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

Begin Flow Chart

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

• No
• Yes

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

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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

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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

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