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Sanitary Sewer / Wastewater System <br />23 <br />A schematic design for sanitary sewer and a subsurface drip irrigation system have been prepared by <br />Tetra Tech. Plans for the Hart's Mill community include residential housing with 67 total bedrooms <br />(when full build -out is achieved), a common house with kitchen and washing machines (for those <br />without a washing machine in their private residence), and an approximately 2,000 square foot <br />education building with no kitchen and seating for 20 people. Additionally, up to four small workshops <br />with sinks only may be developed in the future. Standard design flow rates for each facility type and for <br />the entire system are summarized in the table below, based on the requirements of 15A NCAC 18A <br />.1949. <br />Facility <br /># <br />Unit <br />Unit flow (gpd) <br />Total flow <br />Comments <br />(gpd) <br />Bedrooms <br />67 <br />Bedroom <br />120 /bedroom <br />8040 <br />Common <br />134 <br />People <br />5 /meal <br />670 <br />Kitchen, for grease trap sizing only <br />(assuming 2 people per bedroom)* <br />Education <br />20 <br />People <br />10 /person <br />200 <br />Based on school design flow <br />building <br />requirements <br />Workshops <br />4 <br />Building <br />120 /building <br />480 <br />Based on minimum flow rate per <br />building <br />TOTAL <br />1 8720 <br />* The flow attributed to the common house has not been added to the total system flow, since this house will only be used by <br />residents of the village. A grease trap sized to handle the potential kitchen flow rate will be provided for pretreatment. <br />A preliminary soil and site evaluation report has been prepared by Agri -Waste Technology (AWT), Inc. <br />(Apex, NC), and dated January 12, 2014. The report identifies, describes, and delineates areas suitable or <br />provisionally suitable for onsite wastewater dispersal. Areas identified with the deepest soils were <br />prioritized for siting the active drain fields for the proposed system. The report also recommended a <br />conventional long term application rate (LIAR) of 0.25 gpd /sf, which is the midpoint LTAR for Type IV <br />(clayey) soil types, per 15A NCAC 18A.1955. <br />The proposed system for Hart's Mill includes the use of subsurface drip irrigation for the dispersal of <br />septic tank effluent. Drip irrigation was selected because of its various advantages over other methods <br />of gravity or pressure dispersal, including: <br />• Shallow dispersal depth which allows for better treatment in the soil and vegetative uptake; <br />• Low - impact installation without damaging existing landscapes, trees, and other natural site <br />features; <br />• Very low instantaneous loading rates with effluent dispersed more evenly over the drainfield <br />area, again improving treatment in the soil and hydraulic performance. <br />To determine preliminary drip irrigation system sizing, the approval document for Innovative <br />Wastewater System No. IWWS- 1993- 1 -R7A, American Perc -Rite Subsurface Drip System, Anaerobic, was <br />consulted. This approval document specifies a LTAR range of 0.15 -0.05 gpd /sf (area basis) for Type IV <br />131 II-°Ilart's MHhI MPD CZ ReqUest <br />