HR: 1340h
AN: H33D-1622    [Abstracts]
TI: Groundwater Mounding Beneath Stormwater Infiltration Basins
AU: * Nimmer, M
EM: nimmer@wisc.edu
AF: University of Wisconsin - Madison, 460 Henry Mall, Madison, WI 53706, United States
AU: Thompson, A M
EM: amthompson2@wisc.edu
AF: University of Wisconsin - Madison, 460 Henry Mall, Madison, WI 53706, United States
AU: Misra, D
EM: ffdm1@uaf.edu
AF: University of Alaska - Fairbanks, P.O. Box 755800, Fairbanks, AK 99775-5800, United States
AB: An accurate understanding of groundwater mound formation is important in the proper design of stormwater infiltration basins since these basins are often required to recharge a portion of pre-development infiltration volume. Mound formation due to localized recharge may reduce the infiltration rate of the basin and the ability of the soil to filter pollutants. The goal of this research was to understand groundwater mounding and the potential for contaminant transport resulting from recharge beneath stormwater infiltration basins. A 0.10 ha infiltration basin serving a 9.4 ha residential subdivision in Oconomowoc, Wisconsin was used in this study. Subsurface conditions included sand and gravel material and a groundwater table at 2.3 m below grade. Three storm events, 4.9 cm, 2.8 cm, and 4.3 cm, between August 2006 and April 2007 were modeled using the two-dimensional numerical model HYDRUS. The calibrated model was used to evaluate hypothetical basin operation scenarios for various basin sizes, soil types, ponding depths, and water table depths. The groundwater mound intersected the basin floor in most scenarios with loamy sand and sandy loam soils, an unsaturated thickness of 1.52 m, and a ponding depth of 0.61 m. No groundwater table response was observed with ponding depths less than 0.31 m with an unsaturated zone thickness of 6.09 m. The mound height was most sensitive to hydraulic conductivity and unsaturated zone thickness. A 7.6 cm sediment layer delayed the time to reach maximum mound height, but had a minimal effect on the magnitude of the mound. Mound heights increased as infiltration basin size increased.
DE: 1828 Groundwater hydraulics
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting