Improving Stormwater Quality in Lake George, New York

Nov. 1, 2001
Lake George, the largest body of water located entirely within the Adirondack Park in New York State, has often been called the “Queen of American Lakes” for its pristine waters and natural beauty. The lake has drawn tourists to the region since the 1800s, but the construction of Interstate 87 in the 1960s facilitated a boom in tourism and recreation–and ultimately development of the region. The extreme rate and concentration of development along the southwestern shores of Lake George, particularly in Lake George Village, has led to a variety of environmental problems, including high sedimentation rates from streams. In a scenario that has been played out in waterfront recreation areas around the country, rapid development meant growing concern for the quality of Lake George’s beautiful, clear water.
Lake George has been the focus of study since the late 1970s, when the National Urban Runoff Program (NURP) was launched to demonstrate the nonpoint-source impact of stormwater runoff. Lake George was one of the original sites for NURP, which resulted in the National Pollutant Discharge Elimination System (NPDES) program. In 1993, New York State initiated the development of a stormwater pollution prevention plan to address three areas of concern related to construction in the area: erosion control during construction, increased volume and rate of runoff after construction, and increased pollutant load and wash-off as a result of the proposed land-use changes. General Permit 93-06 requires an applicant to evaluate the impacts of total phosphorus (TP), total nitrogen (TN), biological oxygen demand (BOD), total suspended solids (TSS), and potential thermal changes to receiving water bodies. The results of this evaluation lead to designed mitigation practices to reduce the increased load to acceptable levels.
That same year, as part of an award through the Intermodal Surface Transportation Efficiency Act (ISTEA) program from the New York State Department of Transportation, the Village of Lake George implemented several components of the Marine Village Watershed Plan. In 1997, the village used funds from the 1993 ISTEA grant to install two separate Vortechs Stormwater Treatment Systems as part of its overall stormwater management design for the highly urbanized watershed that drains into Lake George. Manufactured by Vortechnics in Portland, ME, the system consists of a large-capacity, precast concrete structure installed below grade to receive surface runoff. The chambered design combines swirl-concentrator and flow-control technologies to capture sediment and floatables.In 1998, the New York State Department of Environmental Conservation (NYSDEC) Division of Water received a grant from USEPA’s Section 319 (Nonpoint Source Implementation) funds to evaluate the effectiveness of the Vortechs System installed on Canada Street in the watershed. The study found that, of the 13 events sampled over the 11-month testing period, the system removed 88% of the TSS load in the 95% impervious catchment. The system is designed to achieve a minimum TSS reduction of 80%. This was the first known independent study in the Northeast US on the system’s effectiveness in mitigating the pollutants of concern under the NPDES permits. Using the grant funds, NYSDEC worked with Vortechnics to establish a program to monitor all of the pollutants required under the NPDES General Permit 93-06 (TSS, TP, TN, and BOD). The study also monitored specific conductance and fecal coliform bacteria. Samples were collected between February 2000 and December 31, 2000, from the inflow and outflow of the system during different types of events, analyzed for these pollutants, and compared.
The study found that the system exceeded TSS removal expectations during the study period. In addition, the system removed some coarse particulate phosphorus and nitrogen, but the phosphorus and nitrogen in fine particulate and dissolved forms passed through the system. The study concluded that the Village and Town of Lake George should consider installing additional systems in areas where sedimentation and erosion have been identified as nonpoint-source pollution problems. NYSDEC also recommended investigating a way to retrofit the system with a best management practice structure or device to remove fine nutrient particulate and dissolved phosphorous and nitrogen. Because of the rapid accumulation of sediment and other pollutants, it was recommended that the maintenance frequency be increased to twice a year. “The load of other pollutants will be greatly reduced by a regular cleanout schedule,” the study states, also pointing out that metals, such as lead, are often found adsorbed to sediment (West et al.). A midwinter cleanout was also recommended to reduce the seasonally high calcium and chloride loads attributable to winter deicing practices. During the test period the Vortechs System accumulated 3.6 m3 of sediment, which is just below the 4.2-m3 capacity of the system specifications. Event mean concentrations were calculated for each storm based on the concentrations of discreet samples taken by Manning automatic samplers throughout each storm. A pressure transducer installed inside the system measured flow rates, which were recorded at five-minute intervals. Personnel visited the site every 12-24 hours during a storm to download data, check on the equipment, and collect samples, which were transported to the Darrin Fresh Water Institute in Bolton Landing, NY, for analysis.

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