Industrial Demolition Tip: Managing Stormwater Runoff

Backwash  Sudden runoff from something upstream..Today we’re talking about how the industrial demolition industry manages stormwater runoff in general, with a special focus on Portland Industrial Demolition sites. In nature, soil and plants absorb water and act as a natural filtration system. However, in cities, pavement, buildings, and parking lots cover up naturally absorbent materials, so rainwater must wash over these hard surfaces instead. As the water flows, it picks up debris and contaminants (engine oil, heavy metals, dust, etc.) and carries them into rivers and streams. Pollutants such as engine oil can poison downstream life forms. Even extra silt from stormwater runoff can have a huge impact on aquatic life. So contractors have a societal responsibility to minimize the effects of job site stormwater runoff.

Previously, we’ve discussed the typical hazards associated with stormwater runoff in demolition sites, including pollutants and extra sediment. Industrial demolition sites pose an even great danger to people and the environment because they often contain hazardous waste, such as radioactive materials. When disturbed, these toxic wastes may enter stormwater runoff and eventually local watersheds. Let’s take a look at how industrial demolition contractors can prevent hazardous stormwater runoff.

Developing your stormwater runoff plan. The EPA publishes a 50-page document that is worth getting to know if you are a contractor. A contractor should prepare a Stormwater Pollution Prevention Plan (SWPPP), which is a site-specific, written document that identifies potential sources of stormwater pollution. It also describes in detail the practices used to reduce stormwater pollution at the job site, and identifies the procedures operators will use to comply with the general construction permit terms.

Assessing conditions. Assessing the conditions on the ground (also called fingerprinting) is the first step in creating a viable SWPPP. This assessment includes a topographic drawing that indicates how stormwater currently exits the site, as well as the location of discharge points. The topographic drawing identifies slopes and slope lengths, and identifies soil types, particularly erodible soils. The soil’s infiltration capacity is also defined, as well as any past contamination on the site. Additionally, the SWPPP describes natural features such as streams, trees, wetlands, slopes, and other features to be protected.

Although each site will vary, typically an SWPPP plan accounts for the following:

  • Stabilization of the site. Get the final grade finished as soon as possible, and make sure to stabilize bare surfaces as soon as you can. Account for germination time for grasses and vegetation; such germination can stabilize the soil and bare areas.
  • Protect slopes and channels. Use pipe drains or earthen berms to convey concentrated stormwater from the tops of slopes into channels. Avoid disturbing natural channels and the vegetation that you find there.
  • Promote infiltration and minimize impervious surfaces. Find ways for water to percolate down into the soil to reduce runoff.
  • Control the perimeter of the site by diverting rainwater around, through, or under your site.
  • Protect water zones adjoining to the site. The primary purpose of erosion and sediment control is to protect surface waters.
  • Use proper containers for pollutants. Sturdy storage containers minimize the chance of leaks.

Industrial demolition sites require special attention because of the likely presence of hazardous waste. These materials could include solid waste, dangerous building materials, radioactive waste, contaminated spills, sanitary, and septic waste. These hazards must be identified and included in the SWPPP.

Stormwater in Portland. Portland is a very unique city and is lucky to have city planners and developers who have taken a keep eye toward protecting our waterways from stormwater runoff. Portland uses green streets, trees, ecoroofs, and other green infrastructure to manage stormwater and to protect overall water quality. Portland’s plan also includes the use of urban streams, forests, and wetlands to help manage stormwater naturally.

The area around Portland State University has several examples of solutions used by the city of Portland to control rainwater runoff, but you can also find runoff mitigation systems in areas seeing major development, such as Division Street. The New Season Market rain garden at SE 21st and Division is a good example of how the city is slowing down rain runoff. Runoff solutions used by the City of Portland include soakage trenches, turf blocks, pervious pavers, flow through planters, vegetated swales, ecoroofs, rain barrels, drywells, infiltration planters, roof gardens, cisterns, downspout disconnection, and more.

Demolition and industrial demolition companies face huge challenges when dealing with the potential for stormwater runoff at the sites they are taking down. The risks are large because open sites could allow tons of sediment to wash down drains if improperly managed. Companies that are engaged in industrial demolition work would do well to check out techniques used by Portland to handle stormwater runoff. Industrial contractors should develop comprehensive SWPPPs to deal with the runoff challenges that are inherent in industrial demolition.

[Photo by Aidan via CC License]

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