October 17, 2002
Planning Board Town of Southeast
67 Main Street
Brewster, New York, NY 10509
re: Proposed Commercial Development
Terravest International Corporate Park (Terravest II and III)
Town of Southeast DEP Log # 7287
Middle Branch/Diverting Reservoir Basins
Honorable Members of the Board:
Thank you for sending the DEIS for the above referenced project. As you are aware this project is located within the New York City water supply watershed, a regional water supply system that serves more than 9 million people. The site straddles the drainage basin divide between Diverting and Middle Branch reservoirs, both of which are designated as "phosphorus restricted basins". Reservoirs are considered phosphorus restricted when the phosphorus load entering the reservoir causes an exceedance of the water quality values established by New York State Department of Environmental Conservation.
As an involved agency, DEP requires approvals for both a Stormwater Pollution Prevention Plan (SPPP) and for wastewater treatment. This department must make a finding under SEQR before a determination may be issued for any pending application. The following information is needed by this agency to make a finding in keeping with the requirements of SEQR.
Chapter 8: Natural Resources:
The Natural Resources chapter mentions that the site contains wetland corridors and streams. However, the evaluation of the impacts to the wetland/stream systems are limited to describing physical disturbances to each system. The central wetland corridor's relationship to the water table and the streams located on the site must be evaluated, along with the hydraulic/hydro geologic relationship between the local landforms to fully evaluate the potential impacts. The DEIS must evaluate the potential impacts to the wetland and streams that may result from the discharge of 51,800 gallons of sewage or treatment plant effluent per day into the hill slope above the central wetland corridor. Such evaluations must consider the effects of water quality and water quantity on the wetlands and watercourses. For example, a hydraulic relationship between the hills and the adjacent watercourses and wetlands are very likely to exist. The hills, with their topographic high points, may act as a groundwater recharge points. The wetlands and watercourses are situated at the topographic low points that maybe groundwater discharge areas. Due to their geographic proximity to the drainage basin divide, the wetlands and watercourses are part of the headwaters of their respective reservoir basins. Literature shows that wetlands which form along slopes and at the base of hills and valleys (i.e., in landscape positions where the water table actively discharges) are generally considered to be groundwater dominated wetlands and that they may also receive additional overland flow, but it is usually supplemental to groundwater recharge. Research has shown that the neighboring Great Swamp has such a relationship, with approximately 60% to 100% of its water (during wet periods and dry periods, respectively) being derived from groundwater that has been discharged from such recharge areas.
An increase in groundwater elevation resulting from the addition of a large volume of effluent to a groundwater recharge area may lead to an increase in the base flow of the stream and to a reduction in the water storage capacity of the wetland, both of which may lead to increased flooding in the future. The increase in base flow of the stream may alter its flow regime, creating erosion of the streambed and banks. The hydraulic input may also affect the hydro period of the wetland, which can significantly alter the diversity of wetland plant species and overall wetland functionality.
Although stressing that the plans "have minimized and wetland and buffer disturbance to the extent practicable," the DEIS has not presented any alternative configurations that avoid or mitigate the impact, nor has it qualified how this is to the "extent practicable." For instance, approximately 10 acres of disturbance to the wetland buffer zones have been proposed for grading roads, stormwater basins, and ball fields. The changes in grade and in cover of these areas may lead to an increase in the volume and rate of stormwater runoff into the wetlands, which could result in degradation of the wetlands and watercourses. While the increase in loading of pollutants and volume from proposed impervious surfaces and overall site disturbance is addressed by creating stormwater basins, by locating these mitigation measures within a wetland buffer another impact that also must be avoided or mitigated has been created.
As stated in the Scoping letter from this Department to the Town of Southeast Planning Board, dated 22 May 2000 regarding this site, this Department strongly discourages grading within the protective buffer of the wetlands and watercourses, as well as the installation of roadways within these buffers. The potential impacts of contaminated stormwater runoff entering a public water supply are well documented in modem scientific literature and include erosion and sedimentation, nutrient loading, and flooding, among myriad other items. The DEIS fails to demonstrate that the impacts associated with such disturbance has been avoided or mitigated to the extent possible.
Chapter 9: Geology
Most of this section explains site soils, soil erodibility, and proposed grading. This section contains no information regarding the character of the bedrock, including composition and fractured zones. The relationship between groundwater and geology must be evaluated. Potential impacts should include the possible effects of blasting on bedrock fracture zones and groundwater hydrology. The author presented one mitigation plan that reduces grading on the east side of the "upper senior cluster". Alternative grading plans must be presented, including plans that restrict grading in the wetland buffers and plans that provide 3:1 grading to reduce erosion potential.
Chapter 10: Sanitary and Stormwater Management:
Potential impacts associated with wastewater treatment include the ability to remove bacteria and nutrients from the waste before the flow becomes part of ground or surface waters. The DEIS fails to evaluate the potential impacts associated with disposal or treatment of the volume of wastewater proposed at the site. To mitigate or avoid the potential impact associated with wastewater treatment, information must be provided to support the conclusions made in the DEIS.
Alternative plans with different configurations of sewage treatment plants must also be evaluated, including various types of sewage treatment facilities and effluent quality associated with each type of facility. Impacts associated with each type of sewage treatment facility must also be presented. The project includes specified and unspecified uses, including manufacturing. Waste production as a result of possible manufacturing processes must be evaluated.
In the Scoping letter dated 22 May 2000, this Department requested that a groundwater mounding analysis be included in the DEIS. This Department is concerned that the discharge of effluent into the soil on this site may alter groundwater quantity and quality and, subsequently, may degrade the quality of the adjacent wetland and watercourse. In this chapter of the DEIS, the author states that the soil and groundwater conditions in the area of the proposed subsurface disposal system have been "studied extensively" and that "soil capacity tests" were completed in 2000 to determine the "hydraulic capacity of the soil," which was estimated to be 51,800 gallons per day. Supporting information, including the results of the groundwater mounding analysis, must be included in the DEIS to verify these conclusions.
The discharge of 51,000 gallons per day (6,818 cubic feet per day) of treated wastewater into the hillside of T3, which has slopes in excess of 15%, may affect the wetland and watercourse with regard to water quality and water quantity overtime. Other impacts include a risk to public health if the subsurface effluent breaks out onto the ground surface and/or enters the water supply before it is adequately treated. As a result, this Department believes that broad assumptions should not be made regarding the adequacy of the hillside to accept and disperse the proposed large volumes of effluent in a manner that is certain to protect public health, as well as the health of the New York City water supply and its consumers. Therefore, the author must present all alternatives in order to ensure that the sanitary facilities will be designed in an appropriate manner.
This Department is concerned about the long and shortterm effects of stormwater runoff. Increases in pollutant concentrations resulting from stormwater runoff could be avoided or adequately mitigated by an appropriately designed stormwater pollution prevention plan. However the DEIS fails to evaluate the impacts associated with the implementation of a SPPP. Stormwater practices constructed in adjacent areas to wetlands will have an impact on the wetland. It would appear that alternative layouts and configurations could reduce the impervious surfaces thereby reducing the size of practices required. Additionally it appears that there maybe alternatives to locating the stormwater practices within the adjacent areas of the stream and wetlands.
(This document was scanned and digitally recognized with an OCR program by and for the Concerned Residents of Southeast. Any errors in processing will be minor and were not intentional.)
Chapter 11: Traffic and Transportation:
The author states that Holmes Road does not meet today's standards and that Zimmer Road is a local, twolane narrow roadway. Hence, a potential impact of this project would be the widening and regrading of Holmes and Zimmer Roads. The intersection of Zimmer and Holmes is adjacent to a local wetland, which is the source of a watercourse tributary to the New York City water supply. The DEIS mentions grading and vegetation removal along Zimmer Road and along Holmes Road to improve sight distance. The DEIS must address potential impacts to the wetlands and watercourses associated with these activities.
Chapter 14: Infrastructure and Energy:
The DEIS must evaluate the possible impacts of water demand on the local wetlands and watercourses and provide mitigation. The water demand for all alternatives must also be presented, as well as potential impacts. Of note, although the DEIS states that there are two existing wells on T3, Map 141 only shows one well.
Chapter 16: Alternatives:
The DEIS provides a list of 4 alternatives with minimal evaluation of each design. The effects on sanitary sewage disposal, water supply, land disturbance, grading, and wetland/wetland buffer disturbance must be evaluated for each of these designs. Adequate data is not presented in the DEIS to support a conclusion that any of the alternatives avoids or mitigates the identified impacts. In addition, alternatives that include zero wetland buffer disturbance, different sanitary sewage treatment methods, and reducing slopes to 3 :1 should also be considered. Alternative configurations that reduce the amount of impervious surfaces should also be considered.
The majority of the DEIS focuses on one overall project configuration and does not satisfactorily describe all existing resources or address all possible impacts associated with that plan. Without filly describing all existing resources, the full range of potential impacts cannot be reasonably evaluated. Although the proposed project appears to be in accordance with local zoning and designated land uses under the Town of Southeast's Master Plan, the scope of the project, as presented, maybe too large for the site's capacity to adequately avoid adverse impacts to the New York City water supply. This Department believes a reduction in the scope of the proposed project maybe necessary in order to protect the City of New York's regional water supply resources. In addition, the DEIS does not present enough possible alternatives. Evaluation of all alternatives within the DEIS will help determine what overall design will be acceptable to address this Department's concerns.
Associate Project Manager I Engineering Design and Review