CEI provides comprehensive field services that include outfall inspections, illicit discharge identification and investigation as well as GPS and GIS based mapping. A typical outfall inspection project will include verification of outfalls during dry weather conditions for non-stormwater flows and potential illicit discharges. Observations are made at each outfall and are recorded on standardized inspection log forms to document site conditions such as deposits, surrounding vegetation, erodibility, surrounding land use, sediment depth, pipe material, pipe condition, pipe size, type of outlet structure, whether the outlet discharges directly to a surface water, flow depth (if any), appearance/color of flows or surrounding area and odor of flow or surrounding area. This information is recorded on a GPS, along with the outfall coordinates, and by hand on hard copies of log sheets. Comments are also provided as necessary to expand upon the findings.
Once an illicit discharge is identified at an outfall, further investigation is necessary to identify the source. A source investigation generally begins by identifying the drainage network contributing to an outfall and tracing the path of the illicit discharge to the upstream source. Field surveys are conducted to evaluate the drainage system and land area that contributes to an outfall to determine if there are any obvious sources that could be causing the illicit discharge (for example a nearby car washing event). Tracing the drainage system by inspecting manholes and connecting drainage pipes can often lead to the source. Also, field crews can simply follow the non-stormwater discharge if significant flow is present.
In cases where the flow cannot be traced due to blind connections or complicated drainage networks, fluorometric dye can be used to trace flows from unknown pipes to identify illicit connections to the drainage system. It is important to use a fluorometric dye that is non-toxic to humans and aquatic life. Smoke testing is another method used to discover and investigate illicit connections. Non-toxic smoke can be injected into the drainage system or into individual unknown connections to the drainage system, using plugs and barriers to isolate areas of concern to prevent smoke from easily escaping through manholes, catch basins, or daylight areas. CEI can also provide comprehensive water sample collection services if required include the use of in-situ water quality equipment.
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