1996-779STORM WATER MANAGEMENT ORDINANCE
AN ORDINANCE PROMOTING THE HEALTH, SAFETY AND
GENERAL WELFARE OF THE CITIZENS OF HOPKINS
MINNESOTA BY AMENDMENT TO THE ZONING ORDINANCE,
ADOPTING NEW SECTION REQUIRING STORM WATER
MANAGEMENT PRACTICES.
ORDINANCE NO. 96-779
BE IT ORDAINED by the City Council of the City of Hopkins as follows:
That the Hopkins Zoning Ordinance No. 515 be and the same is hereby amended by
adding the following definitions:
Subd. 10. Applicant: Any person who wishes to obtain a building permit, zoning or
subdivision approval.
Subd. 36. Control measure: A practice or combination of practices to control erosion and
attendant pollution.
Subd. 39. Detention facility: A permanent natural or man-made structure, including
wetlands, for the temporary storage of runoff which contains a permanent pool of water.
Subd. 70. Hvdric soils: Soils that are saturated, flooded, or ponded long enough during
the growing season to develop anaerobic conditions in the upper part.
Subd. 71. Hydrophvtic ve etg,, ation: Macrophytic plant life growing in water, soil or on a
substrate that is at least periodically deficient in oxygen as a result of excessive water content.
Subd. 75. Land disturbing or development activities: Any, change of the land surface
including removing vegetative cover, excavation, filling grading, and the construction of any
structure.
Subd. 111. Person: Any individual firm corporation, partnership, franchisee, association
or governmental entity.
Subd. 124. Retention facility: A permanent natural or man made structure that provides
for the storage of storm water runoff by means of a permanent pool of water.
Subd. 127. Sediment: Solid matter carried by water, sewage, or other liquids.
Subd. 149. Wetlands: Lands transitional between terrestrial and aquatic systems where
the water table is usually at or near the surface or the land is covered by shallow water. For
purposes of this definition, wetlands must have the following three attributes:
a) Have a predominance of hydric soils;
b) Are inundated or saturated by surface or ground water at a frequency and duration
sufficient to support a prevalence of hydrophytic vegetation typically adapted for
life in saturated soil conditions; and
c) Under normal circumstances support a prevalence of such vegetation.
That the existing definitions are hereby renumbered.
That the following section is hereby added to the Hopkins Zoning Ordinance:
Section 546 -Storm Water Management
546.01. Purpose. The purpose of this ordinance is to promote, preserve and enhance the natural
resources within the City of Hopkins and protect them from adverse effects occasioned by poorly
sited development or incompatible activities by regulating land disturbing or development
activities that would have an adverse and potentially irreversible impact on water quality and
unique and fragile environmentally sensitive land; by minimizing conflicts and encouraging
compatibility between land disturbing and development activities and water quality and
environmentally sensitive lands; and by requiring detailed review standards and procedures for
land disturbing or development activities proposed for such areas, thereby achieving a balance
between urban growth and development and protection of water quality and natural areas.
a) Have a predominance of hydric soils;
b) Are inundated or saturated by surface or ground water at a frequency and duration
sufficient to support a prevalence of hydrophytic vegetation typically adapted for
life in saturated soil conditions; and
c) Under normal circumstances support a prevalence of such vegetation.
546.02 Applicability. Subdivision 1. Every application for a conditional use permit that
involves construction of a building, subdivision approval, or a permit to allow land disturbing
activities must submit a storm water management plan to the planning department. No
conditional use permit, subdivision approval, or permit to allow land disturbing activities shall be
issued until approval of the storm water management plan or a waiver of the approval requirement
has been obtained in strict conformance with the provision of this ordinance. The provisions of
section 546.07 of this ordinance apply to all land, public or private, located within the City of
Hopkins.
Subd. 2. Exem tions. The provision of this ordinance do not apply to:
a) Any part of a subdivision if a plat for the subdivision has been approved by
the City Council on or before the effective date of this ordinance.
b) Any land disturbing activity for which plans have been approved by the
watershed management organization and the City of Hopkins within six
months prior to the effective date of this ordinance;
c) A lot for which a conditional use permit or building permit has been
approved on or before the effective date of this ordinance;
d) Installation of fence, sign, telephone and electric poles and other kinds of
posts or poles;
e) Waiver of plat, re-plat, plating of a developed lot, or a single lot division;
f) Construction of a single to four family home;
g) An addition to an existing building that does not require a conditional use
permit;
h) Construction of a detached accessory building that does not require a
conditional use permit;
i) Emergency work to protect, life, limb, or property; or;
j) The improvements involve the enlargement of a building that is less than 10
percent of the total floor area of the existing building or 5000 square feet
which ever is less.
546.03. Waiver. The City Council, upon recommendation of the Planning Commission, may
waive any requirement of this ordinance upon making a finding that compliance with the
requirement will involve an unnecessary hardship or the project does not have any significant
alterations of existing stormwater conditions, and the waiver of such requirement will not
adversely affect the standards and requirements set forth in Section 546.04. The City Council
may require as a condition of the waiver, such dedication or construction, or agreement to
dedicate or construct as may be necessary to adequately meet said standards and requirements.
546.04. Application. Subdivision 1. A written application for storm water management plan
approval, along with the proposed storm water management plan, shall be filed with the planning
department, and shall include a statement indicating the grounds upon which the approval is
requested, that the proposed use is permitted by right or as an exception in the underlying zoning
district and adequate evidence showing that the proposed use will conform to the standards set
forth in this ordinance. Prior to applying for approval of a storm water management plan, an
applicant may have the storm water management plan reviewed by the appropriate department of
the City.
Subd. 2. Required information. Two sets of clearly legible blue or black lined copies of
drawings and required information shall be submitted to the planning department and shall be
accompanied by a receipt from the City evidencing the payment of all required fees for processing
and approval as set forth in Section 546.05 subdivision 5. A bond will be required by Section
546.05 subdivision 4 in the amount to be calculated in accordance with that section if the
improvements have not been completed at the time the certificate of occupancy has been
completed. Drawings shall be prepared to a scale appropriate to the site of the project and
suitable for the review to be performed. At a minimum the scale shall be 1 inch equals 100 feet.
Subd. 3. Storm water mana eg ment plan. At a minimum the storm water management
plan shall contain the following information.
a) Existing site mad A map of existing site conditions showing the site and immediately
adjacent areas, including:
1) The name and address of the applicant, the section, township and range,
north point, date and scale of drawing and number of sheets;
2) Location of the tract by an insert map at a scale sufficient to clearly identify
the location of the property and giving such information as the names and numbers of
adjoining roads, railroads, utilities, subdivision, towns and districts or other landmarks;
3) Existing topography with a contour interval appropriate to the topography
of the land but in no case having a contour interval greater than 2 feet;
4) A delineation of all streams, rivers, public waters and wetlands located on
and immediately adjacent to the site, including depth of water, a description of all
vegetation which may be found in the water, a statement of general water quality and any
classification given to the water body or wetland by the Minnesota Department of Natural
resources, the Minnesota Pollution Control Agency, and/or the Untied States Army Corps
of Engineers;
5) Location and dimensions of existing storm water drainage systems and
natural drainage patterns on and immediately adjacent to the delineating in which direction
and at what rate storm water is conveyed from the site, identifying the receiving stream.
river, public water, or wetland, and setting forth those areas of the unaltered site where
storm water collects;
6) A description of the soils of the site, including a map indicating soil types
of areas to be disturbed as well as a soil report containing information on the suitability of
the soils for the type of development proposed and for the type of sewage disposal
proposed and describing any remedial steps to be taken by the developer to render the
soils suitable;
7) Vegetative cover and clearly delineating any vegetation proposed for
removal; and
8) 100 year floodplains, flood fringes and floodways.
Subd. 4. Site construction plan. A site construction plan including:
a) Locations and dimensions of all proposed land disturbing activities and any
phasing of those activities;
b) Locations and dimensions of all temporary soil or dirt stockpiles;
c) Locations and dimensions of all construction site erosion control measures
necessary to meet the requirements of this ordinance;
d) Schedule of anticipated starting and completion date of each land
disturbing activity including the installation of construction site erosion control measures
needed to meet the requirements of this ordinance; and
e) Provisions for maintenance of the construction site erosion control
measures during construction.
Subd. 5. Plan of final site conditions. A plan of final site conditions on the same scale as
the existing site map showing the site changes including:
a) Finished grading shown at contours at the same interval as provided above
or as required to clearly indicate the relationship of proposed changes to existing
topography and remaining features;
b) A landscape plan, drawn to an appropriate scale, including dimensions and
distances and the location, type, size and description of all proposed landscape materials
which will be added to the site as part of the development;
c) A drainage plan of the developed site delineating in which direction and at
what rate storm water will be conveyed from the site and setting forth the areas of the site
where storm water will be allowed to collect;
d) The proposed size, alignment and intended use of any structures to be
erected on the site;
e) A clear delineation and tabulation of all areas which shall be paved or
surfaced, including a description of the surfacing material to be used; and
fj Any other information pertinent to the particular project which in the
opinion of the applicant is necessary for the review of the project.
546.05. Process. Subdivision 1. Storm water management plan meeting the requirements of
Section 546.04 shall be submitted by the planning department to the Planning Commission for
review in accordance with the standards of 546.06. The Commission shall recommend approval,
recommend approval with conditions, or recommend denial of the storm water management plan.
Following Planning Commission action, the storm water management plan along with the
conditional use permit and or subdivision approval shall be submitted to the City Council at its
next available meeting. City Council action on the storm water management plan must be
accomplished within 120 days following the date the application for approval is filed with the
planning department unless there has been no delay caused or requested by the applicant.
Subd. 2. Duration. Approval of a plan submitted under the provisions of this ordinance
shall expire one year after the date of approval unless construction has commenced in accordance
with the plan. However, if prior to the expiration of the approval, the applicant makes a written
request to the planning department for an extension of time to commence construction setting
forth the reasons for the requested extension, the planning department may grant one extension of
not greater than one single year. Receipt of any request for an extension shall be acknowledged
by the planning department within 15 days. The planning department shall make a decision on the
extension within 30 days of receipt. Any plan may be revised in the same manner as originally
approved.
Subd. 3. Conditions. A storm water management plan may be approved subject to
compliance with conditions reasonable and necessary to insure that the requirements contained in
this ordinance are met. Such conditions may, among other matters, limit the size, kind or
character of the proposed development, require the construction of structures, drainage facilities,
storage basins and other facilities require replacement of vegetation, establish required monitoring
procedures, stage the work over time, require alteration of the site design to insure buffering, and
require the conveyance to the City of Hopkins or other public entity of certain lands or interests
therein.
Subd. 4. Performance bond. Prior to approval of any storm water management plan, the
applicant shall submit an agreement to construct such required physical improvements, to dedicate
property or easements, or to comply with such conditions as may have been agreed to. If the
improvements have not been constructed at the time the certificate of occupancy is issued, the
applicant shall provide a bond to cover the amount of the established cost of complying with the
agreement. The agreement and bond shall guarantee completion and compliance with conditions
within a specific time, which time may be extended in accordance with Section 546.02
The adequacy, conditions and acceptability of any agreement and bond shall be determined by the
City Council or any official of the City of Hopkins as may be designated by resolution of the City
Council.
Subd. 5. Fees. All application for storm water management plan approval shall be
accompanied by a process and approval fee as per section X of the City Code.
546.06. Approval Standards. Subdivision 1. No storm water management plan which fails to
meet the standards contained in this section shall be approved by the City Council.
Subd. 2. Site dewaterin~. Water pumped from the site shall be treated by temporary
sedimentation basins, grit chambers, sand filter, upflow chamber, hydro-cyclones, swirl
concentrators or other appropriate controls as appropriate. Water may not be discharged in a
manner that causes erosion or flooding of the site or receiving channels or a wetland.
Subd. 3. Waste and material disposal. All waste and unused building material (including
garbage, debris, cleaning wastes, wastewater, toxic materials or hazardous materials) shall be
properly disposed of off-site and not allowed to be carried by runoff into a receiving channel or
storm sewer system.
Subd. 4. Trackine. Each site shall have graveled roads, access drives and parking areas of
sufficient width and length to prevent sediment from being tracked onto public or private
roadways. Any sediment reaching a public or private road shall be removed by street cleaning
(not flushing) before the end of each workday.
Subd. 5. Drain inlet protection. All storm drain inlets shall be protected during
construction until control measures are in place with a straw bale, silt fence or equivalent barrier
meeting accepted design criteria, standards and specifications contained in the MPCA publication
"Protection Water Quality in Urban Areas."
Subd. 6. Site erosion control. The following criteria (a through d.) apply only to
construction activities that result in runoff leaving the site.
a) Channelized runoff from adjacent areas passing through the site shall be
diverted around disturbed areas, if practical. Otherwise, the channel shall be protected as
described below. Sheetflow runoff from adjacent areas greater than 10,000 square feet in
area shall also be diverted around disturbed areas, unless shown to have resultant runoff
rated of less than 0.5 cubic feet per second across the disturbed area for the one year
storm. Diverted runoff shall be conveyed in a manner that will not erode the conveyance
and receiving channels.
b) All activities on the site shall be conducted in a logical sequence to
minimize the area of bare soil exposed at any one time.
c) Runoff from the entire disturbed area on the site shall be controlled by
meeting either subsections 1 and 2 or 1 and 3.
1) All disturbed ground left inactive for fourteen or more days shall be
stabilized by seeding or sodding (only available prior to September 15) or by
mulching or covering or other equivalent control measure.
2) For sites with more than ten acres disturbed at one time, or if a
channel originates in the disturbed area, one or more temporary or permanent
sedimentation basins shall be constructed. Each sedimentation basin shall have a
surface area of at least one percent of the area draining to the basin and at least
three feet of depth and constructed in accordance with accepted design
specifications. Sediment shall be removed to maintain a depth of three feet. The
basin discharge rate shall also be sufficiently low as to not cause erosion along the
discharge channel or the receiving water.
3) For sites with less than ten acres disturbed at one time, silt fences,
straw bales, or equivalent control measures shall be placed along all sideslope and
downslope sides of the site. If a channel or area of concentrated runoff passes
through the site, silt fences shall be placed along the channel edges to reduce
sediment reaching the channel. The use of silt fences, straw bales, or equivalent
control measures must include a maintenance and inspection schedule.
d) Any soil or dirt storage piles containing more than ten cubic yards of
material should not be located with a downslope drainage length of less than 25 feet from
the toe of the pile to a roadway or drainage channel. If remaining for more than seven
days, they shall be stabilized by mulching, vegetative cover, tarps or other means. Erosion
from piles which will be in existence for less than seven days shall be controlled by placing
straw bales or silt fence barriers around the pile. In-street utility repair or construction soil
or dirt storage piles located closer than 25 feet of a roadway or drainage channel must be
covered with tarps or suitable alternative control, if exposed for more than seven days, and
the storm drain inlets must be protected with straw bale or other appropriate filtering
barriers.
Subd. 7. Storm water management criteria for permanent facilities.
a) An applicant shall install or construct, on or for the proposed land
disturbing or development activity, all storm water management facilities necessary to
manage increased runoff so that the two-year, ten-year, and 100-year storm peak
discharge rates existing before the proposed development shall not be increased and
accelerated channel erosion will not occur as a result of the proposed land disturbing or
development activity. An applicant may also make an in-kind or monetary contribution to
the development and maintenance of community storm water management facilities
designed to serve multiple land disturbing and development activities undertaken by one or
more persons, including the applicant.
b) The applicant shall give consideration to reducing the need for storm water
management facilities by incorporating the use of natural topography and land cover such
as wetlands, ponds, natural swales and depressions as they exist before development to the
degree that they can accommodate the additional flow of water without compromising the
integrity or quality of the wetland or pond.
c) The following storm water management practices shall be investigated in
developing a storm water management plan in the following descending order of
preference:
1) Natural infiltration of precipitation on site.
2) Flow attenuation by use of open vegetated swales and natural
depressions;
3) Storm water retention facilities; and
4) Storm water detention facilities.
d) A combination of successive practices may be used to achieve the
applicable minimum control requirements specified in subsection (a) above. Justification
shall be provided by the applicant for the method selected.
Subd. 8. Design standards. Storm water detention facilities constructed in the City of
Hopkins shall be designed according to the most current technology as reflected in the 1VIPCA
publication "Protection Water Quality in Urban Areas", and shall contain, at the minimum, the
following design factors:
a) A permanent pond surface area equal to two percent of the impervious area
draining to the pond or one percent of the entire area draining to the pond, whichever
amount is greater;
b) An average permanent pool depth for four to ten feet;
c) A permanent pool length-to-width ratio of 3:1 greater;
d) A minimum protective shelf extending ten feet into the permanent pool
with a slope of 10:1, beyond which slopes should not exceed 3:1;
e) A protective buffer strip of vegetation surrounding the permanent pool at a
minimum width of one rod (16.5);
f) All storm water detention facilities shall have a device to keep oil, grease,
and other floatable material from moving downstream as a result of normal operations;
g) Storm water detention facilities for new development must be sufficient to
limit peak flows in each subwatershed to those that existed before the development for the
10 year storm event. All calculations and hydrologic models/information used in
determining peak flow shall be submitted along with the storm water management plan;
h) All storm water detention facilities must have a forebay to remove
coarse-grained particles prior to discharge into a watercourse or storage basin.
Subd. 9. Wetlands.
a) Runoff shall not be discharged directly into wetlands without presettlement
of the runoff.
b) A protective buffer strip of natural vegetation at least one rod (16.5) feet in
width shall surround all wetlands.
c) Wetlands must not be drained or filled, wholly or partially, unless replaced
by restoring or creating wetland areas of at least equal public value. Replacement must be
guided by the following principles in descending order of priority:
1) Avoiding the direct or indirect impact of the activity that may
destroy or diminish the wetland;
2) Minimizing the impact by limiting the degree or magnitude of the
wetland activity and its implementation;
3) Rectifying the impact by repairing, rehabilitation, or restoring the
affected wetland environment;
4) Reducing or eliminating the impact over time by preservation and
maintenance operations during the life of the activity; and
5) Compensation for the impact by replacing or providing substitute
wetland resources or environments.
Subd. 10. Steen slopes. No land disturbing or development activities shall be allowed on
sloped of 18 percent or more.
Subd. 11. Catch basins. All newly installed and rehabilitated catch basins shall be
provided with a sump area for the collection of coarse-grained material. Such basins shall be
cleaned when they are half filled with material.
Subd. 12. Drain leaders. All newly constructed and reconstructed buildings will route
drain leaders to pervious areas wherein the runoff can be allowed to infiltrate. The flow rate of
water exiting the leaders shall be controlled so no erosion occurs in the pervious areas.
Subd. 13. Inspection and maintenance. All storm water management facilities shall be
designed to minimized the need of maintenance, to provide access for maintenance purposes and
to be structurally sound. All storm water management facilities shall have a plan of operation and
maintenance that assures continued effective removal of pollutants carried in storm water runoff.
The director of public works, or designated representative, shall inspect all storm water
management facilities during construction, during the first year of operation, and at least once
every five years thereafter. The inspection records will be kept on file at the public works
department for a period of 6 years. It shall be the responsibility of the applicant to obtain any
necessary easements or other property interests to allow access to the storm water management
facilities for inspection and maintenance purposes.
Subd. 14. Models/methodolgies/computations. Hydrologic models and design
methodologies used for the determination of runoff and analysis of storm water management
structures shall be approved by the director of public works. Plans, specification and
computations for storm water management facilities submitted for review shall be sealed and
signed by a registered professional engineer. All computation shall appear on the plans submitted
for review, unless otherwise approved by the director of public works.
Subd. 15. Watershed mana eg ment plans/groundwater mana eg ment plans. Storm water
management plans shall be consistent with adopted watershed management plans and
groundwater management plans prepared in accordance with Minnesota Statutes section
103B.231 and 103B.255 respectively, and as approved by the Minnesota Board of Water Soil
Resources in accordance with state law.
Subd. 16. Easements. If a storm water management plan involves direction of some or all
runoff off of the site, it shall be the responsibility of the applicant to obtain from adjacent property
owners any necessary easements of other property interests concerning flowage of water.
546.07. Use of impervious surfaces. Subdivision 1. No person shall apply fertilizer to or deposit
grass clippings, leaves, or other vegetative material on impervious surfaces, or within storm water
drainage systems, natural drainage ways, or within wetland buffer areas.
Subd. 2. Unimproved land areas. Except for driveways, sidewalks, patios, areas occupied
by structures or areas which have been improved by landscaping, all areas shall be covered by
plants or vegetative growth.
Subd. 3. Fertilizer content. Except for the first growing season for newly established turf
areas, no person shall apply liquid fertilizer which contained more than one-half percent by weight
of phosphorus, or granular fertilizer which contained more than three percent by weight of
phosphorus, unless the single application is less than or equal to one-tenth pound of phosphorus
per one thousand square feet. Annual application amount shall not exceed one-half pound of
phosphorus per one thousand square feet of lawn area.
Subd. 4. Buffer zone. Fertilizer application shall not be made within one rod (16.5 feet)
of any wetland or water resource.
546.08. Penaltv. Any person, firm or corporation violating any provision of this ordinance shall
be fined not less than five dollars nor more than five hundred dollars for each offense, and a
separate offense shall be deemed committed on each day during or on which a violation occurs or
continues.
546.09. Other controls. In the event of any conflict between the provisions of this ordinance and
_ the provisions of an erosion control or shoreland protection ordinance adopted by the City
Council the more restrictive standard prevails.
546.10. Severability. The provision of this ordinance are severable. If any provision of this
ordinance of the application thereof to any person or circumstance is held invalid, such invalidity
shall not affect other provisions or applicants of this ordinance which can by given effect without
the invalid provision or application.
First Reading
Second Reading:
Date of Publication:
Date Ordinance Takes Effect:
A~'TTE
January 16, 1996
March 19, 1996
March 27, 1996
April 17, 1996
Charles D. Redepenning, yor
1
LEGALITY:
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Date
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Wines A. Genellie, City Clerk