WSDOT begins the large task of inventory and mapping for new stormwater permit

Workers inventory and map all stormwater features within state right-of-way.

Imagine counting every stormwater drain, ditch, pipeline, culvert, and pond within a one-mile area, including paved roads and parking lots. Now multiply that by the thousands and you begin to get a sense of the undertaking WSDOT is facing as it begins an inventory of all of its stormwater features.

This work is part of the new National Pollutant Discharge Elimination System (NPDES) permit that was issued to WSDOT by the State Department of Ecology in 2009 and amended in early 2010. The permit includes regulations WSDOT must meet to comply with the federal Clean Water Act and state water quality laws.

Although WSDOT has been doing its part to protect the environment through stormwater management since the 1990s, the new permit significantly expands stormwater runoff management to a greater degree, over a larger geographic area.

Regulates stormwater runoff from:

• Highways – 1,600 centerline miles
• Ferry terminals – 11
• Park and ride lots – 12
• Safety rest areas – 6
• Maintenance facilities – 32

Some 7,250 miles of ditches that drain highways within the permit area are being counted.

Requires inventory and mapping of all stormwater facilities within the permit area.  

These include an estimated:

• 7250 lineal miles of open ditches – some draining both sides of the highway and median area
• 25,000 discharge points – the point at which stormwater leaves the WSDOT right of way, or enters water within the state right of way. These points may include outfalls to Puget Sound, lakes, rivers, streams, ponds and wetlands; an adjacent city or county's storm sewers; a land surface area such as a forest or field; or to a stormwater treatment and flow control facility designed for infiltration.
• 30,000 catch basins – a structural device in the drainage system designed to trap debris so that it cannot enter the drainage system. These will need to be inspected, cleaned and repaired on an annual basis.
• 1,893 stormwater treatment and flow control facilities – also known as Best Management Practices (BMPs) which may include ponds, bioswales, dry wells, media filter drains, vaults, and natural and engineered dispersion areas.
• Unknown number of pipelines – there is a vast network of pipelines that carry water away from roadway surfaces and bridges, into and out of BMPs and connect to municipal storm sewers.

Catch basins along high speed and high volume highways are difficult to access without disrupting traffic.

This inventory creates some unique challenges
In addition to the increased geographic scope of coverage associated with WSDOT's new permit, other challenges to the stormwater inventory and mapping include:

• Worker safety and access to features – many stormwater features are along high speed or high volume roadways which may require workers to close a lane to safely do their work.
• Coordination with city, county or other permitted jurisdictions that share a common boundary. This will ensure that WSDOT stormwater systems are mapped and match up to connections with other jurisdictions' stormwater systems.
• Sheer number and complexity of many Western Washington stormwater systems will take considerable time and effort.

WSDOT is using a variety of sources to collect stormwater data in order meet the permit requirements in the most efficient and cost-effective manner possible. All information will need to be confirmed, updated and/or added to an inventory database. These sources include:

• Using existing documents – Digitizing and gathering feature location and attribute information from existing highway plan sheets, called "as builts", and other documentation, such as hydraulic reports, will be used to develop a base map.
• Existing field data – previous or current field data from activities that share common features and attributes.
• New field inventories – these initial efforts will focus on areas where there are data gaps, then expand to areas with existing information needing confirmation

Anticipated costs associated with the new permit

Specialized equipment, such as this vactor truck, will be used to maintain each of 30,000 catch basins in the permit area.

Next steps
Once these stormwater features are inventoried and mapped, WSDOT will implement an ongoing process to maintain and inspect them on an annual basis. We will also begin monitoring water quality from paved surfaces and evaluate a number of BMPs for their pollutant removal effectiveness.

While some funding to begin implementation of the permit was included in the 2009 – 2011 budget and FY 2011 supplemental budget, many of the key requirements of this permit will require additional funding from the legislature.
 
More information
More details about the permit requirements and information on BMPs are available in WSDOTs 2011 publication, " WSDOT Improving Stormwater Management – Implementing a New Permit. " (pdf 438 kb)

For questions or more information contact:
Cory Simon, Stormwater Features Inventory Coordinator, SimonC@wsdot.wa.gov , 360-570-2589.