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Minnesota Stormwater Manual

MIDS design sequence flow chart
Revision as of 17:36, 28 December 2021 by Mtrojan (talk | contribs) (→‎Box 65)

Box 1

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

Yes

No or Unsure

Box 2

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

  • Conduct site review
  • Define performance goal

Conduct site review

PROCEED TO THE NEXT STEP

Box 3

  • 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

Box 4

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

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

Box 5

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

Box 6

image of a project where ROW will not be constraining
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

Box 7

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

Yes

No

Box 8

Is Flexible Treatment Option (FTO) 2 feasible?

[ Box 57 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

Box 9

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

Select Flexible treatment Option 2. You have completed the flow chart.

  • Provide documentation of offsite runon to project area
  • Provide documentation of lack of right-of-way

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 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.

Box 10

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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.

Box 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

Box 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

Box 13

Is Flexible Treatment Option (FTO) 1 feasible?

[ Box 61 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

Box 14

Is Flexible Treatment Option (FTO) 2 feasible?

[ Box 54 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.

Box 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

Box 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

[ Box 58 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

Box 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

[ Box 21 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

Box 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

Box 19

Is Flexible Treatment option (FTO) 1 feasible?

[ Box 62 Yes]

No

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

Box 20

Is Flexible Treatment Option (FTO) 2 feasible?

[ Box 54 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.

Box 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

Box 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

Box 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

Box 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

Box 25

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 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

Box 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

Box 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

Box 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

Box 30

Can the BMP be raised?

Yes

[ Box 66 No]

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

Box 31

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 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

Box 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

Box 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

Box 35

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 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

Box 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

Box 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

Box 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

Box 40

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

[ Box 59 Yes]

No

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

Box 41

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 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

Box 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

Box 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

Box 45

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Information: 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

Box 46

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

[ Box 47 Yes]

[Box 51 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

Box 47

Can the BMP be relocated to avoid adverse hydrologic impacts?

[ Box 51 Yes]

[ Box 48 No]

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

Box 48

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

[ Box 50 Yes]

[ Box 49 No]

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

Box 49

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 50

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 51

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 52

Do the following conditions apply?

and

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

Yes

No

Box 53

Do the following conditions apply?

and

  • BMP relocation is not feasible

Yes

[Box 63 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.

Box 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

[ Box 56 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

[ Box 25 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

[ Box 31 Yes]

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

[ Box 35 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)

[ Box 41 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

[Box 45 Yes]

[Box 63 No]

Box 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

[ Box 56 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.

Box 56

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 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.

[ Box 56 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.

[ Box 25 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.

[ Box 31 Yes]

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

[ Box 35 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, 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 not feasible.

[MIDS design sequence flow chart - Box 41 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

[ Box 45 Yes]

[Box 52 No]

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

Box 58

Is Flexible Treatment Option 2 feasible?

[ Box 56 Yes]

[ Box 10 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.

Box 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.

[ Box 45 Yes]

[Box 60 No]

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

Box 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

[ Box 50 Yes]

[ Box 49 No]

Box 61

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

[ Box 20 Yes]

[ Box 62 No]

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

Box 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.

[ Box 56 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.

[MIDS design sequence flow chart - Box 25 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.

[ Box 31 Yes]

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

[ Box 35 Yes]

  • Soils on the site have an infiltration rate of less than 0.2 inches per hour, the BMP cannot be relocated to an area 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 not feasible.

[ Box 41 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, and the subgrade cannot be modified to slow the infiltration rate to less than 8 inches per hour

[ Box 45 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.

[ Box 60 Yes]

[ Box 60 No]

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

Box 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

[ Box 65 Yes]

[ Box 64 No]

Box 64

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 65

image of stop sign
You have completed the flow chart. Return to Flexible treatment options

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

Box 66

Is Flexible Treatment Option (FTO) 2 feasible?

[ Box 31|Yes]

[Box 10|No]

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

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

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

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