Stormwater management - Southwest Washington

Vault stormwater filter

Above: well maintained stormwater filter vault. Below: lid and entrance to an underground closed detention facility.

Closed detention system





Signs that maintenance is needed and a checklist for maintaining the facilities below, including how to fix problems.

Stormwater filter

A stormwater filter is a passive, flow-through filtration system. It is comprised of a vault that houses rechargeable filter cartridges. It works by passing stormwater through the filters, which traps particulates and/or absorbs pollutants such as dissolved metals and oils.

The filter material is housed in cartridges enclosed in concrete vaults or manholes. Various filter materials are available from private companies.

Vortex sedimentation vault

A vortex-enhanced sedimentation vault consists of a cylindrical vessel in which incoming water spirals like a whirlpool, causing the heavier particles to settle out. It uses a vortex-enhanced settling mechanism (swirl-concentration) to capture solids, floatables, oil and grease.

Closed detention system

A closed detention system is an underground structure, typically a concrete vault or series of large diameter pipes, which temporarily stores stormwater and releases it slowly. They typically are used on sites that do not have space for a pond. These underground detention systems are enclosed spaces where harmful chemicals and vapors can accumulate. Therefore, the inspection and maintenance of these facilities can only be done by individuals trained and certified to work in hazardous, confined spaces.

Additional elements to vault facilities

Flow controlFlow control structure/flow restrictor
Underground flow control structures and flow restrictors direct or restrict flow in or out of facilities. They slowly release stormwater at a specific rate. It is important to make sure they do not become plugged or damaged because the facility could release water too quickly or too slowly and overflow. They are usually found in manholes.