SU0011280_SSNL - Laserfiche WebLink

Home Browse Search

Soil Suitability/ Nitrate Loading Study 1 f�rracon Sun Valley Express Truck Center ■ Acampo, California August 14, 2017 ■ Terracon Project No. NA177026 The following table presents the proposed septic wastewater use for the site. The rates presented from the references provide general guidance but do not always reflect a match in usage. Careful examination, professional judgment, and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for the uses associated with this project are presented below. These flow rates are average daily rates over the entire year and should not be used for septic system design. These average daily rates are for nitrate loading purposes. Septic system design should take into account maximum daily rates during the season. Table 7. Typical Quantity of Effluent. Total Average Quantity Average days of Category People per Person Average Daily Flow • per Day (gallons) use per year Permanent (12 person x 15 gal x 152 Employees 12 *15 152 days) 1365 days per year = 74.96 gpd (67 person x 5 gal x 152 Visitors 67 *5 152 days) /365 days per year = 139.51 gpd Average Daily Flow 214.47 gallons per day Note:gpd is gallons per day.*Value cited from the San Joaquin County On-Site Wastewater Disposal Standards(2003)6.1.15. The average total nitrogen concentration of domestic wastewater is normally considered to be 20- 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. It is estimated that the average concentration for total nitrogen in wastewater for the project is approximately 85 mg/L-N over the long term. 2.3.4.2 Denitrification Estimate • Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Based on the results of the soil borings, the proposed new leach field is expected to be located within sandy silt soils in the upper 5 feet with seepage pits extending into the underlying cemented soils and clayey sand layer extending to 25.0 feet bgs. Given the geology and separation from groundwater, a denitrification estimate of 25 percent is anticipated. • Responsive n Resourceful n Reliable 14