Urban Impacts on Ground Water Quality and Flow Characteristics in Schmeeckle Reserve

Abstract

Schmeeckle Reserve is a 190 acre natural area located in the Central Sands Region of Wisconsin. The area is predominantly wetland with sandy loam soil and a depth to ground water of five feet or less. The Reserve is bordered to the north and west by expanding commercial and urban development. Runoff from this development and from major roadways is diverted into the Reserve which functions as a catchment basin. In addition, ground water recharge occurring on these areas flows under the Reserve. This study was initiated to evaluate the impacts of urban storm water runoff on the ground water quality in the Reserve. Single-depth and nested wells were used to map local ground water flow and to sample for contamination. Land surface contours were mapped to determine storm water runoff drainage patterns. The study concentrated on chloride and sodium concentrations related to road salt, benzene, toluene, and xylene concentrations related to gasoline and oil, and lead, zinc, and copper concentrations related to motor vehicles and gasoline. Nitrogen, phosphorus and basic water chemistry parameters were also analyzed to document any water chemistry changes. Sampling began in the fall of 1985 and continued through July of 1987. Mean chloride concentrations ranged from 1 mg/1 at a control well to 2054 mg/1 at a well nearest to storm water drainage. Corresponding mean sodium concentrations were 2 mg/1 and 655 mg/1 respectively. Of the volatile petroleum components, only benzene was detected at concentrations above 1.0 ug/1 within the Reserve and then only at one well. The mean benzene concentration at the well was 6.7 ug/1 and does not appear to be attributable to runoff. This contamination may be attributable to an underground petroleum storage tank or to improper disposal of petroleum products. Mean dissolved and total concentrations of lead, zinc, and copper in ground water did not suggest contamination was occurring. A secondary objective was to evaluate atmospheric contributions of metals to the Reserve. Lead accumulations in moss ranged from 16.86 mg/kg at a control site outside the Reserve to 140.90 mg/kg within the Reserve. Zinc ranged from 57.58 mg/kg at the control to 747.72 mg/kg within the Reserve. These data suggest that atmospheric contributions of lead and zinc to the Reserve are significant.