HomeMy WebLinkAbout2026-005 lt
-SRuEHILLS
ORDINANCE NO. 2026-005
CITY OF ARDEN HILLS
RAMSEY COUNTY, MINNESOTA
AN ORDINANCE AMENDING CHAPTER 11 OF THE ARDEN HILLS CITY CODE
CONCERNING SUBDIVISIONS
THE CITY COUNCIL OF THE CITY OF ARDEN HILLS, MINNESOTA, ORDAINS:
SECTION 1. Chapter 11 — Subdivision Code, Section 1140.08— Stormwater Management is
hereby amended by deleting the strike language and adding the underlined language to
read as follows:
1140.08 Stormwater Management.
Stefmwater-management plans shall eemply with Rule Q Stefmwatef Management PIMS of the
Stormwater management plans shall comply with the following: the standards established by the
Minnesota Pollution Control Agency's National Pollutant Discharge Elimination System/State
Disposal System (NPDES/SDS) Construction Permit MNR 100001 (Construction Storm Water
(CSW) Permit) as amended in its entirety and now constituted and from time to time amended;
Rule C: Stormwater Management Plans of the Rice Creek Watershed District Rules; and the
standards listed below, whichever is more restrictive.
Subd. 1 Post-Construction Stormwater Management
A. Submittal of Site Plans consisting of Post-Construction Plans
1. Site plans must be submitted for review and confirmation that ordinance
requirements have been met,prior to start of construction activity.
2. Site plans must consist of, at a minimum, the following items:
(i) All calculations for the permanent stormwater treatment system,
(ii) The water quality volume that will be treated through volume reduction
practices:
(iii) Rationale and documentation supporting the location of any off-site
permanent stormwater treatment projects;
(iv) All legal mechanisms related to Part c. (Long-term Maintenance).
B. Post-Construction Stormwater Management BMPs must meet the following criteria:
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1. Designed with accepted engineering_practices and in accordance with part d.
(Permanent Stormwater Management System Design Criteria).
2. Designed so that discharges from the project during and after construction
activities do not cause a violation of state water quality standards, including
nuisance conditions, erosion in receiving channels or on downslope properties, or
a significant adverse impact to wetlands caused by inundation or decrease of flow.
3. Treat the water quality volume on any project where the sum of the new
impervious surface and the fully reconstructed impervious surface equals one or
more acres.
4. For construction activity (excludinglinear near projects), water quality volume must
be calculated as one(1) inch times the sum of the new and the fully reconstructed
impervious surface.
5. For linear projects, water quality volume must be calculated as the larger of one
(1) inch times the new impervious surface or one-half(0.5) inch times the sum of
the new and the fully reconstructed impervious surface. Where the entire water
guality_volume cannot be treated within the existing right-of-way, a reasonable
attempt to obtain additional right-of-way, easement, or other permission to treat
the stormwater during the project planning_process must be made. Volume
reduction practices must be considered first, as described in Section 3.b.vi.
Volume reduction practices are not required if the practices cannot be provided
cost effectively. If additional right-of-way, easements, or other permission cannot
be obtained, the owner/operator of construction activity must maximize the
treatment of the water quality volume prior to discharge from Arden Hill's MS4.
6. Volume reduction practices e.g., infiltration or other) to retain the water quality
volume on-site must be considered first when designing the permanent
stormwater treatment system. Wet sedimentation basins and filtration systems are
not considered volume reduction practices. If infiltration is prohibited, as
described in Part d.i.14. (Infiltration System), other volume reduction practices, a
wet sedimentation basin, or a filtration basin may be considered.
C. Post Long-term Maintenance
1. The Permitee must enter into a long-term maintenance agreement with the City of
Arden Hills that documents all responsibilities for long-term operation and
maintenance of stormwater treatment practices that are not owned or operated by
the City of Arden Hills. At a minimum, the long-term maintenance agreement
must include provisions that:
(i) Allow the City of Arden Hills to conduct inspections of structural stormwater
BMPs not owned or operated by the City of Arden Hills,perform necessary
maintenance, and assess costs for those structural stormwater BMPs when the
City of Arden Hills determines the owner of that structural stormwater BMP
has not ensured proper function;
(ii) Are designed to preserve the City of Arden Hills right to ensure maintenance
responsibility, for structural stormwater BMPs not owned or operated by the
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City of Arden Hills when those responsibilities are legally transferred to
another party; and
(iii) Are designed to protect/preserve structural stormwater BMPs. If structural
stormwater BMPs change causing decreased effectiveness, new, repaired, or
improved structural stormwater BMPs must be implemented to provide
equivalent treatment to the original BMP.
D. Permanent Stormwater Management System Design Criteria
1. Infiltration System
(i) Infiltration options include but are not limited to: infiltration basins,
infiltration trenches rainwater gardens,bioretention areas without
underdrains swales with impermeable check dams, and natural depressions;
(ii) To determine if an infiltration system is suitable, either the MPCA's
contamination screening checklist must be completed or an assessment must
be conducted. The checklist or assessment must be documented in the site
plan For more information and to access the MPCA's "contamination
screening checklist" see the Minnesota Stormwater Manual;
(iii) Must be designed such that pre-existing hydrologic conditions of wetlands in
the vicinity are not impacted e.g., inundation or breaching a perched water
table supporting a wetland);
(iv) Must not be excavated to final grade, or within three(3) feet of final grade,
until the contributingdrainage rainage area has been constructed and fully stabilized
unless they provide rigorous erosion prevention and sediment controls (e.g.,
diversion berms)to keep sediment and runoff completely away from the
infiltration area.
(v) When excavating to within three(3) feet of final grade, the Permitee must
stake off and mark the area so heave construction vehicles or equipment do
not compact the soil in the infiltration area;
(vi) A pretreatment device such as a vegetated filter strip, forebay, or water quality
inlet(e.g., grit chamber) to remove solids floating materials, and oil and
grease from the runoff, to the maximum extent practicable, must be used
before the system routes stormwater to the infiltration system;
(vii) Designed to provide a water quality volume as described in Section b.iii, b.iv,
and b.v;
(viii) Designed to discharge all stormwater(including stormwater in excess of the
water quality volume)routed to the system through the upper most soil surface
or engineered media surface within 48 hours. Additional flows that cannot
infiltrate within 48 hours must bypass the system through a stabilized
discharge point;
(ix) Must provide a means to visually verify the infiltration system is discharging
through the soil surface or filter media surface within 48 hours or less;
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(x) Must provide at least one soil boring test pit or infiltrometer test in the
location of the infiltration practice for determining infiltration rates;
(xi) For design purposes, divide field measured infiltration rates by 2 as a safety
factor or use soil-boring results with the infiltration rate chart in the Minnesota
Stormwater Manual to determine design infiltration rates. When soil borings
indicate type A soils, field measurements should be performed to verify the
rate is not above 8.3 inches per hour.
(xii) Must employ appropriate on-site testing to ensure a minimum of three(3) feet
of spparation from the seasonally saturated soils(or from bedrock) and the
bottom of the proposed infiltration system;
(xiii) Must design a maintenance access, typically eight (8) feet wide;
(xiv) Infiltration Systems are prohibited in the following areas (See "higher level of
engineering review" in the Minnesota Stormwater Manual for more
information):
i. Areas that that receive runoff from vehicle fueling and maintenance
areas;
ii. Areas where infiltrating stormwater may mobilize high levels of
contaminants in soil or groundwater;
iii. Areas where soil infiltration rates are field measured at more than 8.3
inches per hour unless the soils are amended to slow the infiltration
rate below 8.3 inches per hour;
iv. 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;
v. Areas of predominately Hydrologic Soil Group type D soils(clay);
vi. The following areas within a Drinking Water Suppler eg ment
Area(DWSMA) as defined in Minn. R. 4720.5100, subp. 13:
1. In an Emergency Response Area(ERA) within a DWSMA
classified as having high or very high vulnerability as defined
by the Minnesota Department of Health; or
2. In an ERA within a DWSMA classified as moderate
vulnerability unless a higher level of engineering review
sufficient to provide a functioning treatment system and to
prevent adverse impacts to groundwater has been approved by
the City of Arden Hills; or
3. Outside of an ERA within a DWSMA classified as having high
or very_high vulnerability unless a higher level of en ineering
review sufficient to provide a functioning treatment system and
to prevent adverse impacts to groundwater has been approved
by the City of Arden Hills.
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4. Areas within 1,000 feet upgradient or100 feet downgradient of
active karst features; and
5. Areas that receive runoff from the following industrial facilities
not authorized to infiltrate stormwater under the NPDES
stormwater permit for industrial activities:
a. Automobile salvage yards;
b. Scrap recycling and waste recycling facilities;
c. Hazardous waste treatment, storage, or disposal
facilities,
d. Wood preserving facilities; or
e. Air transportation facilities that conduct deicing
activities.
ii. Filtration System
1) Filtration options include,but are not limited to: sand filters with underdrains,
biofiltration areas, swales using underdrains with impermeable check dams and
underground sand filters;
2) Must not install filter media until the contributingdrainage rainage area is constructed and fully
stabilized unless they provide rigorous erosion prevention and sediment controls (e.g_
diversion berms)to keep sediment and runoff completely away from the filtration area;
3) Designed to remove at least 80 percent of TSS;
4) Must use a pretreatment device such as a vegetated filter strip, small sedimentation
basin, water quality inlet, forebay or h dy rodynamic separator to remove settleable
solids, floating materials, oils and grease from the runoff to the maximum extent
practicable,before runoff enters the filtration system;
5 Designedprovide a waterguality volume as described in Section b.iii,b.iv, and b.v;
6 Designed to discharge all stormwater(including stormwater in excess of the water
quality volume)routed to the system through the uppermost soil surface or engineered
media surface within 48 hours. Additional flows that the system cannot filter within 48
hours must bypass the system or discharge through an emergency overflow;
7 Designed to provide a means to visually verify the system is dischargingthrough hrough the
soil surface or filter media within 48 hours;
8) Employ appropriate on-site testing to ensure a minimum of three (3) feet of separation
between the seasonally saturated soils(or from bedrock) and the bottom of the proposed
filtration system;
9) Construct with an impermeable liner when the system has less than three(3) feet of
separation between seasonally saturated soils or bedrock;
10) Designed with a maintenance access, typically eight(8) feet wide.
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iii. Wet Sedimentation Basin
1) Permanent volume of 1,800 cubic feet of storage below the outlet pipe for each acre
that drains to the basin;
2) Permanent volume must reach a minimum depth of at least three(3) feet and must have
no depth greater than 10 feet;
3) Must be configured to minimize scour or resuspension of solids;
4) In addition to the permanent volume the basin must provide the water quality volume
as live storage. Water Quality volume is described in Section b iii b iv and b v•
5) Water Quality volume discharges at no more than 5.66 cubic feet per second (cfs)per
acre of surface area of the basin;
6) Designed to prevent short-circuiting and the discharge of floating debris;
7) Basin outlets must have energy dissipation;
8)Must include a stabilized emergency overflow to accommodate storm events in excess
of the basin's hydraulic design;
9) Must have a maintenance access typicallyeight ight(8) feet wide for the basin;
10) Must be located outside of surface waters and any buffer zones identified in
Construction Stormwater General permit.
11) Permittees must design basins using an impermeable liner if located within active
karst terrain.
iv. Regional Wet Sedimentation Basins
1) When the entire water quality volume cannot be treated by volume reduction practices
onsite, regional wet sedimentation basins can be used or created,_provided they are
constructed basins, not a natural wetland or water body.
2)The regional basin conforms to all requirements for a wet sedimentation basin as
described in Part d.iii. (Wet Sedimentation Basin)
3) Must be large enough to account for the entire area that drains to the basin
4) Waterways between the project and the regional basin must not be significantly
degraded.
5)Written authorization from the City of Arden Hills or private entity that owns and
maintains the regional basin.
SECTION 2. This Ordinance shall become effective immediately upon its passage and
publication according to law. A Summary of this Ordinance will be published in accordance with
state statute.
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PASSED and ADOPTED this 9th day of March 2026,by the City Council of the City of
Arden Hills, Minnesota.
CITY OF ARDEN HILLS
By C�VZd./ � '�/ "
David Grant, Mayor
ATTEST:
0AJ
q=anson, City Clerk
To view the final document, access adopted Ordinances via Arden Hills Public Laserfiche Weblink by visiting
cityofardenhills.org and clicking on Archived Documents under Helpful Links on our main webpage
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