Stormwater Discharge Sampling on LUP Projects: Solutions for Effective Sheet Flow Sampling
Background. Identifying representative discharge sampling locations and collecting samples at active linear underground/overhead projects (LUPs) pose numerous challenges. These challenges include geographically separate and remote work locations, varying ground cover (e.g., asphalt, vegetation, gravel, soil, mulch, sand, etc.), and small disturbance areas. Sampling staff also need to work in the rain and adjust to changing site conditions throughout the project lifecycle. Unlike an industrial or traditional project where discharge locations can be identified and established before a rain event, LUPs have limited space and multiple geographically disparate project locations where samples may need to be collected. These challenges may be compounded when supporting multiple projects and/or multiple clients.
Approach. ETIC has developed several strategies and tools to control risk and mitigate concerns for clients with LUP projects: 1) Standard sampling procedures and forms; 2) Sheet flow sampling kits; and 3) Annual training for sampling staff. Creating standard sampling procedures and forms has allowed for quick and efficient data evaluation, which facilitates timely site evaluation and corrective actions if numeric action levels (NALs) are exceeded. Issues are quickly detected and can be corrected during the same sampling event or rain event where they are identified, bringing discharge sample results back within the acceptable range. The biggest challenge to sheet flow sampling is being able to collect representative samples from sheet flow discharges. ETIC has identified best practices for sheet flow sampling and equips our sampling staff with the appropriate tools to address the project and a myriad of environmental challenges. These tools include pre-made kits, assembled using readily available materials, that can be used to concentrate the sheet flow and collect samples that are representative of the stormwater discharge from a project site. ETIC provides annual training to sampling staff which includes a classroom presentation and hands-on simulation to demonstrate how to collect sheet flow samples. The training emphasizes the importance of proper sample collection and demonstrates alternative sampling techniques for different environments using readily available materials.
Conclusions. The sampling tools and techniques that ETIC has developed address the challenges associated with collecting samples on LUPs and have provided an effective way to sample sheet flow while minimizing the time required for sampling. These tools and techniques also can be applied to industrial projects where it is necessary to collect stormwater discharge samples from multiple locations where there is minimal water flow and depth.