Reducing Stormwater Runoff Volumes with Biochar Addition to Highway Soils

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CAIT project no.: CAIT-UTC-NC44

Fiscal Year: 2015/2016

Status: Final

Rutgers-CAIT Author(s): Paul T. Imhoff, Ph.D., Julia A. Maresca, Ph.D., Patrick Szary, Ph.D

External Author(s): Peter Mattejat, PE

Sponsor(s): USDOT-FHWA, Maryland Transportation Authority


Through funding from the National Fish and Wildlife Foundation (NFWF), we recently constructed and instrumented a section of highway roadway soils at the intersection of state route 896 and Bethel Church Road in Summit Bridge, DE. One stretch of roadway soils was amended with biochar, while an adjacent control section was not. In-ground sampling trenches upgradient and downgradient from the test sections are used to quantify the stormwater runoff from each section and the nutrients in the runoff: thus, we are documenting the direct effect of biochar on reducing stormwater runoff and reducing concentrations of nutrients (nitrogen compounds) in the runoff.

This field site will be operated for the next 1-1.5 years, quantifying the effect of biochar-amended highway soils on reducing stormwater runoff and improving runoff quality. In this CAIT at UD project, a disc infiltrometer will be used at monthly intervals to track the time-varying soil infiltration capacity, which we expect will increase with time as biochar alters microbial communities. Concurrently, soil samples will be extracted and microbiological tools used to assess changes in microbial communities, and soil aggregation will also be quantified in these samples using standard soil analysis methods.

Reductions in stormwater runoff data from the NFWF project will be paired with water infiltration, microbial assay, and soil aggregation data collected from this project. Combined, these data will allow us to understand the mechanism(s) by which biochar reduces stormwater volume, which is critical for extrapolating the results from this field test to longer time periods and other highway soils.