SU0002249 SSNL - Laserfiche WebLink

Home Browse Search

l�3 C. SOIL TEST RESULTS SSS§ 6.2. To assess the permeability of the two proposed disposal areas adequately, six 1 percolation:tests were completed at the east and west test site locations. The aerial photo found in Appendix C illustrates the test locations. The test depths were 20; 36, 40 and 48 inches below existing grade, giving a comparatively detailed observation of subsurface permeability within the proposed areas. Only the 36 and 42 inch test depths are recognized as "Off cial" by EHD. The other four tests are recognized as "Unofficial," as illustrated in Tables 2 and 3 below. These test depths represent the.following: Between 20 and 36 inches.below existing.grade is the approximate elevation of the future soil-effluent interface since the height of the Infiltrator Chambers is approximately 12 inches, plus six inches of sand bedding, plus six-to-twelve inches of native sail cover. The 42-inch depth represents typical leachline depth. Although leachlines are not specified design criteria for this project,measured permeability at this depth is useful,information. Permeability information also applies to the 48-inch test depth where two dramatically and inexplicably different percolation test results were obtained between the two test sites. In addition-.to the conventional perc tests conducted.an unconventional backhoe trench test was conducted whereby a 2 x'2 x;2 ft trench was excavated. Pictures of this test are found in Appendix K. The bottom ofthis trench is near the anticipated soil-effluent interface depth. The trench was filled with three inches of water, with the water level decline measured over a four-hour time period. This test replicates infiltration-of water into the soil surface,:similar to what will occur within the -- =chambers. Test results reveal an application rate of 0.531 gallon's/ft'/day, which is comparable to the averageapplication rate of the soil profile. SSS§ 6.3. On August 31, 2009, 0800'hrs the six test borings were hand-drilled for. g g o the east potential disposal area. The sidewall's of each boring were.scored with a pry-bar and the loose material removed. Scoring the sidewalls opens potentially smeared surfaces:. Two 'inches of fine gravel was placed at the bottom and three-inch perforated PVC pipe was inserted inthesix test borings. Each test boring was pre-saturated with 12 inches of water at 0900 hrs,=approximately 24 hrs before the start of testing. SSS:§6.4;.6.5. On September 1, 2009, 0930 hrs, percolation testing comm nced for the east test _ borings. No standing water was observed after the-24-hr,soak period in.any of the test borings. Consequently, EHD Perc Test Procedure#2 was conducted in which testing was done over a four- hour period to induce maximum soil saturation. Test results:for the east:area reveal.that the two official perc.tests had unfavorable permeability results far the 36 and 42 inch test borings. The other 36-'inch unofficial test depth also had unacceptable perc rates. On September 3, 2009; 0830 hrs the six test borings for the west site were prepared under the same procedures as noted above. On September 4, 2009, 0930 hrs, percolation testing commenced. Test results-for the west test site reveal favorable permeability for the two official test boring depths. The perc test results reveal relatively dramatic rates between the two official tests of the east and west test sites. The 36.inch test depths for the east test site is approximately 6.5x slower than the west test site, while the test results for the 40 inch borings show the east test location to be 1.8x slower than the west test site. 6 Chesney Consulting