The City of Moscow owns and operates a storm sewer system that drains surface water from rain and snow events throughout the City. In October 2019, the EPA designated Moscow’s storm sewer system as a regulated small “Municipal Separate Storm Sewer System,” or MS4. An MS4 is defined as a conveyance or system of conveyances that:
- It is owned by a public entity that discharges to waters of the U.S.,
- Is designed or used to collect or convey stormwater (e.g., storm drains, pipes, ditches),
- Is not a combined sewer,
- And is not part of a sewage treatment plant, or publicly owned treatment works (POTW).
To prevent harmful pollutants from being washed or dumped into the storm sewer, and downstream receiving waters (rivers and streams), Federal law requires cities like Moscow to obtain a National Pollutant Discharge Elimination System (NPDES) permit and to develop a stormwater management program (SWMP). Moscow is now required to create a comprehensive SWMP.
The City’s physical stormwater infrastructure is composed of a range of physical assets:
- Over 2000 stormwater inlets and catch basins
- Just over 1000 manholes
- Almost 100 miles of storm drain pipe
- About one mile of culverts
- 10 miles of open ditch
- Just under 10 miles of receiving waters - Paradise Creek, Hogg Creek, and the South Fork of the Palouse River
- Over 200 known outfalls to these receiving waters
- And 43 surface detention facilities (basins and ponds)
The video below provides an overview of the City of Moscow Stormwater System and changes that are currently being implemented to manage stormwater in Moscow to meet the requirements of our NPDES permit.