MN Stormwater News - January 2017

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MN Stormwater News

January 2017

Stormwater manual webinars

The MPCA is conducting webinars to share the many updates to the Minnesota Stormwater Manual. The first webinar, on Dec. 15, covered infiltration practices; to see it, go to the Stormwater Manual webinar page. 

The next webinar on Wednesday, Jan, 25, 1:30 to 3:00 p.m., will cover stormwater and rainwater harvest and use/reuse. To access this webinar and see other future webinars, go the events page in the Stormwater Manual.

Reducing runoff and pollution with MIDS

Stormwater runoff pic

In 2009, the Minnesota Legislature directed the Minnesota Pollution Control Agency to “develop performance standards, design standards, or other tools to enable and promote the implementation of low impact development and other stormwater management techniques.” "Low impact development" means an approach to stormwater management that mimics a site's natural hydrology as the site is developed. With low impact development, stormwater is managed on site, and the rate and volume of stormwater that reaches receiving waters is unchanged by the development.

The MPCA, with the support of a diverse group of stakeholders, spent three years creating Minimal Impact Design Standards (MIDS) for designers, engineers, planners, contractors, stormwater managers, and others involved in development projects that may generate stormwater runoff. MIDS are low-impact development standards, approaches, and credits that can be applied in communities around the state. The concepts behind MIDS can be used by all Minnesotans; we can all do our part in minimizing stormwater runoff and pollution.

Using low-impact development approaches can reduce the amount of pollution reaching our lakes, rivers, and streams and help recharge groundwater resources. MIDS tools also help quantify these reductions in runoff and pollutant loading. MIDS helps communities measure progress toward water and natural resource protection and restoration goals, and will serve as the highest stormwater standard for Minnesota Green Step Cities.

A MIDS Community Assistance Package provides ordinances and tools, including the MIDS performance goals and calculator (see below), that help local governments achieve MIDS performance goals for stormwater. The package includes instructions, training materials, and descriptions of implementation in several pilot communities. More than 40 of Minnesota’s regulated MS4s report adopting MIDS to meet Minimum Control Measure #5 of the MS4 permit. 

In 2014, the Middle St. Croix Watershed Management Organization used a Clean Water grant to help nine communities in the St. Croix Basin to adopt ordinance and code revisions that incorporate MIDS stormwater standards. As of December 2016, eight of them — Bayport, Baytown Township, Lakeland Shores, Lakeland, Lake St. Croix Beach, Oak Park Heights, St. Mary's Point, and West Lakeland Township — have adopted the ordinances.

If your community is interested in adopting the MIDS Community Assistance Package, or has adopted MIDS and you are not listed on this page in the Stormwater Manual, please contact Anne Gelbmann. 

MIDS calculator updates

The Minimal Impact Design Standards (MIDS) calculator is a widely used tool for stormwater management in Minnesota. It assists with permit compliance, BMP design, calculation of volume or pollutant reductions, and more.

The MIDS calculator is a relatively simple tool not intended to replace more sophisticated modeling. However, it provides technically defensible information with fairly simple input requirements. Because the tool is relatively simple, we continue to look for ways to improve the applicability and accuracy of the tool.

 In 2016, the MPCA contracted with an engineering firm to provide numerous updates to the calculator, scheduled to be available in mid-January. The modified calculator, Version 3.0, is now available in the Minnesota Stormwater Manual. Significant updates include:

  • New BMPsOn the opening screen, users are asked if they are using the calculator for Construction Stormwater permit compliance. If they answer “No”, a new BMP called “Stormwater disconnection (impervious disconnection)” becomes available. This BMP allows users to route runoff from impervious surfaces to pervious areas, where some of the water will infiltrate. The BMP is not allowed for permit compliance because it does not constitute an instantaneous volume reduction, as required in the permit. For more information, see guidance in the manual.
    A new BMP was also added for underground infiltration systems.
  • Altered volume credit — A BMP with a raised underdrain previously only received volume credit for water stored below the underdrain. The calculator now allows that volume plus infiltrating water, calculated as 0.06 inches per hour (D soil) multiplied by the drawdown time.
  • Reduced infiltration rate — For permeable pavement with compacted subsoil, the infiltration rate was reduced from 0.06 inches per hour to 0.03 inches per hour.
  • Iron-enhanced sand filter option — An iron-enhanced option is available for sand filters. If a user indicates they have included an amendment to reduce dissolved phosphorus, they receive a 40 percent credit for dissolved phosphorus.
  • Updated harvest and reuse BMP — The harvest and use/reuse BMP underwent significant updates

The calculator now calculates daily potential evapotranspiration (PET). A user can also enter a daily maximum rate of use. The calculator uses the smaller of these two values to calculate the volume credit.

— Users can enter a weekly volume used for non-irrigation purposes. This volume is credited toward the performance goal. For A soils, the user can specify a weekly application rate of up to two inches per week.

— If precipitation on a given day is less than the daily use (for irrigation and non-irrigation), the difference between daily use and precipitation is credited, if water is available in storage.

— For more information, see the manual.

  • Version 2 uploads — Version 2 files can be uploaded into the new version (Version 3). The user will be required to update the Version 2 file to a Version 3 file.

Several minor changes were also made to the calculator. All changes to the calculator will be discussed in a webinar, currently planned for mid-March.

Harvesting and using stormwater

The MPCA has been developing guidance for stormwater and rainwater harvest and use/reuse systems (with funds from the Clean Water Land and Legacy Amendment):

Stormwater Manual updates: In 2015, the MPCA contracted with an engineering firm to update the harvest and use guidance in the Minnesota Stormwater Manual, with the help of a technical advisory team. Now incorporated into the manual, the guidance on includes design criteria, construction specifications, operation and maintenance, water quality considerations, environmental concerns, cost benefit considerations, case studies, calculating credits, definitions and more. We are looking for case studies for the Stormwater Manual.  If you have stormwater or rainwater reuse projects that you would like to highlight, please contact Anne Gelbmann.

Interagency Water Reuse team: With funding from the Clean Water Fund, an interagency team was formed to develop best practices and policies recommendations — both regulatory and non-regulatory — for water reuse. The team seeks input from a Stakeholder Advisory Group on its recommendations. The next stakeholder meetings are scheduled for February and April 2017. For more information, go to the water reuse web site. 

St. Anthony stormwater reuse
The City St. Anthony Village's water reuse facility collects stormwater runoff from Hennepin County Road 136, city hall, local streets, and backwash water from the city’s water treatment plant in a half million-gallon reservoir located underground. Water stored in the reservoir is recycled to irrigate a 20-acre site that includes a municipal park and St. Anthony’s City Hall campus.

Caution! Regulated MS4s and infiltration prohibitions

Managing the amount of stormwater runoff from new impervious surfaces is critical to protecting nearby waters from pollutants and recharging groundwater. Designed infiltration is generally preferred by regulatory agencies and stormwater practitioners and is the most commonly used technique for reducing stormwater volume.

However, designed infiltration is a bad idea in situations where there is heightened risk to groundwater. Minnesota’s general stormwater permit for MS4s requires that every municipality prohibit, without exception, the use of designed infiltration of stormwater runoff under the following conditions:

  • When the infiltration device will receive stormwater runoff from one of these entities regulated under NPDES for industrial stormwater: automobile salvage yards; scrap recycling and waste recycling facilities; hazardous waste treatment, storage, or disposal facilities; or air transportation facilities that conduct deicing activities
  • When the infiltration device will receive stormwater runoff from vehicle fueling (e.g., gas stations) and maintenance areas
  • When the infiltration device will have less than three feet of separation between the bottom of the device and groundwater or the top of bedrock
  • Where high levels of contaminants in soil or groundwater will be mobilized by the infiltrating stormwater. Note: If stormwater infiltration is proposed in areas with contamination, please conduct a screening assessment using the guidelines found in the Minnesota Stormwater Manual.

For more information on the general topic of stormwater infiltration, please see the Minnesota Stormwater Manual.

NPDES permit for construction activity

Construction stormwater BMP

Stormwater runoff from construction sites is a major contributor to surface water pollution, according the U.S. EPA. Construction activity in Minnesota that will disturb more than one acre must have an NPDES stormwater permit for construction. 

The Construction General Permit is typically re-issued every five years. Although the current permit is scheduled to expire in August of 2018, the MPCA anticipates re-issuing the permit in fall 2017. With this early issuance, the MPCA can put various NPDES permits in a cycle that better serves permittees. The new permit will feature minor permit requirement revisions, clarifications, and streamlined language that eliminates redundancies. The permit will also be re-formatted to fit MPCA’s new data management system. 

The MPCA will post the draft permit for public comment in summer 2017, and invites all to participate. We’ll post updates on the construction stormwater web page.

Industrial stormwater training sessions

The industrial stormwater permit requires annual staff training for those carrying out the requirements of the industrial stormwater permit.  Internal staff can train themselves, hire a consultant, or choose to attend a U of M workshop to satisfy their training requirements.  Be sure to read the section in the industrial stormwater permit to ensure you’re meeting all of the training requirements.

U of M industrial stormwater training workshops now open:

Tuesday, Jan. 31, 2017, Verizon Wireless Center, Mankato

  • Part of the MECA pre-conference events, this half-day session will address SWPPP modifications due to benchmark monitoring test result exceedances. 
  • MECA members can register at

Tuesday, March 7, 2017, MNDOT Training Facility, Arden Hills

Wednesday, May 10, 2017, MNDOT Training Facility, Arden Hills

Winter stormwater management

Salt in storm drain

We know it rains in the winter and brief warm temperatures produce snow melt conditions. But winter stormwater runoff takes salt and sand with it. Salt and sand help keep people and drivers safe, but must be used appropriately. Prevent ice build-up and keep up with shoveling and snow-blowing to save time, money, and help the environment. Check out the Mississippi Water Management Organization’s excellent article on winter stormwater management: “How to Fight Snow and Ice Without Polluting

Want to take winter stormwater management to the next step?  Check out the MPCA’s Winter Parking Lot and Sidewalk Maintenance Manual for tips and suggestions for smart winter maintenance. 

Paying for stormwater projects

Are you looking for ways to fund your stormwater projects? Minnesota has funds available for stormwater projects from several sources: Clean Water Land and Legacy Amendment, Clean Water Partnership, Federal 319, Point Source Implementation Grants, State Revolving Fund, and grants and loans from the Metropolitan Council, watershed districts, and soil and water conservation districts. Sources of funding and recently funded projects are listed in the Minnesota Stormwater Manual

The Board of Soil and Water Resources recently approved several stormwater projects funded with the Clean Water Land and Legacy Amendment, including:

  • Forest Lake High School stormwater reuse project
  • Perro Creek urban stormwater quality improvements
  • Shields Lake stormwater harvest and irrigation reuse system and alum treatment
  • Iron enhanced sand filter basin at the Golden Lake stormwater treatment pond
  • Lakeville stormwater hydrodynamic separator retrofit
  • Alimagnet Lake stormwater improvement projects
  • Six Mile Creek-East Auburn stormwater enhancement project
  • Oasis pond iron enhanced sand filter project

Recipients of the Metropolitan Council’s Livable Communities grants (with many stormwater projects among them) are listed on the council’s web site.

Learn about available funding for stormwater projects at two upcoming presentations

  • Wednesday, Jan. 25, 2017, Earl Brown Center, Brooklyn Park — MPCA’s Bill Dunn, Becky Sabie from the Public Facilities Authority, and Brad Wozney from the Board of Water and Soil Resources will present at the City Engineers Association of Minnesota.  
  • Monday, Feb. 6, 2017, MPCA headquarters, St. Paul At the third annual Stormwater Funding Strategies Workshop, from 1:00-4:30 p.m. on Feb. 6, staff from the Board of Water and Soil Resources, Public Facilities Authority, Metropolitan Council and the MPCA will discuss sources of funding for stormwater projects. Past recipients of the funding sources will be there to discuss their experiences of the process. The workshop will also be available online via WebEx — details will be posted on the Funding page in the Stormwater Manual

Newsletter contact

If you have questions about or suggestions for this newsletter, contact Anne Gelbmann, MPCA-St. Paul, 651-757-2384