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HomeMy WebLinkAboutSP201400005 Assessment 2014-01-171/17/2014 Capacity Assessment Onsite Wastewater System 117 Regents School of Charlottesville .1 vltm- I. X59 0 010 6'5 1, Physical Address: 3045 Ivy Road Charlottesville, VA 22903 `' Mailing Address: PO Box 852 Keswick, Virginia 22947 ROFESS10 ATTN: VDH - Albemarle County Assessment conducted by Old Dominion Engineering (ODE) Increased Occupancy The Regents School of Charlottesville is located in the Administration Building at the Christian Aid Mission Ivy Road Campus (TM 59 -23G -119). The building is served by its own separate drainfield (VDH Permit Number 101 -98- 0630). The Regents School of Charlottesville wants to increase its occupancy (students and staff). Current occupancy is 83 students and 10 staff. Water meter readings were taken from November 6, 2013 to the present. Current Onsite Wastewater Treatment and Dispersal System The onsite septic system consists of a 4200 gallon septic tank, a 5000 gallon flow equalization tank, and 1920 sqft of drainfield. The permitted amount of flow equalized effluent that can be pumped to the drainfield is 691 gallons per day. Monitored Water Meter Readings Water meter readings were done every school day by the staff of the Regents School. Water usage was not recorded on the weekends or school holidays. The summary of the water usage is presented below; the raw data is presented on the following page. School Days 28 Other Usage Days 1 Total Usage Days 29 Total Water Usage 12630 Maximum Water Usage per Day 758 Minimum Water Usage per Day 236 Average Daily Usage (occupancy days) 436 Number of current occupants 93 Average Water Usage per Day per Occupant Equivalent 4.7 Maximum Daily Water Usage per Occupant Equivalent 8.2 Minimum Daily Water Usage per Occupant Equivalent 2.5 Median Daily Water Usage per Occupant Equivalent 4.5 Page 1 of 4 Old Dominion Engineering - 2036 Forest Drive - Waynesboro, VA 22980 - olddomeng @ntelos.net 1/17/2014 Date Day Water Meter Reading (Gallon) Daily Use (GPD) Weekly Total 7 Day Weekly Average Occupants Daily Water Usage per Occupant 6- Nov -2013 Wednesday 42 93 7- Nov -2013 Thursday 462 420 93 4.5 8- Nov -2013 Friday 890 93 4.6 9- Nov -2013 Saturday Break 93 10- Nov -2013 Sunday Break 93 11- Nov -2013 Monday 1231 93 3.7 12- Nov -2013 Tuesday 1677 4 93 4.8 13- Nov -2013 Wednesday 2189 93 5.5 14- Nov -2013 Thursday 2707 518 93 5.6 15- Nov -2013 Friday 3063 356 2173 310 93 3.8 16- Nov -2013 Saturday Break 633 93 6.8 17- Nov -2013 Sunday Break 93 18- Nov -2013 Monday 4329 633 93 6.8 19- Nov -2013 Tuesday 4744 415 93 4.5 20- Nov -2013 Wednesday 5240 496 93 5.3 21- Nov -2013 Thursday 5649 409 93 4.4 22- Nov -2013 Friday 6035 386 2972 425 93 4.2 23- Nov -2013 Saturday Break 93 24- Nov -2013 Sunday Break 93 25- Nov -2013 Monday Break 93 26- Nov -2013 Tuesday Break 93 27- Nov -2013 Wednesday Break 93 28- Nov -2013 Thursday Break 93 29- Nov -2013 Friday Break 93 30- Nov -2013 Saturday Break 93 1- Dec -2013 Sunday Break 93 2- Dec -2013 Monday 6517 E482 93 5.2 3- Dec -2013 Tuesday 7275 93 8.2 4- Dec -2013 Wednesday 7881 606 93 6.5 5- Dec -2013 Thursday 8250 369 93 4.0 6- Dec -2013 Friday 8618 368 2583 369 93 4.0 7- Dec -2013 Saturday Break 93 8- Dec -2013 Sunday Break 93 9- Dec -2013 Monday 8986 368 93 4.0 10- Dec -2013 Tuesday 9230 244 93 2.6 11- Dec -2013 Wednesday 9466 236 93 2.5 12- Dec -2013 Thursday 9831 365 93 3.9 13- Dec -2013 Friday 10237 406 1619 231 93 4.4 14- Dec -2013 Saturday Break 93 15- Dec -2013 Sunday Break 93 16- Dec -2013 Monday 10652 415 93 4.5 17- Dec -2013 Tuesday 10998 346 93 3.7 18- Dec -2013 Wednesday 11373 375 93 4.0 19- Dec -2013 Thursday 11867 494 93 5.3 20- Dec -2013 Friday 12230 363 1993 285 93 3.9 21- Dec -2013 Saturday Break to 5- Jan -2014 Sunday Break 6- Jan -2014 Monday 12672 442 1 93 4.8 Note -Highlighted cell is estimated based upon total water usage measured over the time period. The school was used for a church event on November 16, 2013. The water meter reading on the following Monday was divided among the Monday and the preceding Saturday. The school is used infrequently for church events. This water usage was considered in the analysis. Page 2 of 4 Old Dominion Engineering - 2036 Forest Drive - Waynesboro, VA 22980 - olddomeng @ntelos.net 1/17/2014 Measure Water usage per Occupant The average water usage per occupant during the study period was 4.7 gpd. A design usage per occupant of 6.0 gpd captures 86% of all individual daily readings and 100% of the weekly average readings taken in the study period. This recorded water usage is consistent with EPA estimates of 5 -17 gpd per student (Per EPA/625/R- 00/008 Onsite Wastewater Treatment Systems Manual Table 3 -5 range of wastewater flow rates from a school without cafeteria, gym, or showers). The flow equalization volume in the system is large enough to easily equalize peak weekly flows over the week for the measured flows. Wastewater System Capacity for School Usage 4200 gallon septic tank capacity @ 2 day detention time V 4,200gal - 2100 gpd Q 0 2days gP 161 Occupant x 8.2 gpd/Occupant (peak) = 1320 gpd (OK) Dra infield Capacity per Week at Septic Tank Effluent 691 gpd x 7 days = 4,837 gallons per week Drainfield Capacity (5 Day Water Usage Flow Equalized over 7 Days) 4,837 gallons per week - 5 days per week water usage = 967.4 gpd Maximum Occupancy of School based upon 63 gpd per occupant (Water Usage Study Considering Weekly Flow Equalization) 967.4 gpd - 6.0 gpd/occupant = 161 occupants Minimum and Recommended Flow Equalization Capacity Storage Volume Minimum = [5 days X (967.4 gpd - 691 gpd)] = 1,382 gallons Recommended = 1.5 x Minimum = 2,073 gallons Actual Flow Equalization Capacity Storage Volume Required 5000 gallons - 250 gallons (emergency storage) - 650 gallons (wet well pump cover) = 4100 gallons The maximum occupancy of the school that the onsite wastewater and disposal system can handle is 161. Page 3 of 4 Old Dominion Engineering - 2036 Forest Drive - Waynesboro, VA 22980 - olddomeng @ntelos.net 1/17/2014 The wastewater effluent strength will not exceed residential strength for BOD or TSS. The wastewater strength is estimated at <250 mg /l BOD /TSS. The existing onsite wastewater system will be able to handle the anticipated wastewater effluent strength and flows for upcoming school session in which occupancy is less than or equal to 161. ODE Recommendations 1. The school should continue to monitor and record the installed water meter readings daily. These readings should be verified by a licensed Alternative Onsite Waste Water Operator and submitted to the Health Department yearly with an inspection report of the system. Page 4 of 4 Old Dominion Engineering - 2036 Forest Drive - Waynesboro, VA 22980 - olddomeng @ntelos.net