Project INFRASTRUCTURE: Sewer

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Sewer System

The project includes an onsite wastewater collection and treatment system capable of treating 197,000 gallons per day of wastewater associated with the project. The wastewater treatment plant (WWTP) will also reserve capacity for another 181,375 gallons per day of wastewater to serve the Hamlet of Amenia. The proposed sanitary system will consist of a gravity collection and conveyance system supplemented by low pressure sewers and the WWTP.

The projected wastewater flow for the project is an average volume of approximately 197,000 gallons per day (gpd). The footprint of the proposed WWTP is identified on Sheet SP-4 of the MDP. The proposed site plan for the WWTP and proposed elevations for the WWTP are also provided in the MDP on Sheet U-2 and U-3, respectively.
Gravity sewers have been selected in areas of the site where practical. Low pressure sewers have been selected in areas where widely varying topography makes gravity sewers impractical. All low pressure sections of the system will ultimately empty into a gravity section or into a pump station. Each served building or house in the low pressure sewer areas of the collection network will be equipped with a grinder pump station that will convey wastewater to a low pressure collection trunk. There will be two pump stations that discharge to the same force main, which itself discharges to that portion of the gravity system flowing directly to the WWTP.
The WWTP will consist of advanced biological treatment, gravity settling of solids, advanced filtration to remove residual solids, and disinfection prior to a surface water discharge. The wastewater will be treated to intermittent stream standards, the highest level of treatment available, without treating to drinking water standards. This treated water from the onsite WWTP is discharged through a force main, which is routed in a southerly direction to a point of outfall at the Island Green Pond. From there it will be used to irrigate the golf course, a practice that is acceptable to the regulatory agencies.

The applicant proposes to build the WWTP with additional capacity for the Town of Amenia, 181,375 gallons per day. The cost of constructing the larger facility with excess capacity to accommodate the Town’s wastewater will be borne solely by the Silo Ridge development.

This WWTP, including the excess capacity reserved for the Town, shall be constructed during Phase 1 of the project at no cost to the Town and/or any improvement district that the Town or County may form. No portion of the cost of constructing the WWTP shall be included in any rates, fees, or other amounts that are charged to end-users in the anticipated hamlet of Amenia sewer system. There shall be a continuing offer of dedication of the WWTP to the Town of Amenia, the County of Dutchess, or any improvement district that they may create, at no cost to those entities.

Surface Water Quality - The wastewater treatment technology for this project will be selected to meet all effluent quality requirements as required by NYSDEC. The anticipated effluent quality values can be readily achieved. When met, these stringent standards will help preserve the water quality of the downstream Class C irrigation ponds, Amenia/Cascade Brook (Class Ct), and downstream water bodies. Onsite public health will be protected by disinfection of the effluent, and by the fact that the effluent will be diluted in the Irrigation Pond before reuse.
The reuse of treated WWTP effluent for golf course irrigation, combined with captured storm water, will eliminate the need to use potable water for irrigation. Since the Silo Ridge project will utilize onsite wells for potable water, this will further reduce impact on the underlying aquifer. It should be noted that the Irrigation Pond is already a spring-fed water body, and some groundwater is therefore used for irrigation in that manner.

The proposed location of the WWTP is on the north side of Route 44. It is proposed that the tanks be placed outdoors, with low-profile engineered covers for odor control, except that any tank within 500 feet of other structures will be placed inside the building housing the tertiary treatment processes. A building next to the tanks would contain the tertiary treatment processes (filtration and UV disinfection) and support facilities (office, chemical room, blower room, solids dewatering room, storage, etc.). The WWTP is anticipated to be steel-frame, with roof and siding materials selected by the project architect to blend with the surrounding buildings and landscape. The low pressure sewer pump stations will be entirely subsurface, with only an at-grade access hatch for each. The community pump stations will be either entirely below-grade with an access hatch, or will consist of a small above-grade structure containing pumps and controls. Each of the community pump stations also will be equipped with an enclosed emergency generator with appropriate muffling, and will have sufficient landscaping, fencing, or architectural features to allow them to have a negligible visual impact. Pavement has been kept to a minimum, with enough paved area only to provide truck access and maneuvering for deliveries and solids hauling, and a small number of parking spaces for WWTP operators.

Odor - Odor issues will be mitigated by proper operation of aerated processes and by enclosing the treatment process inside a building or under covered tanks. The main treatment process tanks will be aerated and mixed to maintain oxygen levels and prevent septic conditions that lead to the generation of most offensive odors. Odor control technology options, if needed, include activated carbon or a scrubber. All other portions of the WWTP process are expected to yield negligible odors and will be subjected simply to standard ventilation and climate control in the building.

Any future equipment used for odor control would be located within the building. All ventilation will conform to the Ten States Standards, NFPA, and any other applicable standards.