Winter 2020

• Municipal program highlight: City of Chanhassen
• Winter inspections needed at construction sites
• Tips for managing BMPs in winter
• Updates to MIDS Calculator and MPCA Simple Estimator
• MPCA is proposing water permit fee increases
• Requirements for construction stormwater permits issued before Aug. 1, 2018
• MPCA grants for adapting to climate change
• MS4 staff update

Photo courtesy of Mississippi Watershed Management Organization

Municipal program highlight: City of Chanhassen

MS4 staff recently interviewed Chanhassen on their experience adopting pervious pavement requirements into their ordinance.

1. Why did the City of Chanhassen create a pervious pavement ordinance?

"The City Council asked staff to look into pervious pavements as a possible option for allowing homeowners up against their property’s lot cover limits an opportunity to improve their property. Staff had been receiving inquires about these technologies prior to this and felt that these systems had been in operation long enough in Minnesota that their long term efficacy could be evaluated. After a lengthy research process, staff determined that an ordinance establishing minimum design guidelines and maintenance agreements for these systems would be the best way of allow residents to take advantage of these technologies and ensure that the systems worked as intended."

2. What types of projects has the city seen implement pervious pavement?

"Chanhassen has seen both public and private projects implement the use of pervious pavements. The most typical application of pervious pavement can be found in parking areas. Two examples of publicly installed pervious pavements are at the city’s Public Works and Bandimere Heights Park parking areas. These areas utilized a porous pavement. While city street rehabilitation projects typically lend themselves best for the installation of public pervious pavement systems, there are opportunities to partner with watershed districts and cost-share standalone projects. Bandimere Heights Park’s pervious pavement system was a cooperation between the city and Riley Purgatory Bluff Creek Watershed District through their cost-share program."  

"An example of a private project that used a pervious pavement system in their parking area was the Villages on the Ponds 11^th Addition, a commercial area near Lake Drive and Pond Promenade. This system utilized permeable pavers. The permeable pavers allow stormwater to infiltrate the surface into a series of perforated pipes, which then conveys the runoff to a proprietary stormwater treatment device (privately developed and owned)."

3. Has the pervious pavement ordinance increased interest in implementing this practice?

"The city experienced a large number of inquiries about the pervious pavement ordinance immediately after it passed, especially after an article on it was published in the city’s newsletter. While many people still ask questions about pervious pavements and what they would need to do to meet the ordinance’s requirements, most end up realizing that they can do their project without going over their zoning district’s lot cover limits or decide they are unwilling spend the money required for a properly designed system. That being said, staff are aware of residents who installed pervious paver systems even when they do not need to take advantage of the additional lot cover because they believe it is the environmentally responsible thing to do."

"Probably the largest increase in interest in these systems has been as part of the variance process; with residents offering to use pervious pavement systems meeting the city’s requirements as part of requests for lot cover variances. Reviewing, evaluating, and ultimately passing the pervious pavement ordinance has made the Planning Commission significantly more comfortable with taking the use of these technologies into account when evaluating variance requests."

4. Who maintains the pervious pavement? What is maintenance like in the spring vs. the winter time?

"Pervious pavement systems are like any other stormwater best management practice (BMP) in the city and require the owner to both operate and maintain the system. The required maintenance for the city’s porous pavement BMPs is straightforward – twice a year the city will sweep and vacuum the pavement to ensure it does not plug with small particles such as organics or sand. This type of maintenance cannot occur in winter due to snow, thus the city performs maintenance in Spring and Fall. Periodic vacuuming and sweeping is also a common maintenance practice for permeable pavers. As pervious pavement systems are specifically designed to allow water to infiltrate through their surface, it is critical that maintenance activities typically performed on impervious surfaces are not performed on pervious systems. This would include re-sealing, re-surfacing, or sanding (for winter conditions) in areas where a pervious pavement system exists. In order to ensure proper maintenance activities are performed when systems are privately owned, owners will enter into a maintenance agreement with either the city or the watershed district. These maintenance agreements help enforce that the proper maintenance activities specific to the installed pervious pavement system are performed, and that the owner has the proper technical expertise, funding mechanisms, and inspection program in place to promote their intended benefit for the life of the system."

5. If another city would be interested in implementing something similar, what is some advice you would give them?

"Probably the biggest thing for us was doing our homework. Staff spent a lot of time researching pervious pavement systems and how other cities were regulating them. Feeling like we had a good understanding of the potential benefits, drawbacks, and applications of these systems let us answer questions from the city’s decision makers as well as engage in informed and meaningful dialogues with proponents and opponents of pervious pavements. Having a solid technical understanding of these systems allowed us to create an ordinance that we were confident would have the intended result and not pose a risk to the city’s aquatic resources."

Winter inspections needed at construction sites

Where construction has been suspended due to frozen conditions, weekly inspections are no longer required. However, if runoff occurs during winter months due to thawing or precipitation, the inactive site must be inspected within 24 hours to ensure the integrity and effectiveness of the erosion and sediment control BMPs. These inspections must be documented the same as if construction was still active. If construction resumes in winter, weekly inspections must resume. If inspections find that BMPs need repair or need to be replaced, the repair or replacement method may differ from non-frozen conditions.

Tips for managing BMPs in winter

Unprotected inlet at construction site receiving sediment runoff during snow melt.

Winter can be challenging for achieving erosion and sediment control requirements. The erosion and sediment control requirements (i.e. inlet protection, soil stabilization, perimeter controls, etc.) that apply during none-frozen months are also required in winter to keep sediment out of downstream waters. However, the BMPs that are used in winter require some creativity and modification to work in frozen or snow-covered conditions. For example, inlet protection can be placed below the storm grate to allow for passage of snow plows. Snow berms or heavy filter logs can be used as perimeter control and straw mulch can be crimped into snow. The Minnesota Stormwater Manual offers numerous tips for construction practices and BMPs that work in winter. More detailed information with examples can be found in Minnesota Department of Transportation’s (MnDOT) Winter Guidance and Winter BMP Guidance2.

Stormwater research updates: Contaminants of Emerging Concern

Environmental Science: Water Research & Technology recently published “Hydrophilic trace organic contaminants in urban stormwater: occurrence, toxicological relevance, and the need to enhance green stormwater infrastructure” (Spahr et al. 2020). The authors review current data and knowledge on soluble contaminants of emerging concern (CECs) in urban stormwater, with an excellent bibliography. CECs include organic compounds such as pesticides, plasticizers, and flame retardants that may pose threats to ecosystems and human health. They may be washed off during storms and enter surface waters via stormwater. BMPs to address contaminated stormwater such as detention basins, constructed wetlands, and biofilters, often fail to remove soluble CECs. The article highlights research needs to enhance stormwater green infrastructure with respect to water quality, non-potable reuse, and groundwater recharge, and to augment chemical monitoring with bioassessments to understand chemical mixture effects, BMP performance, and assure safe stormwater reuse. It also discusses potential benefits of BMP amendments including activated carbon, biochar, and metal oxides.

Updates to MIDS Calculator and MPCA Simple Estimator

Two widely used tools, the Minimal Impact Design Standards (MIDS) Calculator and the MPCA Simple Estimator, will be updated in spring 2020. The updates will make these tools more flexible for Total Maximum Daily Load (TMDL) and other water quality calculations.

The primary change to the MIDS Calculator is creation of a new water quality calculator using the basic MIDS Excel file. The water quality calculator will allow the user to adjust event mean concentrations across a site and for individual BMPs, allow the user to adjust particulate to dissolved phosphorus ratios, and will include links to guidance in the Stormwater Manual.

The modified MPCA Simple Estimator will allow users to model up to 10 catchments to adjust inputs (event mean concentrations, runoff coefficients, and pollutant removal efficiencies), and to incorporate non-structural practices such as street sweeping. Extensive guidance will be provided in the Stormwater Manual.

These changes will be completed before the reissuance of the MS4 General permit, expected in late spring or early summer. For more information, see the Minnesota Stormwater Manual.

MPCA is proposing water permit fee increases

The MPCA is seeing an increase in demand from permittees for more innovative approaches and tailored technical assistance. These types of activities and complex projects take more time and resources. Water quality fees have not kept pace with costs, so the current fees authorized in rule for water-related permitting do not generate sufficient revenue to administer the associated water quality programs. The MPCA is planning amendments to the water quality fee rules that would revise permit application fees, additional fees, and annual fees.

Revised fees are also needed to distribute permit costs equitably across affected permittees. This includes fees for municipal and industrial wastewater permits, stormwater permits, feedlot permits and registration fees, and subsurface sewage treatment systems (SSTS) tanks and licensing. These amendments would also change the implementation of variance fees, though would not increase them. These amendments will build on strategies identified in Water Fee Advisory Committee: Findings and Recommendations as well as feedback from stakeholder meetings held this past fall.

The MPCA held several pubic meetings in February to share information on revising these fee rules. The Public comment period ends March 13, 2020. More information on the rulemaking, including rule documents, a presentation and WebEx are available for viewing on the rulemaking webpage .

Requirements for construction stormwater permits issued before Aug. 1, 2018

On August 1, 2018, the MPCA issued a new general NPDES permit for construction activity. Permittees who started their project before that date, were either to finish the project or update their stormwater pollution prevention plan by February 1, 2020 to reflect the new requirements. A notice of termination must be submitted when the project is complete using the state e-Services system.

Permittees are only responsible for complying with the new erosion and sediment control practices and are not required to make any changes to the permanent stormwater treatment system. A summary of all the permit changes is available here.

MPCA grants for adapting to climate change

Apply now for an MPCA grant for community strategies to adapt to the impacts of climate change.

The MPCA is accepting applications for grants intended for projects that will help communities adapt to the impacts of climate change and improve community resiliency. Eligible applicants are Minnesota not-for-profit organizations, institutions, political subdivisions of the state, and tribal governments. Total funding available is approximately $250,000.

Examples of fundable projects are listed in the RFP document and include projects for the design/installation of blue-green stormwater infrastructure to reduce localized flooding, prevention of wastewater bypass and much more. The funding is intended to prevent or reduce the environmental impacts caused by warming temperatures, extreme precipitation, and other climate impacts while protecting public health and well-being.

Forms and details can be found at this webpage and the links on that page.

Submit questions to grants-loans.pca@state.mn.us using subject line: EA Question.

Applications are due no later than 2:00 p.m. Central Time, Wednesday, March 11, 2020.

MN GreenCorp site application period ends March 18, 2020

The MPCA is accepting host site applications for the 2020-2021 Minnesota GreenCorp program year. Minnesota GreenCorps is an environmentally focused AmeriCorps program coordinated by the MPCA that places AmeriCorps members with organizations around the state to spend a year of service addressing critical environmental issues. Host site application materials are available on the Minnesota GreenCorps website.

MS4 staff update

Recent staffing changes in the MPCA’s Municipal Stormwater Program include the hiring of Nick Nistler. Nick’s role in the program includes permitting, compliance evaluations, outreach, education and technical assistance for the MS4 regulated community. Nick is no stranger to the stormwater world; he has several years of experience with the MPCA's construction stormwater program. Please visit the Stormwater Manual’s MS4 contact page to find which MPCA Municipal Stormwater staff is assigned to your MS4.

Events

Central States Water Environment Association 93rd annual meeting, May 18-20, 2020, River Centre – Saint Paul, Minnesota

To see ongoing events, link here.

Newsletter contact

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