Urban development usually involves soil compaction through converting large pervious land into
developed land. This change typically increases runoff during runoff events and consequently may add to
flooding and additional volume of runoff. The wash off of pollutants may also create numerous water
quality and environmental problems for receiving waters. To alleviate this problem many municipalities
are considering low impact development. One technique to reduce runoff in an urban area is to improve
the soil infiltration. This study is specifically undertaken to investigate tilling and compost addition to
improve infiltration rate, and to investigate measurement tools to assess the effectiveness of remediated
soil.
Soil remediation was performed at three sites in an urban area metropolitan area. Each site was
divided into three plots: tilled, tilled with compost addition, and a control plot with no treatment. The
infiltration effectiveness within each plot was assessed by measuring saturated hydraulic conductivity
(Ksat) using the modified Philip Dunne (MPD) infiltrometer during pre- and post-treatment. In addition,
the use of soil bulk density and soil strength as surrogate parameters for Ksat was investigated.
Results showed that deep tillage was effective at reducing the level of soil strength. Soil strength was
approximately half that of the control plot in the first six inches of soil. At two of the sites, tilling was also
ineffective at improving the infiltration capacity of the soil. The geometric mean of Ksat was 0.5e2.3 times
that of the control plot, indicating little overall improvement. Compost addition was more effective than
tilling by reducing the soil strength and compaction and increasing soil infiltration. The geometric mean
of Ksat on the compost plots was 2.7e5.7 times that of the control plot. No strong correlations were
observed before remediation between either soil bulk density or soil strength and Ksat. Simulation
results showed that the amount of runoff generated from a selection of design storms for treated soil
was less than for untreated soil. The results presented in this study may be used as guidance for
urban hydromodification and stormwater management plans.