1981-11-27 Septic System Design Report

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#615 Ringer Subdivision Page 4 Lot 2, Block 1 Peres PB21 thru PB26. Borings BB21 thru BB23. Average perc rates for bath primary and alternate sites are acceptable. Slopes are nearly leve_ at the tested sites, ranging from 0 to 3%. Mottling indicated below 2', with actual water table at 3.2 to 4.21. A standard mound system should be used due to the presence of shallow saturation Ines. Lot 3, Block 1 Peres PB31 thru PB26. Borings BB31 thru BB33. Slopes in the primary site are approximately 6-8%, on a slight flattening Of the 10-12% slopes surrounding it. Borings in the primary sites indicate 1 to 2 ' of loamy topsoil over a 6" layer of organic clay topsoil over a plastic sandy clay. Actual water table at the primary site was below 51. However, the high plasticity indicates a heavy clay that is probably saturated. The secondary site was mottled below 1.5 feet with an actual saturated zone at l' depth. Coupled with a slope of 10% the secondary site is marginal for a mound system and would require at least 2' of sand base as part of the design. I suggest that a standardpressure mound system be required for both sites with added sand depth for the secondary system. Please note that this lot is the most tenuous in the subdivision in terms of slope and soils consideration for using a mound system. Should a proposed house location encroach on either of the tested sites, careful review and possible additional testing will be needed to ensure that a mound can still be used. The site does not appear capable of supporting any kind of a trench system. Lot 4, Block 1 Peres PB41 thru PB46. Borings 3B41 thru BB43. Slopes average 5% - 7% overall. Borings indicate actual water table at 4' with mottling at a depth of 3-4' for the primary and 2' at the secondary site. Perc xates were fairly uniform throughput these tested sites. A depression/drainageway to the immediate south of the tested sites must be avoided during construction of the systems. I would recommend a standard pressure mound for both sites. Lot 5, Block 1 Peres PB51 thru PB56. Borings BB51 thru BB53. Slopes are 3% to 6% overall. Mottling at the primary site started at 2.7 to 3.5' with actual water table at 3.7 to 5.0'. This site is acceptable for a standard mound system. The alternate site has a perc rate considered too slow for any system by code. However, close scrutiny shows that the peres were taken at depth in the sandy clap subsoil, not in the topsoil. In general, throughout the entire subdivision the testing done at a depth of 12", in the topsoil, indicates acceptable percolation rates, with testing at 24" or more indicating slower, marginal perc rates. In my opinion, this site is no different than most of the others, and would have an acceptable perc rate if tested at the 12" depth in the sandy loam topsoil. No further'testing should be required; a mound system is recommended.