The Minimal Impact Design Standards Program (MIDS) is an enhanced set of regulatory tools, modeling methods, ordinance templates, and development credit systems to promote the implementation of effective techniques to limit water pollution from stormwater runoff. The program is the result of an initiative by the Minnesota Stormwater Steering Committee to re-tune the public development review process to better enable low-impact development practices. The process was initiated when the Minnesota Legislature allocated funds to “develop performance standards, design standards or other tools to enable and promote the implementation of low impact development and other stormwater management techniques.” (Minnesota Statutes 2009, section 115.03, subdivision 5c). Based on this revision to the state statutes, an interdisciplinary working group has assembled to create a set of user-friendly tools that can be adopted by LGUs to encourage new development to be built in ways that streamline the site review process, legitimize LID techniques, and focus on tangible water quality improvements. The group has recently finalized their recommendations, is about to release their toolkit, and is in the process of working with a number of pilot cities to integrate MIDS into their local ordinances.
The program, which has gestated within the Minnesota Pollution Control Agency (MPCA), aims to address several longstanding barriers to reducing the water quality impact from non-point source pollution. Stormwater mitigation as a component of site design has suffered as a result of outdated regulations that focus only on establishing a ceiling for impervious surfaces on a site and the control of runoff rates with little regard to pollutant loading and the cumulative impacts of stormwater volume. While these considerations are important, they are often the only performance requirements within development ordinances and therefore set a least common denominator in terms of a new development’s performance from a stormwater perspective. The status quo approach essentially guarantees that many of the more progressive approaches to stormwater management that treat runoff onsite (bioswales, rain gardens, rainwater harvesting, etc) are value engineered out. These practices are additional expenditures that don’t affect the entitlements process as the traditional pipe and pond approach is still required regardless. In addition, there is a lack of methodological consistency across cities and watersheds for quantifying runoff volumes/rates, pollutant load reductions, and permeable surface limits for different land uses.
The other reality is that cities must report on their efforts to comply with their Multiple Separate Storm Sewer Systems permits (MS4) as well as Total Maximum Daily Load implementation plans (TMDL). What this means is that cities often have specific targets for pollution load reduction for common pollutants (Phosphorus, Total Suspended Solids, Etc.) and need to demonstrate progress in addressing this ongoing pollution. The problem is that many of the practices required by local ordinances are ineffective at preventing the types of pollution that these cities are grappling with. These are the issues that MIDS was developed to help address.
Detention Cisterns under a parking lot are they the only answer on a tight site?
Still with me? Taking it back to the title, what MIDS means for Minnesota Urbanism is the expectation of higher performance for onsite stormwater management, combined with new development incentives, and greater flexibility in creating onsite stormwater design that is appropriate to the site context. One of the ways that MIDS accomplishes this goal is by coordinating the organization of stormwater mitigation ordinances and performance goals with a calculator tool that allows site designers to iteratively attempt to meet required performance goals by modeling their site plan to estimate BMP performance. This reflects an understanding that dense urban sites have different performance goals than do low density sites, so why have the same requirements apply to each?
The tool, created by Barr Engineering, allows for the recognition of practices such as filter strips, stormwater harvest and re-use, and other techniques to be respected for the benefits they actually provide. This has the potential to shift low-impact development from an optional set of design strategies funded by public grants or genuine altruism, to what is required by local ordinances.
Typical Site
We are all familiar with how a typical commercial site that complies with a city ordinances looks. Just imagine most strip malls you have ever visited. Here is an example pulled from Google Earth. The site is about 80% impervious with the building and parking area concentrated in a large central mass. The impervious area is a grassed strip around the perimeter of the parking lot and the areas directly adjacent to the storm pond. The site is set up to comply with the regulations in the most basic possible way. This makes sense when there is no incentive to try to do something better.
Site Developed with Low Impact Development Principles
This is an example of how a site can be developed in a way that is respectful of context. The site is the Amery Regional Medical Care Center with a site plan by EOR. The site plan is responsive to the natural features of the site, maintaining a wooded buffer between the development and the nearby river. Likewise, areas of the site that had prime farmland were protected and remained in production. The parking lot also is organized around a bioretention facility that performs the required volume control, while at the same time breaking up the parking area and adding green space. This project is a textbook example of what MIDS is hoping to change from a progressive outlier to how we can expect site plans to perform.
The MIDS program is currently in the process of working with several pilot project communities in Washington County to integrate MIDS into their ordinances and to test out the calculator packages in a site plan review. Likewise, they are collaborating with MN-DOT and other transportation agencies to get them to adopt a set of practices designed for public transportation networks. The ultimate vision is that cities across Minnesota could adopt this package of tools. In doing so it would result in site design that does less damage to our water resources and helps give developers and site planners the chance to start doing things better.