Effects of biological activity and precipitation on stormwater retention basin water chemistry in Bryn Mawr, PA

Abstract

The Rhoads Pond waterway on Bryn Mawr College’s campus is a small, but complex and dynamic system that accomplishes the job it was created to carry out. The scope of this study allowed for assertions to be made regarding the state of the waterway during the fall 2006 season as well as on a longer term time-scale. Data shows rain events dilute dissolved ion concentrations and cause electrical conductivity levels to drop. Two diurnal dissolved-oxygen studies as well as biweekly sampling put bounds on the date of autumnal cessation of biological uptake between the end of September and the second week of October. Comparison of all monitoring datasets since 2003 reveals chemical buildups in the retention basin. An assessment of water quality parameters reveals that the character of water leaving the retention basin and entering Mill Creek is less variable than the water entering the retention basin. Lastly, the derivation of an equation relating chloride concentrations and electrical conductivity can allow future estimations of chloride levels using only a handheld EC meter.