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The firms who completed engineering studies of Lake Kitchawan, Lake Truesdale and Lake Waccabuc presented their recommendations to the town on Monday, Nov. 15, to reduce phosphorus pollution through three separate multi-million dollar septic system projects.

In July 2020, Lewisboro received a grant from the New England Water Pollution Control Commission of up to $425,000 to study the three lakes. The program was funded by the New York City Department of Environmental Protection in an effort to analyze and minimize wastewater in the East of Hudson region of New York City’s water supply watershed.

The presentation on each lake opened with comments on current conditions and the factors contributing to water quality.

Ken Kohlbrenner, the project manager with Woodard & Curran for the Lake Kitchawan study, said all three of the lake’s catch basins had elevated levels of fecal coliform and E. coli levels. Mr. Kohlbrenner said samples from the lake itself also showed substantial levels of phosphorus and fecal coliform, resulting in hazardous conditions for public health and the lake habitat, according to limits set by New York State Department of Health.

Michael Manning, the projector manager with Ramboll Americas Engineering Solutions for the Lake Truesdale study, and David Hanny, an engineer with the firm Barton & Loguidice working on the Lake Waccabuc study, echoed similar findings. Lake Truesdale was found to have high concentrations of phosphorus, resulting in water quality below the threshold for recreational use, increased algae blooms and poor water visibility.

Barton & Loguidice also reported that Lake Waccabuc had a significant increase in phosphorus levels since 1986, and that its current concentrations were two to three times greater than state limits. These conditions also resulted in harmful algae blooms and can make the lake more vulnerable to invasive species, according to the firm. 

Mr. Hanny said the data collected for Lake Waccabuc also showed the highest concentrations of phosphorus on the lake’s eastern shore near the inlet where Lake Rippowam and Lake Oscaleta flow in.

Despite the town’s efforts to have lakes Rippowam and Oscaleta included in this lake study, Town Supervisor Peter Parsons said the DEP refused to fund the expanded scope. 

Each lake study pointed to poor functioning or failing septic systems along the lakes as large contributors to the high concentrations of phosphorus. 

Several factors that affect the performance of septic systems outlined by each study were depth to groundwater, depth to bedrock, slope at its location, soil type, proximity to lakes, water courses and wetlands, and the distance from adjoining drinking water wells.

In the case of all three lakes, the studies found that clusters of homeowner parcels were small in size, had a high percentages of steep slopes, had poor soil quality, had shallow depths to bedrock and groundwater, and had septic systems that were past their lifespan and improperly maintained.

Each firm provided recommendations on how to address the issues causing poor conditions for septic systems. These included options for upgrading a designated cluster of parcels’ septic tanks, constructing a community septic system and connecting to an already-existing wastewater treatment plant.

For Lake Kitchawan, Woodard & Curran recommended replacing existing septic tanks with individual on-site advanced treatment systems at 187 parcels surrounding the lake that were deemed to have the greatest impact on water quality due to their small sizes and steep slopes.

Mr. Kohlbrenner said the advanced treatment systems reduce the size of the fields needed for leaching, so this measure would utilize existing leaching fields. The estimated capital cost for the project is $3.9 million.

All the recommended solutions require long-term maintenance of the septic systems. Mr. Kohlbrenner said their recommendation also includes the formation of a Lake Kitchawan Septic District to ensure proper maintenance of the systems.

For their evaluations of Lake Truesdale, Ramboll, who also teamed up with Insite Engineering, Surveying & Landscape Architecture, split the project into two zones. Zone 1 was comprised of smaller lots immediately surrounding the lake with 274 residents, and Zone 2 was made up of larger parcels with 145 residents. 

For Zone 1, the engineering firms recommended that the town creates a low-pressure sewer collection system and expands the wastewater treatment system at the former Lewisboro Elementary School.

Mr. Manning said the low-pressure system will have grinder pumps at each residence with connections to a smaller pipeline that will carry the wastewater to the Lewisboro Elementary School treatment center. The current capacity of LES’s facility is 8,000 gallons per day and would need to be upgraded to treat 140,000 gallons per day.

For Zone 2, due to the parcels being larger and flatter, the experts proposed implementing a septic remediation program that would upgrade the current systems to have improved nutrient removal.

Mr. Manning said their recommendation has an estimated capital cost of $31 million. He added that the annual cost per user is currently around $4,900 with an additional estimated $1,475 annually for maintenance. In order to make the project feasible, Mr. Manning said the town would need at least $27 million in grant funding.

The Truesdale Lake project would also result in the formation of districts for each zone to oversee maintenance and repairs.

Barton & Loguidice split their study of Lake Waccabuc into four regions: northwest, eastern, mid and southern. With seven possible alternative solutions, the firm recommended that a new wastewater treatment plant be built on land owned by the South Shore Waccabuc Association to treat the eastern region of the study area.

Barton & Loguidice also recommended that an engineering study be completed for lakes Rippowam and Oscaleta.

The estimated capital cost of the recommended project for Lake Waccabuc was $18.8 million. Once implemented, the project is expected to reduce 67% of the phosphorus concentration from septic systems, the firm said.

Councilmember Daniel Welsh pointed to one of the alternative recommendations, the replacement of the septic systems and installation of phosphorus treatment systems, as possibly being more cost-effective with a capital cost of $7.7 million and estimated to remove 100% of the lake’s phosphorus from septic systems. However, Rachel Schnabel, an engineer with Barton & Loguidice, said that option would only remove phosphorus and not address the other nutrients in the lake like nitrates and bacteria.

With over 80 participants in the meeting, residents of each lake community and members of their respective associations inquired about the projects funding and its effect on homeowners. 

Members of the Truesdale Lake Property Owners Association also inquired about the data used to come to the conclusions regarding water quality. Many noted that the TLPOA has worked hard to improve the lake quality, and that older data didn’t reflect that.

Mr. Manning explained to TLPOA members that his firm presented modeling for the worst-case scenario of septic failures around the lake and that data from 2009, 2016 and more recent data provided by the federal Environmental Protection Agency databases.

Following the presentation from Barton & Loguidice for Lake Waccabuc’s recommended project, many members of the South Shore Waccabuc Association, including president Tim Kennedy, emphasized that the association has not agreed to permit building a treatment center on their land.

Mr. Kennedy said the association did agree to explore the possibility of a community septic for members of their organization only. He also noted that the inclusion of additional properties in the study’s eastern region in this community septic also was not approved. 

Ms. Schnabel confirmed that while his firm has been working with the association, no agreements were yet reached, and that the South Shore Waccabuc Association would have to vote in favor of the project before any construction could take place on their property.

The next step for each engineering study is for the firms to submit their final reports to the New England Water Pollution Control Commission by Dec. 1. 

Mr. Welsh urged a more in-depth look at alternative options, especially for Lake Waccabuc. 

Mr. Parsons noted that since each lake is private, the town cannot use funds raised from Lewisboro taxes for the proposed projects. Because of this limitation, Mr. Parsons said it will be up to each lake association to decide which project, if any, they want to advance.

Jessica Leibman is a staff reporter at The Record-Review where she covers the Town of Lewisboro the Katonah-Lewisboro School District.

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