Water
Quality Assessment, Recommendations & Status
In
August of 2001 the board invited Bob Heideman of Aquatic EcoSystems to perform
an informal 'situation assessment' of
The
recommendations resulting from that review are presented below, along with the
current status of the Board's resulting actions.
Summary of Findings
·
· The lake has been responsibly managed. While there is always a difference of opinion about the best treatment options, the information, focus and treatment programs we have indicate good stewardship.
· Fortunately, the lake is fed by an enormous natural watershed area that is relatively free of structures such as houses and roads. This watershed acts as a natural filter.
· The water is perfect for good fishing.
· The lake appears to be 'overfed' with too many nutrients, which stimulate growth of weeds and algae.
·
Biggest issue in
· Despite the amount of muck, Bob's tests did indicate more oxygen in the water than expected at the bottom muck levels. While these readings were low, any oxygen in the lower levels is advantageous.
·
He would classify
· Our annual draw-down of lake level is very beneficial. The more bottom that is exposed the better. Interestingly, the benefit comes from dry conditions rather than freezing temperatures.
Recommendations
Description: A Nutrient Budget is a scientific analysis of
the composition of the lake water. Its
purpose is to analyze the amount and source of
nutrients coming into the lake that stimulate the growth of weeds.
Heideman stressed that without having this quantified diagnosis, we
can’t know where the nutrients are coming from and therefore can't know what
course of action will give us the greatest return on our investment. And without that data, each of us will
continue to champion our favorite theories about how to best maintain the lake.
Unwanted weeds and algae grow in lakes that are over-rich in
nutrients. The nutrients come from a number of sources. The recommended
procedure is to find out which source or sources are primarily responsible for overfeeding the lake, and (if possible) take action to
change the situation.
The 3 possible sources of nutrients are:
1.
Internal
nutrient cycling: muck
layer supports plant growth which in turn dies and contributes to muck layer,
releases new nutrients, reduces oxygen, etc.
2.
External: nutrients enter from surrounding watershed,
leaves, etc.
3.
Human: environmental factors such as fertilizer and
septic leachate.
Our present chemical treatment program attacks the weeds and algae
but doesn’t address the cause.
The
board has performed considerable research on how and where to obtain a Total Nutrient Budget and obtained
proposals for the analysis. A full
Nutrient Budget will cost in the range of $10,000 or more. We had originally hoped that a local college
would perform the analysis at a reduced cost as part of their limnology
program, but none of the schools responded to our inquiries.
Due
to the high cost of the Total Nutrient Budget, it was the Board's opinion that we should begin with a less extensive analysis to
simply establish a baseline of the lake's chemical and nutrient makeup.
This
test was performed in July of 2002 by '
The
board is currently evaluating a proposal to continue the testing at least twice
per year. This will provide a method to
track the nutrient levels, evolution and rate of eutrophication of the lake and, most importantly,
identify when key metrics fluctuate out of acceptable ranges.
Description: The North end of the lake is becoming
increasingly shallow, which in turn can stimulate plant growth. A portion of this sediment is swept into the
lake through Post Brook. A common
technique used by many lakes is to dig a 'sedimentation basin' at the point
where the stream enters the lake. In our
case, this would be either just before or just after the bridge. A sedimentation basin is simply a deeper pit
dug into the stream bed that will catch the sediment before it flows into and
gets distributed in the lake itself.
This works by slowing down the flow of the water (which allows faster
sedimentation) before the water enters the lake).
The advantages are twofold: first, it minimizes the amount of sediment
that enters the lake, and second, it is much easier and less costly to dig out
or empty the sedimentation basin as it fills in than it is to dredge part of
the lake. It would have the added
benefit of providing a 'draw point' for the fire department, and also give an
indication of the amount of sediment entering the lake from Post Brook.
Status: A suitable site has been selected (upstream
from the
Description: Grass carp are fish that feed on plants and algaes in the lake, apparently with a fairly prodigious
appetite. They are sterile and can not
reproduce, so there is no danger of an out of control population increase. While they live 10 - 14 years and can be
relatively large, they will not prey upon our existing fish population. They are used in relatively low concentrations
- probably in the range of 3 fish per acre (but only counting shallow/weedy
areas). They have been used in similar
situations in other states with very positive results.
Status: We have researched the application of grass
carp, and the appropriate number of fish to introduce. State regulations currently require a permit
to obtain grass carp, which to date have not been issued for bodies of water
larger than 5 acres (Lake Iosco is about 70 acres). This is a frustrating and irrational policy,
especially given the carp's very proven success in other states. Give the state regulations,
however, this does not appear to be an option at this time.
We
have also recently learned of a similar fish that has been introduced
successfully to other lakes in
Description: Copper Sulfate has been the primary chemical
treatment we have used for many years to treat algae blooms. 2 other chemicals, Sonar and Reward, have
been used to spot-treat weeds. While it
is reasonably effective in killing algae, it also kills the natural benthic
organisms (aquatic animals) that live in the muck on the bottom of the lake and
which are absolutely essential in breaking the cycle of algae blooms. Further, copper sulfate also leaves heavy
metal concentrations on the bottom of the lake.
(Fortunately, improved chemical media and application techniques have
allowed us to use very low doses of copper sulfate for years).
Bob's
recommendation is to switch to an improved version called chelated copper sulfate. Chelated copper
kills algae but is far less toxic to the lake bottom. It accordingly allows necessary benthic
organisms to live and reduce the muck layer.
Reduction in muck layer in turn results in less algae and weed
growth.
Chelated copper is
significantly more expensive than regular copper sulfate, but could conceivably
be used in lower concentrations with similar effectiveness. While there may be higher costs for chelated copper, the objective would be to maintain the
benefits of copper treatment while reducing or eliminating the negative
effects.
Status: The difference between the costs, dosage, and
effects of chelated vs. regular copper sulfate is a
fairly complex issue that we have and will continue to research. We are currently conducting research to get a
more definite picture of the potential dosage and costs compared to our current
use of regular copper sulfate. We are
hopeful that chelated will be an affordable
alternative.
Description: Fertilizers used to enhance lawns and shrubs
are one of the most notorious causes of weed and algae growth in the lake. Most people use generic fertilizers without
analyzing their soil to determine what fertilizer - if any - would be most
appropriate for their lawns. Some or
many lawns here may require no fertilizer.
Non-phosphorous fertilizers do exist that are not harmful to the
lake. However, it would still be
preferable to not use any fertilizers at all.
Status: The board advised residents of the problems with
fertilizer in a newsletter, and requested that 1) we all refrain from using any
fertilizer at all, and 2) if absolutely necessary to fertilize that you first
have a soil analysis performed to determine what specific nutrients are lacking
in the soil so that only the necessary nutrients be applied. The board is
considering providing this soil analysis service to people who fertilize if a
vendor can be found that will provide the service for a reasonable fee.
Description: Like fertilizer, septic systems are the
biggest external enemy to our water quality.
Even with relatively few houses, most of our septic systems are quite
old, and while there is no visible evidence of failure, it is quite possible
that nutrient-rich leachate is reaching the lake
water.
Status: All residents are asked to have their septic
systems inspected and emptied at least every other year. The inspection should include a probe of all
leach fields.
The
lake also plans to contact several septic companies in an attempt to arrange
for these inspections as a service to residents. This may be at the
Further,
education and awareness of septic conditions are essential. Contact a Board member if you have any
questions regarding routine care and maintenance of your septic system.
Description: The healthiest lakes are those with a
high degree of oxygen in the water.
Aeration systems are available that pump oxygen into the water through
the use of compressors and 'bubblers' or fountains. Aeration has the effect of compressing the
muck on the bottom, reducing algae blooms, and supporting a gradual improvement
of water quality over several years. It
generally works best in deeper lakes, although can be very effective in smaller
lakes and ponds as well. Their success
depends on the other nutrient factors involved with the body of water. There is an initial cost of about $10,000 and
annual operating costs of around $1,000.
Status: Heideman
recommended that we first complete the nutrient budget to determine whether
increased oxygenation will compensate for other nutrient loading factors. In the mean time, we have contacted other
lakes (including
Description: Alum sulfate is a one-time chemical treatment
that essentially forms a barrier on the bottom of the lake. It also removes phosphate from the water as
it sinks. The combined effect is to
limit weed growth and improve clarity.
Status: A nutrient analysis must be completed and
tracked for several years to determine whether this will be an effective
treatment for
Description: dredging involves the removal of all or part
of the lake bottom to eliminate the weeds and muck. It generally involves a very costly and
complex permit and extensive excavation.
Drying and disposing the removed material is complex and difficult. Spot dredging can be done on a much less
complex and costly basis, however.
Contrary to common opinion, dredging is not universally effective. It may be a wasted effort if other nutrient loading factors are in
fact the root cause of the muck and weeds.
Status: Full scale dredging is not considered to be
appropriate or realistic for