Many facilities throughout the Pacific Northwest are in the midst of updating their stormwater plans and looking at ways to make additional improvements in their stormwater quality. Our team has assembled this list of tips that we have accumulated over the years of supporting our industrial clients. It is easier (and usually cheaper) to prevent stormwater contamination than it is to treat it. Luckily, not every site needs an expensive solution. We hope some of these are of help to you.
Operational Tips
- Bring Activities Indoors – When practicable, bring activities under cover, or better yet, indoors. Things like cutting, grinding, and welding will generate dust and particles that are bound to get into stormwater.
- Hand Sweep – On days that the street sweeper is coming, use a leaf blower and broom ahead of the sweeper to clean up those hard to reach areas the sweeper will normally miss. Don’t forget to hand sweep all around the catch basins (especially if they are in a low spot the sweeper can’t get to), material staging areas, and outdoor equipment and tanks.
- Clean Up Before the Rainy Season – If you operate in a region with a dry season followed by a wet season, take extra measures at the end of the dry season to reduce that ‘first flush’ load on stormwater. Schedule the sweeper truck (don’t forget to hand sweep!), clean out catch basins, replace catch basin inserts, perform maintenance on stormwater treatment units, check swales and ditches for trash, etc..
- While many permits mandate employee training for those staff responsible for the operation, maintenance, and inspection of stormwater best management practices (BMPs), we recommend stormwater awareness training for everyone. Awareness training can go a long way toward improving stormwater quality at a site and preventing problems before they occur. Consider adding stormwater training to ongoing health and safety training.
Sampling Tips
- Peristaltic Pump – Depending on your sampling point, you may be able to use disposable tubing and a peristaltic pump in place of a dipper cup for sampling. Sampling with tubing stirs up less sediment than a dipper cup. Position the tubing into the middle of the water column for sampling. You may need to zip tie a weight onto the tubing, approximately 4-6 inches above the sampling end, to help keep the tubing in the water column if water currents are fast or the sampling location is well below you (e.g. manhole or vault access).
- Retrofit Sampling Points – If you don’t have a place that is easy to sample (e.g. sheet flow), construct a spot that will give you one. Think of a low spot with a weir or a flume. Here is a good example – King County Road Services BMPs
Treatment Tips
- Make improvements to ditches and swales – If you have the benefit of a ditch or swale before stormwater leaves your site, you may have room for a rain garden or biofiltration swale. Consider amending the soils with compost and landscape with fescues, sedges, rushes, or other hardy (and preferable native) plants and make yourself a compost-amended vegetated filter strip. If water won’t infiltrate, consider installing an underdrain. Or engineer and construct a full retrofit and install a bioretention (water infiltrates) or biofiltration (equipped with underdrain) system. Volume 5 of the Western Washington Stormwater Management Manual (Ecology Publication 14-10-055) has design considerations and maintenance activities. Check out Chapter 3 of the Rain Garden Handbook (Ecology Publication 13-10-027) for Western Washington for plant guidelines. Your state requirements may vary, but the ideas are fairly universal.
- Pipeline Treatment – Place bags of biochar or adsorptive filtration media mixture (adsorptive media mix) directly in pipelines. The adsorptive media mix is contained within mesh filter bags and is intended to treat stormwater by filtering and retaining solids inside the media and surrounding fabric. The mesh filter bags are installed in existing stormwater structures, including pipelines, catch basins, manholes, and manholes equipped with spill control devices.
- Oyster Shells – Some facilities have seen an improvement in stormwater quality with the addition of oyster shells. They can be added directly into a catch basin, or placed on the surface of a biofiltration system. See this video from the Washington Stormwater Center about a project at the Port of Seattle: https://www.youtube.com/watch?v=NEeNFU80rqM
- Downspout Filters – No proprietary system is needed to implement filters for downspouts, you can build these yourself with materials available at your local hardware and landscape supply store. For a great example see the Port of Vancouver and their “Grattix” box and their video.
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