What is Dry Weather Screening?
Dry weather screening is a field areas activity performed to help locate and identify harmful and illegal discharges to a municipal storm water system. The field activity (screening) involves inspecting stormdrain outfalls during dry weaether and testing flowing water discharges from the outfall to detect water quality problems in any urban waterway.
The field observations and measurements are performed at each outfall. Those outfalls can consist of pipes, headwalls, ditches and flumes. These outfalls can be located in city's right-of-way or in a drainage easement. The screenings help to detect pollutants such as oil and grease, litter, heavy metals, and sediment. Water quality sampling is used to detect fluoride and surfactants (detergents) that can be found in an illicit discharge due to wash water and tap water.
Investigating for dry weather flow is also an opportunity to identify illegal structures that maybe connected to the municipal separate storm sewer system. An illegal connection can cause serious problems to our water resources by discharging pollutants into the storm sewer system that can go undetected for days, months and years.