• MS4 General Permit coverage issuance update
• Stormwater pretreatment issues
• Get Stormwater Manual updates
• Reminder to submit Subdivision Registrations for change of ownership
• Stormwater, a major source of microplastics in the environment
• MPCA stormwater staff help with Minneapolis tree planting
• Events/Opportunities

MS4 General Permit coverage issuance update

As of the end of July, 67 of the 247 regulated municipalities in Minnesota have had their MS4 permit application placed on public notice for 30 days. The MS4 permit application contains information about the municipality’s current Stormwater Pollution Prevention Program (SWPPP) as it relates to the new 2020 MS4 General Permit, to manage and reduce pollutants in their stormwater runoff. The 180 remaining municipalities will have their application placed on public notice in batches over the rest of the summer and fall.

Once the public notice period ends for a municipality’s MS4 permit application and any applicable public comments have been addressed, the MPCA will extend coverage to the municipality under the new permit. The municipality will have 12 months from the date coverage is extended to meet any new permit requirements. 

If you would like to be notified whenever an MS4 permit application is placed on public notice, make sure you are signed up to the MPCA’s Municipal stormwater GovDelivery email list. You may manage your MPCA email subscriptions here.

Stormwater pretreatment issues

Filter strip with sediment buildup

The Minnesota Construction Stormwater Permit requires pretreatment for filtration and infiltration practices. Forebays or other pretreatment practices are highly recommended for constructed stormwater ponds. The permit, however, does not specify the type of or sizing for pretreatment practices. We are discovering that many stormwater best management practices (bmps, also often called stormwater control measures or scms) are not performing as designed, often due to heavy sediment loads to the bmp and to poor design.

Proper pretreatment can extend the life and improve performance of downstream bmps. But we frequently hear stories about inadequate or improperly designed pretreatment. This is unfortunate, since the Manual contains a wealth of information on pretreatment. For example, did you know the Manual contains the following?

• A pretreatment selection tool
• Tables with information and links to information on design, sizing, pollutant removal, installation, and maintenance
• Sizing guidelines
• Guidance for managing wastes from pretreatment practices
• Case studies

Below are examples of some design issues that have been brought to our attention:

• Pre-treatment baffles with shallow sumps showing up on plans; such as 2 or 3 foot deep sumps regardless of inlet/outlet pipe size diameters and/or manhole housing diameter. Questions have been raised whether shallow sumps would function the same for large (24 inch +) inlet pipes as they would for smaller inlet pipes. Same issue goes for diameter of the structure. Much deeper sumps would seem to be required for larger inlet pipes.
• Hoods or skimmer devices are being placed over an outlet pipe with baffles, which results in a change to the flow path and likely performance of the baffle. Stormwater should flow “unimpeded” from inlet to outlet as tested in past studies. In addition to effecting the hydraulic flow, trash and floatables will build up and can negatively impact the baffle function.   
• Multiple inlet pipes entering a manhole with a baffle. Observations have been made where the design shows the flows short-circuit the baffle, undermining expected treatment and promoting premature bypass.
• Grated inlets which do not direct flows to one side of baffle, resulting in flows and pollutants prematurely bypassing the pretreatment device.

The information in the manual could be better organized and made more accessible. So, we hope to execute a work order this summer to better organize the information on pretreatment. You can help by providing the following: (NOTE: We cannot endorse or promote specific commercial products, processes, or services).

• Examples (case studies) of good and bad pretreatment practices you are finding
• Photos
• Comments and suggestions for improving information on pretreatment

Email Mike Trojan at mike.trojan@state.mn.us.

Get Stormwater Manual updates

Join the Minnesota Stormwater Manual email list to receive notices of updates to the Minnesota Stormwater Manual. People subscribing to this list will receive an email every 6 to 12 weeks. Emails will or may contain the following:

• Recent updates to the Minnesota Stormwater Manual
• Summary of what we are working on
• A feature article on a relevant topic
• Upcoming events
• A fun (?) quiz
• Anything else of interest and relevancy

Subscribe to the email list here

See the June 2021 update here

Reminder to submit Subdivision Registrations for change of ownership

MPCA compliance staff are still finding that new owners of subdivided construction sites are failing to obtain NPDES/SDS General Construction Stormwater Permit coverage via the Subdivision Registration process. When the original owner of a permitted construction site sells a portion of the original plan of development, such as a single lot or group of lots or the entire site to another party, they need to submit a Subdivision Registration form to the MPCA that identifies the change in ownership. By doing so, the Owner transfers permit coverage to the new owner. The original owner also needs to supply a Stormwater Pollution Prevention Plan (SWPPP) that describes the remaining construction to the new owner. New owners and contractors doing construction activities on a portion of the original development are required to have their own permit coverage and comply with permit requirements even if they are completing construction on a portion of the original site that is less than than 1 acre. The Subdivision Registration form is submitted online and there is no cost for obtaining the permit coverage in this manner. Failure to obtain the coverage is a violation of the CSW Permit. For more information and how to submit a Subdivision Registration form, check out the MPCA Construction Stormwater Website .

Stormwater, a major source of microplastics in the environment

Stormwater is known to contain many contaminates from urban environments such as sediment, bacteria, nutrients, petroleum byproducts, chemicals and other pollutants that degrade water quality. Now plastic is arising as yet another contaminate of concern. Microplastics are defined as extremely small particles of less than 5 millimeters in length. Microplastics result from human activities, commonly from microbeads in personal care products, fibers from clothing and the degradation of mismanaged larger plastic waste. They are found suspended in the water columns of oceans, streams and lakes and are also found in sediment. They circulate through the environment via wastewater and stormwater discharges, atmospheric deposition and are distributed via ocean currents. Microplastics are now even found in remote areas like the Antarctic, see study and remote mountain areas such as in our national parks. When ingested, microplastics are known to have potential harmful effects for aquatic and other wildlife. We know that vegetation used in stormwater management systems helps to control sediment, phosphorus and other contaminates in stormwater. A recent study shows that vegetation may be key for helping to address microplastic in stormwater too. The American Chemical Society recently published a paper by ACS EST Water on microplastics in stormwater and how they might be mitigated through use of bioretention practices. Bioretention involves use of vegetation, usually deep rooted native vegetation, in stormwater management systems to help trap sediment and take up phosphorus.

MPCA stormwater staff help with Minneapolis tree planting

MPCA’s Stormwater Section staff, Carlee Kjeldahl, who manages Environmental Assistance Grants, recently helped the City of Minneapolis (a grant recipient) replace the trees that were lost in the 2011 tornado. Carlee (pictured), along with Tree Trust staff (orange vest on her left)  participated in a tree planting event for the grant last June where a total of 30 new trees were planted in Minneapolis. Carlee planted 10 of them on homeowners properties. Before the planting, homeowners have a consultation with a Tree Trust staff member to talk about tree type, location and determine if the area in their yard is suitable for a planting. After the tree is planted, the homeowner is given a tree planting guide and is responsible to water and maintain the tree. Each tree planted is helping replace the canopy that was lost and also provide more resilience to Minnesota’s wetter weather by absorbing lots of water from storm events. Other benefits of trees include: curbing the urban heat island effect of urban areas, reducing energy use, improving air quality, providing bird habitat, and improving aesthetics for a better quality of life for residents. Trees also play a major role in intercepting stormwater runoff from impervious surfaces. Check out EPA's Technical  Memorandum for more information on how trees reduce stormwater runoff and provide other benefits. Environmental Assistance Grants provide financial assistance for projects that aim to develop environmentally sustainable practices through partnerships and goal-orientated, economically driven approaches. The MPCA seeks projects that further the MPCA’s mission of working to improve our environment and enhance the quality of life in Minnesota. If you are interested in learning more or how to be notified when the grant application is available see this link: https://www.pca.state.mn.us/about-mpca/environmental-assistance-grants-and-loans

Events/Opportunities

Smart Salting certification trainings being offered online will be free for Symposium participants Aug. 5-6, 2021.

FEMA grant funding webinars beginning August 11, 2021: https://www.fema.gov/grants/mitigation/2021-building-resilient-infrastructure-and-communities-and-flood-mitigation-assistance-programs

The U of M Resilient Communities Project is taking applications until August 15, 2021 https://rcp.umn.edu/

GreenStep Cities Workshop: Maintaining Green Infrastructure Sept. 8, 2021: https://www.eventbrite.com/e/maintaining-green-infrastructure-tickets-164009899023

*MIDS Calculator training. Two trainings on September 21. Introduction to MIDS Calculator, 10AM-12PM. Intermediate level training, 1-3. Registration is limited to 8. Go to this link to register:   https://stormwater.pca.state.mn.us/index.php?title=Training_and_webinar_schedule#Calendar.

The Minnesota Water Resource Conference Oct. 19-20, 2021. Registration: Minnesota Water Resources Conference | College of Continuing & Professional Studies (umn.edu)

Newsletter contact

If you have questions about or suggestions for this newsletter, contact Roberta Getman, MPCA-Rochester, 507-206-2629.