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SIGNET �Vd STL Project No. 0010771 7L-sUng Labs Page 4 i. Methemoglobinemia occurs when infants, particularly under six months of age, ingest drinking water r with a concentration of nitrate-nitrogen greater than 10 parts per million. These young children lack the necessary bacteria to transform nitrate properly. As a result, the nitrate oxidizes the iron in the hemoglobin of red blood cells to form methemoglobin. Methemoglobin lacks the capacity to carry r oxygen and the resulting condition can be fatal if undetected. The determination of the concentration of nitrate-nitrogen was conducted utilizing a simple mass r balance equation, often referred to as the Hantzsche and Finnemore Equation. The equation is somewhat conservative as it represents the worst-case long-term effects and does not take into account factors that may lower the over-all nitrate concentrations, s�a�5 r Additionally, two down-hole percolation tests were condaeL at a depth of 6 feet b w existing site grades. The results of our test determination were noted to be favora a as noted further in this r writing. Two selected soil samples were tested for nitrate as NO3, please refer to Appendix D. In summary, the site was noted to exhibit satisfactory percolation rates within the soil profile to be r utilized for the septic disposal field. The soils encountered within the upper zones were identified as fine sandy silts and were underlain by silty clays. The depth to groundwater was estimated at 30 feet below site grade within the project vicinity. Our analysis has shown that the use of a standard septic system should not ady_etsely impact the groundwater quality with respect to the accumulation of nitrates. The highlights_of our analysis are presented in Appendix D. SOIL, PROFILE AND SUBSURFACE CONDMONS r Based on our findings, the subsurface conditions encountered appear typical of those found in the geologic region of the site. In general, the subsurface soils consisted of sandy silts (ML) and silty sands (SM) in the upper six to eight feet below existing site grades (bsg). A representative sample consolidated approximately 4.5 percent when subjected to a 2-ksf load in a saturated condition. In boring B2, a clayey sand (SC) was encountered to a depth of seven feet bsg. These soils were typically r classified as loose or soft within the upper two feet with standard penetration values ranging from 7 to 10 blows per foot. A representative soil sample from 3 feet bsg noted an angle of internal friction of IS degrees with a cohesion of 950 psf. Dry densities ranged from 92 to 100 pounds per cubic foot with in- situ moisture contents ranging from 5 to 8 percent. Below two feet, the consistency of the silts and sands ranged from firm to hard as noted by standard penetration resistance values between 9 and 67 bpf. Dry densities ranged from 93 to 112 pcf with moisture contents between 4 and 15 percent. The sands and silts were underlain by stiff to hard silty clays (CL). Dry densities were noted to vary between 100 and 116 pcf with in-situ moisture contents ranging from 15 to 23 percent. r No expansive soils or shallow groundwater were encountered with any of our exploratory borings. For additional information about the soils encountered, please refer to the logs of borings in Appendix A. 6. 1417 No. Market Blvd.,Suite 1 • Sacramento, CA 95834 . (916) 568-5858 • Fax: (916)568-5813