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v December 14, 2005 NOA Project Number: E05116B ` r3.3 Current On-Site Sources of Nitrate One residence is currently located at the northwest comer of the Site; the remainder of the Site is ` vineyard and fallow land. The sources of on-site sources of nitrates are percolating septic effluent, 3 rainfall,and application fertilizers applied to the vineyard. V 3.3.1 Existing Septic System One residential septic system exists on the Site. y� 3.3.2 Agricultural Contribution ` A large portion of the site contains drip-irrigated vineyard. Vineyard plants are regarded as relatively low consumers of nitrogen fertilizers especially when compared to row crops and orchards. Fertilizers on the site may be applied through the drip irrigation system as needed. These types of systems generally perform well and tend to minimize the over application irrigation water and fertilizers. The presence of fine-grained soils further minimize the potential of excess leaching of fertilizers. / For the purpose of this study, the over application of fertilizers and over irrigation of vineyards is considered minimal. An assumption will be made that the vineyard system is in balance;the proper ` amount of irrigation and nutrients are applied to the plants and excess leaching of fertilizers and irrigation water is minimal. It is unclear weather future residential development will cause a significant loss of vineyard acreage. ba Y/3.4 Future On-Site Sources of Nitrate 113.4.1 Quantity and Quality ofDomestic Wastewater From Proposed Project The following discussion is for determining the long-term waste water flow generated from the proposed residences for the nitrate loading analysis and should not be used for septic system design b" purposes. Typically,use estimates for the sizing of septic stems include a peak use factor,whereas PSP S P � Y P the numbers discussed here are based on long-term averages. One single-family residence and one shop are located at the northeast comer of the property. Each future new parcel is presumed to be four to five bedrooms which may be occupied by up to five people over the long term.A legal second dwelling unit up to 1,500 square feet,could also be constructed on the parcel and is presumed to be occupied by up to three people. Therefore, a total of eight people per parcel will be used to calculate the residential septic tank usage for each parcel. 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 4 L '404 L