
p. 41. ii) Vista Grande Stormwater: First paragraph =AD not Table
4-6 and 4-7, but Table 4-8 and 4-9? Do you really get paid for doing
p. 46. v) Summary: This summary should be substantive.
p. 51 b) Response of vegetation to rising water levels: One modeling
reference that could be used to suggest revegetation patterns would be to
reference historic photos. This might suggest areas where mitigation
is possible and others where it is not. The lake's edge was completely
altered with construction of Skyline Blvd. and Harding Park in the late 20's
and with subsequent efforts to increase water volume. The marsh was
removed at one point and reestablished itself naturally. The pattern
of that reestablishment should prove valuable in mitigating impacts of increasing
GGAS RECOMMENDATION: A significant factor related to vegetation
around the lake is the buffer zone between the perimeter road and the open
water. This is an significant habitat consideration because increased
water levels will reduce and alter wetland and upland habitats. It
needs to be modeled so we have a better sense of potential impacts.
p. 54. a) Recycled Water: Where would the treatment wetland for
nitrate removal be? What would it's impact be on wildlife?
This section is incomplete. There is no mention of treatment of water
for chloramine. Once local water is chloraminated, it can no longer
be directly pumped into fresh water lakes. We understand the reason
for this is that the ammonia in this chemical doesn't breakdown or evaporate.
Recycled water would seemingly still need to be treated to eliminated residual
GGAS RECOMMENDATION: Add the necessary section regarding the treatment
of recycled water to rid it of residual chloramonia.
p. 57. d) Westside Basin Groundwater: In reference to the second
bulleted item, please see our comments regarding p. 29. Just how can
nitrogen enriched water be placed in a eutrophic lake and not "exacerbate
eutrophication" without treatment. We can't have it both ways, which
one is it so we can comment.
The last bulleted item on this page need much more development and discussion.
This concludes the comments of the Golden Gate Audubon Society.
Daniel P. Murphy
2945 Ulloa St.
San Francisco, CA 94116