[Ord. No. 5852 § 2, 12-20-2012]
A. With continued growth and development the
community has been confronted with issues of increased stormwater
runoff and its impact upon streams, the environment and quality of
life. Increased stormwater runoff causes more frequent and intense
flooding problems as well as erosion, rechannelization, and sedimentation
of the natural watercourses and creeks. In addition, changing and
proposed new water quality regulations impact the City's ability to
meet the requirements of the community's Municipal Separate Storm
Sewer System (MS4) discharge permit.
B. The natural condition of the land before
development is in relative balance with the natural capacity of the
receiving streams. Undeveloped conditions provide natural absorption
of water into the ground and longer periods of concentration. Modification
of the ground surface from its natural vegetated state to solid paved
surfaces and buildings causes water to run off site at faster rates.
The solid surfaces don't allow absorption and filtering of the stormwater,
and all the benefits that vegetated ground cover provides. It is the
policy of the City of St. Peters to protect and promote the public
health, safety and general welfare. The management of stormwater will
reduce the possibility of damage to public and private property, will
reduce the erosion on land and creek channels, will assist in the
attainment and maintenance of water quality standards, and will preserve
and enhance the environmental quality of the watercourses in the City
of St. Peters.
C. Stormwater management must be performed
on a watershed basis. A City-wide Stormwater Master Plan was developed
in 2011, studying watersheds and subwatersheds throughout the City.
The study assessed stream stability and habitat, flooding, and water
quality for streams and detention basins. The Stormwater Master Plan
will be used for the planning of future capital improvement projects,
improving water quality through the reduction of pollutants into streams,
and continuing compliance with Missouri Department of Natural Resources
MS4 regulations.
[Ord. No. 5852 § 2, 12-20-2012]
For the purposes of this Chapter,
the following terms, phrases, words, and their derivations shall have
the meanings given herein. Unless the context clearly indicates to
the contrary, words used in the present tense include the future tense;
words used in the singular shall include the plural, and vice versa;
the words "these regulations" mean "this Chapter"; and the word "shall"
is always mandatory.
25-YEAR FLOOD
A flood having a four percent (4%) probability of occurrence
in a given year.
25-YEAR PEAK FLOW
The peak rate of flow of water at a given point in a channel,
watercourse, or conduit resulting from the 25-year flood.
25-YEAR STORM
Rainstorms of a specific duration having a four percent (4%)
probability of occurrence in any given year.
100-YEAR PEAK FLOW
The peak rate of flow of water at a given point in a channel,
watercourse, or conduit resulting from the base flood.
100-YEAR STORM
Rainstorms of a specific duration having a one percent (1%)
probability of occurrence in any given year.
ALLOWABLE RELEASE RATE
The pre-development or existing condition peak flow corresponding
to a selected rainfall frequency event.
APPLICANT
The specific person applying for the permit for an approved
stormwater management system.
BASE FLOOD
The flood having a one percent (1%) probability of being
equaled or exceeded in any given year, i.e., the 100-year flood. (The
base flood, adopted by the Federal Emergency Management Agency, FEMA,
is the 100-year flood.)
BEST MANAGEMENT PRACTICES (BMP)
Practices, procedures or a schedule of activities to reduce
the amount of sediment and other pollutants in stormwater discharges
associated with construction and land disturbance activities.
CULVERT
A closed conduit for the free passage of surface drainage
water under a highway, railroad, or other embankment.
DEDICATION
The process by which the owner gives approved storm sewers
and facilities to the City for public use and maintenance.
DETENTION BASIN
Any man-made area or facility designed to detain (hold) stormwater
temporarily during and immediately after a runoff event.
DETENTION STORAGE
The temporary detaining or storage of stormwater in reservoirs,
on rooftops, on parking lots and other areas under pre-determined
conditions.
DEVELOPED RUNOFF RATE
The peak flow corresponding to a selected rainfall event
as a result of developed site conditions.
DIFFERENTIAL RUNOFF
The difference between the calculated developed runoff rate
and the calculated pre-developed runoff rate.
DRAINAGE FACILITY
Any system of artificially constructed drains, including
open channels and sewers, used to convey stormwater, surface or ground
water either continuously or intermittently to natural watercourses.
DRY BOTTOM BASIN
A facility designed for the temporary storage of stormwater
runoff.
ESCROW
A form of security to guarantee the completion or performance
of a stormwater management plan or the maintenance of drainage improvements,
established as a cash or letter of credit escrow deposit in an amount
and form satisfactory to the Governing Body.
FLOODPLAIN
A geographic area susceptible to periodic inundation from
the overflow of natural waterways during the base (100-year) flood.
FLOODWAY
The channel of a river or other watercourse and the adjacent
land areas that must be reserved in order to discharge the base flood
without cumulatively increasing the water surface elevation more than
one (1) foot and so delineated in the Federal Emergency Management
Agency (FEMA) Flood Insurance Study.
FOREBAY
An area or device to trap silt before it enters a detention
pond.
FREEBOARD
The difference in elevation between the hydraulic grade line
elevation and:
1.
The inlet sill elevation; or
2.
The top of structure elevation; or
3.
The top of channel bank elevation;
or
4.
The top of wall elevation.
HYDRAULIC GRADE LINE
A line coinciding with the level of flowing water at any
given point along an open channel; or the level to which water would
rise in a vertical tube connected to any point along a pipe or closed
conduit flowing under pressure.
LAND DISTURBANCE
Any activity which affects the ground surface and/or vegetation
(i.e., clearing and grubbing, grading, excavating, etc.).
LEVEL OF SERVICE (LS)
The level of water quality protection recommended for a development
or provided by a post-development stormwater management system. The
LS requirement for the development is determined by the change in
runoff from the pre-development condition. The LS provided by the
stormwater management system is determined by a combination of detention
and water quality treatment.
MAINTENANCE
The act of maintaining or preserving including, but not limited
to, operation, construction, and reconstruction.
MS4
Municipal Separate Storm Sewer System.
OUTFALL
The point location or structure where drainage discharges.
PERMIT
A permit granted by the City to a person to construct a stormwater
management system.
PERMITTEE
Any person to whom a permit has been granted by the City
under this Chapter.
PERSON
An individual, corporation, partnership, and/or unincorporated
association of persons.
PRE-DEVELOPED RUNOFF RATE
The amount of flow from an existing site prior to new development
or improvements as computed using the rational formula.
RATIONAL METHOD
An empirical formula for calculating peak rates of runoff
resulting from rainfall.
SITE
The area to be developed or improved.
SOIL CONSERVATION SERVICE METHOD
A technique for calculating stormwater runoff volume and
peak flow described in Soil Conservation Service (SCS) Technical Release
55.
STORMWATER MANAGEMENT PLAN
The drawings, computations, data, reports, etc., which identify
how stormwater runoff is to be managed.
STORMWATER MANAGEMENT SYSTEM
All means, natural or man-made, used for conducting stormwater
runoff to, through, or from a drainage area to the point of outlet.
STORMWATER POLLUTION PREVENTION PLAN (SWPPP)
A management plan, the purpose of which is to ensure the
design, implementation, management and maintenance of Best Management
Practices (BMPs) in order to reduce the amount of sediment and other
pollutants in stormwater discharges associated with land disturbance
activities.
STORMWATER RUNOFF
Water that results from precipitation which is not absorbed
by the soil, evaporated into the atmosphere, or entrapped by ground
surface depressions and vegetation.
STORMWATER SEWER
A pipe or closed conduit that carries surface runoff and
subsurface waters.
SWALE
A broad, shallow watercourse.
STRUCTURE
Any object constructed above or below ground.
TIME OF CONCENTRATION
Consists of inlet time plus the travel time in the sewer
or channel from the most remote point in the watershed to the point
under consideration.
TRIBUTARY AREA
All of the area that contributes stormwater runoff to a given
point.
VALUE RATING (VR)
The assumed water quality improvement value of a cover type
or BMP, based on its ability to improve water quality and mitigate
runoff volume.
WATERCOURSE
Any natural or artificial stream, river, creek, channel,
ditch, canal, culvert, drain, waterway, gully, ravine, street, roadway,
swale, or wash in which water flows, either continuously or intermittently,
and which has a definite channel, bed or bank.
WATER QUALITY
The chemical, physical, and biological characteristics of
water. This term also can refer to regulatory concerns about water's
suitability for swimming, drinking, agriculture, industrial activity,
and healthy aquatic ecosystems.
WATER QUALITY STORM
The storm event that produces less than or equal to ninety
percent (90%) stormwater runoff volume of all 24-hour storms on an
annual basis. In the St. Peters area this is the 1.14" storm.
WATER QUALITY VOLUME (WQv)
The storage needed to capture and treat ninety percent (90%)
of the average annual stormwater runoff volume. It is calculated by
multiplying the water quality storm times the volumetric runoff coefficient
and site area.
WATERSHED
All the land that drains to a given point (also described
as a basin, catchment, and drainage area).
[Ord. No. 5852 § 2, 12-20-2012]
A City-wide stormwater management
plan (SWMP) was prepared in 2011, studying watersheds and subwatersheds
in the City of St. Peters. The study assessed stream stability and
habitat, flooding, and water quality for our streams and detention
basins. The plan contains recommendations for future locations of
capital improvements and retrofits to provide for improved stabilization,
storage capacity, and water quality best management practices. This
plan shall serve as a guide for public policies to protect the watersheds
and for the selection and scheduling of specific activities that will
protect and promote the public health, safety and welfare. The basic
goal of stormwater management is to align water quantity and water
quality management techniques in such a way as to prevent further
deterioration and to begin improving the quality of the City's watersheds.
The three (3) basic methods for addressing these goals include maintaining
existing conditions, decreasing peak flows and reducing or removing
pollutants. As outlined in the SWMP, this will be accomplished by
preserving and protecting quality stream corridors, renovating and
improving degraded stream sections, and retrofitting detention basins
for water quality benefits.
[Ord. No. 5852 § 2, 12-20-2012]
A. Any development or area which is to be
paved, expanded, redeveloped or otherwise improved shall be required
to provide on-site stormwater management unless the City Engineer
waives such requirement for the reasons contained below:
1.
Off-Site Or Regional Facility, Two
(2) Or More Developments. If two (2) or more developments, including
that of the applicant, have provided for a common system, a stormwater
agreement shall be developed and signed by all developments or properties
contributing to a common system that clearly defines maintenance responsibilities
between all parties.
2.
Off-Site Or Regional Facility By
City. If an off-site stormwater management system has been either
constructed or programmed or identified for construction by the City,
and applicant has agreed to contribute to or participate in the construction
thereof.
3.
Contribution In Lieu Of On-Site Detention. A financial contribution may be considered in lieu of on-site detention if the increased amount or velocity of stormwater generated by the development will have minor detrimental effect on the receiving watercourse and there are no known downstream flooding, erosion or water quality issues, and the applicant has agreed to contribute to the Stormwater Management Improvements Fund an amount equal to the cost of the otherwise required on-site stormwater management system. Reference Section
550.090, Subsection
(A)(5) of this Code for criteria to qualify for this option.
a.
For the purpose of establishing an
amount to be contributed, the developer shall prepare an estimate
of cost for a detention basin, including, but not limited to, the
land value for the detention basin area, and construction costs (including
grading and vegetation) which shall be reviewed and approved by the
City Engineer.
b.
Contributions to the Stormwater Management
Improvements Fund shall only be required if the amount of runoff is
increased.
4.
Other Management Techniques. Management
techniques other than detention facilities may be utilized by the
development provided the proposed techniques meet the intent of this
Chapter and provide a benefit to the watershed that equals or exceeds
the benefit that a detention facility would provide.
[Ord. No. 5852 § 2, 12-20-2012]
The Stormwater Management Improvements Fund, which was created by Ordinance 753, shall be continued and shall be reserved for funding improvements to stormwater systems owned and maintained by the City, and for no other purposes unless authorized in this Chapter. All contributions made by parties developing within the City in accordance with Section
550.040 of this Chapter shall be deposited to said fund. Said fund shall be deposited in an interest-bearing account.
[Ord. No. 5852 § 2, 12-20-2012]
When the City Engineer determines
that additional storage capacity beyond that required by the applicant
for on-site stormwater management is necessary in order to correct
an existing problem, or to provide protection in a more desirable
method for future development, or to complete improvements as outlined
in the City's Stormwater Master Plan, the City may acquire from the
applicant or owner, by purchase or dedication, the construction of
stormwater management systems to the extent that it exceeds the required
on-site stormwater management.
[Ord. No. 5852 § 2, 12-20-2012]
A. The City Engineer shall inspect, or cause
to be inspected, all stormwater management systems constructed within
the City of St. Peters, Missouri. Through such inspections the City
Engineer shall ensure that the facilities under construction are being
constructed in accordance with the approved plans for such development.
B. If it is determined that construction is
not in accordance with the approved plans, the City Engineer shall
immediately issue written notice to the permittee and the surety,
of the nature and location of the non-compliance, specifying what
remedial work is necessary to bring the construction into compliance.
The notified permittee shall immediately, unless weather conditions
or other factors beyond the control of the permittee prevent immediate
remedial action, commence the remedial action and shall complete the
remedial work within seventy-two (72) hours, or within a reasonable
time, not to exceed seven (7) calendar days, after receipt of said
notice. Upon satisfactory completion of the remedial work, the City
Engineer shall issue a notice of compliance.
C. In the event that the remedial action is
not taken, the City Engineer may then issue a stop work order, which
stop work order shall direct all parties involved to cease and desist
all or any portion of the work on the development except such work
necessary to bring the project into compliance. If such stop work
order is ignored, the parties shall be in violation of this Chapter
and subject to the penalties contained herein.
D. Each owner of the property being developed
has the responsibility and duty to properly operate and maintain any
stormwater management system, which has not been accepted for maintenance
by the City. The responsibility of maintenance of the system in subdivision
projects shall remain with the developer until such time as the stormwater
management system escrow for such development has been released. Upon
release of escrow the maintenance responsibility shall be vested in
the trustees of the subdivision, by virtue of a trust indenture. The
indenture of trust shall clearly indicate resident responsibility
for maintenance. The responsibility for maintenance in single lot
development shall remain with the general contractor and owner until
final inspection of the development is approved, and an occupancy
permit is issued. After occupancy, the maintenance of the management
system shall be vested in the owner of the project. All such privately
owned and maintained systems and BMPs shall be subject to periodic
inspection by the City Engineer or his representative.
E. If, after an inspection by the City Engineer,
the City Engineer determines that the condition of a privately owned
stormwater management system is an immediate danger to the public
health or safety, because of an unsafe condition, or if the trustees
or owner fail to provide a reasonable degree of maintenance, the City
Engineer shall take such action as may be necessary to protect the
public health and safety and make the system safe and correct. Any
costs incurred by the City, as a result of the City Engineer's actions,
shall be assessed against the owner(s) of the system.
F. Upon acceptance by the Board of Aldermen,
a stormwater management system may be dedicated to the City for perpetual
maintenance. Any such system shall include adequate perpetual access
and sufficient area for maintenance by City personnel and vehicles.
[Ord. No. 5852 § 2, 12-20-2012]
Upon approval of the final plans
for any stormwater management system, but before the issuance of any
permits, the City Engineer shall require the applicant to post an
escrow in the form of a letter of credit, cash escrow, or certified
check for the amount of the work to be done pursuant to the approved
stormwater management plan. This performance security shall not be
fully released by the City Engineer until a final inspection has been
made and the facility has been found to be in compliance with the
approved plans, and in the event the facility is to remain privately
owned, provisions have been made to assure perpetual maintenance.
A one (1) year maintenance escrow against defects in workmanship will
be required by the City Engineer for any system dedicated to the City.
[Ord. No. 5852 § 2, 12-20-2012]
A. Applicability. The requirements of stormwater
management outlined in this Chapter shall apply to all developments
within the corporate limits of the City of St. Peters, Missouri. Stormwater
management plans shall be provided and designed in accordance with
the requirements of this Chapter and all design and construction specifications
adopted by this Chapter. Each development is to strive to maintain
or improve pre-development peak flows, runoff volumes and water quality.
Stormwater quality and quantity management requirements will be evaluated
for all projects, and specifically, will be required for projects
including:
1.
All new development and redevelopment
projects that disturb greater than or equal to one (1) acre, including
projects less than one (1) acre that are part of a larger common parcel
or project that is greater than one (1) acre.
2.
All projects that have a differential
runoff of one (1) cfs or greater for the 15-year, twenty (20) minute
storm event. The differential runoff is calculated by the Rational
Method using PI factors.
3.
Development or redevelopment of sites
without prior stormwater detention shall provide detention or retention,
when the cumulative differential increase equals one (1) cfs or greater.
Projects with prior detention shall provide additional detention or
retention for all increased runoff.
4.
When existing stormwater management
(detention or retention) facilities are going to be used to accommodate
additional runoff, the facilities shall be retrofitted to meet the
current stormwater management requirements. Projects which cannot
meet this requirement due to physical constraints will be evaluated
for alternatives on a case-by-case basis.
5.
New development projects that disturb less than one (1) acre and have less than one (1) cfs differential runoff may be given a waiver by the City Engineer in accordance with Section
550.040 of this Chapter.
B. Affidavit Of Disclosure Of Property Interest.
The effective acreage for a site is not limited to a fractional part
of the total. If a project is developed in phases or small plats,
the total acreage of the project site will be considered. At the time
the owner of any development submits a preliminary plat or development,
the owner shall also identify to the City Engineer all contiguous
property or property in the watershed that the owner has interest
in.
[Ord. No. 5852 § 2, 12-20-2012]
A. Preliminary Stormwater Management Plans.
Concurrent with the filing of a preliminary plat or development plan,
the following information shall be submitted to the City Engineer:
1.
Topographic map outlining the limits
of the contributing watershed. Topographic maps should be the best
available. Topographic maps with two (2) foot contour intervals will
be accepted as a minimal requirement.
2.
Site plan of suitable scale and contour
interval, showing the land to be developed and such adjoining land
whose topography may affect the layout or drainage patterns for the
site.
3.
The location of streams and other
floodwater runoff channels, the extent of floodplains, the limits
of the floodway, if pertinent, and any additional information, all
of which shall be properly identified.
4.
The normal elevation and shoreline
of lakes, ponds, swamps, and detention basins including their floodplains
and inflow and outflow structures, if such structures exist.
5.
Specific information regarding the
type and characteristics of soils which will be encountered within
the project, and the locations of any sinkholes on the site.
6.
Concepts that will be considered
within the site to handle the quantity of stormwater runoff, including
the methods for detention or control of increased stormwater runoff
generated by the development, and how stormwater quality will be addressed.
7.
A general plan showing the extent
and nature of the stormwater system planned to serve the site including
preliminary calculations indicating the runoff which must be handled
by such systems, the methods and criteria which have been utilized
in calculating such runoff, and basic information regarding the receiving
watercourse into which such system will discharge.
8.
A general plan indicating the exterior
perimeter of the site, the general development proposed for the project,
and an indication by means of rough contours showing the terrain after
grading of the site.
9.
All computations, plans, and specifications
must be prepared and sealed by a professional engineer registered
in the State of Missouri.
Following receipt of preliminary
stormwater management plan and information to be included with such
plan, the general concepts and planning proposals will be reviewed
by the City Engineer. The City Engineer will schedule a review meeting
with representatives of the developer, including, but not limited
to, the developer's engineer, to review the overall concepts included
in the preliminary stormwater management plan. The purpose of this
review shall be to jointly agree upon an overall stormwater management
concept for the proposed development and to review criteria and design
parameters, which shall apply to the final design of the project.
|
B. Final Plans. Following review of the preliminary
stormwater management plan and after the concept review meeting and
approval of the preliminary plan by the City Engineer, a final stormwater
management plan shall be prepared for each phase of the proposed project
as each phase is developed. The final plan shall constitute a refinement
of the concepts approved in the preliminary stormwater management
plan with preparation and submittal of the following additional detailed
information unless specifically excluded during the preliminary concept
review meeting:
1.
A topographic map of the site and
adjacent areas, of suitable scale and contour interval, which shall
define the location of watercourses, the extent of floodplains and
calculated high water elevations, the shoreline and elevation of lakes,
ponds, swamps, and detention basins including their inflow and outflow
structures.
2.
The location and flowline elevation
of all existing sanitary and storm sewers.
3.
Detailed determination of runoff
anticipated for the site following development, indicating design
volumes and rates of proposed runoff for each portion of the watershed,
the calculations used to determine said runoff volumes and rates,
and restatement of the criteria which have been used.
4.
A layout of the proposed stormwater
management system including the location and size of all drainage
structures, storm sewers, channels and channel sections, detention
basins, water quality BMPs, and other stormwater improvements, and
analysis regarding the effect said improvements will have upon the
receiving channel and its high water elevation.
5.
A planting palette and seeding rates
for vegetated water quality BMPs.
6.
The location and calculated flow
rates of other existing storm drains, inlets and outfalls.
7.
The location and calculated flow
rates of any existing storm sewers which occur within the site, or
adjacent thereto within a distance of approximately two hundred (200)
feet from the perimeter of said site; or as conditions warrant.
8.
The location and observed flow rates
of any flowing springs, existing wells or any existing seepage areas
as determined by means of a field inspection of the property.
9.
The slope, type, size, and flow calculations
for all existing and proposed storm sewers and other waterways.
10.
For all detention basins, a detention
analysis report for each basin, including, but limited to, a plot
or tabulation of storage volumes with corresponding water surface
elevations and the basin outflow rates for those water surface elevations.
11.
For all detention basins, design
hydrographs of inflow and outflow for the 2-year storm and 25-year
storm differential runoff rates from the site under proposed development
conditions.
12.
A refined grading plan for the entire
project site drawn at a suitable scale and contour interval, or the
terrain within the proposed project site including contours of the
existing terrain, along with contours indicating final grades which
will be established during completion of the project. The grading
plan shall also include a plot of the line defining the high water
elevation to be expected under the 100-year peak flow conditions produced
by the projected development of the contributing watershed based on
the best available land use information.
13.
Profile and cross section drawings
of all existing and proposed channels or other open drainage facilities,
showing existing and proposed conditions, flow volume (Q) and velocity,
together with the high water elevations expected from stormwater runoff
under the controlled conditions called for by these regulations and
the relationship of structures, streets, and other utilities to such
channels.
14.
Calculations supporting the method
and capacity needed for the safe and temporary storage of increased
runoff resulting from the proposed development, if temporary storage
is needed.
15.
Calculations for water quality volume
(WQv) to determine the amount of storage needed to capture and treat
ninety percent (90%) of the average annual stormwater runoff volume.
16.
Calculations for flood protection
volume (Qp) to protect downstream areas from flooding.
17.
Calculations for the level of service
(LS) and value rating (VR) to determine the level of water quality
protection needed for a development.
18.
Basic information regarding the receiving
watercourse into which the proposed stormwater system will discharge
including the watercourse location, general cross section, existing
downstream culverts and bridges and other waterway openings within
a reasonable distance; any existing detention basins or lakes and
other information required to determine, in final form, the effect
which the proposed development will have on downstream drainage conditions.
19.
A Stormwater Pollution Prevention
Plan (SWPPP) which shall include the following information:
a.
Name, address and phone number of
the site owner.
b.
Site address or parcel identification
number(s).
c.
A site map showing the outlines of
the total project area, the areas to be disturbed, existing land uses,
locations and names of surface water bodies, discharge points, locations
of floodplains, locations of temporary and permanent BMPs, and a location
map.
d.
Existing contours of the site and
adjoining strips of off-site property, and proposed contours.
e.
A natural resources map identifying
soils.
f.
Estimated quantity of land to be
disturbed.
g.
Details of the site drainage pattern
both before and after the land disturbance activities.
h.
Stabilized access to the construction
site.
i.
Description of the BMPs to be utilized
to control erosion and sedimentation during the period of land disturbance.
A table is to be provided that lists each BMP to be utilized and the
quantity of each (the quantity for silt fence, etc. is to be listed
in linear footage). Label each BMP in the table as temporary or permanent.
j.
Identify potential sources of pollution,
waste and construction materials expected to be stored on site and
a description of the BMPs to be utilized to prevent the potential
pollutants (construction wastes, toxic or hazardous substances, petroleum
products, paints, solids, pesticides, herbicides, site litter, sanitary
wastes, etc.) from entering the natural drainage ways and/or waters
of the U.S. during the period of construction and land disturbance.
k.
Description of the BMPs that will
be installed during land disturbance to control pollutants in stormwater
discharges that will occur after land disturbance activity has been
completed.
l.
Location of stabilized temporary
off-street parking, wash-down, and maintenance area for related vehicles.
m.
Sources of off-site borrow material
or spoil sites, and all information relative to haul routes, trucks
and equipment.
n.
Narrative describing the timing and
schedule of installation of erosion, sediment, and good housekeeping
controls.
o.
Provisions for maintenance of control
facilities, including easements.
p.
Schedules and procedures for routine
inspections of any structures provided to prevent pollution of stormwater
or to remove pollutants from stormwater and of the site in general
to ensure all BMPs are continually implanted and effective.
q.
Description of measures that will
be installed during construction process to control pollutants in
stormwater discharges that will occur after construction operations
have been completed. During construction, strategies shall be implemented
to protect post- construction BMPs.
r.
Location/description of industrial
activities like temporary, on site, concrete or asphalt batch plants.
s.
Special measures may need to be taken
to ensure conformance with the required total maximum daily load (TMDL)
on the implementation plan for developments located in an area draining
to a water body that has been listed on Missouri's impaired water
body list.
20.
All computations, plans, and specifications
must be prepared and sealed by a professional engineer registered
in the State of Missouri.
21.
The City Engineer, or his/her designee,
shall review final stormwater management plans.
a.
If it is determined that the proposed
development will provide stormwater quantity and quality control in
accordance with the purposes, design criteria and performance standards
of these regulations and will not be detrimental to the public health,
safety, and general welfare, the City Engineer shall approve the plan
or conditionally approve the plan setting forth the conditions thereof.
b.
If it is determined that the proposed
development will not manage stormwater quantity and quality in accordance
with these regulations, the City Engineer shall disapprove the final
stormwater management plan. If disapproved, the data shall be returned
to the applicant for resubmittal.
[Ord. No. 5852 § 2, 12-20-2012]
The "Standard Construction Specifications
for Sewers and Drainage Facilities of the Metropolitan St. Louis Sewer
District", 2009, as published by Metropolitan St. Louis Sewer District,
is hereby adopted as the Standard Construction Specifications for
the City and made a part hereof, as if fully set out in this Chapter,
with the additions, insertions, deletions, and changes prescribed
in this Chapter.
[Ord. No. 5852 § 2, 12-20-2012]
Chapter 4 of "THE METROPOLITAN ST.
LOUIS SEWER DISTRICT — RULES AND REGULATIONS AND ENGINEERING
DESIGN REQUIREMENTS FOR SANITARY SEWAGE AND STORM WATER DRAINAGE FACILITIES",
February 2006, is hereby adopted as the design requirements for storm
drainage facilities for the City and made a part thereof, as if fully
set out in this Chapter with the additions, insertions, deletions,
and changes prescribed in this Chapter.
[Ord. No. 5852 § 2, 12-20-2012]
The Mid-America Regional Council
(MARC) "MANUAL OF BEST MANAGEMENT PRACTICES FOR STORMWATER QUALITY",
August 2009, is hereby adopted as the design requirements for stormwater
quality for the City and made a part thereof, as if fully set out
in this Chapter, with the additions, insertions, deletions, and changes
prescribed in this Chapter.
[Ord. No. 5852 § 2, 12-20-2012]
Throughout the Standard Construction Specifications adopted in Section
550.110 and the Rules and Regulations and Engineering Design Requirements for Storm Water Drainage Facilities adopted in Section
550.120, whenever the term "District" appears, it shall be deemed to mean the City of St. Peters, Missouri. Wherever the phrase "St. Louis County" appears in the Standard Construction Specifications or the Rules and Regulations and Engineering Design Requirements for Storm Water Drainage Facilities, the phrase shall be replaced with the phrase "St. Charles County". Throughout the Manual of Best Management Practices for Stormwater Quality adopted in Section
550.125, whenever the terms "Kansas City, Kansas City Metropolitan Area, Kansas City Region or MARC Region" appears, it shall be deemed to mean the City of St. Peters, Missouri.
[Ord. No. 5852 § 2, 12-20-2012]
Throughout the Standard Construction Specifications adopted in Section
550.110, the Rules and Regulations and Engineering Design Requirements for Storm Water Drainage Facilities adopted in Section
550.120, and the Manual of Best Management Practices for Stormwater Quality adopted in Section
550.125, wherever the term "Director" or "Engineer" appears, it shall be deemed to mean the City Engineer.
[Ord. No. 5852 § 2, 12-20-2012]
A. Standard Construction Specifications. The standard construction specifications adopted in Section
550.110 are amended as follows:
1.
Delete: Materials of Construction,
Part 2, Section (G)(1)(e): Fiberglass pipe (RPM).
2.
Delete: Materials of Construction,
Part 2, Section (G)(2)(a): Vitrified clay pipe — 12 inch and
larger.
3.
Delete: Materials of Construction,
Part 2, Section (G)(2)(e): Fiberglass pipe (RPM) — 12 inch and
larger.
4.
Delete: Materials of Construction,
Part 2, Section (G)(2)(f) High density polyethylene: 12 — 24
inch, and replace with: 12 — 48 inch.
5.
Delete: Materials of Construction,
Part 2, Section (G)(11) High Density Poly-Ethylene (HDPE) Corrugated
Pipe in its entirety and replace with: The use of HDPE corrugated
pipe with an integrally formed smooth waterway is approved for use,
with the exception that HDPE pipe cannot be used under or through
existing street right-of-way or through an area where potential future
right-of-way may occur. Reinforced concrete pipe shall be installed
to the next structure outside of the right-of-way. The HDPE corrugated
pipe shall be installed, inspected, and tested according to manufacturer
specifications or in accordance with ASTM 2390, D2321, C969, C924,
and C1103. Nominal sized HDPE pipe 12 to 36 inches in diameter shall
conform to the AASHTO M294 classification "Type S"; and 42-inch to
48-inch diameter HDPE corrugated pipe shall conform to AASHTO MP6-95
classification "Type D".
6.
Add: Materials of Construction, Part
2, Section (G)(11)(a): All HDPE corrugated pipe joints shall consist
of bell and spigot joining system with the bell covering two pipe
corrugations as recommended in AASHTO M294. Pipe joints with rubber
O-ring gaskets meeting ASTM F477 shall be installed on the spigot
end of the pipe. Both the bell and spigot (with O-ring gasket) ends
of each pipe shall be lubricated as recommended by the manufacturer
and inserted to the homing mark on the spigot end of the pipe.
7.
Add: Materials of Construction, Part
2, Section (G)(11)(b): HDPE corrugated pipefittings may be either
molded or fabricated and shall conform to the requirements of AASHTO
M252 and M294. The fittings shall not reduce or impair the overall
integrity or function of the pipeline. Only fittings supplied or recommended
by the pipe manufacturer shall be used.
8.
Delete: Materials of Construction,
Part 2, Section (G)(13) Fiberglass Pipe: delete this Section in its
entirety.
9.
Delete: Materials of Construction,
Part 2, Section (H)(1)(a) Sanitary and Combined Sewers: Vitrified
Clay Pipe (VCP) and Fiberglass Pipe (RPM).
10.
Delete: Materials of Construction,
Part 2, Section (H)(1)(a) Stormwater Sewers: Vitrified Clay Pipe (VCP)
and Fiberglass Pipe (RPM)
11.
Delete: Materials of Construction,
Part 2, Section (H)(7) Type F Joints.
12.
Delete: Excavation, Part 3, Sections
(F)(2)(b and c) in their entirety.
13.
Add: Pipe Sewer Construction, Part
4, Section (B)(5): HDPE corrugated pipe manufactured for this specification
shall comply with the requirements for test methods, dimensions, and
markings found in AASHTO designations M252 and M294. HDPE corrugated
pipe and fittings shall be made from virgin PE compounds which conform
with the requirements of cell class 335420C as defined and described
in ASTM D3350.
14.
Amend: Pipe Sewer Construction, Part
4, Section (G)(4)(a): The use of precast concrete inlet covers (Detail
Sheet 46) is prohibited. Where precast concrete structures are permitted
or required by the project plans, they will be manufactured in accordance
to Part 2 of this Specification and to the sizes and shapes detailed
in the drawings for this Specification.
15.
Amend: Pipe Sewer Construction, Part
4, Section (1)(2) Pipe Sewers: Any reference to locator disks shall
be changed to locator balls.
16.
Delete: Channel Construction, Part
6, Section (C)(1)(c) and replace with: The rock shall be neatly placed,
and shall not be less than one foot thick on the sides and on the
bottom. The surface shall be reasonable regular and uniform.
17.
Delete: Detail Sheet 48, Steel Grates.
18.
Delete: Detail Sheet 49, Steel Vane
Grate.
19.
Delete: Detail Sheet 71, Signs.
[Ord. No. 5852 § 2, 12-20-2012]
A. Rules And Regulations. The Rules and Regulations and Engineering Design Requirements for Storm Water Drainage Facilities adopted in Section
550.120 are amended as follows:
1.
Section 4.020 General Requirements
Of Storm Sewer Construction. Hydraulic Grade Line and Inlet/Flow Capacity
Data Computations shall be submitted on Attachment A ("Hydraulic Data
Form") for all projects. The form may be computerized; however, all
information required on the form shall be included in the computerized
version.
2.
Section 4.020.11 Overflow/Design
System, Paragraph 2. Whenever the phrase "100-year, 20-minute" appears
in the design requirements, the phrase shall be replaced with "15-year,
20-minute".
3.
Section 4.030.01 (1) Rainfall Frequency.
This Section shall be deleted and replaced as follows:
A fifteen (15) year rainfall frequency
is to be used in St. Charles County. In the design of local storm
sewer systems, a twenty (20) minute time of concentration shall be
used. Figure 4-1 gives rainfall curves for 2- 5- 10- 15- 20- and 100-year
frequencies.
4.
Section 4.030.03 Hydraulic Grade
Line Limits, Paragraph 5. This paragraph shall be deleted.
5.
Section
4.030.04 Inlets, Paragraph 2: Inlet capacity should not be less than
the quantity flow tributary to the inlet and by-pass flow shall be
avoided whenever possible. Inlets at low points or grade pockets should
have extra capacity to compensate for possible flow by-pass of upstream
inlets. Figure 4-3 shows inlet capacity/maximum gutter capacity with
a given gutter line grade and flow. The value for inlet capacity obtained
from Figure 4-3 shall be multiplied by a factor of 0.85 and the result
will be used for the capacity of the inlet. The multiplication factor
is to account for clogging of inlets and by-pass around the inlet.
An example is presented below.
Example: Street/Gutter at a 3% Grade
has an inlet capacity of approximately 1.6 cubic feet per second (CFS)
for a single inlet and approximately 5.1 CFS for a double inlet capacity.
1.6 CFS * 0.85 = 1.36 CFS >>>> single
inlet capacity
5.1 CFS * 0.85 = 4.34 CFS >>>> double
inlet capacity
The following guidelines shall also
apply to inlets:
a.
Inlets shall be appropriately sized
and spaced, taking into consideration by-pass, depth of flow and gutter
capacity. Inlets shall be required when the pavement is super elevated
or warped causing water to flow from the gutter line across the roadway.
b.
For inlets in vertical sag curves,
the center of the main chamber shall be placed within one (1) foot
of the computed mathematical low point.
c.
Inlets shall be located so the inlet
face is a maximum of two and one-half (2.5) feet behind the back of
the roadway curb in new residential subdivisions. The sump shall begin
two (2) feet in front of the back of curb. The top elevation of the
stone shall remain three (3) inches above the top of rolled curb and
level with the top of vertical curb. When required, the nearest two
(2) sections of sidewalk on each side of the inlet shall be warped
down to the top of the inlet stone elevation. At intersections, inlets
shall be placed so no part of the inlet structure or sump is in the
curb rounding.
d.
Area inlets in roadway ditches shall
be compatible with the ultimate pavement improvements. Rear yard area
inlets shall be required when more than one (1) cubic foot per second
(CFS) is concentrated between buildings and crossing sidewalks or
curbs.
e.
By-pass shall be minimized at inlet
structures and shall be shown on the hydraulic computations and site
drainage map. By-pass shall be used in determining gutter flow downstream.
By-pass shall not be considered in sizing of the storm sewer pipe
system (i.e., pipe shall be designed for total tributary "Q" regardless
of by-pass). Curb inlets shall be required to intercept runoff when
more than one (1) CFS crosses street intersections.
6.
Section 4.030.06 Culverts. Add Paragraph
3. Crossroad Culverts. Crossroad culverts, not at low points shall
be designed on a storm frequency of fifteen (15) years with entrance
control and a minimum of two (2) feet of freeboard at the shoulder
line. Culverts, functioning as the low point in floodplains, shall
be designed on a storm frequency of one hundred (100) years with entrance
control and a minimum of two (2) feet of freeboard at the shoulder
line. Culverts, functioning as the low point not in floodplains, shall
be designed on a storm frequency of fifty (50) years with entrance
control and a minimum of two (2) feet of freeboard at the shoulder
line. Refer to the U.S. Department of Transportation Hydraulic Engineering
Circular No. 5 entitled "Hydraulic Charts for the Selection of Highway
Culverts".
7.
Section 4.030.06 Culverts. Add Paragraph
4. Drainage Pipes (Inlet). At all intake structures such as flared
end sections or headwalls, entrance control shall be applied. Two
(2) foot minimum freeboard shall be required. Upstream inundation
shall be checked. Where inundation extends beyond the site property
line and exceeds the Design Water Surface Elevation of the natural
drainageway/channel, a backwater ponding easement from the affected
off-site property owner shall be required prior to approval of the
improvement plans. Concrete outfall pipes shall have a reinforced
concrete headwall or flared end section with cut-off wall and properly
sized, placed revetment underlain with a woven geotextile fabric or
paved ditch. Cut-off walls shall be two (2) feet deep on upstream
headwalls/end sections.
8.
Section 4.030.06 Culverts. Add Paragraph
5. Drainage Pipes (Outlet). Outfall termination shall occur at a natural
drainageway/channel so that the flow does not exceed the natural capacity
of the drainageway/channel. Discharge velocities in an outfall pipe
shall not exceed eight (8) feet per second, where practical. Special
approved methods of energy dissipation will be required when discharge
velocities in outfall pipes exceed five (5) feet per second. Concrete
outfall pipes shall have a reinforced concrete headwall or flared
end section with cut-off wall and properly sized, placed revetment
underlain with a woven geotextile fabric or paved ditch. Revetment
shall be a minimum length of ten (10) feet or ten (10) times the diameter
of the discharge pipe (in feet) whichever is greater when not discharging
to a lake or pond. Revetment in lakes or ponds shall be placed between
the outlet pipe and the low water elevations. Cut-off walls shall
be three (3) feet deep on downstream headwalls/end sections.
9.
Section 4.040.02 Clearance. This
Section shall be deleted and replaced as follows: The lowest point
of the bridge superstructure, not at low points, shall be designed
on a storm frequency of fifteen (15) years with entrance control and
a minimum of two (2) feet of freeboard clearance. Bridges, functioning
as the low point in floodplains, shall be designed on a storm frequency
of one hundred (100) years with entrance control and a minimum of
two (2) feet of freeboard clearance. Bridges, functioning as the low
point not in floodplains, shall be designed on a storm frequency of
fifty (50) years with entrance control and a minimum of two (2) feet
of freeboard clearance.
10.
Section 4.060 Limitations On Areas
Draining Across Sidewalks Or Driveways. Delete this Section.
11.
Section 4.070 Impervious Areas In
The City Of St. Louis. This Section shall be renamed "Impervious Areas"
and the second paragraph shall be deleted.
12.
Section 4.080 General Performance
Criteria For Stormwater Management. Wherever the phrase "100-year"
appears in the design requirements, the phrase shall be replaced with
"25-year". Wherever a 24-hour event is specified, Technical Release
55 (TR-55) shall be used as the method for calculating flows. Wherever
a 20-minute event is specified, flow rates shall be determined using
the method set forth in Section 4.030.01 Flow Quantities.
13.
Section 4.080.01 When Required, Paragraph
1. Paragraph 1 shall be deleted and replaced as follows:
1.
The requirements of the stormwater
quantity and quality management shall be evaluated for all projects
submitted to the City for review and approval. Stormwater management
facilities shall be provided and designed in accordance with the requirements
of this Section and of the Kansas City MARC Manual adopted herein.
14.
Section 4.080.01 When Required, Paragraph
2. Whenever the phrase "2 cfs" appears, it is to be replaced with
"1 cfs".
15.
Section 4.080.02 Unified Stormwater
Sizing Criteria. Delete this Section in its entirety and replace with:
Section 4.080.02 Design Considerations
1.
General. This Section presents the
summary for sizing stormwater BMPs to meet pollutant removal goals,
to prevent flooding, and to pass extreme floods.
Water Quality Volume
(WQv) (acre-feet)
|
WQv=[(P)(Rv)(A)]/12
P=rainfall depth in inches=1.14
Rv=volumetric
runoff coefficient
Rv=0.05 +
0.009(I)
Where I = percent impervious cover
A=area in acres
|
Flood Protection
Volume
(Q2'Q25 and Q100)
|
The post-developed peak flow from
the site must be released at a rate not to exceed the allowable release
rate for the appropriate rainfall events, as discussed in Section
4.080.03.
|
The following Subsections provide
more information on WQv and Flood Protection Volume.
|
2.
Water Quality Volume (WQv).
a.
The Water Quality Volume (denoted
WQv) is the storage needed to capture and treat the runoff from 90%
of the recorded daily rainfall events. It is equivalent to 1.14 inches
of rainfall multiplied by the volumetric runoff coefficient (Rv) and
site area. The WQv is directly related to the amount of impervious
cover created at a site. Refer to the MARC Manual for methods and
coefficients.
b.
The following assumptions may be
made:
(1) The Water Quality Volume
WQv for off-site areas is not required.
(2) Measuring Impervious
Cover. The measured area of a site plan that does not have vegetative
or permeable cover shall be considered total impervious cover.
(3) Multiple Drainage Areas.
When a project contains or is divided by multiple drainage areas,
the WQv shall be analyzed for each drainage area. BMPs are not required
to be located within each drainage area, but shall be placed to provide
the greatest impact on water quality (i.e., the placement of BMPs
in drainage areas discharging directly into a creek or body of water
is strongly encouraged, rather than placing BMPs in drainage areas
that have an existing downstream treatment train).
Although BMPs are not required to
be placed within each drainage area, the WQv shall be accounted for
the overall tract.
(4) Off-Site Drainage Areas.
The WQv shall be based on the impervious cover of the proposed site.
Off-site existing impervious areas may be excluded from the calculation
of the WQv.
(5) BMP Treatment. The final
WQv shall be treated by acceptable BMPs, as provided in the MARC Manual.
3.
Flood Protection Volume.
a.
To protect downstream areas from
flooding, stormwater shall be detained on-site or off-site as approved
and released at a rate not to exceed the allowable release rates for
the 2-year, 24-hour storm and 25-year, 24-hour rainfall events for
sites larger than 10 acres. For sites less than 10 acres, the developed
release rate from the site may not exceed the existing peak flow for
the 2-year, 20-minute event and the 25-year, 20-minute event. Note
that stormwater pipes, downstream from the control structure, shall
be sized to carry the runoff from the 15-year, 20-minute design storm
for the total tributary upstream watershed. No reduction in outfall
pipe size shall be permitted because of detention.
The outlet structure for the basin
shall be sized to pass the 100-year, 24-hour storm event for sites
larger than ten (10) acres. For sites less than ten (10) acres, the
100-year, 20-minute rainfall event shall be used. The basin shall
have a minimum of two (2) feet of freeboard above the high water elevation
for the 100-year storm event.
b.
The existing and developed peak flows
shall be determined by using Technical Release 55 (TR-55) for sites
with a drainage area of ten (10) acres or more. All assumptions that
are required for the TR-55 method shall be approved, in writing, by
the proper agency prior to commencing grading activities or issuance
of a grading permit. For sites less than ten (10) acres, flow rates
shall be determined using the method set forth in Section 4.030.01
Flow Quantities.
c.
The 2-year, 25-year, and 100-year
24-hour inflow hydrographs shall be determined by using Technical
Release 55 (TR-55) "Urban Hydrology for Small Watersheds" from the
Natural Resources Conservation Service, formerly Soil Conservation
Service (SCS). The inflow hydrograph shall be developed based on the
actual flow and timing characteristics upstream of the detention facility.
The rainfall distribution shall be Type II.
d.
The volume of detention may be provided
through permanent detention facilities such as extended dry detention
basins, permanent ponds or lakes, underground storage facilities or
parking lots. The engineer shall make every effort to locate the detention
facility at or near the lowest point of the project such that all
of the on-site runoff will be directed into the detention facility.
Multiple use of detention basins is encouraged. Multiple use may include
parking lots, ball fields, tennis courts, playgrounds, and picnic
areas. This is subject to the approval of the City.
Flows from off-site, upstream areas
should be by-passed around the detention facility to ensure that the
proposed detention facility will function as designed and will provide
effective control of downstream flows with development in place. If
off-site flows are directed into a detention facility, the allowable
release rates shall not be modified without City approval. Modifying
the release rate to accommodate off-site flows may reduce or eliminate
the effectiveness of the detention facility, because it will no longer
control the increased volume of runoff during the critical time period
of the watershed.
The engineer has the option to calculate
a site specific release rate based on the procedures provided by the
City's Engineering Department. The engineer shall provide detailed
modeling to prove that the increase in runoff volume has been limited
to existing conditions during the critical time period of the watershed.
e.
Detention basin volume will be based
on routing the post-developed 2-year and 25-year inflow hydrographs
through the detention facility while satisfying the appropriate release
rate. The routing computations shall be based on an application of
the continuity principle (i.e., level pool routing).
16.
Section 4.080.03 Limits Of Maximum
Ponding In Stormwater Ponds, Paragraph 1. Paragraph 1 shall be deleted
and replaced with:
1.
For sites larger than ten (10) acres,
the maximum ponding elevation shall be calculated based on a routing
of the design storm (100-year, 24-hour event) assuming the low-flow
outlet is blocked. For sites less than ten (10) acres, the 100-year,
20-minute rainfall event shall be used.
17.
Section 4.080.03 Limits Of Maximum
Ponding In Stormwater Ponds, Paragraph 4. Paragraph 4 shall be deleted
and replaced with:
4.
|
A minimum of two (2) feet of freeboard
shall be provided from the top of the basin to the maximum ponding
elevation.
|
18.
Section 4.080.03 Limits Of Maximum
Ponding In Stormwater Ponds, Paragraph 5. Paragraph 5 shall be deleted.
19.
Section 4.080.04 General Stormwater
Basin Design Requirements, Paragraph 1(b). Paragraph 1(b) shall be
deleted and replaced with:
1(b).
|
For sites larger than ten (10) acres,
the basin should have sufficient volume and spillway capacity to pass/contain
the 100-year, 24-hour storm event with the low flow outlet blocked.
For sites less than ten (10) acres, the 100-year, 20-minute rainfall
event shall be used.
|
20.
Section 4.080.04 General Stormwater
Basin Design Requirements, Paragraph 13. Paragraph 13 shall be deleted
and replaced with:
13.
|
Detention Basin Elevation. If the
detention basin discharges to a piped sewer system, the low elevation
of the detention basin shall be above the 15-year, 20-minute hydraulic
elevation of the receiving storm system.
|
21.
Section 4.080.04 General Stormwater
Basin Design Requirements, Paragraph 15. Paragraph 15 shall be deleted.
22.
Section 4.080.05 Acceptable Urban
BMP Options. This entire Section shall be deleted and replaced with:
Acceptable Urban BMP Options
The design and selection of BMPs
shall comply with the Mid-America Regional Council (MARC) "MANUAL
OF BEST MANAGEMENT PRACTICES FOR STORMWATER QUALITY", August 2009,
with the additions, insertions, deletions and changes prescribed by
the City.
23.
Section 4.080.06 Stormwater Credits.
This entire Section shall be deleted.
24.
Section 4.080.08 Maintenance Agreement.
Delete the existing paragraphs and insert the following:
Maintenance Agreement
Maintenance of detention basins shall
be the responsibility of the property owner. The detention basin shall
be kept in working order, per the approved plans, at all times. By
submittal of improvement plans, the owner grants the City of St. Peters
the right to inspect the basin at any time, prior to and after development.
The City may submit a list of deficiencies to the owner, which shall
be corrected at the owner's expense, in a reasonable time.
25.
Section 4.100 Detention Report. Delete
Section 6.
26.
Exhibit 4-A. Delete Exhibit 4-A in
its entirety.
27.
Table 4-5. Delete Table 4-5.
[Ord. No. 5852 § 2, 12-20-2012]
A. Volume Of Detention Required. The volume
of storage required shall be sufficient to provide enough storage
to control the differential runoff and the water quality storm.
B. Flows From Upstream Areas.
1.
No materials (fence, shed, landscaping,
decorative blocks, etc.) shall be placed in a manner that blocks or
alters the drainage of adjacent properties.
2.
Flows from upstream areas outside
the site should be based upon the assumption that those areas are
fully developed under forecast land use patterns. For detention sizing,
the required storage volume will be based upon the site only, with
the flow from upstream areas being by-passed or discharged via overflow
spillways or other devices.
C. Early Installation Of Control Systems.
Runoff control measures shall be installed prior to any land disturbance.
1.
Land disturbances that fall under
the requirements for a grading permit, and that are greater than or
equal to one (1) acre in size, are required to have a Stormwater Pollution
Prevention Plan.
2.
Land disturbances less than one (1)
acre are required to have perimeter siltation controls that protect
off-site properties, road rights-of-way, storm sewer systems and drainageways.
D. Facilities In Floodplains. If detention
storage is provided within a floodplain, only the storage above the
100-year base flood elevation (BFE) will be credited to the development.
No credit will be granted for detention volumes below the 100-year
BFE at that location, unless compensatory basin storage is provided
elsewhere above the 100-year BFE.
E. Surface Drainage. Sheet flow in excess
of one (1.0) cubic feet per second (cfs) shall not be allowed over
terraces. Berms and/or vegetated swales shall be provided to collect
the flow at the top or the bottom of the terrace and carry it to a
drainage structure. Total accumulation inside berms and/or swales
shall be a maximum of four (4) cfs. Critical cross sections, profiles,
and hydraulic computations for ditches and swales with flows in excess
of one (1) cfs and relocated or man-made creeks with flows in excess
of four (4) cfs shall be provided.
F. Pipe Slope And Velocity. The minimum grade
shall be the grade establishing a self-cleansing velocity of three
(3) feet per second. Velocities shall not exceed twenty-five (25)
feet per second, where practical.
G. Drainage Structures. The lateral location
of all street drainage structures shall be shown on the plans by the
street centerline stationing and the perpendicular offset distance.
1.
All manholes shall be located outside
of the proposed roadway pavements.
2.
Erosion protection in the form of
asphalt curb, gutters, additional structures, paving and/or revetment
may be required at the temporary termination of pavements.
3.
Subsurface pre-cast stormwater structures
may be used provided detailed drawings are submitted and approved
prior to construction plan approval.
H. Open Channel Setback Requirement. Development
along natural watercourses shall have residential lot lines, commercial
or industrial improvements, parking areas or driveways set back a
minimum of twenty-five (25) feet from the top of existing stream bank
or 15-year, 20-minute water surface elevation, where no defined bank
exists. The watercourse and twenty-five (25) foot setback area shall
be maintained and made the responsibility of the subdivision trustees.
Residential lots having an area of one (1) acre or greater which shall
be exempt from this regulation if the stream bank is not erosive.
In the case of a site plan, commercial or industrial site, the watercourse
and twenty-five (25) foot setback area shall be maintained and made
the responsibility of the property owner. Permanent native vegetation
and existing ground elevation and grades within the twenty-five (25)
foot setback shall be left intact and undisturbed. Variances will
include designed stream bank erosion control measures and shall be
approved by the appropriate government agency, which has jurisdiction
over the land and/or development in question. FEMA and U.S. Army Corps
of Engineers guidelines shall be followed where applicable regarding
site development areas designated as floodplains and wetlands.
I. Natural Drainageway Enclosure. Engineered
construction plans and a permit are required for the enclosure of
an existing natural drainageway, or for any channel crossing that
causes a restriction to the natural drainageway, if the channel carries
greater than ten (10) cubic feet per second (cfs) of stormwater during
a 15-year, 20-minute storm event. The enclosure shall be sized for
a 50-year, 20-minute storm event for flows equal or greater than one
hundred (100) cfs. The enclosure shall be sized for a 15-year, 20-minute
storm for flows less than one hundred (100) cfs. For flows equal or
greater than one hundred (100) cfs, two (2) foot minimum freeboard
shall be required and upstream inundation shall be checked for the
100-year, 20-minute storm event. Where inundation extends beyond the
site property line and exceeds the design water surface elevation
of the natural drainway/channel, a backwater ponding easement from
the affected off-site property owner shall be required prior to approval
of the improvement plans.
J. General Design Features.
1.
Dry Basins. Basins may be constructed
to temporarily detain the stormwater runoff so that the rate at which
it is released is the same rate as before development. In addition
to the design requirements set forth in the MARC Manual, the following
features shall be incorporated into the design of any dry detention
basin:
a.
Storage Volume. The volume of storage
provided shall be sufficient to provide enough storage to control
the differential runoff from the 2-year and 25-year storm events.
b.
Freeboard. Detention storage areas
shall have adequate capacity to contain the storage volume of tributary
stormwater runoff with at least two (2) feet of freeboard above the
water surface.
c.
Outlet Control Works. Outlet works
shall be designed to limit peak outflow rates from detention storage
areas to or below peak flow rates that would have occurred prior to
the proposed development. Outlet works shall not include any mechanical
components or devices and shall function without requiring attendance
or control during operation, unless specifically approved by the City
Engineer.
d.
Spillway. Emergency spillways shall
be provided to permit the safe passage of runoff generated from a
100-year storm.
e.
Multi-Purpose Basins. If the detention
basin is to have other uses, the design of the basin bottom should
include underdrains to expedite drying of the bottom between runoff
events.
f.
Aesthetics. Designs should result
in aesthetically pleasing configurations, which will enhance public
acceptability.
2.
Rooftop Storage. Detention storage
may be met in total or in part by detention on roofs. Details of such
design, which shall be included in the building permit application,
shall include the depth and volume of storage, details of outlet devices
and downdrains, elevations of overflow scuppers, design loadings for
the roof structure and emergency overflow provisions. Direct connection
of roof drains to sanitary sewers is prohibited.
3.
Parking Lot Storage. Paved parking
lots may be designed to provide temporary detention storage of stormwater
on all or a portion of their surfaces. Outlets will be designed so
as to slowly empty the stored waters and depths of storage must be
limited so as to prevent damage to parked vehicles. Maximum depth
shall not exceed eight (8) inches of water.
4.
Other Detention Methods. All or a
portion of the detention storage may also be provided in underground
or surface detention facilities, to include basins, tanks, or swales,
etc.
K. Maintenance Of Stormwater Systems And BMPs.
Designs of stormwater systems and BMPs shall incorporate features
which facilitate their inspection and maintenance. The growth of obnoxious
weeds, the creation of conditions which support the growth of mosquitoes
and other insects, and the decrease in available storage by accumulated
sediments must be controlled. The cleanup of accumulated debris, flotsam
and other materials after runoff events have subsided must be assured.
Maintenance of stormwater and detention systems, and BMPs, shall be
the responsibility of the property owner. Assignment of responsibility
for maintaining facilities serving more than one (1) lot or holding
shall be documented by appropriate covenants to property deeds unless
responsibility is formally accepted by the City.
1.
Inspections. All privately owned
detention storage facilities will be inspected by representatives
of the City not less often than once every three (3) years, and BMPs
will be inspected yearly. A letter will be sent to the owner, with
a checklist, notifying them of the results of the inspection and listing
any deficiencies found that are in need of correction.
2.
Corrective Measures. If deficiencies
are found by the inspector, the owner of the detention facility and/or
BMP(s) will be required to take the necessary measures to eliminate
nuisances and correct the deficiencies. If the owner fails to do so,
the City may undertake the work necessary and recover all expenses
from the owner.
L. Safety Features. Designs of stormwater
systems shall incorporate safety features, particularly at outlets,
on steep slopes, and at any attractive nuisances to include, as necessary,
fencing, handrails, lighting, steps, grills, signs, and other protective
or warning devices so as to restrict access during critical periods
and to afford some measure of safety to both authorized and unauthorized
persons.
[Ord. No. 5852 § 2, 12-20-2012]
A. Stormwater Quality. The Manual of Best Management Practices for Stormwater Quality adopted in Section
550.125 are amended as follows:
1.
Section 3.2 Water Quality Concepts,
Paragraph 6. The last sentence shall be deleted and replaced as follows:
In the St. Peters area, the Water Quality Storm is the 1.14" rain
event.
All future references in the Manual
to the 1.37 inch Water Quality Storm shall be replaced with the 1.14
inch Water Quality Storm.
2.
Section 4.2.1 Predevelopment And
Postdevelopment Conditions, Paragraph 3. The following sentence shall
be deleted: Assume that soils which will be disturbed by development
are assigned a HSG rating one (1) higher than the predevelopment condition
unless they are preserved in accordance with the specifications in
Appendix A.
3.
Table 4.4 Best Management Practice
Value Ratings. Table 4.4 shall be modified to include the following
Cover Type or BMPs and Overall Value Ratings:
Cover Type or BMP
|
Overall Value Rating
|
Rock Filter Strip
|
3.0
|
Rock Filter Strip with underdrain
system
|
4.0
|
Amended Soils
|
5.0
|
4.
Add Section 4.5 Stormwater Quality
Credits. Credits towards the weighted Value Rating (VR) or LS can
be given by the City Engineer, if the design features of a site, or
its BMP(s) are part of a Treatment Train that includes existing off-site
downstream BMPs that the stormwater will filter through before reaching
its ultimate discharge point (creek, drainageway, lake, etc.) or if
the site conditions restrict the ability to meet the VR or LS required.
All sites will be evaluated on a case-by-case basis.
5.
Worksheet 1A On Page 4-17 Of The
MARC Manual, Titled Required Level Of Service--Developed Site, Section
2, Subsection E, Shall Be Deleted And Replaced As Follows:
2.E.
|
Level of Service
|
|
Use percent Impervious to Enter Table
4.3
|
|
LS = 3.0 for a Percent Impervious
= 0
|
6.
Worksheet 1A On Page 4-17 Of The
MARC Manual, Titled Required Level Of Service--Developed Site, Section
3 Shall Be Deleted And Replaced As Follows:
3.
|
Minimum Required Total Value Rating
of BMP Package
|
|
Total Value Rating = LS X Required
Treatment Area plus "existing impervious area inside disturbed area
that is to remain Impervious in post development condition" X 1
|
7.
Table 6.1 Volumetric Coefficients
For Urban Runoff For Directly Connected Impervious Areas. Table 6.1
shall be modified to include the following information for a 1.14
inch storm event:
Rainfall (inches)
|
Flat roofs and unpaved parking lots
|
Pitched roofs and large impervious
areas (large parking lots)
|
Small impervious areas and narrow
streets
|
Silty soils HSG-B
|
Clayey soils HSG-C and D
|
---|
1.14
|
0.85
|
0.98
|
0.72
|
0.12
|
0.22
|
8.
Table 6.2 Reduction Factors To Volumetric
Runoff Coefficients For Disconnected Impervious Surfaces. Table 6.2
shall be modified to include the following information for a 1.14
inch storm event:
Rainfall (inches)
|
Strip commercial and shopping center
|
Medium- to high-density residential
with paved alleys
|
Medium- to high-density residential
without alleys
|
Low-density residential
|
---|
1.14
|
0.99
|
0.44
|
0.22
|
0.22
|
9.
Table 6.3 Rainfall Intensity For
Water Quality Rainfall Event (1.37 Inches). Delete Table 6.3.
10.
Appendix A, Page A-35, Trees. Delete
all Ash trees (White Ash, Green Ash).
11.
Appendix A. Add the following supplemental
lists of plants and trees to Appendix A:
A.
Plants lists from the St. Louis MSD
guidance and Missouri Botanical Garden resources.
B.
Plant Palette Recommendation, Wet
Detention Basin.
Botanical name
|
Common Name
|
Height (ft)
|
Spacing*
|
Water
|
Light
|
Comments
|
---|
Upper 5 feet
|
Asclepias incarnate
|
Marsh Milkweed
|
2 to 3
|
18" o.c.
|
moist soil
|
full sun
|
|
Carex grayi
|
Gray's Sedge
|
2 to 3
|
18" o.c.
|
moist soil
|
full to medium sun
|
|
Carex muskingumensis
|
Palm Sedge
|
2 to 3
|
18" o.c.
|
moist soil
|
full to medium sun
|
Plant in massings for best foliage
effect
|
Middle 10 feet
|
Acorus calamus
|
Sweet Flag
|
2 to 4
|
18" o.c.
|
moist soil to shallow water
|
full sun
|
|
Carex stricta
|
Tussock Sedge
|
1 to 3
|
18" o.c.
|
moist to wet soil
|
full to medium sun
|
|
Iris fulva
|
Copper iris
|
2 to 3
|
18" o.c.
|
moist to wet soil
|
full sun
|
Plant individuals with other plant
massings
|
Iris virginica
|
Southern Blue Flag iris
|
2 to 3
|
18" o.c.
|
moist to wet soil
|
full sun
|
Plant in massings for best flower
effect
|
Saururus cernus
|
Lizard's Tail
|
2 to 4
|
18" o.c.
|
moist soil to shallow water
|
full to medium sun
|
|
Lower 5 feet
|
Juncus effusus
|
Soft Rush
|
2 to 3
|
18" o.c.
|
moist soil to standing water (up
to 4" deep)
|
full sun
|
Good for erosion control on moist
banks
|
Pontederia cordata
|
Pickerel Weed
|
2 to 4
|
18" o.c.
|
standing water (3" to 5" deep)
|
full sun
|
Plant in massings for best foliage/
flower effect
|
Sagittaria latifolia
|
Arrowhead
|
1 to 4
|
18" o.c.
|
wet soil to shallow water
|
full sun
|
|
Scirpus validus
|
Softstem Bulrush
|
1 to 6
|
24" o.c.
|
wet soil to shallow water
|
full sun
|
|
C.
Dominant Tree Species.
Silver Maple Acer saccharinum (not
recommended for yards and landscapes)
Sugar Maple Acer saccharum
Cottonwood Populus deltoides
Sycamore Platanus occidentalis
Box Elder Acer negundo
American Elm Ulmus americana
Slippery Elm Ulmus rubra
Hackberry Celtis occidentalis
Sugarberry Celtis laevigata
Black Willow Salix nigra
Bur Oak Quercus macrocarpa
White Oak Quercus alba
Swamp White Oak Quercus bicolor
Black Walnut Juglans nigra
Bitternut Hickory Carya cordiformis
Shellbark Hickory Carya laciniosa
River Birch Betula nigra
Kentucky Coffeetree Gymnocladus dioica
Bald Cypress Taxodium distichum Appendix
F — 2
D.
Understory Trees And Shrubs.
Sandbar Willow Salix exigua
Gray Dogwood Cornus foemina
Swamp Dogwood Cornus amonum
Pawpaw Asimina triloba
Ohio Buckeye Aesculus glabra
Red Buckeye Aesculus pavia
Horse Chestnut Aesculus hippocastanuum
Eastern Witch Hazel Hamamelis virginiana
Vernal Witch Hazel Hamamelis vernalis
Buttonbush Cephalanthus occidentalis
Spicebush Lindera benzoin
Blackhaw Viburnum Viburnum prunifolium
Shrubby St. John's Wort Hypericum
prolificum
Deciduous Holly Ilex decidua
Ninebark Physocarpus opulifolius
[Ord. No. 5852 § 2, 12-20-2012]
A. Compliance With Laws. Each applicant shall
comply with all applicable Federal and State laws as well as City
ordinances, resolutions, rules and regulations heretofore and hereafter
adopted or established.
B. Judicial Appeals. Any party shall have
the right to appeal decisions of the City Engineer to the Board of
Adjustment of the City.
C. Penalties For Violations.
1.
General. Violation of the provisions
of this Chapter or failure to comply with any of its requirements,
including conditions and safeguards established, shall constitute
an ordinance violation. Each day such violation continues shall be
considered a separate offense.
2.
Corrective Action. Nothing herein
contained shall prevent the City of St. Peters from taking such other
lawful action as is necessary to prevent or remedy any violation.
All such costs connected therewith shall accrue to the person or persons
responsible.
D. Calculation Of Time. Unless otherwise indicated,
when the performance or doing of any act, duty, matter, or payment
is required under this Chapter or any permit, and a period of time
is prescribed and is fixed herein, the time shall be computed to as
to exclude the first and include the last day of the prescribed or
fixed period of time.
E. Standard Construction Specifications Applicable
To The City. Standard construction specifications outlined herein
and adopted by this Chapter relating to storm water drainage facilities
shall be fully applicable to work performed by the City and its departments.
F. Implementation. The Standard Construction
Specifications, the Rules and Regulations and Engineering Design Requirements
for Stormwater Drainage Facilities, and the Manual of Best Management
Practices for Stormwater Quality adopted by this Chapter shall be
enforced for all developments for which the preliminary plat is approved
by the Planning and Zoning Commission after the effective date of
this Chapter, and for all single lot developments for which the site
plan is approved by the Planning and Zoning Commission after the effective
date of this Chapter. Sites previously approved that are requesting
an extension of time or a minor modification to the previously approved
plan shall be exempted from the new code requirements and shall comply
with the codes intact at the time of their initial approval. Previously
approved sites that have no infrastructure constructed and that submit
a new reconfiguration of the site shall comply with the codes adopted
herein.