Adopt and implement guidelines or design standards/incentives for at least one of the following stormwater infiltration/reuse practices:

The National Pollutant Discharge Elimination System (NPDES) permit program addresses water pollution by regulating point sources that discharge pollutants to waters of the United States. Created in 1972 by the Clean Water Act, the NPDES permit program is authorized to state governments by EPA to perform many permitting, administrative, and enforcement aspects of the program.

The State Disposal System (SDS) is a Minnesota program established under Minn. Stat. § 115. The SDS permit regulates water discharges to the ground surface or subsurface to protect groundwater.

The Municipal Separate Storm Sewer System (MS4) stormwater program is designed to reduce the amount of sediment and pollution that enters surface and ground water from storm sewer systems. Public entities that own or operate an MS4 play a key role in preventing or reducing the negative impacts stormwater runoff has on our valuable water resources.

Incentives:

• Clean Water Partnership loan funds at 1.5% interest are available on an ongoing basis from the MPCA for public installation of, or re-loaning to others for, green infrastructure and other types of projects that are called for in TMDLs, WRAPS, and/or local water plans. 
• Find funding programs in the Minnesota Stormwater Manual. Note that you can search the Manual by topic (e.g., permeable pavement) to read the MN-specific information on topics such as best management practices, design, construction, maintenance and pollutant removal. 
• See State and Federal Funding Programs and Practices for Soil Health (BWSR, 2020)
• The National Wildlife Federation’s interactive Nature-Based Solutions Funding Database for communities interested in pursuing federal funding and/or technical assistance for nature-based solutions.

Design Guidelines: 

• See the City of Eagan’s Post-construction Stormwater Management Requirements (Sec. 4.34 F.) for sites with over 10,000 SF land disturbance.
• See U.S. EPA green infrastructure resources for planning and design tools, funding opportunities, and more. 
• Green Infrastructure Toolkit (Georgetown Climate Center: 2016)
• NOAA Atlas 14, Volume 8, which provides precipitation frequency estimates for Minnesota. These estimates (analyses of the historical frequency of heavy rainfall events) are the most up-to-date and must be used by engineers and others involved in designing and operating grey and green stormwater infrastructure.
• Green Infrastructure Opportunities that Arise During Municipal Operations (US EPA: 2015) is a comprehensive, visual, readable document detailing approaches that local government officials and municipal program managers in small to midsize communities can use to incorporate green infrastructure components into work they are doing in public spaces. 
• The Green Infrastructure Toolkit (Georgetown Climate Center, 2016) provides strategies and techniques that manage stormwater, reduce urban heat island effects, improve air quality, and promote economic development and other sustainability goals.
• Low Impact Development (LID) Barrier Busters fact sheets from the US EPA are intended for local decision makers who are considering adoption of LID techniques but who have concerns. LID includes a variety of practices that mimic or preserve natural drainage processes to manage stormwater.
• See, for example, Inver Grove Heights’ national award-winning low-impact development of Agenta Hills. It aims for zero stormwater discharge and cuts capital and operations/maintenance costs 70% over 30 years compared to a conventional 'pump and pipe' stormwater system. 

Rain Gardens & Infiltration:

• Infiltration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium and into underlying soil, where it may eventually percolate into groundwater.
• Bioretention (often called ‘rain gardens’) employs a simplistic, site-integrated design that provides opportunity for runoff infiltration, filtration, storage, and water uptake by vegetation.
• The UofMN Extension offers tips on how to build a rain garden. 
• In 1996, Maplewood installed its first rain garden to help manage stormwater. Today the city has over 700 home rain gardens and over 60 rain gardens on city land during street reconstruction projects. 

Rainwater Harvesting: 

• See guidance for stormwater reuse and rainwater harvesting in the MN Stormwater Manual. 
• A Woodbury redesign project used existing stormwater ponds at 2 golf courses so that the irrigation systems could reuse runoff water from the adjacent road to water the golf course greens instead of pumping groundwater from the aquifer below. 
• See also reuse projects and data from the City of Hugo.

Pervious Materials and Green Alleys & Parking Lots:

• Note that pervious concrete use in roadways both reduces stormwater infrastructure and salt use, with Shorewood as a national exemplar.
• ‘Green alleys’ offer stormwater and public health benefits (UofMN Center for Transportation Studies, 2021)
• See examples of pervious (porous) concrete, asphalt and porous pavers in the well-illustrated Chicago Green Alley Handbook (2010).
• See Greening Surface Parking Lots (City of Toronto, 2013) and the Green Parking Lot Resource Guide (U.S. EPA, 2008). Guidelines include performance standards, such as 50% tree coverage of a lot at 15 years.
• Light-colored, high-albedo materials and/or an open-grid pavement with a minimum Solar Reflective Index of 0.6 over at least 30% of a site's hardscaped area are recommended. See Using Cool Pavements to Reduce Heat Islands (U.S. EPA).
• See also BPA 29.6 for related heat-island resources.

Green Roofs & Walls:

• Green roofs typically occur at the beginning of stormwater treatment trains. Green roofs provide filtering of suspended solids and pollutants associated with those solids, although total suspended solid (TSS) concentrations from traditional roofs are generally low. Green roofs provide both volume and rate control, thus decreasing the stormwater volume being delivered to downstream Best Management Practices (BMPs).
• The national organization Green Roofs for Healthy Cities provides resources, including a green roof energy calculator.
• Green Walls can be facades, living walls, vertical gardens, and more. 

Tree Trenches & Boxes:

• Trees can be an important tool for retention and detention of stormwater runoff. Trees provide additional benefits, including cleaner air, reduction of heat island effects, carbon sequestration, reduced noise pollution, reduced pavement maintenance needs, and cooler cars in shaded parking lots.
• The Hoyer Heights pilot project (MWMO, 2020) in Northeast Minneapolis installed tree trenches in boulevards to capture and treat stormwater runoff directly from the street. The tree trenches reduce the amount of runoff reaching the river by 305,000 gallons each year.

Soil Amendments & Native Plants: 

• Note that the MnDOT compost specification 3890 (p. 715) is recommended as a soil amendment for landscape planting and turf establishment purposes. 
• One design practice Eagan requires is that sites adding 10,000 sq. ft. or more of disturbed/graded/compacted soils must assure 5% organic matter remains, typically by adding compost so the soils allow water infiltration.
• See Using Compost in Stormwater Management (U.S. Composting Council, 2008) for ideas and guidance on using compost in rain and infiltration gardens, infiltration zones, green roofs, and erosion control. 
• Additional specifications for compost stormwater management can be found on the US Composting Council website. 
• Biochar is a charcoal-like substance that’s made by burning organic material from biomass. Biochar is black, highly porous, lightweight, fine-grained and has a large surface area with a number of benefits for soil and stormwater management. See the City of Minneapolis Biochar Program for local application. 
• The deep roots of many native plants hold soil and prevent erosion, and they help control stormwater by taking up water that might otherwise pour into streets and, eventually, streams.