Town experimenting with less costly solutions
By Michael S. Hoey
Correspondent
Delavan Town Board Chairman Ryan Simons announced Aug. 22 that the Delavan Lake Sanitary District has been experimenting with pellets and floc logs in Delavan Lake in an effort to find cost effective ways to keep the lake clean.
Former Lake Committee members Don Holst and Dan Lemanski spoke to the Lake Committee on Sept. 6 and advocated dredging the Mound Road ponds instead.
The Mound Road ponds were last dredged 10 years ago, according to certified lake professional Peter Berrini, who has worked extensively with Delavan Lake. The ponds filter sediment that enters the lake from Jackson Creek. Berrini said their job is to slow down the flow of water enough so that sediment remains in the ponds rather than flowing on to the lake. When the lakes get too shallow, they need to be dredged because they can no longer slow down the flow enough.
Simons said the pellets and floc logs are two ways to remove sediment and phosphorus from the lake. He said the test locations have been in the lake, not the Mound Road ponds. He said neither option would be effective in the ponds where there is no water flow. Simons said he agrees the ponds are full but dredging them would only prevent further sediment and phosphorus from entering the lake. Dredging would do nothing to address what is already in the lake.
Simons said, if money were no object, all areas that need dredging including some areas in the inlet, in front of Lake Lawn Resort, Brown’s Channel and the outlet, would be dredged and then the lake would be monitored and the use of pellets and floc logs could help maintain the investment in the lake as long as possible. Simons said that is not financially feasible and the town must answer to the taxpayers and conduct a cost-benefit analysis to determine if the use of pellets and floc logs, which have been approved by the Environmental Protection Agency and the Department of Natural Resources, could help delay costly dredging.
“The lake committee and the DLSD are doing as much due diligence as we can,” Simons said. “We are working together to find cost-effective solutions.”
Holst said he is not sure the two methods were applied correctly. He said he believes the pellets were just dumped into the lake in June, measurements were taken, and then more measurements were taken in August that might show faulty data as a result of the huge rain event that hit the area July 12. Berrini said huge rain events can move sediment around, making those measurements inaccurate.
DLSD Administrator Jim DeLuca agreed the rain event may have affected the data and more testing might have to be done. He said it is too early to draw any conclusions from the data. DeLuca said the DLSD and the Lake Committee are still conducting the research.
“We are looking at every option possible to take care of the lake,” he said.
DeLuca said the possibility of dredging the ponds might be investigated this fall.
Holst said the pellets and floc logs rely on bacteria and enzymes to break down organic sediment, but they do nothing to break down physical things like rocks and sand. Berrini agreed. They both said pellets and floc logs would do little or no good in the ponds. Berrini said they might have some benefits in the lake itself under the right conditions, but only after the ponds have been dredged. He said he looked at those options as maintenance options, not as solutions to the overall problem. He also said some experimentation has been done with pellets in Brown’s Channel with no verifiable increases in water depth.
Holst said the real solution would be to dredge the ponds, which were as deep as 10 feet 10 years ago and are only 3 to 4 feet deep today. Berrini agreed and said he recommended in a report that was posted on the town’s website early in the summer making an area of the east pond even deeper than it was to better filter sediment.
Holst also said the floc logs need to be replaced frequently and as many as 45 at a time are needed. Berrini said bacteria and enzymes are typically more effective in area with high organic content and are not effective in still environments.
Holst said dredging the lake should be seen as an investment in the lake, a resource that the community depends on as a primary asset. He said a study done 15 years ago showed the lake brought $63 million a year into the community. Holst said he and Lemanski have been telling the Lake Committee since 2013 the ponds need to be dredged.
Berrini said the dredging has been put off for years and now is the time to get it done. He recommended dredging the ponds as soon as possible and then establishing a maintenance schedule that evaluates the ponds every two to three years. Berrini said he thinks experimenting with pellets and floc logs without dredging the ponds is a waste of money.
Simons said dredging the ponds could cost as much as $600,000. The testing that has been done with pellets has cost $10,000 so far and will cost another $30,000 annually after that. Simons had no cost estimate for floc logs because they are being utilized by the DLSD.
According to Berrini’s report, which can be found on the township website, floc logs cost about $200 each and would have to be replaced at least eight times a year at a cost of $5,400 per log each year.
Berrini said the use of pellets and floc logs might have some benefit in areas with more organic enriched sediment if sufficient dissolved oxygen is present. He said lakes that have seen such benefits have used a laminar flow aeration system and even then overall reductions in sediment were measured in inches, not feet, per year. Areas with primarily inorganic sediment could see less of a reduction. Berrini also said an accurate assessment of gains is difficult in areas with high flows where soft sediment can become agitated and re-mobilized.
Berrini said some sheltered areas of the lake might have organically enriched sediment where a test application might produce measurable results, but all indications are that aeration would be necessary to achieve optimum results. He said several lakes have experimented with aeration and bio-augmentation like pellets and floc logs and seen improved water quality and reduced algae growth, but those lakes were much smaller than Delavan Lake.
In the summary to his report, Berrini said the Mound Road ponds have been very effective at removing sediment. Since the last time they were cleaned out, Berrini said the north and east ponds have successfully retained almost 15,000 cubic yards of sediment that would otherwise have made its a way to the lake. Berrini recommended removing all accessible soft sediment at an estimated cost of $530,600. Berrini also recommended removing all carp from the ponds and surrounding areas because they contribute to the nutrient-loading problem by re-suspending bottom sediments and phosphorus, and they reduce aquatic plant density.
Berrini said the introduction of aerobic bacteria and enzymes in the form of pellets or floc logs might be effective in improving water quality overall, but he didn’t believe it would work in the ponds because of the low percentage of organic material there.
“Any pilot testing effort to utilize bio-augmentation should be considered only as a post-clean out management tool for future evaluation,” Berrini said. “Therefore, this alternative is not recommended for any initial pond restoration efforts as it has not been proven to eliminate or significantly reduce excessive sediment deposition.”
Simons said pellets and floc logs have proven effective. He said each can produce some negative effects, and that is why the town and the DLSD are experimenting to see if any negative effects would be realized in Delavan Lake. He said none have been seen so far. If benefits are seen and no negative effects are reported, Simons said the use of pellets and floc logs could be expanded. He said no timeline has been set to determine that.
“This has been the only action we have taken that has effectively reduced phosphorus,” Simons said.
Simons also said Berrini is in the dredging business and is entitled to his opinion, but the town and the DLSD must consider as many unbiased opinions as it can in finding cost-effective methods to keep the lake clean.
Berrini said he has substantial experience with planning and implementing lake dredging projects, and he is a recognized for that work regionally and nationally, but he disagrees that he is specifically in the “dredging business.” He said he is a professional geologist and a certified lake professional with the North American Lake Management Society with considerable experience in all aspects of lake management and restoration.
“I feel I can provide an unbiased opinion and always seek to find the most appropriate and cost-effective solutions for surface-water and groundwater related issues,” Berrini said.
