Lake Iosco

Water Quality Assessment, Recommendations & Status


In August of 2001 the board invited Bob Heideman of Aquatic EcoSystems to perform an informal 'situation assessment' of Lake Iosco water quality.The study was performed at no cost to Lake Iosco.Bob was on-site at Lake Iosco for about 6 hours and spent the majority of that time either in or on the water itself.Several Board Members and residents participated in an informal discussion with Bob at the end of the day to review his observations and suggestions.


The recommendations resulting from that review are presented below, along with the current status of the Board's resulting actions.


Summary of Findings

             Lake Iosco has better than average water quality, particularly for a lake that is this shallow (6 - 12 feet average depth) and the lack of rainfall this year (2001).

             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 Lake Iosco is the amount of muck on the bottom.Presence of muck means that here is not enough oxygen available to enable decomposition.Must have oxygen available to support benthic organisms that feed off of the nutrients.

             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 Lake Iosco as being in the very early stages of eutrophication (the inevitable aging of lakes which is marked by the reduction of fish and other aquatic organisms and the escalation of plant growth).All lakes gradually become eutrophic, but this may be slowed to a large extent through treatment options.

             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.




Total Nutrient Budget

Sedimentation Basin

White Amur Grass Carp

Chelated Copper Sulfate



Alum Sulfate




Total Nutrient Budget

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 canít 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 doesnít 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 'Lake to Tap' (professional lake consultants).The initial test was done as a courtesy and at no charge to Lake Iosco.The results were generally very favorable. Click here to see the full results and explanation of the findings.


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.


Sedimentation Basin

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 thelake).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 West Shore Drive bridge) to dig the basin and a contractor has been selected.The cost is expected to be relatively low.We are simply waiting for reduced water flow in Post Brook and contractor availability.


White Amur Grass Carp

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 New Jersey, the hybrid striped bass.We are presently investigating this option as well.



Chelated Copper Sulfate:

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 Lakeís expense or at least provided at a reduced rate.We hope to find a vendor that will perform the inspections at no charge based on the potential business generated from the probes.


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 Morse Lakes) who have implemented aeration systems to review their experience and satisfaction.


Alum Sulfate

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 Lake Iosco.We will continue to watch the results at other lakes with similar dynamics.



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 Lake Iosco.Spot dredging may be considered in the future based on the findings of the nutrient analysis and the effectiveness of other treatments.