ST. MARYS — A nationally recognized science firm has whittled down potential solutions that could help Grand Lake St. Marys.
Battelle recently unveiled a comprehensive, draft report that details its recommendations to help restore the water quality of Grand Lake St. Marys as well as how to limit phosphorus from entering the body of water. Earlier this year, members of the Grand Lake Restoration Commission tabbed the firm to review the more than 70 proposals it received regarding possible solutions to help the lake.
Battelle screened each of the 75 vendors and scored each to determine the feasibility of the solution. During the review process, Battelle met with lake officials to determine strategies to help the lake. Those included: reduction of external loading by source reduction or treatment, reduction of internal loading by removal or inactivation of phosphorus already in the lake’s sediment, aeration and circulation and algaecidal agents.
Battelle also recommended the following firms and solutions be explored further to address external phosphorus loading: alum treatment of tributaries, Thieman Enterprises LLC for manure solidification, NuVention Solutions Inc. for manure solidification, Amiran Technologies for manure solidification and SePro and Harsco Metals, North America, for steel slag.
The treatment of tributaries, as cited in the report, could help control the amount of phosphorus that finds its way into the lake.
“Treatment of streams to intercept and inactivate phosphorus loads from tributaries is recommended,” the report noted. “Inactivated phosphorus sediments could be captured in a settling basin or other discrete location where they can be efficiently and permanently removed. Alternatively, some portion of the inactivated phosphorus could be allowed to enter the lake where it may provide additional benefits by contributing to sequestration in the sediments or stripping phosphorous from the water column.”
The report also stressed the importance of tackling internal loading of phosphorus. Battelle officials encouraged the continuation of dredging and rough fish removal to combat phosphorus. The report also indicated additional alum applications could have an impact on the lake.
“Sediment removal is permanent, but will require a long time to accomplish,” the report noted. “Without effective reduction of external loadings, in-lake methods, including rough fish removal or alum applications, are unlikely to be effective. After external loadings into the lake are substantially reduced, lakewide alum treatments may be effective, but will need to be a much greater amount — only 12 percent of the alum dose required to inactivate the sediment phosphorus was added to the lake. Alum applications will need to be repeated periodically.”
The report also touched upon issues surrounding the spillway. While the report did not take into consideration specifics regarding the spillway because of ongoing litigation, Battelle officials noted removing water from the bottom of it could be beneficial.
“Release of water at the spillway from the bottom of the lake, rather than from the surface of the lake, will increase the concentration of phosphorus in the outflow,” the report noted. “This will increase the rate of export of phosphorus from the lake. The amount of phosphorus removed via changes in spillway release is expected to be small compared to the inventory in lake sediments.”
Aeration and improving circulation in open lake channels also could help in the process. For this, Battelle recommended the addition of more devices to increase water flow, including Airy Gators.
“Aeration/circulation in channels and coves may reduce algal biomass in eutrophic lakes,” the report noted. “The theoretical loss of ideal light conditions for the cyanobacteria and disruption of the ability of the cyanobacteria to aggregate in the euphotic zone appear plausible.”
For closed channels, Battelle recommended pumping lake water to the back of the channel. This process should flush out the channel.
“Another possible configuration could be to pump water from the back of one channel to the back of an adjacent closed channel,” the report noted. “Since the purpose of the pumping is to create horizontal movement and mixing, pumping water from the back of two adjacent channels would create inward movement in one channel and outward flow in the receiving channel.”
By implementing a multi-faceted approach, Battelle officials believe lake officials can successfully quell outbreaks of cyanobacteria.
“Reduction of external loading by removing phosphorus from tributaries, preventing internal loading from sediments, and rough fish removal provide a comprehensive approach believed most likely to end cyanobacteria dominance,” the report noted. “While lake phosphorus levels remain high, ensuring water column mixing throughout the lake is most likely to prevent cyanobacteria scum formation.”
To determine scalability and feasibility, Battelle suggested several pilot projects take place around the lake.
“If these methods are cost-effective and can resolve at scales that could help direct mitigation efforts, then their tool should be evaluated as a means to establish baselines that will improve pilot test sampling design,” the report noted. “Pilot studies will be most productive if agreements are reached beforehand on experimental design, objective evaluation metrics and processes, site selection, timing, and the possibly of coupling more than one solution with others underway in GLSM.”
Lake Improvement Association President Tim Lovett said the report helped officials hone in on a handful of options that could prove beneficial to Grand Lake St. Marys.
“We’ll get those numbers down to something that is more manageable and based upon that selection process, we have some basis to say that these people are more capable of helping versus some of the others,” Lovett said. “It’s a pretty extensive report and at the end of the day, I think we will get the right answers.”
One aspect that Lovett identified as a strength is the report’s encouragement of residents to help increase the flow in back channels. This, Lovett noted, will help increase dissolved oxygen levels in those channels that receive little flow.
“It gives us an overview of the circulation potentials in those channels and back waters to help reduce the sediment and phosphorus loading,” Lovett said. “That’s a good thing.”
Lovett said he planned to discuss some of the options further at Saturday’s Lake Improvement Association meeting. The group is scheduled to meet at 10 a.m. Saturday at the Celina Moose Lodge.
|battelle-glsm-report-2011.pdf ||2.04 MB|