Land Application of Urban Horizontal Directional Drilling Residuals to Established Grass and Bare Soils

Horizontal directional drilling (HDD) is a non-invasive alternative to trenching used for the installation of many common utilities. The process involves drilling fluid used to stabilize the borehole, lubricate the bit, and float cuttings to the surface. A sustainable alternative to landfill disposal is land application. Two field studies were conducted to determine the optimum application rate of HDD residuals to both established bermudagrass and bare soil seeded with bermudagrass. Residuals were applied at six rates ranging from 0 to 112 tons solid ha −1 for both trials. Soils were sampled 7, 30, and 90 days after application. Saturated paste and Mehlich-3 extractions were performed on all samples. Grass biomass was measured at the end of the study. No significant amount of nutrients or trace metals were found in the treated soils. All concentrations were in the range of typical soils. However, total dissolved solids (TDS) and sodium absorption ratio (SAR) increased with application rate. There was no significant difference in the yields of forage harvested on the established grass plots 110 days after application. Bare plots that received 22 tons solid ha −1 had higher percent ground cover than other rates. It is ecologically safe to apply HDD residuals up to 112 tons and 90 tons solid ha −1 to established bermudagrass and bare soil, respectively.