HomeMy WebLinkAbout2023-10-13 MSCWMO Review Letter MIDDLE ST. CROIX 455 Hayward Ave N
WATERSHED MANAGEMENT ORGANIZATION Oakdale, MN 55128
651-796-2227‘:
r www.mscwmo.org O
October 13, 2023
Eric Johnson
City of Oak Park Heights
14168 Oak Park Blvd. N
Oak Park Heights, MN 55082
Dear Mr.Johnson,
The Middle St. Croix Watershed Management Organization (MSCWMO) received submittal items on July
11th, 2023 for a warehouse development at 5416 Stagecoach Trail North within the MSCWMO
boundaries and the City of Oak Park Heights.The proposed project qualifies for full review under the
MSCWMO 2015 Watershed Management Plan (WMP)since it involves land alteration activities greater
than 10,000 square feet and creates more than 6,000 square feet of impervious surface.The MSCWMO
staff recommends Approval with the following eight conditions:
1. Drainage easements up to the 100-yr HWL have been secured for stormwater management
facilities. Proposed easements have been drawn but a legal description and recording are not
yet complete.
2. A proposed maintenance easement is provided A proposed maintenance agreement was not
provided for review or comment.
3. The SWPPP and Erosion and Sediment control notes are updated with a 7 day(not 14 day)
stabilization timeframe of exposed soils since the site drains to and is within one mile of
impaired waters and pipe outlets have energy dissipation within 24 hours of connecting. Erosion
and sediment control notes on plans still reference a 14 day stabilization timeframe. Please
correct this to a 7 day timeframe. Plans must also note that pipe outlets must have energy
dissipation within 24 hours of connecting.
4. The design infiltration rate is revised to be based upon the least permeable soil texture(SM)and
design infiltration rates recommended in the Minnesota Stormwater Manual.The applicant
responded that "SM soils are evident during soil testing" and "calculations are very conservative
in nature"yet they are using an infiltration rate of 1 inch/hour in the stormwater calculations
which is double the recommended infiltration rate provided in the Minnesota Stormwater
Manual of 0.45 inches/hour of SM soil texture. If they do not wish to use the infiltration rate
recommended in the stormwater manual,they can provide testing results of measured
infiltration rates to support their design infiltration rate however a factor of safety of 2 must be
applied to the measured infiltration rate(design infiltration rate = measured infiltration rate/2).
providcd.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores• Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
Eric Johnson Page 2 10/13/2023
6. Construction plans provide adequate construction guidance of infiltration practices to prevent
clogging or compaction. i he plans do not contain all necessary construction guidance contained
within the review checklist (see attached).The following construction plan guidance must be
provided:
a. Excavation within 2.0 feet of final grade for infiltration/filtration systems is prohibited
until contributing drainage areas are constructed and fully stabilized.
b. Rigorous sediment and erosion controls planned to divert runoff away from the system.
c. Installation of volume control facilities must occur in dry soil conditions. Excavation,soil
placement and rapid stabilization of perimeter slopes must be accomplished prior to the
next precipitation event.
d. Excavation shall be performed by an excavator with a toothed bucket. Use excavator
bucket to place materials. Construction equipment shall not be allowed into the basin.
e. Prior to the release of any remaining fee or security,the permit holder must provide
documentation that constructed volume control facilities perform as designed
7. The SWPPP describes pollution prevention management measures.The plans do not contain all
necessary pollution prevention measures within the review checklist(see attached).The
following pollution prevention guidance must be provided in the plans or SWPPP(a SWPPP was
not provided for review and comment, only the construction plans):
a. Fueling and maintenance of equipment or vehicles; spill prevention and response.
b. Vehicle and equipment washing.
c. No engine degreasing allowed on site.
d. Containment of Concrete and other washout waste.
e. Portable toilets are positioned so that they are secure.
8. The SWPPP or construction plans contain tabulated quantities of erosion and sediment control
items. . The plans do not contain tabulated quantities of erosion and sediment control items and
a SWPPP was not provided for review and comment, only the construction plans.
This recommended conditional approval is based on the technical review of the MSCWMO performance
standards and does not constitute approval by the City of Oak Park Heights. MSCWMO review process
information can be downloaded from www.mscwmo.org. Please contact me at 651-796-2227 or
mdowning@mnwcd.org if you have any questions or comments regarding this correspondence.
Sincerely,
Matt Downing Administrator
Middle St. Croix Watershed Management Organization
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores• Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
0 MIDDLE ST. CROIX PROJECT REVIEW
WATERSHED MANAGEMENT ORGANIZATION CHECKLIST
MSCWMO Review ID: 23-020 Review Date:8/10/2023
Project Name:Croixview Holdings, LLC Location: 5416 Stagecoach Trail, Oak Park Heights
Applicant:Tim Siegfried Purpose: Office warehouse development
Recommendation:Approval with the following 8 conditions:
1. Drainage easements up to the 100-yr HWL have been secured for stormwater management facilities
2. A proposed maintenance easement is provided
3. The SWPPP and Erosion and Sediment control notes are updated with a 7 day(not 14 day)stabilization
timeframe of exposed soils since the site drains to and is within one mile of impaired waters and pipe outlets
have energy dissipation within 24 hours of connecting.
4. The design infiltration rate is revised to be based upon the least permeable soil texture (SM)and design
infiltration rates recommended in the Minnesota Stormwater Manual.
5. A method to demonstrate and visually verify the underground infiltration is functioning is provided.
6. Construction plans provide adequate construction guidance of infiltration practices to prevent clogging or
compaction.
7. The SWPPP describes pollution prevention management measures.
8. The SWPPP or construction plans contain tabulated quantities of erosion and sediment control items.
Applicability:
® Any project undertaking grading,filling, or other land alteration activities which involve movement of 100 cubic
yards of earth or removal of vegetation on greater than 10,000 square feet of land.
® Any project that creates or fully reconstruct 6,000 square feet or more of impervious surface.
❑ All major subdivisions or minor subdivisions that are part of a common plan of development. Major
subdivisions are defined as subdivisions with 4 or more lots.
❑ Any project with wetland impacts,grading within public waters,grading within buffers or within 40-
feet of the bluff line.
❑ Development projects that impact 2 or more of the member communities.
❑ New or redevelopment projects within the St.Croix Riverway that require a building permit that add
500 square feet of additional impervious surface.
❑ Any project requiring a variance from the current local impervious surface zoning requirements for
the property.
❑ Any land development activity, regardless of size,that the City determines is likely to cause an adverse impact to an
environmentally sensitive area or other property, or may violate any other erosion and sediment control standard
set by the member community.
Submittal Items:
MSCWMO Member Communities
Afton • Bayport • Baytown • Lakeland • Lakeland Shores• Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 2
M A completed and signed project review application form and review fee.
Z Grading Plan/Mapping Exhibits:
® Property lines and delineation of lands under ownership of the applicant.
® Delineation of existing on-site wetlands,shoreland and/or floodplain areas (including any buffers).
NA Ordinary High Water(OHW) elevations and datum,as determined by the MDNR (if applicable).
Z Existing and proposed site contour elevations related to NAVD 1988 datum (preferred)or NGVD, 1929. Datum
must be noted on exhibits.
❑ Drainage easements covering land adjacent to ponding areas,wetlands, and waterways up to their 100-year
flood levels and covering all ditches and storm sewers.Access easements to these drainage easements and to
other stormwater management facilities shall also be shown. (Not required for sites within public right-of-way)
® Minimum building elevation for each lot.
® Identification of downstream water body.
® Delineation of the subwatersheds contributing runoff from off-site, proposed and existing on-site
subwatersheds, and flow directions/patterns.
® Location, alignment,and elevation of proposed and existing stormwater facilities.
II1 Existing and proposed normal water elevations and the critical (the highest)water level produced from the 100-
year 24-hour storms.
® Location of the 100-year flood elevation, natural overflow elevation,and lowest floor elevations.
® A Stormwater Pollution Prevention Plan in compliance with the requirements of the NPDES SDS Construction
Stormwater Permit.
Permanent Stormwater Management System in compliance with the requirements of the NPDES SDS Construction
Stormwater Permit and MSCWMO Performance Standards.
® Impervious areas (Pre-and Post-Construction).
r Construction plans and specifications for all proposed stormwater management facilities.
NA Location(s)of past,current or future onsite well and septic systems (if applicable).
® Other exhibits required to show conformance to these Performance Standards.
❑ Hydrologic/Hydraulic Design Exhibits:
❑ All hydrologic and hydraulic computations completed to design the proposed stormwater management facilities
shall be submitted. Model summaries must be submitted.The summaries shall include a map that corresponds
to the drainage areas in the model and all other information used to develop the model.
❑ A table (or tables) must be submitted showing the following:
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores • Lake St. Croix Beach •Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 3
❑ A listing of all points where runoff leaves the site and the existing and proposed stormwater runoff rates and
volumes.
❑ A listing of the normal water levels under existing and proposed conditions and the water levels produced
from the storm and runoff events listed above for all on-site wetlands, ponds, depressions, lakes, streams,
and creeks.
❑ A proposed maintenance agreement, which may be in the format of Appendix K, or other form approved by the city.
❑ This site drains to, and is within one mile of special or impaired water and complies NPDES CSW additional
requirements. Drains to Perro Creek and St. Croix with construction related impairments,stabilization timeframe (in
erosion control standard note 5) must be 7 days, not 14.
STORMWATER MANAGEMENT PERFORMANCE STANDARDS
® Water quality treatment is provided prior to direct discharge of stormwater to wetlands and all other water
bodies.
Rate and Flood Control Standards
® The peak rate of stormwater runoff from a newly developed or redeveloped site shall not exceed the 2-, 10-, and
100-year 24-hour storms with respective 2.8,4.2, and 7.3-inch rainfall depths with MSCWMO approved time
distribution based on Atlas 14 for existing and proposed conditions. The runoff curve number for existing
agriculture areas shall be less than or equal to the developed condition curve number.The newly developed or
redeveloped peak rate shall not exceed the existing peak rate of runoff for all critical duration events, up to and
including the 100-year return frequency storm event for all points where discharges leave a site during all phases of
development.
® Predevelopment conditions assume"good hydrologic conditions"for appropriate land covers as identified in TR-55
or an equivalent methodology. Runoff curve numbers have been increased where predevelopment land cover is
cropland:
Hydrologic Soil Group A Runoff Curve Number 56
Hydrologic Soil Group B Runoff Curve Number 70
Hydrologic Soil Group C Runoff Curve Number 79
Hydrologic Soil Group D Runoff Curve Number 83
® Computer modeling analyses includes secondary overflows for events exceeding the storm sewer systems level-of-
service up through the critical 100-year event.
NA In sub-areas of a landlocked watershed,the proposed project does not increase the predevelopment volume or rate
of discharge from the sub-area for the 10-year return period event.
❑ Flowage easements up to the 100-yr flood level have been secured for stormwater management facilities (such as
ditches and storm sewers).
® Lowest floor elevations of structures built adjacent to stormwater management features and other water bodies are
a minimum of two feet above the 100-year flood elevation and a minimum of two feet above the natural overflow of
landlocked basins.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores • Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg.4
Volume Control Standards
® Calculations/computer model results indicate stormwater volume is controlled for new development and
redevelopment requirements per the MSCWMO Design Standards.
Volume Retention Required (cu.ft.) Volume Retention Provided (cu.ft.)
40,500 sq.f t.x 12 171/f
m =3,713 cu.f t. BMP Volume
lft Underground TDA 8398 cu.ft.
Total Required Volume Retention =3,713 cu.ft. Total Provided Volume Retention =8,398 cu.ft.
Flexible Treatment Options(when applicable)
NA Applicant demonstrated qualifying restrictions as defined in Section 7.2.2 (4)of the 2015 MSCWMO Watershed
Management Plan that prohibits the infiltration of the entire required volume.
NA FTO#1: MIDS calculator submission removes 75%of the annual total phosphorous.
NA FTO#2: MIDS calculator submission removes 60%of the annual total phosphorous.
NA FTO#3:Offsite mitigation equivalent to the volume reduction standard is provided.
Infiltration/Filtration Design Standards
❑ Proposed stormwater management features meet or exceed NPDES General Construction Permit requirements are
designed in conformance with the most recent edition of the State of Minnesota Stormwater Manual. Infiltration
rate based upon the SP-SM soil texture of 1 in/hr exceeds recommended rates of the Minnesota Stormwater
Manual.
® None of the following conditions exist that prohibit infiltration of stormwater on the site
a. Areas where vehicle fueling and maintenance occur.
b. Areas where contaminants in soil or groundwater will be mobilized by infiltrating stormwater.
c. Areas where soil infiltration rates are field measured at more than 8.3 inches per hour unless amended to slow
the infiltration rate below 8.3 inches per hour.
d. Areas with less than three (3)feet of separation distance from the bottom of the infiltration system to the
elevation of the seasonally saturated soils or the top of bedrock.
e. Areas of Hydrologic Soil Group D (clay)soils
f. Areas within DSWMAs and ERAs unless infiltration is deemed appropriate based on Minnesota Stormwater
Manual Guidance ,e is within a UWSMVMA that is low vulnerability therefore inhitration is appropriate following
proper design, construction, and maintenance of infiltration practice in compliance with local and state
requirements.
g. Areas within 1,000 feet up-gradient, or 100 feet down-gradient of active karst features unless allowed by a local
unit of government with a current MS4 permit.
h. Areas that receive runoff from industrial facilities not authorized to infiltration stormwater under the NPDES
stormwater permit for industrial activites.
® Minimum setbacks from the Minnesota Department of Health for infiltration practices are met
Setback Minimum Distance(ft.)
Property line 10
Building foundation* 10
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores • Lake St. Croix Beach •Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 5
Private well 35
Public water supply well 50
Septic system tank/leach field 35
*Minimum with slopes directed away from the building
• Pretreatment devices(s) remove at least 50%of sediment loads. If downstream from a potential hot spot, a
skimmer is in place to facilitate cleanup.
® Water quality volume will be discharged through infiltration or filtration media in 48 hours or less.
NA For bioretention (biofiltration and bioinfiltration)volume control management facilities above ground with
vegetation the period of inundation shall be calculated using the maximum water depth below the surface discharge
elevation and the soil infiltration rate.
® For infiltration basin volume control management facilities the period of inundation shall be calculated using the
maximum water depth below the surface discharge elevation and the soil infiltration rate.
• Appropriate soil borings have been conducted that meet the minimum standards.
a. A minimum of one boring was conducted at the location of the infiltration facility for facilities up to 1,000 ftZ;
between 1,000 and 5,000 ftZ,two borings; between 5,000 and 10,000 ftZ,three borings;and greater than 10,000
ftZ,4 borings plus an additional boring for every 2,500 ftZ beyond 12,500 ftZ.
b. Soil borings extend a minimum of five feet below the bottom of the infiltration practice. If fractured bedrock is
suspected,the soil boring goes to a depth of at least ten feet below the proposed bottom of the volume control
facility.
c. A minimum of three feet of separation to the seasonal water table and/or bedrock.
d. Identify unified soil classification.
❑ The least permeable soils horizon identified in the soil boring dictated the infiltration rate.Test pits 6 and 7 indicate
SM soil texture and which would correspond to a recommended design infiltration rate of 0.45 in/hr per the
Minnesota Stormwater Manual
►Z� Additional flows are bypassed and are routed through stabilized discharge points.
NA Filtration basin demonstrates a basin draw down between 24 hours and 48 hours.
NA Filtration system Iron Enhanced Sand Filter is sized to bind soluble phosphorous removal for 30 year functional life
of the system using the published value of 17lbs.phosphorous removal per 20 yards of 5% by weight iron filings to
95%sand.
❑ Identify as build survey and method to demonstrate infiltration or filtration basin is functioning.
❑ Construction plans provide adequate construction guidance to prevent clogging or compaction and demonstrate
performance.
a. Excavation within 2.0 feet of final grade for infiltration/filtration systems is prohibited until contributing
drainage areas are constructed and fully stabilized.
b. Rigorous sediment and erosion controls planned to divert runoff away from the system.
c. Installation of volume control facilities must occur in dry soil conditions. Excavation,soil placement and rapid
stabilization of perimeter slopes must be accomplished prior to the next precipitation event.
d. Excavation shall be performed by an excavator with a toothed bucket. Use excavator bucket to place materials.
Construction equipment shall not be allowed into the basin.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores• Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 6
e. Prior to the release of any remaining fee or security,the permit holder must provide documentation that
constructed volume control facilities perform as designed.
® There is a way to visually verify the system is operating as designed.
® A minimum 8.0' maintenance access is provided to all stormwater facilities.
EROSION AND SEDIMENT CONTROL PERFORMANCE STANDARDS
® A Stormwater Pollution Prevention Plan (SWPPP) that meets the National Pollutant Discharge Elimination
System (NPDES) requirements.
Narrative
® Identify the person knowledgeable and experienced who will oversee the implementation of the SWPPP; the
installation, inspection, and maintenance of the BMPs.
a. Identifies the person who will oversee the BMP inspection and maintenance.
b. Identify the training requirements are satisfied.
c. Inspections performed once every 7 days.
d. Inspections performed within 24 hours of a rain event greater than 0.5 in/24 hours.
e. Inspection and Maintenance records include:
i. Date and time of inspection.
ii. Name of person(s) conducting inspections.
iii. Finding of inspections, including the specific location where corrective actions are needed.
iv. Corrective actions taken (including dates, times, and party completing maintenance activities).
v. Date and amount of rainfall events greater than 0.5 in/24 hours.
vi. Rainfall amounts must be obtained by a properly maintained rain gauge installed onsite, or by a
weather station that is within one mile or by a weather reporting system.
vii. Requirements to observe, describe, and photograph any discharge that may be occurring during the
inspection.
viii. All discovered nonfunctional BMPs must be repaired, replaced, or supplemented with functional BMPs
within 24 hours after discovery, or as soon as field conditions allow.
@ Describes procedures to amend the SWPPP and establish additional temporary ESC BMPs as necessary for site
conditions.
® Describes the installation timing for all Erosion Sediment Control (ESC) Best Management Practices (BMPs).
® Describes final stabilization methods for all exposed areas.
® Methods used to minimize soil compaction and preserve topsoil must be described.
NA Describes dewatering technique to prevent nuisance conditions, erosion, or inundation of wetlands.
NA Identifies any specific chemicals and the chemical treatment systems that may be used for enhancing the
sedimentation process on the site, and how compliance will be achieved with the permit requirements.
❑ Describes the following pollution prevention management measures:
a. Storage, handling, and disposal of construction products, materials, and wastes.
b. Fueling and maintenance of equipment or vehicles; spill prevention and response.
c. Vehicle and equipment washing.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores • Lake St. Croix Beach •Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 7
d. No engine degreasing allowed on site.
e. Containment of Concrete and other washout waste.
f. Portable toilets are positioned so that they are secure.
Plan Sheets
NA Temporary Sediment Basins required (10 acres draining to common location or 5 acres App. A) and design
meets the following criteria:
a. Adequately sized — 2-year, 24-hour storm, minimum 1,800 feet/acre; or no calculative minimum
3,600ft3/acre.
b. Designed to prevent short circuiting.
c. Outlets designed to remove floating debris.
d. Outlets designed to allow complete drawdown.
e. Outlets designed to withdraw water from the surface
f. Outlets have energy dissipation.
g. Have a stabilized emergency spillway.
h. Situated outside of surface waters and any natural buffers.
❑ Locations and types of all temporary and permanent Erosion Control BMPs.
Exposed soils have erosion protection/cover initiated immediately and finished within 7 days. Stabilization
timeframe not specified in SWPPP
b. Wetted perimeters of ditches stabilized within 200 feet of surface water within 24 hours.
c. Pipe outlets have energy dissipation within 24 hours of connecting. Timeframe not specified in SWPPP
® Locations and types of all temporary and permanent Sediment Control BMPs.
a. Sediment control practices established on down gradient perimeters and upgradient of any buffer zones.
b. All inlets are protected.
c. Stockpiles have sediment control and placed in areas away from surface waters or natural buffers.
d. Construction site entrances minimize street tracking
e. Plans minimize soil compaction and, unless infeasible to preserve topsoil.
f. Fifty foot natural buffers preserved or (if not feasible) provide redundant sediment controls when a
surface water is located within 50 feet of the project's earth disturbances and drains to the surface water.
❑ Tabulated quantities of all erosion prevention and sediment control BMPs. Not provided
® Stormwater flow directions and surface water divides for all pre- and post-construction drainage areas.
® Locations of areas not to be disturbed (buffer zones).
NA Location of areas where construction will be phased to minimize duration of exposed soil areas.
NA Blufflines are protected from construction activities in urban (40 foot buffer) areas and rural areas (100-foot
buffer).
WETLAND PERFORMANCE STANDARDS
NA Direct discharge of stormwater to wetlands and all other water bodies without water quality treatment is
prohibited.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores• Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland
MSCWMO Project Review Checklist pg. 8
NA Any potential changes to the hydrology of the wetland (i.e. changes to the outlet elevation or contributing
drainage area) must be reviewed to evaluate the impact of both the existing and proposed wetland conditions
and approved by the MSCWMO.
NA Land-altering activities shall not increase the bounce in water level or duration of inundation from a 2.0-inch
24-hour storm for any downstream wetland beyond the limit specified in Table 7.2 for the individual wetland
susceptibility class.
LAKE, STREAM AND WETLAND BUFFER PERFORMANCE STANDARDS
NA A buffer zone of unmowed natural vegetation is maintained or created upslope of all water bodies (wetlands,
streams, lakes).
NA A 50 foot natural buffer or (if a buffer is infeasible) provide redundant sediment controls when a surface water
is located within 50 feet of the project's earth disturbances and stormwater flows to the surface water.
NA If adjacent to a Special or Impaired Water an undisturbed buffer zone of not less than 100 linear feet from the
special water is maintained both during construction and as a permanent feature post construction.
MSCWMO Member Communities
Afton • Bayport• Baytown • Lakeland • Lakeland Shores • Lake St. Croix Beach • Oak Park Heights
St. Mary's Point• Stillwater•West Lakeland