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The lumber yard is proposed to have seven to twelve employees per day and will not serve / customers.We understand that the lumber yard is planned to be open regular business hours, five days a week. The current residence will be transformed into an office building and will not have permanent residents. The estimated sewage flow rates for use categories are available from a number of references. The / uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal Standards (2003),Crites and Tchobanoglous (1998),and EPA (1980).The references indicate that 13 gallons r for each employee is typical for an office worker (Crites and Tchobanoglous, 1998). The following tables presents the septic waste water uses associated with the site. The rates r presented from the references provide general guidance but do not always reflect a match in usage. Careful examination,professional judgement,and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for the uses associated with this project are presented next. Table 1. Typical Quantity of Effluent Category Total People per Average Quantity per Average Daily Flow Day Person Per Parcel Commercial 12 13ad al (12 ployees x gpd) 156 gpd x 5/7 = g / y/employee 112 Note —gpd is gallons per day. -- For the subject property, the total daily waste water quanti is 112 ons per day. The average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/LN 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. The result.-for-th,i.�-estmatedncentration for total nitrogen in waste water for the ` project is approximately mg/L- over the long term. 3.4.2 Denieri6ca6on Estmate 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 (N� to the atmosphere. / 6" 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. A typical denitrification factor of 35 percent was selected for the site because of the fine grained ` soils that exist at the site. 5 r