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3 <br />Permitted sewage design flowrates range from 100 to 2,850 gallons per day (gpd), with <br />a total specified sewage design flowrate for the entire property of 6,310 gpd. As <br />indicated in Table 1, sewage design flowrates are not specified in the septic system <br />permits for Birch, Crane, and Maple cabins, so permitted flows for these structures are <br />not included in this calculation. Septic system permits provided by Orange County are <br />attached to this report. <br /> <br /> <br />IV. Current Usage and Available Capacity <br /> <br />Sand Filter LPP System <br />Septic system use data was collected for the sand filter LPP system from May 27 to <br />October 19, 2017, covering a period of 145 days. Summer camps started Sunday, June <br />11, and ended Friday, August 25, with a total of 11 weeks of summer camp. Facility <br />usage outside of this period was for staff training, year-round residences, and <br />maintenance activities. Weekly summer camps started on either Sundays or Mondays, <br />but always finished on Fridays. <br /> <br />For the entire period of data collection, a total of 96,372 gallons of wastewater was <br />pumped to the sand filter LPP system, with a resultant average daily wastewater flow of <br />665 gpd. To assess anticipated increased flowrates during summer camp weeks, <br />weekly wastewater volume was calculated for every Sunday to Saturday period of record <br />(21 total weeks; 2 with partial data). As anticipated, wastewater flowrates were highest <br />during summer camp weeks, with weekly flows ranging from 3,095 to 10,170 gallons per <br />week. Non-summer camp weeks produced wastewater flows ranging from 0 to 5,723 <br />gallons per week. Resultant average daily wastewater flows for summer camp weeks <br />ranged from 442 to 1,453 gpd. By comparison, the top 10 percent of adjusted daily <br />wastewater volumes during summer camp weeks ranged from 1,771 to 2,921 gpd. The <br />numerical average of the top 10 percent of adjusted daily wastewater volumes is 2,184 <br />gpd, which represents the alternative sewage design flowrate for the sand filter LPP <br />system, per 15A NCAC 18A .1949 (c)(1). Compared to the permitted flowrate of 2,850 <br />gpd, current usage is only 77 percent (2,184 gpd / 2,850 gpd = 0.77, or 77%) of the <br />available capacity of this system. Per these calculations, residual available capacity in <br />this system is 666 gpd. <br /> <br />Flow equalization (FE) technologies could be added to this system per Innovative <br />Wastewater System Approval No: IWWS-2004-01 (copy attached) to further increase <br />available capacity for new or expanded structures. FE is accomplished through the <br />utilization of a large pump tank that is sized to hold wastewater produced over the entire <br />FE period, minus equalized effluent doses that are disposed of in the existing nitrification <br />field. Using the highest calculated average daily wastewater volume per week (1,453 <br />gpd), the utilization of FE with a one week cycle could theoretically reduce current usage <br />to only 51 percent (1,453 gpd / 2,850 gpd = 0.51, or 51%) of the available capacity of <br />this system. Per these calculations utilizing FE, residual available capacity in this <br />system could be as high as 1,397 gpd. <br /> <br /> <br /> <br />92