SR0084717_SSNL - Laserfiche WebLink

Home Browse Search

January 11, 2022 BGG No. G130.09B of the average rainfall was estimated for the subject site area. The estimated recharge rainfall for this study was calculated based upon 80 percent of annual rainfall for the project area. Rainfall data for the Bacardi Residence site area was reviewed from many sources, including data from the California Irrigation Management Information System (CIMIS) Manteca Station #70 and the U.S. Department of Commerce National Oceanic and Atmospheric Administration (NOAA). The CIMIS Manteca Station, located approximately 3.2-miles northeast of the site, reports the average monthly evapotranspiration (ETo) to be 4.38 inches. The NOAA Tracy Carbona Station, the closest active station located approximately 11.8-miles southwest of the site, reports the average total annual rainfall from 1906 through 2021 to be 12.42 inches. Assuming 80 percent of this rainwater percolates to the aquifer, a value of 9.94 inches of average recharge of rainfall is calculated. H&F estimates the nitrate concentration of rainfall is approximately 1 mg/L-N. Quantity and Quality of Domestic Wastewater The proposed residence will have four bedrooms and four bathrooms, with five estimated residents. Additionally, the residence will contain a total of four toilets, four showers, one bathtub, and six sinks. The estimated sewage flow rates for various uses are available from several references. The uses presented below were guided by the San Joaquin County Onsite Wastewater Treatment Systems Standards (2017) and US EPA (1980). The SJC EHD calculates nitrates loading based on number of bedrooms, with 100 gallons of wastewater per day for the first bedroom and 50 gallons per day for each additional bedroom; hence these rates were used for the proposed residence. The estimated flow values discussed here should not be used for the design and sizing of the septic system. The design and sizing of the septic system should utilize the SJC EHD Onsite Wastewater Treatment Systems Standards which incorporate peak and surge flow factors. The estimates used in the Onsite Wastewater Treatment Systems Standards may be greater than those discussed herein. A typical nitrate as nitrogen (N) concentration for residential use is 35 mg/L (Crites and Tchobanoglous, 1998). This value was used in calculations for the proposed residents. No contributions from crop irrigation or soil amendments are considered for the Hantzsche/Finnemore method. It is reasonably assumed that the irrigation and soil amendments would be applied at close to agronomic rates for a net balance of plant irrigation and nutrients. Additionally, the proposed residence is in a residential area so crop contributions are not applicable. The following tables present the calculated maximum average daily flow for the site and weighted average concentrations: Table 1 – Average Daily Flow Calculation Use Units Rate Subtotal Average Daily Flow Residents (full-time) 1st Bedroom 100 gal/bedroom 100 gpd 100 gpd Residents (full-time) 3 Bedrooms 50 gal/bedroom 150 gpd 150 gpd Total h 250 gpd