Orange County NC Website
Browse       Search
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 /> IV. Current Usage and Available Capacity <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 /> 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 /> 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/Z850 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 /> 3 <br /> 92 <br />