MIDS design sequence flow chart

Click on image to enlarge. Note the steps in this image may differ from the steps described on this page.

A flow chart was developed to determine the appropriate performance goal or Flexible Treatment Option for a new development, redevelopment, or linear site. You may access a pdf version of the flow chart (File:Final MIDS Flow chart.pdf) or follow the flow chart through the sequence of questions starting at Step 1 below. If you would like a copy of the flowchart in Visio, so that you can edit it, please contact us.

The wiki version of the flow chart, which starts below at Step 1, takes you through a series of questions and steps to ultimately arrive at a performance goal. The wiki version does not necessarily take you through each step nor does it completely match the pdf version of the flow chart. However, the sequence of questions and answers takes you to the same result.

Two advantages of using the wiki version on this page are that 1) the path through questions and answers is straightforward and 2) there are links, discussions, and images to assist you in answering questions.

Step 1

Did you gather the site information necessary to proceed through the flow chart?

Yes

No or Unsure

Step 2

Prior to using the flow chart, gather the following preliminary information.

• Conduct site review
• Define performance goal

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, conceptual/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

PROCEED TO THE NEXT STEP

Step 3

Impervious surfaces includes roads, roofs, sidewalks, and parking lots.

• 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 or 0.55 inches from all new and fully reconstructed impervious surfaces

PROCEED TO THE FIRST QUESTION

Links

• Performance goals for new development, re-development and linear projects
• For background and derivation of the performance goals, see technical documents and presentations on the MIDS website. We provide links to some of these documents and presentations below.
  • Preliminary Performance Goal Alternatives Evaluation
  • Assessment of MIDS Performance Goal Alternatives: Runoff Volumes, Runoff Rates, and Pollutant Removal Efficiencies
  • Credit Methodology System Review
  • Performance goal review

Step 4

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

• Yes
• No

PREVIOUS QUESTION and ANSWER: The previous question defined the performance goals.

Step 5

You have completed the flow chart

MIDS PERFORMANCE GOAL DOES NOT APPLY
The project creates less than 1 acre of impervious surface.

You have completed the flow chart.

Return to Minimal Impact Design Standards main page

Step 6

Example of a linear project where site constraints likely do not exist

File:Example limited ROW.jpg

Example of a linear project where ROW will likely be constraining

Is the project linear?

Yes

No

PREVIOUS QUESTION and ANSWER: Does project create one acre or more of new and/or fully reconstructed impervious surfaces? Answer - Yes

Step 7

Are there constraints due to lack of available ROW, off site drainage and/or rate control requirements?

Yes

No

Step 8

Is Flexible Treatment Option (FTO) 2 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Are there restraints due to lack of available right-of-way, off-site drainage, and/or rate control requirements? Answer: Yes

Step 9

You have completed the flowchart

Select Flexible treatment Option 2

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. Options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

Provide the following information

• Documentation of offsite runon to project area
• Documentation of lack of right-of-way

PREVIOUS STEP: It was determined that the site is linear, there are constraints due to lack of right-of-way or off/site drainage and/or rate control requirements, and a reasonable effort to acquire all of the right-of-way cannot be made.

Step 10

SELECT FLEXIBLE TREATMENT OPTION 3

Off-site mitigation (including banking or cash or treatment on another project, as determined by the local authority) equivalent to the volume reduction performance goal can be used in areas selected in the following order of preference:

1. Locations that yield benefits to the same receiving water that receives runoff from the original construction activity.
2. Locations within the same Department of Natural Resources (DNR) catachment area as the original construction activity.
3. Locations in the next adjacent DNR catchment area up-stream.
4. Locations anywhere within the local authority's jurisdiction.

PREVIOUS QUESTION: It was determined that Flexible Treatment Option 2 is not feasible.

Step 11

Are there zoning and land use requirements that make the Performance Goal not feasible?

Yes

No

PREVIOUS QUESTION and ANSWER:

• Is the project linear? Answer: No

or

• Are there constraints due to lack of available ROW, off site drainage and/or rate control requirements? Answer: No

Step 12

Is BMP relocation feasible

Yes

No

PREVIOUS QUESTION and ANSWER: Are there zoning and land use requirements that make the Performance Goal not feasible? Answer: Yes

Step 13

Is Flexible Treatment Option (FTO) 1 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation feasible - Answer: No

Flexible Treatment Option 1 (FTO #1)

Applicant attempts to comply with the following conditions:

1. Achieve at least 0.55 inch volume reduction goal, and
2. Remove 75 percent of the annual total phosphorus load, and
3. Options considered and presented shall examine the merits of reloacting project elements to address varying soil conditions and other constraints across the site

Step 14

Is Flexible Treatment Option (FTO) 2 feasible?

Yes

No

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS QUESTION and ANSWER: Is Flexible Treatment Option (FTO) 1 feasible? - Answer: No

Step 15

Is the site located in a DWSMA (Drinking Water Supply Management Area), wellhead protection area, or within 200 feet of a drinking water well?

Yes

No

Discussion

A drinking water supply management area (DWSMA) is the Minnesota Department of Health (MDH) approved surface and subsurface area surrounding a public water supply well that completely contains the scientifically calculated wellhead protection area and is managed by the entity identified in a wellhead protection plan. The boundaries of the drinking water supply management area are delineated by identifiable physical features, landmarks or political and administrative boundaries.

Links

• The Minnesota Department of Health maintains maps, shapefiles and other information on source water protection in Minnesota, including maps of Drinking Water Supply Management Areas (DWSMAs).
• Minnesota Department of Health Source Water Protection main page
• http://water.epa.gov/infrastructure/drinkingwater/sourcewater/protection/index.cfm United States Environmental Protection Agency] Source Water protection page
• Evaluating Proposed Stormwater Infiltration Projects in Vulnerable Wellhead Protection Areas

PREVIOUS QUESTION and ANSWER

• Are there zoning and land use requirements that make the Performance Goal not feasible? - Answer: No

or

• Is BMP relocation feasible? - Answer: Yes

Step 16

Can a Local Government Unit (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater?

Yes

No

PREVIOUS QUESTION and ANSWER: Is the site located in a DWSMA, Wellhead Protection Area, or within 200 feet of a drinking water well? - Answer: Yes

Step 17

Are there existing or proposed structures or infrastructure (e.g. rate control BMPs, utilities, buildings, roadway, easements) that make the Performance Goal not feasible?

Yes

No

PREVIOUS QUESTION and ANSWER

• Is the site located in a DWSMA, wellhead protection area, or within 200 feet of a drinking water well? - Answer: No

or

• Can a Local Government Unit (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater? - Answer: Yes

Step 18

Is BMP relocation feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: - Are there existing or proposed structures or infrastructure (e.g. rate control BMPs, utilities, buildings, roadway, easements) that make the Performance Goal not feasible? - Answer: Yes

Step 19

Is Flexible Treatment option (FTO) 1 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation feasible? - Answer: No

Step 20

Is Flexible Treatment Option (FTO) 2 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Is Flexible Treatment Option (FTO) 1 feasible? - Answer: No

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

Step 21

Is karst present on the site?

Yes

No

If you are unsure, we recommend you review the guidance for karst in this manual. To retain your place in this flowchart, either open the karst guidance page in a new tab (right click on the link and select Open Link in New Tab), use the back arrow after visiting the karst guidance page, or use the Breadcrumbs at the top of the page.

PREVIOUS QUESTION and ANSWER:

• Are there existing or proposed structures or infrastructure that make the performance goal not feasible? - Answer: No

or

• Is BMP relocation feasible? - Answer: Yes

Step 22

Can a local unit of government (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater?

Yes

No

PREVIOUS QUESTION and ANSWER: Is karst present on the site? - Answer: Yes

Step 23

Is BMP relocation onsite to a location without karst feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Can a local unit of government (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater? - Answer: No

Step 24

Is Flexible Treatment Option (FTO) 2 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to a location without karst feasible? - Answer: No

Step 25

Select Flexible treatment Option 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide soil borings or report from a professional geologist or geotechnical engineer

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

Information: Previous step: It was determined that karst is present within 1000 feet of the site and the BMP cannot be reloacted so that it is more than 1000 feet from karst

You have completed the flow chart

Step 26

Is shallow groundwater or shallow bedrock present on site?

Yes

No

If you are unsure, we recommend you review the guidance for shallow groundwater in this manual. To retain your place in this flowchart, either open the shallow groundwater guidance page in a new tab (right click on the link and select Open Link in New Tab), use the back arrow after visiting the shallow groundwater guidance page, or use the Breadcrumbs at the top of the page.

PREVIOUS QUESTION and ANSWER:

• Is karst present on the site? - Answer: No

or

• Can a local unit of government (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater?- Answer: Yes

or

• Is BMP relocation onsite to a location without karst feasible? - Answer: Yes

Step 27

Conduct a detailed site investigation of shallow groundwater or shallow bedrock

Next question

PREVIOUS QUESTION and ANSWER: Is shallow groundwater or shallow bedrock present on site? - Answer: Yes

Step 28

Is there more than 3 feet of soil depth from bottom of BMP to bedrock or groundwater (more than 10 feet is preferred)?

Yes

No

PREVIOUS STEP: You were asked to conduct a detailed site investigation of shallow groundwater or shallow bedrock

Step 29

Is BMP relocation onsite to avoid shallow groundwater or shallow bedrock feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Is there more than 3 feet of soil depth from the bottom on the BMP to bedrock and groundwater (more than 10 feet is preferred)? - Answer: No

Step 30

Can the BMP be raised?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to avoid shallow groundwater and shallow bedrock feasible? - Answer: No

Step 31

Select Flexible treatment Option 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide soil borings or report from a professional geologist or geotechnical engineer

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUIS STEP: It was determined that shallow groundwater or shallow bedrock is present within 3 feet of the bottom of the BMP and the BMP cannot be relocated or raised in elevation to achieve a 3 foot or greater separation from bedrock or groundwater.

You have completed the flow chart

Step 32

Raise BMP enough to ensure 3 feet (preferably 10 feet) of soil between bottom of BMP and top of bedrock and groundwater

Proceed to Next Step

PREVIOUS QUESTION and ANSWER: Can the BMP be raised? Answer - Yes

Step 33

Is there presence of contaminated soils and/or contaminated groundwater, or hotspot runoff?

Yes

No

PREVIOUS QUESTION and ANSWER:

• Is shallow groundwater or shallow bedrock present on the site? - Answer: No

or

• Is there more than 3 feet of soil depth from the bottom of the BMP to bedrock and/or groundwater? - Answer: Yes

or

• Is BMP relocation onsite to avoid shallow bedrock and/or shallow groundwater feasible? - Answer: Yes

or

• Can the BMP be raised? - Answer: Yes

Step 34

Can hotspot or contamination be isolated or remediated to mitigate risk of increased contamination?

Yes

No

PREVIOUS QUESTION and ANSWER: Is there presence of contaminated soils and/or contaminated groundwater, or hotspot runoff? - Answer: Yes

Step 35

Select Flexible treatment Option 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide Phase I or II ESAs or other documentation of potential contamination or hotspot runoff
• Provide documentation of extent of contamination and remediation alternatives considered

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS STEP: It was determined that contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated.

You have completed the flow chart

Step 36

Are there very low infiltrating soils (less than 0.2 inches per hour) on site?

Yes

No

PREVIOUS QUESTION and ANSWER:

• Is there presence of contaminated soils, contaminated groundwater, or hotspot runoff on the site? - Answer: No

or

• Can hotspot or contamination be isolated or remediated? - Answer: Yes

Step 37

Is BMP relocation onsite to a higher-infiltrating location feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Are there very low infiltrating soils (less than 0.2 inches per hour) on site? - Answer: Yes

Step 38

Can BMP be sized to drain dry within 48 hours (24 hours in locations that are tributary to trout streams)?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to a higher-infiltrating location feasible? - Answer: No

Step 39

Provide soil boring or infiltration test results documenting low-infiltration soils.

Next question

PREVIOUS QUESTION and ANSWER: Can BMP be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams)? Answer: No

Step 40

Is Flexible Treatment Alternative No 1 feasible, allowing BMP to drain in 48 hours?

Yes

No

PREVIOUS STEP: You were asked to provide soil boring or infiltration test results documenting low-infiltration soils.

Step 41

Select Flexible treatment Option 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide soil boring or infiltration test results documenting low-infiltration soils

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS STEP: It was determined that soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to areas with a higher infiltration rate, and the BMP cannot be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams)

You have completed the flow chart

Step 42

Are there very high infiltrating soils (more than 8 inches per hour) on site?

Yes

No

PREVIOUS QUESTION and ANSWER:

• Are there very low infiltrating soils (less than 0.2 inches per hour) present on site? - Answer: No

or

• Is BMP relocation onsite to a higher-infiltrating location feasible? - Answer: Yes

or

• Can BMP be sized to drain dry within 48 hours (24 hours in locations that are tributary to trout streams)? - Answer: Yes

Step 43

Is BMP relocation onsite to a lower-infiltrating location feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Are there very high infiltrating soils (more than 8 inches per hour) on site? - Answer: Yes

Step 44

Can subgrade be modified to slow the rate of infiltration to less than 8 inches per hour?

Yes

No

PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to a lower-infiltrating location feasible? - Answer: No

Step 45

Select Flexible treatment Option 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide soil boring or infiltration test results documenting high-infiltration soils

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS QUESTION and ANSWER: It was determined that soils on the site have an infiltration rate greater than 8 inches per hour, the BMP cannot be relocated to an area with an infiltration rate lower than 8 inches per hour, or the subgrade cannot be modified to slow the infiltration rate to less than 8 inches per hour

You have completed the flow chart

Step 46

Are there adverse surface water hydrologic impacts from infiltration practices (e.g. impacting perched wetland)?

Yes

No

PREVIOUS QUESTION and ANSWER: Are there very high infiltrating soils (greater than 8 inches per hour) present on site)? - Answer: No or

• Is BMP relocation onsite to a lower infiltrating location feasible? - Answer: Yes

or

• Can subgrade be modified to slow the rate of infiltration? - Answer: Yes

Step 47

Can the BMP be relocated to avoid adverse hydrologic impacts?

Yes

No

PREVIOUS QUESTION and ANSWER: Are there adverse surface water hydrologic impacts from infiltration practices (e.g. impacting perched wetland)? - Answer: Yes

Step 48

Would BMPs accomodating Flexible treatment option 1 avoid adverse hydrologic impacts?

Yes

No

PREVIOUS QUESTION and ANSWER: Can the BMP be relocated to avoid adverse hydrologic impacts? - Answer: No

Step 49

Select FTO Alternative No. 2

• Maximize infiltration BMPs to treat up to the 0.55 inch goal, if possible
• Explore non-infiltration volume reduction practices
• provide report documenting potential hydrologic impacts from infiltration on the site, prepared by a registered engineer, hydrologist, or wetland specialist

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

You have completed the flow chart

Step 50

Select FTO Alternative No. 1

Flexible Treatment Option 1 (FTO #1)

Applicant attempts to comply with the following conditions:

1. Achieve at least 0.55 inch volume reduction goal, and
2. Remove 75 percent of the annual total phosphorus load, and
3. Options considered and presented shall examine the merits of reloacting project elements to address varying soil conditions and other constraints across the site

Additional considerations

• Maximize infiltration BMPs to treat more than 0.55 inch goal if possible
• If Flexible Treatment Option 1 was determined based on presence of low infiltrating soils, provide soil boring or infiltration test results documenting low-infiltrating soils
• if Flexible Treatment Option 1 was determined based on presence of adverse surface water hydrologic impacts from infiltration practices, provide a report that documents the potential hydrologic impacts from infiltration on the site, prepared by a registered engineer, hydrologist, or wetlands specialist.

You have completed the flow chart

Step 51

Complete design using the following performance goals

• New development projects
  • 1.1 inches from new impervious surfaces
  • Redevelopment projects - 1.1 inches from new impervious surfaces
• Linear projects
  • 0.55 inches of runoff from the new and fully reconstructed impervious surfaces
  • 1.1 inches of runoff from the net increase in impervious area

You have completed the flow chart

Step 52

Do the following conditions apply?

• Zoning and land use requirements make Flexible Treatment Option 2 not feasible

and

• The BMP cannot be relocated to accommodate zoning and land use restrictions

Yes

No

Step 53

Do the following conditions apply?

• There are existing or proposed structures or infrastructure that make Flexible Treatment Option 2 not feasible

and

• BMP relocation is not feasible

Yes

No

PREVIOUS QUESTION and ANSWER: You determined that Flexible Treatment Option 2 is feasible and there are no limitations resulting from zoning and land use requirements.

Step 54

Do any of the following conditions apply? (NOTE: If any condition applies, you do not need to answer the remaining questions.)

• The site is located within a DWSMA, wellhead protection area, or within 200 feet of a drinking water well, and infiltration is not allowed by the LGU

Yes

• Karst is present within 1000 feet of the site and the BMP cannot be relocated so that it is more than 1000 feet from karst

Yes

• Shallow groundwater or shallow bedrock is present within 3 feet of the bottom of the BMP and the BMP cannot be relocated or raised in elevation to achieve a 3 foot or greater separation from bedrock or groundwater

Yes

• Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated

Yes

• Soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to areas with a higher infiltration rate, and the BMP cannot be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams)

Yes

• Soils on the site have an infiltration rate greater than 8 inches per hour, the BMP cannot be relocated to an area with an infiltration rate lower than 8 inches per hour, or the subgrade cannot be modified to slow the infiltration rate to less than 8 inches per hour

Yes

No

Step 55

Do the following conditions apply?

• There are existing or proposed structures or infrastructure that make FTO 2 not feasible

and

• BMP relocation is not feasible

Yes

No

PREVIOUS QUESTION and ANSWER: You determined that Flexible Treatment Option 2 is feasible and there are no limitations resulting from zoning and land use requirements.

Step 56

Select Flexible Treatment Option (FTO) 2

• No infiltration practices allowed
• Explore non-infiltration volume reduction practices
• Provide DWSMA or well location map

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS STEP: It was determined that the site is located within a DWSMA, wellhead protection area or within 200 feet of a drinking water well and infiltration is not allowed by the LGU.

You have completed the flow chart

Step 57

Do any of the following conditions apply? (NOTE: If any condition applies, you do not need to answer the remaining questions.)

• The site is located within a DWSMA, wellhead protection area or within 200 feet of a drinking water well and Can a Local Government Unit (LGU) provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater.

Yes

• Karst is present within 1000 feet up-gradient or 100 feet down-gradient of the site, a local unit of government cannot provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater, and the BMP cannot be reloacted so that it is more than 1000 feet from karst.

Yes

• Shallow groundwater or shallow bedrock is present within 3 feet of the bottom of the BMP and the BMP cannot be relocated or raised in elevation to achieve a 3 foot or greater separation from bedrock or groundwater.

Yes

• Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated

Yes

• Soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to areas with a higher infiltration rate, and the BMP cannot be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams)

Yes

• Soils on the site have an infiltration rate greater than 8 inches per hour, the BMP cannot be relocated to an area with an infiltration rate lower than 8 inches per hour, or the subgrade cannot be modified to slow the infiltration rate to less than 8 inches per hour

Yes

No

PREVIOUS STEP: You determined that flexible Treatment option 1 is feasible.

Step 58

Is Flexible Treatment Option 2 feasible?

Yes

No

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

Step 59

Do the following conditions apply?

• There are very high infiltrating soils (more than 8 inches per hour) on the site;
• BMP relocation to an area with lower infiltration rates is not feasible; and
• The subgrade cannot be modified to slow the rate to less than 8 inches per hour.

Yes

No

PREVIOUS QUESTION and ANSWER: Is Flexible Treatment Alternative No 1 feasible, allowing BMP to drain in 48 hours? - Answer: Yes

Step 60

Do the following conditions apply?

• There are adverse hydrologic impacts from infiltration practices
• The BMP cannot be relocated to avoid adverse hydrologic impacts; and
• BMPs accomodating FTO 1 would avoid adverse hydrologic impacts

Yes

No

Step 61

Are there existing or proposed structures or infrastructure that make Flexible Treatment Option 1 not feasible?

Yes

No

PREVIOUS STEP: You determined that flexible Treatment option 1 is feasible.

Step 62

Do any of the following conditions apply? (NOTE: If any condition applies, you do not need to answer the remaining questions.)

• The site is located within a DWSMA, wellhead protection area, or within 200 feet of a drinking water well, and a Local Government Unit (LGU) can provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater.

Yes

• Karst is present within 1000 feet up-gradient or 100 feet down-gradient of the site, a local unit of government cannot provide a higher level of engineering review to ensure a functioning system that prevents adverse impacts to groundwater, and the BMP cannot be relocated so that it is more than 1000 feet from karst.

Yes

• Shallow groundwater or shallow bedrock is present within 3 feet of the bottom of the BMP and the BMP cannot be relocated or raised in elevation to achieve a 3 foot or greater separation from bedrock or groundwater.

Yes

• Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated

Yes

• Soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to areas with a higher infiltration rate, and the BMP cannot be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams)

Yes

• Soils on the site have an infiltration rate greater than 8 inches per hour, the BMP cannot be relocated to an area with an infiltration rate lower than 8 inches per hour, or the subgrade cannot be modified to slow the infiltration rate to less than 8 inches per hour

Yes

• Soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to areas with an infiltration rate greater than 0.2 inches per hour, the BMP cannot be sized to drain within 48 hours (24 hours in locations that are tributary to trout streams), and Flexible Treatment Option 1 is feasible.

Yes

No

PREVIOUS STEP: You determined that Flexible Treatment Option 1 is feasible.

Step 63

Do the following conditions apply?

• There are adverse hydrologic impacts from infiltration practices; and
• The BMP cannot be relocated to avoid adverse hydrologic impacts

Yes

No

Step 64

Select Flexible Treatment Option (FTO) 2

• Provide regulations and/or cost estimates documenting infeasibility of meeting the original Performance goal

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. Options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS STEP: It was determined that

• there are no site conditions that prevent infiltration and there are no adverse surface water hydrologic impacts from infiltration practices, but
  • there are zoning and land use requirements that make the Performance Goal not feasible and BMP relocation is not feasible; or
  • there are existing or proposed structures or infrastructure that make the Performance Goal not feasible and BMP relocation is not feasible.

You have completed the flow chart

Step 65

Select Flexible Treatment Option (FTO) 2

• Provide regulations and/or cost estimates documenting infeasibility of meeting the original Performance goal;
• Maximize infiltration BMPs to treat up to the 0.55 inch goal, if possible;
• Explore non-infiltration volume reduction practices; and
• Provide report documenting potential hydrologic impacts from infiltration on the site, prepared by a registered engineer, hydrologist, or wetland specialist

Flexible Treatment Option 2 (FTO #2)

Applicant attempts to comply with the following conditions:

1. Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
2. Remove 60 percent of the annual total phosphorus load, and
3. options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.

PREVIOUS STEP: It was determined that

• there are no site conditions that prevent infiltration but
  • there are adverse surface water hydrologic impacts from infiltration practices and BMP relocation is not feasible; and
  • there are zoning and land use requirements that make the Performance Goal not feasible and BMP relocation is not feasible; or
  • there are existing or proposed structures or infrastructure that make the Performance Goal not feasible and BMP relocation is not feasible.

You have completed the flow chart

Step 66

Is Flexible Treatment Option (FTO) 2 feasible?

Yes

No

PREVIOUS QUESTION and ANSWER: Can the BMP be raised? - Answer: No