§ 34-513. Field data procedures.
Percolation tests shall be performed by state-registered civil engineers and land surveyors or certified soils scientists. A property owner may be allowed to conduct percolation tests on his own individual lot only if deemed qualified by the board of health.
(1)
Percolation tests.
a.
Location. Percolation test holes shall be spaced at least 50 feet apart (spacing may be reduced if approved) and located in the area proposed for the absorption field. The holes shall not be located in floodplains, easements, nor in any other area restricted by this article. Test holes shall not be located in or near streams, draws, banks, stump holes or any other location where percolation test rates would not be representative of typical soil and terrain conditions. Tests holes shall be flagged, staked and numbered in accordance with the soil data record and site plan. All test hole locations including those with passing and failing results shall be shown, including depth of test holes.
b.
Preparation of test hole. Percolation test holes shall be dug or bored with vertical sides, shall be no less than four inches in width and shall extend to the proposed depth of the absorption field. On slopes less than 20 percent, minimum depth of test holes shall be 30 inches to 48 inches, and on slopes greater than 20 percent, the depth of test holes shall be 84 inches. On projects where grading in the field area is proposed, the test holes shall be 30 inches to 48 inches below the proposed finished elevation. Sides of test holes shall be scratched with a pointed instrument to remove smeared soil surfaces and to provide a more natural soil interface into which water may percolate. Loose material shall be removed and no less than two inches of clean gravel shall be added.
c.
Saturation and swelling of soil. Percolation test holes shall be filled with water (and kept completely filled in 30-inch to 48-inch test holes) and kept to an elevation at least three feet above the bottom of the deeper test holes until the soil is saturated and clays have had an opportunity to swell. No tests shall be performed until the soil has been soaked at least four consecutive hours. Overnight soaking is prohibited.
d.
Percolation rate measurement. After soaking, water depths in the percolation test holes shall be adjusted until approximately six inches of water remains over the gravel. From a fixed reference point, established at or near ground surface, repeated measurements shall be made at equal time intervals of the vertical distance in inches from the reference point to the water surface. Water shall be added to restore a six-inch depth if the water falls to less than two inches above the gravel surface. Measurements shall be continued until a constant percolation rate is evidenced, i.e., the water surface drops the same vertical distance each time interval. The time in minutes required for the water column to drop one inch at this constant rate shall be recorded as the percolation rate. When percolation rates vary significantly or exceed 90 minutes/inch fall within the proposed absorption field, additional tests may be required and data on all tests performed (passing and failing) must be submitted for review.
(2)
Borings.
a.
Location. Borings shall be located in areas proposed for the absorption field and shall not be located in floodplains, easements nor in any other area restricted by this article. Borings shall be flagged and numbered accordingly with the soil data record and site plan. All test hole locations, including those with passing and failing results, shall be shown including depth of borings.
b.
Water table borings. Borings to determine groundwater elevation in low areas may be required by the board of health. Borings shall be made to a minimum depth of seven feet. On projects where grading in the field area is proposed, the borings shall be at least seven feet below the proposed finished elevation. Water table elevations shall not be recorded until 48 hours have elapsed for stabilization of groundwater. Location, identification number and depth to water table shall be recorded on the site plan and soil data record. Other records of water table elevation, including seasonal peaks, may be submitted or required.
c.
Rock borings. Where surface outcroppings or subsurface rock or hardpan exist or are suspected, a sufficient number of borings to a minimum depth of seven feet shall be required by the board of health to determine if such conditions may interfere with installation, performance or repair of the proposed onsite sewage management system.
d.
Additional depth. Water table and rock borings shall be required at a minimum depth of 11 feet in areas with slopes greater than 20 percent.
e.
Negative evidence. Evidence of the presence of water or rock in the borings shall negate approval for present and future use of the area tested for installation of an onsite sewage management system.
(Res. of 9-7-88(3), § 30-2-7-8; Ord. No. 18-0340, Att. A, 5-16-18)