Evaluation of Soil Erosion and Sediment Control Products for Release of Heavy Metals

Introduction

The purpose of this study is to determine if construction site erosion and sediment control best management practices (BMPs) will meet wet weather waste load allocations (WLAs) for copper, cadmium, lead, and zinc required by total maximum daily load (TMDL) regulations. The TMDLs cover the Los Angeles River and the San Gabriel River in southern California and were adopted in 2005 and 2006, respectively. The construction industry in southern California has until 2013 to demonstrate that deployment of construction site erosion and sediment control BMPs will meet the metals WLAs in TMDLs for each river system. If study is not done by 2013, the TMDLs require construction general permit holders working within the two river system watersheds to implement site-specific BMPs and monitoring to demonstrate BMP effectiveness to control the four metals. These measures would be in effect numeric effluent limits at the property boundary.

Literature Review

Little published research from the U.S. and world-wide has been done measuring specific construction site erosion and sediment control BMP performance measurements, such as turbidity, total suspended solids, or metals concentrations or loadings, as most research has focused on performance of BMPs to retain a percentage of available sediment supply compared to an untreated control. No research has been performed to measure BMP ability to meet TMDL waste load allocation performance standards for metals or other constituents. The study described here attempts to fill that data gap and assist the construction industry and regulatory agencies in meeting TMDL compliance requirements. Nonpoint source (NPS) pollution remains a leading cause of degraded water quality in the U.S. (USEPA, 2009). The transport of NPS pollutants is commonly associated with the migration of soil particles, particularly in stormwater runoff (Zhao et al., 1999). Therefore, the development of technologies for soil erosion and sediment control is critical in protecting water quality (Balascio and Lucas, 2009; Harbor et al., 1995; Sojka and Lentz, 1997). Research on the potential of these control products to release their own pollutants is limited, yet some data are now emerging. For example, Beighley et al. (2009) showed that certain products used to control soil erosion can actually lead to degraded water quality. Stormwater runoff from construction sites is an important component of NPS pollution because soil loss from unprotected construction sites is estimated to approach 1000 times the average natural rate of natural soil erosion (USEPA, 2000). The Clean Water Act (CWA) requires that a National Pollutant Discharge Elimination System (NPDES) permit be obtained to discharge runoff from construction sites where more than 2 ha (5 ac) of land is disturbed (USEPA, 1992). To obtain permit coverage, a Storm Water Pollution Prevention Plan (SWPPP), which includes the description of appropriate sediment and erosion controls that will be implemented at a construction site, is required. The pollution control measures specified in the SWPPP are designed to prevent NPS pollution and are known as best management practices (BMPs) (CASQA, 2003; Faucette et al., 2009; Hayes et al., 2005; McLaughlin et al., 2009; Persyn et al., 2007).