Impacts of Soil Texture, Structure, and Compaction on Bioinfiltration Device Performance: Results of Lab and Field Investigations

Biofiltration devices are a potentially effective option for the treatment and disposal of stormwater runoff from urban areas. However, the performance of these systems, and other infiltration devices, are affected by factors such as the texture, structure, and degree of compaction of the media during their construction. This paper presents the results of laboratory and field-scale studies conducted to provide insight on media characteristics of a poorly operating biofilter facility located in Tuscaloosa, AL. Double ring infiltrometer tests and soil compaction measurements were conducted along a large biofilter to determine the in-situ characteristics of the media. Infiltration measurements were also made during rain events for comparison to the results from the lab tests and the double-ring infiltration measurements. The effects of different compaction levels on the infiltration rates through the soil media were also examined during laboratory column tests, along with benefits associated with adding sand to the media mixture. The results indicated that soil compaction has dramatic effects on the infiltration rates; therefore, care needs to be taken during stormwater treatment facilities' construction to minimize detrimental compaction effects. Adding sand to a media having large fractions of clay-sized particles helps minimize the detrimental effects of compaction on the infiltration rates also.