Evaluation of Exfiltration Systems
Exfiltration systems release water from underground storage to the surrounding soil. Because of increasing growth in urban areas less surface storage areas are available, thus underground storage with exfiltration of the stored water becomes a viable option. Actual construction practices for exfiltration systems were examined. During construction fine material and construction debris has to be eliminated from the rock and pipe. The removal of fine material from the aggregate by washing also will improve life expectancy. Four design parameters were postulated to be the most important for exfiltration system performance over time, namely, initial stormwater solids loading, type of existing parent soil material (sandy or silty), woven or non-woven fabric, and water table location (wet or dry system). Sixteen experimental exfiltration tanks were built and stormwater added until the equivalent of 2 years of runoff from an impervious surface was added. Each system was designed to store the runoff from one inch of rainfall. About two years of rainfall-runoff processes were simulated. The experimental data indicate that a reduction in stormwater solids results in higher exfiltration rates. The type of parent existing soil material must be defined before a permeable fabric is chosen. The woven (Mirafi 700XG) fabric performed with a higher exfiltration rate when silty soil was present and a lower rate when sandy soil present. On the other hand, the non-woven (Mirafi 140N) fabric performed best when sandy soil was present. A comparison of systems built in the water table with those not in the water table indicated that significant storage is lost in the high water table situation but exfiltration rates are not significantly different between the low and high water table situations.
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Wanielista, Martin P.
Master of Science (M.S.)
College of Engineering
Civil and Environmental Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic
Evans, David L., "Evaluation of Exfiltration Systems" (1990). Retrospective Theses and Dissertations. 3983.