The sand and gravel general permit requires the permittee to develop and maintain a stormwater pollution prevention plan (SWPPP). The SWPPP must contain information on all the best management practices (BMPs) and structures that control and treat Type 3 stormwater.
Type 3 Stormwater means stormwater discharges from:
The permit includes a list of specific items that must be included in the SWPPP. These items include:
1). Site Map: The site map must identify the stormwater drainage areas and discharge points as well as industrial activities that may impact stormwater. This site map for the SWPPP and for the Monitoring Plan can be the same map as long as it includes the required information to satisfy both requirements.
2). Inventory of Materials: The inventory of materials must list all of the types of materials handled at the site (for example: cement and cement admixtures, petroleum products, gravel piles, recycle storage) that can be exposed to precipitation or run-off. Note: this inventory of materials can also be used in the spill plan.
3). Source Control BMPs: The SWPPP must include a list of the physical, structural, and mechanical devices or facilities intended to prevent pollutants from entering stormwater. These BMPs may include channeling and berming to maintain separation of stormwater and process water. The permit also requires BMPs that comply with (or are equivalent to) Volume IV of Ecology's Stormwater Management Manual for the Puget Sound Basin for:
a. Fueling Stations - SWMM BMP S1.10
b. Vehicle/Equipment Washing and Steam Cleaning - SWMM BMP S1.20
c. Loading and Unloading Liquid Materials - SWMM BMP S1.30
d. Liquid Storage in Above-Ground Tanks - SWMM BMP S1.40
e. Container Storage of Liquids, Food Wastes or Dangerous Wastes - SWMM BMP S1.50
f. Outside Storage of Raw Materials, By-Products or Finished Products - SWMM BMP S1.60
NOTE: The Stormwater Management for Western Washington is the current source of BMPs. Although the revised manual does not use the S1.xx naming convention, it does include the same set of BMPs. see discussion below on "Stormwater Management Manual"
4). Stormwater Treatment: If operational and source control BMPs are not sufficient to prevent contamination of stormwater, treatment may be necessary. Treatment BMPs may include: oil/water separators, biofiltration, infiltration basins, detention facilities, and constructed wetlands.
5). Stormwater Inspections (Permit S4.F): There must be at least one wet season inspection and one dry season inspection of all active mining sites and asphalt batch and concrete batch facilities. The primary purpose of the wet season inspection is to determine how well all SWPPP BMPs are working when exposed to a major storm event (e.g., do covered areas really keep out the rain, are there any unusual odors, etc.). The primary purpose of the dry season inspection is to inspect the stormwater drainage system for the presence of non-stormwater discharges. The results of these inspections must be written down and kept with the stormwater pollution prevention plan.
The SWPPP provides a list of the best management practices (BMPs) that are in place at a site to protect stormwater. The actual content of the SWPPP will vary depending on site-specific conditions. A "Pollution Prevention Team" for instance, would only be one person at a facility owned and operated by one individual. A facility that does not conduct refueling onsite would not include the refueling BMP. Some BMPs that will often be part of a SWPPP include:
Covered Storage: Chemicals stored outside should be covered so that rainfall does not become contaminated by contact with the chemical containers. The SWPPP should include this as a standard practice at the facility and the map should identify the covered storage areas.
Equipment Maintenance: The SWPPP should identify equipment that can spill or leak contaminants such as petroleum products. Provide an inspection and maintenance schedule for each piece of equipment that is identified.
Employee Training: The first line of defense will often be the employee that is onsite working. With proper training, employees can make a big difference in properly managing stormwater and protecting it from contamination.
Site Maintenance: Grading the site to provide even infiltration of rain and keeping the site clean will minimize contamination of stormwater.
Infiltration: Typically it will be desirable to infiltrate all or part of the stormwater that falls on a site. A grassy swale, infiltration trench, or a constructed wetland may provide adequate infiltration for all or most stormwater events. However, when stormwater has become contaminated with pollutants such as oil and grease, treatment may be required before infiltration.
Detention Pond: At sites that discharge stormwater to surface water, a detention pond will typically be required to control turbidity. Careful attention to pond dimensions and design is necessary to accommodate major storms and provide adequate settling.
Ecology released The Stormwater Management Manual for Western Washington in 2005. This updated manual replaces the previous manual, Stormwater Management Manual for the Puget Sound Basin. The Stormwater Management Manual for Eastern Washington was released in 2004. Facilities should transition to the new manuals. In the revised manual, Volume IV Source Control BMPs is a very good source of information on BMPs to include in the stormwater pollution prevention plan. In addition to the BMPs listed in Volume IV, Volume I provides information on developing a plan, Volume II provides BMPs for erosion and sediment control, and Volume III provides information on hydrologic analysis. It is highly recommended that permittees obtain a copy of the revised manual and read through it. Stormwater Management and Design Manuals
The plan is not intended to just sit on the shelf after completion. The permit requires periodic review and updates to keep the plan current. The plan should also be used during employee training. The plan is intended to become a part of doing business at a site and to be a living document.
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