2021 Kitsap County Stormwater Design Manual
2021 Kitsap County
Stormwater Design Manual

3.5.2 S429: BMPs for Storage or Transfer (outside) of Solid Raw Materials, Byproducts, or Finished Products

Description of Pollutant Sources: Some pollutant sources stored outside in large piles, stacks, etc. at commercial or industrial establishments include:

  • Solid raw materials

  • Byproducts

  • Gravel

  • Sand

  • Salts

  • Topsoil

  • Compost

  • Logs

  • Sawdust

  • Wood chips

  • Lumber

  • Concrete

  • Metal products

Contact between outside bulk materials and stormwater can cause leachate, and erosion of the stored materials. Contaminants may include TSS, BOD, organics, and dissolved salts (sodium, calcium, and magnesium chloride, etc.).

Pollutant Control Approach: Provide impervious containment with berms, dikes, etc. and/or cover to prevent run-on and discharge of leachate pollutant(s) and TSS.

3.5.2.1 Applicable Operational BMPs

  • Do not hose down the contained stockpile area to a storm drain or a conveyance to a storm drain, or to a receiving water.

  • Maintain drainage areas in and around storage of solid materials with a minimum slope of 1.5 percent to prevent pooling and minimize leachate formation. Areas should be sloped to drain stormwater to the perimeter for collection or to internal drainage “alleyways” where no stockpiled material exists.

  • Sweep paved storage areas regularly for collection and disposal of loose solid materials.

  • If and when feasible, collect and recycle water-soluble materials (leachates).

  • Stock cleanup materials, such as brooms, dustpans, and vacuum sweepers near the storage area.

3.5.2.2 Applicable Structural BMPs

For stockpiles smaller than 5 cubic yards, place temporary plastic sheeting (polyethylene, polypropylene, hypalon, or equivalent) over the material (see Material Covered with Plastic Sheeting figure in Volume IV of the Ecology Manual).

The source control BMP options listed below are applicable to:

  • Stockpiles larger than 5 cubic yards of erodible or water soluble materials such as:

    • Soil

    • Road deicing salts

    • Compost

    • Unwashed sand and gravel

    • Sawdust

  • Outside storage areas for solid materials such as:

    • Logs

    • Bark

    • Lumber

    • Metal products

Choose one or more of the following Source Control BMPs:

  • Store in a building or paved and bermed covered area (see Covered Storage Area for Bulk Solids figure in Volume IV of the Ecology Manual).

  • Place temporary plastic sheeting (polyethylene, polypropylene, hypalon, or equivalent) over the material (see Material Covered with Plastic Sheeting figure in Volume IV of the Ecology Manual).

  • Pave the area and install a drainage system. Place curbs or berms along the perimeter of the area to prevent the run-on of uncontaminated stormwater and to collect and convey runoff to treatment. Slope the paved area in a manner that minimizes the contact between stormwater (e.g., pooling) and leachable materials in compost, logs, bark, wood chips, etc.

  • For large uncovered stockpiles, implement containment practices at the perimeter of the site and at any catch basins as needed to prevent erosion and discharge of the stockpiled material off site or to a storm drain. Ensure that no direct discharge of contaminated stormwater to catch basins exists without conveying runoff through an appropriate treatment BMP.

In addition to the requirements listed above, Kitsap County also requires the following for site access:

  • Limit vehicle access and exit to one route, if possible.

  • Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize tracking sediment onto roads. See BMP C105: Stabilized Construction Access in Volume II of the Ecology Manual.

  • Locate wheel wash or tire baths on site, if the stabilized entrance is not effective in preventing tracking sediment onto roads. See BMP C106: Wheel Wash in Volume II of the Ecology Manual.

  • If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example, during wet weather). Remove sediment from roads by shoveling, sweeping, or pickup and transport of the sediment to a controlled sediment disposal area.

  • Conduct street washing only after sediment removal in accordance with the previous bullet. Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State.

3.5.2.3 Applicable Treatment BMPs

Convey contaminated stormwater from the stockpile area to: