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LBA Realty Draft Soil Suitability and Nitrate Loading Study Chapter 4. Sources and Calculated Impact of Nitrate on Groundwater 4.1. Sources of Nitrate to Soil and Groundwater Septic systems and dairies are significant sources of nitrate found in ground water. Farming activities using soil fertilization where sandy soils are present may also contribute to nitrate contamination, especially in shallow unconfined aquifers.The proposed project will add nitrate to the groundwater through the use of on-site septic disposal systems. Although there is no data to determine the groundwater gradients at the site it is likely to follow the slope of the ground, general south to north. The distance between the property and a groundwater boundary (costal hills) is short, so areas/activities that may contribute a nitrate load upgradient are limited.According to satellite photography agrarian use is minor, and there are only 5 to 10 houses on large AR zone lots that are assumed to have on-site septic systems. The project consists of commercial warehousing so the septic load will include bathrooms(toilets,sinks, urinals), and small breakroom areas (sinks,dishwashers).Since the sewage characteristics are not the same as residential (which would include wastewater from showers, washing machines, food preparation, hygiene activities), the nitrate concentration is greater. EPA estimates industrial effluent nitrate concentrations between 25-75 mg/I. Thus, a value of 50 mg/I as Nitrate was used for this study. 4.2. Impact of Rainfall Contribution of Nitrate Load to Project Site An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The Hantzsche and Finnemore method utilizes the "average recharge rate of rainfall" in calculating potential adverse nitrate impacts to the aquifer. It is assumed that not all rainfall will percolate to the aquifer, as water will be lost to evaporation and transpiration. Rainfall recharge is a significant factor in the nitrate loading estimate in the Hantzsche and Finnemore model.A review of the rainfall data from various sources indicate an average rainfall of 13.05 inches in a year. A majority of the rainfall runoff on the project site will be detained in detention basins on site. This method of detention increases the percolation of rain each year. Schaaf and Wheeler investigated the evaporation and transpiration near the project site to determine the percentage of runoff that will percolate to the ground water. Based on a variety of sources it was determined approximately 26% of rainfall runoff will percolate to ground water. Nitrogen concentration for rainfall was estimated to be 1 mg/I nitrate based on Hantzsche and Finnemore. 4.3. Existing On-Site Sources of Nitrate to Soil and Groundwater Currently,there are no septic systems in use at the project site.There was a small leech field and septic tank to serve the previous the industrial application on the site.There is no paperwork or supporting documentation on this according to EHD.There is a septic system to the west of the project site at 14900 W Schulte Road. 4.4. Future On-Site Sources of Nitrate to Soil and Groundwater Three onsite wastewater treatment systems will be constructed to serve each building as a part of this development. Each system includes its own septic tank and leach field.There are no additional sources of Nitrate to the soil or groundwater proposed for this project. November 30, 2020 4-1 Schaaf & Wheeler CONSULTING CIVIL ENGINEERS