SU0006059 SSNL - Laserfiche WebLink

Home Browse Search

F7CONCLUSIONSUSIONS AND RECOMMENDATIONS tion and testingof the soil properties within the proposed disposal area reveal that the oils under the plowed layer are highly fractured and blocky, which enable them to t large volumes of water. However, when the soils become saturated, they swell, acking, and macropores and micropores to seal, thus leading to impermeability. Because of the small pore space characteristics of the clay soil, capillary action is facilitated, and the soils rapidly dry out to restore permeability. Consequently, with rotational applications of effluent in the drip irrigated disposal area, along with carefully applied domestic irrigation water,the surface soils should manage the anticipated effluent flow volumes through evapotranspiration six, and possibly eight months out of the year. In addition, nitrate-nitrogen loading will also decrease by landscape grass root uptake. It is theoretically possible that the grass groundcover may absorb most of the nitrogen in the effluent. This can be partially quantified and monitored by analyzing the nitrogen content and the volume of the mowed grass clippings over the drip irrigated disposal area. The landscape grass groundcover can be any perennial grass that does not go dormant in the wintertime. Kentucky blue grass was used as an example in the calculations. The grass may be a mixture of blue grass and tall fescue. It is important the grass be medium-to-deep rooted to transpire effluent and uptake ammonium and nitrate molecules. When the grass is mowed, the clippings must not be mulched back into the thatch; clippings must be bagged and discarded. Mulching continues and completes the nitrogen cycle, and introduces additional nitrogen back into the root zone through mineralization. The subsurface clay soils from 1.5 to 3 feet below the plowed layer are compacted and impermeable. Soil infiltration test results suggest this stratum cannot manage effluent under any conditions. The distinctive fine silty sand material underlying the dense clay stratum exhibited excellent permeability characteristics even under severely saturated conditions. Using the conservative percolation test results (43 mpi) for correlation with an effluent application rate, we find the Long-Term Acceptance Rate(LTAR) is 0.465 gals/ftZ/day. As calculated on Page 19, the St. Bernard's Church Complex is the land-use that will theoretically contribute the lowest nitrate-nitrogen loading, in comparison to agricultural production and residential housing on septic systems. From the nitrate analysis of the water table, it can be deduced that nitrate impact is from historical agricultural inputs and naturally occurring geological formations. Safety factors incorporated into wastewater flow volumes and nitrate loading calculations include the following: 1. Historical water usage contains an unknown percentage of landscaping water. 2. Assumption that all water usage from the existing Church water meter is eventually wastewater. 2. The Total Nitrogen used is extremely high according to the scientific literature. 3. "Two years in ten"data was used for rainfall volume. 4. There will be unquantifiable dilution effect from stormwater drainage structures downgradient from the wastewater disposal areas. Page -23- Chesney Consulting