*Flexible treatment options
*MIDS flow chart
*List of steps in flow chart
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.
Contents
- 1 Step 1
- 2 Step 2
- 3 Step 3
- 4 Step 4
- 5 Step 5
- 6 Step 6
- 7 Step 7
- 8 Step 8
- 9 Step 9
- 10 Step 10
- 11 Step 11
- 12 Step 12
- 13 Step 13
- 14 Step 14
- 15 Step 15
- 16 Step 16
- 17 Step 17
- 18 Step 18
- 19 Step 19
- 20 Step 20
- 21 Step 21
- 22 Step 22
- 23 Step 23
- 24 Step 24
- 25 Step 25
- 26 Step 26
- 27 Step 27
- 28 Step 28
- 29 Step 29
- 30 Step 30
- 31 Step 31
- 32 Step 32
- 33 Step 33
- 34 Step 34
- 35 Step 35
- 36 Step 36
- 37 Step 37
- 38 Step 38
- 39 Step 39
- 40 Step 40
- 41 Step 41
- 42 Step 42
- 43 Step 43
- 44 Step 44
- 45 Step 45
- 46 Step 46
- 47 Step 47
- 48 Step 48
- 49 Step 49
- 50 Step 50
- 51 Step 51
- 52 Step 52
- 53 Step 53
- 54 Step 54
- 55 Step 55
- 56 Step 56
- 57 Step 57
- 58 Step 58
- 59 Step 59
- 60 Step 60
- 61 Step 61
- 62 Step 62
- 63 Step 63
- 64 Step 64
- 65 Step 65
- 66 Step 66
Step 1
Did you gather the site information necessary to proceed through the flow chart?
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
Step 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
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.
Step 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.
Step 5
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
Return to Design Sequence Flowchart-Flexible treatment options
Step 6
Is the project linear?
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?
Step 8
Is Flexible Treatment Option (FTO) 2 feasible?
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
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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:
- Locations that yield benefits to the same receiving water that receives runoff from the original construction activity.
- Locations within the same Department of Natural Resources (DNR) catachment area as the original construction activity.
- Locations in the next adjacent DNR catchment area up-stream.
- 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?
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
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?
PREVIOUS QUESTION and ANSWER: Is BMP relocation feasible - Answer: No
Flexible Treatment Option 1 (FTO #1)
Applicant attempts to comply with the following conditions:
- Achieve at least 0.55 inch volume reduction goal, and
- Remove 75 percent of the annual total phosphorus load, and
- 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?
- Flexible Treatment Option 2 (FTO #2)
Applicant attempts to comply with the following conditions:
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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?
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?
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?
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?
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?
PREVIOUS QUESTION and ANSWER: Is BMP relocation feasible? - Answer: No
Step 20
Is Flexible Treatment Option (FTO) 2 feasible?
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:
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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?
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?
PREVIOUS QUESTION and ANSWER: Is karst present on the site? - Answer: Yes
Step 23
Is BMP relocation onsite to a location without karst feasible?
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?
PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to a location without karst feasible? - Answer: No
Step 25
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- 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:
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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 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
Step 26
Is shallow groundwater or shallow bedrock present on site?
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
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)?
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?
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?
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
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- Soil borings or report from a professional geologist or geotechnical engineer
PREVIOUS 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.
Step 32
Raise BMP enough to ensure 3 feet (preferably 10 feet) of soil between bottom of BMP and top of bedrock and groundwater
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?
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?
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
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- 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
PREVIOUS STEP: It was determined that contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated.
Step 36
Are there very low infiltrating soils (less than 0.2 inches per hour) on site?
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?
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)?
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.
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?
PREVIOUS STEP: You were asked to provide soil boring or infiltration test results documenting low-infiltration soils.
Step 41
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- Provide soil boring or infiltration test results documenting low-infiltration soils
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)
Step 42
Are there very high infiltrating soils (more than 8 inches per hour) on site?
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?
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?
PREVIOUS QUESTION and ANSWER: Is BMP relocation onsite to a lower-infiltrating location feasible? - Answer: No
Step 45
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- Provide soil boring or infiltration test results documenting high-infiltration soils
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
Step 46
Are there adverse surface water hydrologic impacts from infiltration practices (e.g. impacting perched wetland)?
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?
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?
PREVIOUS QUESTION and ANSWER: Can the BMP be relocated to avoid adverse hydrologic impacts? - Answer: No
Step 49
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- Maximize infiltration BMPs to treat up to the 0.55 inch goal, if possible, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- provide report documenting potential hydrologic impacts from infiltration on the site, prepared by a registered engineer, hydrologist, or wetland specialist
Step 50
- Select Flexible Treatment Option 1 (FTO #1)
Applicant attempts to comply with the following conditions:
- Achieve at least 0.55 inch volume reduction goal, and
- Remove 75 percent of the annual total phosphorus load, and
- 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.
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
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
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
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
- 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
- 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
- Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated
- 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)
- 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
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
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 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- Options considered and presented shall examine the merits of relocating project elements to address varying soil conditions and other constraints across the site.
- No infiltration practices allowed
- Explore non-infiltration volume reduction practices
Provide the foillowing information
- Provide DWSMA or well location map
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.
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.
- 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.
- 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.
- Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated
- 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)
- 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
PREVIOUS STEP: You determined that flexible Treatment option 1 is feasible.
Step 58
Is Flexible Treatment Option 2 feasible?
Flexible Treatment Option 2 (FTO #2)
Applicant attempts to comply with the following conditions:
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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.
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
Step 61
Are there existing or proposed structures or infrastructure that make Flexible Treatment Option 1 not feasible?
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.
- 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.
- 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.
- Contaminated soil, contaminated groundwater, or hotspot runoff is present on the site and cannot be isolated or mitigated
- 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)
- 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
- 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.
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
Step 64
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- No infiltration practices allowed, and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- Provide regulations and/or cost estimates documenting infeasibility of meeting the original Performance goal
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.
Step 65
Select Flexible treatment Option 2
Applicant attempts to comply with the following conditions:
- Maximize infiltration BMPs to treat up to the 0.55 inch goal, if possible and
- Explore non-infiltration volume reduction practices, and
- Achieve volume reduction to the maximum extent practicable (as determined by the Local Authority), and
- Remove 60 percent of the annual total phosphorus load, and
- 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
- Provide regulations and/or cost estimates documenting infeasibility of meeting the original Performance goal;
- Provide report documenting potential hydrologic impacts from infiltration on the site, prepared by a registered engineer, hydrologist, or wetland specialist
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.
Step 66
Is Flexible Treatment Option (FTO) 2 feasible?
PREVIOUS QUESTION and ANSWER: Can the BMP be raised? - Answer: No