Mike Hardin

Runoff Curve Numbers for Simulated Highway Slopes under Different Slope, Soil-Turf, and Rainfall Conditions

AbstractHighway infrastructure is a major non-point source of storm water runoff and associated pollutants. Forty-four simulated rainfall tests were conducted over a turf-covered plot-scale test bed that represented typical highway slopes of 25, 33, and 50%. The two soil-turf combinations were Argentine Bahia over AASHTO A-3 soil (fine sand) and Pensacola Bahia over AASHTO A-2-4 soil (silty fine sand). All the tests were conducted in central Florida, where the weather is subtropical. This paper presents the analysis of curve numbers (CN) obtained from simulated rainfall-runoff data. The CN values for the 24 tests conducted on the Argentine Bahia A-3 soil combination varied from 70.4 to 93.0 with a mean value of 79.6. The CN values for the 20 tests conducted on the Pensacola Bahia A-2-4 soil combination varied from 89.0 to 97.2 with a mean of 94.0. The scatter of the CN values was more for fine sand (standard deviation of 8.31) than for silty fine sand (standard deviation of 2.48). Single factor ANOVA sugg...

Total Nitrogen Losses from Fertilized Turfs on Simulated Highway Slopes in Florida

AbstractFertilized highway slopes constitute nonpoint sources of nitrogenous nutrients that are degrading the surface water and groundwater resources. This paper presents the results of simulated rainfall experiments conducted on a plot-scale test bed (slope-adjustable) that was fully exposed to weather for closely representing the conditions of a fertilized turf-covered highway slope in Florida. Thirty-six tests were conducted on three slopes (25, 33, and 50%), simulating two rainfall intensities (12.5 and 25  mm/h). The soils used were fine sand (AASHTO A-3 class) and silty sand (AASHTO A-2-4 class). Following the local highway practices, the tests were conducted after compacting the soils and establishing Argentine Bahia turf over A-3 soils and Pensacola Bahia turf over A-2-4 soils. Two fertilizers were used: a quick release (QR) 10-10-10 and a slow release (SR) 16-0-8. Weather conditions varied considerably during the duration of the project, affecting soil moisture, soil—grass—nutrient interactions, ...

In Situ Permeability Determination Device for Porous Pavement Systems

Porous pavement systems allow for the percolation of rainwater through the system to the underlying subsoil, which results in reduced runoff and pollutant transport. Several devices have been proposed and/or developed to determine the infiltration rates of the porous pavement systems. However, most of the devices only provide the infiltration rate of the pavement system surface layer, or are destructive techniques such as pavement coring for laboratory testing. The objective of this study was to develop and test the efficacy of a new testing device, called the embedded ring infiltrometer kit (ERIK), for field determination of the in situ permeability of porous pavement systems. The ERIK device provides a means to measure the pavement system’s surface course percolation rate as a maintenance indicator and the entire pavement system to evaluate a recovery time throughout the service life. Performance evaluation of the ERIK device showed good reproducibility with a coefficient of variation equal to 7% and repeatability at a 95% confidence interval. The results suggested that the ERIK device is a viable option for field determination of in situ permeability of porous pavements.