Hydraulic Test of a Bioretention Media Carbon Amendment

Abstract

Rain gardens effectively remove some stressors from storm water, but in most cases they show much smaller removal rates of nitrate, likely due to the high sand and low organic matter content of rain garden media inhibiting denitrification. A bench-scale experiment was conducted to test the drainage capability of media containing shredded newspaper layers as a carbon amendment. Storm water was introduced at low and high rates to bins containing zero, one, and two layers of newspaper at varying depths. While there were differences in effluent volumes and flow rates between control and newspaper treatments, surface ponding occurred in all three treatments, suggesting that some other factor besides the newspaper had an effect on drainage properties. Grain size and clay mineralogy analyses indicated the migration of finer particles into the deeper soils, which could have inhibited drainage.