In 2013, the Nevada Department of Transportation (NDOT) installed two side-by-side stormwater treatment vaults on State Route 431 (SR431) in Washoe County above Incline Village, Nevada. 

The purpose of the project was to evaluate and compare the effectiveness of two adjacent stormwater treatment vaults, the Contech Media Filtration System (MFS) and the Contech Jellyfish, each containing a different type of filter. Both filter types are designed to remove fine sediment particles, the particles that are primarily responsible for the loss of lake clarity.

NDOT wanted to investigate which filter type worked best for the type of stormwater runoff generally associated with a relatively steep highway with moderate to high traffic density and near 100% impervious surface. Stormwater from this type of roadway tends to have high sediment loads, primarily due to the road sanding necessary to keep vehicles from sliding on ice and snow in the winter. 

Stormwater runoff from approximately 1.4 acres of traffic lanes enters a transverse drain adjacent to SR431. It then flows through a pipe to a splitter vault that theoretically routes equal amounts of flow through two inflow pipes to each type of filtration vault.  After the runoff has been treated in each filter vault, the flow exits through respective pipes that lead to a perennial stream called Deer Creek. Deer Creek is a tributary to Incline Creek, which discharges to Lake Tahoe.

The inflows and outflows of both vaults have been monitored for the last seven years. We have learned that though sediment removal efficiencies are similar when both vaults are clean, the Jellyfish gets overwhelmed by accumulated sediment more easily and needs to be maintained more often. The Jellyfish vault is much smaller than the Contech MFS vault and can therefore not accommodate as much accumulation before clogging. However, the Jellyfish filters can be cleaned and reused, while the MFS filters must be replaced. Therefore, in a location with lower sediment loads, where the Jellyfish wouldn’t be overwhelmed as often, it may be the cheaper option. 

To view the NDOT SR431 seasonal reports visit Publications & Helpful Links

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