Design sequence flow chart

This is intended to take you through a design sequence that allows you to determine the appropriate performance goal at a site. Follow the questions below sequentially to arrive at a performance goal appropriate for your site.

Preliminary information

Conduct site review

• Aerial photos and topographic maps
• County soil surveys and other soil information as available
• County Geologic Atlas
• Local groundwater levels
• DWSMA and Wellhead Protection maps
• FEMA and local floodplain maps
• Soil borings and site survey
• MPCA listing of potentially contaminated sites
• Phase 1 and 2 Environmental Site Assessments
• TMDLs and local water quality standards
• Wetland delineations, MNRAM assessments, and wetland classifications
• Proposed conditions, conceptural/preliminary site design
• Local zoning and land use requirements/ordinances, including stormwater rate control requirements
• Communication with local landowners, LGU, or others knowledgeable about the site
• Site inspection

Define treatment goal

• New and redevelopment projects: Retain on site a volume of 1.1 inches from impervious surfaces
• Linear projects: Retain on site the larger of 1.1 inches from all new impervious surfaces or 0.55 inches from all new and fully reconstructed impervious surfaces

BeginFlow chart

[[Does the project create one acre or more of new and/or fully reconstructed impervious surfaces?

• No
• Yes

Goal does not apply

The MIDS performance goal does not apply

DWSMA

Is the site located in a DWSMA, wellhead protection area, or near a drinking well?

• Yes
• No

DWSMA1

• Select Flexible Treatment Option
• (FTO) Alternative No. 2
• Revise Treatment Goal
• No infiltration practices allowed
• Provide DWSMA or well location map

next

Utilities, structures, land use requirements

Are there existing or proposed utilities, structures, or land use requirements (density, parking, setbacks, etc.) that make the Treatment Goal infeasible or cost prohibitive?

• yes
• no

Utilities1

Is BMP relocation possible?

• Karst, shallow groundwater, shallow bedrock|yes
• Utilities2|no

Utilities2

Are Flexible Treatment Option Alternatives number 1 or number 2 feasible?

• yes
• no

Utilities3

Investigate Off-Site Considerations:

1. Banking within watershed with goal of:

• Linear: 0.55 inches over impervious
• Nonlinear: 1.1 inches over impervious

1. Cash as determined by LGU

Provide site survey, maps, regulations, and/or cost estimates documenting infeasibility and cost-prohibitive nature of meeting the original Treatment Goal or FTO Alternatives

END

Utilities4

• Select Flexible Treatment Option Alternative No. 1 or No. 2
• Revise Treatment Goal
• Provide site survey, maps, regulations, and/or cost estimates documenting infeasibility and cost-prohibitive nature of meeting the original Treatment Goal

next