[R.O. 1992 § 420.020; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
No person shall construct, alter,
relocate, remove, or destroy any ditch, drain, or drainage structure
upon any real property within the City, whether subdivided or not,
without complying with this Chapter.
[R.O. 1992 § 420.025; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
No person shall alter the contours
of any real property within the City, whether subdivided or not, so
as to change the flow of water into or through any ditch, drain, or
drainage structure without obtaining a permit and complying with the
provisions of this Chapter.
[R.O. 1992 § 420.030; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
A. No person shall commence any construction,
substantial improvement or other development that affects the drainage
of surface or subsurface water without first obtaining a building
permit and grading permit (if applicable) from the Department of Public
Works. No permit shall be issued for any proposed alteration which:
1.
Will increase the amount and/or rate,
or adversely affect the quality, of surface water draining onto other
properties;
2.
Will damage other properties;
3.
Does not conform to the general drainage
laws of the State, the ordinances of the City, and, in particular,
the rules, regulations, and standards of this Chapter; and
4.
Alters or removes wetlands from their
present location without City, State, Federal permits as may be required.
[R.O. 1992 § 420.035; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
A. Sediment And Erosion Control Standards.
1.
General. Sediment and erosion control
will be accomplished by applying conservation practices that will
reduce the potential for damage from these hazards. Control practices
use trapping, filtering or diversion techniques to protect adjacent
properties from land disturbance activities.
2.
NPDES Stormwater Permits. Construction
sites, where the area to be disturbed is one (1) acre or more, must
apply for a stormwater discharge permit from the Missouri Department
of Natural Resources. If required, the applicant must obtain and submit
proof of an NPDES stormwater permit to the City, before plans will
be approved. Permit requirements are set forth in 10 CSR20-6.200 of
the Missouri clean water laws.
3.
When Controls Are Required. Sediment
and erosion control shall be implemented whenever necessary, in the
opinion of the City Engineer, to prevent damage to off-site property,
drainage facilities or watercourses. Generally, standard vegetative
and structural practices, as specified below, that filter, divert
or promote the settlement of sediment particles from storm runoff
shall be provided in the following situations:
a.
To prevent sediment-laden runoff
from leaving disturbed areas.
b.
To isolate disturbed areas from erosive
surface runoff associated with significant undisturbed areas.
c.
To protect storm drainage conveyance
systems at operable inlets.
4.
Types Of Controls.
a.
The stormwater management plan shall
be selected, installed, operated and maintained to adequately control
erosion, capture sediment and prevent pollution. To achieve these
goals BMPs in accordance with the concepts and methods described in
either of the following two (2) documents should be utilized.
(1) Protecting Water Quality,
MDNR (Latest Edition).
(2) Field Manual on Sediment
and Erosion Control BMPs. Jerald S. Fifield, Ph.D., CPESC, Forester
Press, Latest Edition.
b.
The developer is not limited to the
use of BMPs identified in the above publications. Engineering professionals
are encouraged to design innovative ways to address site specific
conditions.
5.
Filter Strip. Clearing and grubbing
within twenty-five (25) feet of the top of an existing stream bank
should be avoided. If the twenty-five-foot filter strip is disturbed,
site specific erosion controls that protect the stream bank shall
be implemented.
6.
Construction Plans.
a.
The applicant shall submit a sediment
and erosion control plan which must be approved by the City Council
prior to preliminary plat approval. The plan shall include a contoured
development map clearly indicating the pattern of surface water runoff,
both upstream and downstream of the development, the existing and
proposed grading contours and the planned sedimentation and erosion
control facilities. The phasing of construction activities shall be
presented. Such phasing shall identify the sequence of construction
activities and the related BMPs to include clearing, installing BMP,
rough grading, installing utilities, paving streets, final grading
and vegetative cover.
b.
The City Council shall have authority
to require proper controls as specified herein. The City Engineer
may require a revised plan to be submitted for approval at any time
due to changing site conditions.
B. Design Criteria.
1.
Purpose. A development's stormwater
drainage system shall be designed to:
a.
Protect natural waterways.
b.
Convey upstream and on-site stormwater
runoff to a natural watercourse or to a storm drainage facility.
c.
Provide protection from the design
storm event and address the major storm so as to prevent major property
damage and loss of life.
2.
Rainfall Frequency. All facilities
shall be designed to carry a ten-year storm of a duration which produces
the maximum peak flow rate of stormwater runoff. The stormwater conveyance
system shall be designed to allow for a 100-year storm to pass through
the subdivision without destroying or damaging property or inundating
dwellings. Design information which substantiates both conditions
shall be provided. See Figure A for rainfall curves for the two-,
five-, ten-, fifteen-, twenty- and 100-year frequencies.
3.
Calculation Of Runoff.
a.
The method of calculating and routing
stormwater runoff shall be as stated herein. The drainage area shall
consider all on- and off-site lands contributing to the proposed development's
drainage system. Capacity for such facilities shall be based on the
maximum potential water shed development permitted by the Zoning Ordinance.
b.
Either the Rational Method or the
TR-55 Method for calculating stormwater runoff may be used for watersheds
up to ten (10) acres.
c.
Figures A (rainfall intensity - referenced
above) and B (runoff factors) shall be utilized with the Rational
Method.
d.
For watersheds larger than ten (10)
acres, the SCS TR-55 Method shall be utilized. Other methods to determine
peak runoff must be approved by the City Engineer prior to acceptance.
e.
The minimum percentage of imperviousness
to be used in design shall be based on the zoning district as shown
in the following table:
Zoning District
|
Minimum Percentage Impervious
|
---|
Pre-developed
|
5%
|
R-1A Single-Family
|
45%
|
R-1B Single-Family
|
50%
|
R-1C Single-Family Attached
|
50%
|
R-1D Single-Family
|
50%
|
R-2 Two-Family
|
60%
|
R-3 Multiple Family
|
70%
|
C-1 Limited Commercial
|
85%
|
C-2 General Commercial
|
85%
|
C-3 Central Commercial
|
90%
|
M-1 Industrial
|
90%
|
M-2 Industrial
|
90%
|
PD Planned Development Districts
|
TBD based on plan type
|
Parking, streets, roofs
|
100%
|
f.
The minimum percentage of imperviousness
for Planned Development Districts shall be dictated by the development
plan proposed for the specific district.
g.
Special uses, such as schools, churches,
etc., shall have the differential runoff computed and approved by
the City Engineer.
h.
Special circumstances may dictate
that the developed impervious area may differ from that shown in the
above table. An example may be single-family lots of larger than ten
thousand (10,000) square feet. Calculations prepared by a registered
professional engineer may be submitted to the City Engineer for his/her
evaluation to determine if a minimum impervious area which differs
from that shown in the above table may be utilized. Likewise, the
City Engineer may determine that the percent of impervious area for
a particular development differs from that shown in the above table.
i.
See Figure B for the runoff factor to be utilized for various impervious
conditions and rainfall durations.
4.
Open Channels.
a.
Open channels consist of swales,
ditches or depressions, both natural and man-made, that convey water.
Channels shall be protected from scour and erosion by providing a
channel lining adequate to sustain the velocity of the ten-year design
storm. If velocities in channels exceed five (5) feet per second during
ten-year design storms, then erosion control other than vegetation
shall be provided in channel construction. Total accumulation contained
by man-made berms/swales shall be a maximum of four (4) cubic feet
per second.
b.
Manning's Equation shall be used
for calculating the hydraulic capacity of open channels.
c.
Acceptable improvements to channels
include fabrics, gabion lining, concrete channels, concrete slope
paving, cribbing, bin walls, etc. The roughness coefficient for each
material shall be per manufacturer or as indicated below:
n= Amount
|
Channel/Pipe Type
|
---|
0.012
|
For cast-in-place concrete, box culverts
and reinforced concrete pipe (RCP) over 48 inches in diameter
|
0.013
|
For concrete pipe less than 48 inches
in diameter
|
0.015
|
For vitrified clay pipe
|
0.020
|
For grouted rip rap
|
0.024
|
For corrugated metal pipe
|
0.033
|
For gabion walled channels
|
d.
Channels shall have the hydraulic
capacity to carry the ten-year design storm runoff within the channel
bed and banks. Out-of-bank flow may be permitted on land slopes parallel
to the channel where it can be shown that no erosion damage or serious
property damage will result. Channels function as part of the major
drainage system and shall be evaluated for the 100-year design storm
to determine the impacts of runoff on adjacent property. The channel's
hydraulic capacity shall be increased where adjustments to channel
geometry provide significant protection to adjacent properties during
the 100-year event.
5.
Closed Conduit Storm Sewers.
a.
Pipe sizes for closed conduit flow
shall be based on the ten-year design storm runoff and minimum allowable
velocities. The system shall provide for the cleaning of sediment
and other deposits by maintaining a minimum velocity of three (3)
fps during the ten-year storm.
b.
Manning's Equation, the most common
method of estimating the capacity and flow resistance in closed conduits,
shall be utilized.
c.
Closed conduit storm sewer systems
shall convey the ten-year design storm to a point of discharge by
gravity or pressure flow. In surcharge conditions, the hydraulic grade
line shall be calculated to reflect losses in pipes and structures
and shall not rise to an elevation greater than the three (3) feet
above the top of the sewer or two (2) feet below the inlet sill, whichever
is lower.
d.
Generally, gravity flow occurs where
the capacity of pipe run exceeds the design flow and the outfall point
does not control discharge. Storm sewer systems may be designed for
pressure flow when the hydraulic grade line is above the crown of
the pipe. The decision to design a pressure flow system may be based
on aesthetics, the need to submerge outfalls, economics, limitations
associated with reduced pipe sizes or grade constraints in outfalling
the system.
6.
Inlets. Calculations shall be submitted
to demonstrate the capacity of all inlets. Such calculations must
consider the cross-slope of the pavement, depth of water at the curb
face, size of opening and the longitudinal grade of street. Street
inlets and inlets in parking areas shall reduce the spread and depth
of flow to acceptable levels during the ten-year design storm. The
acceptable level of flow for a minor access or local access street
would maintain an eight-foot travel lane with a maximum one-inch depth.
One clear ten-foot travel lane must be maintained for a collector
street, and two (2) clear ten-foot travel lanes must be maintained
for a major street. Any area inundated by water ponding at an inlet
during the ten-year storm event shall be located within an easement
or right-of-way. The effects of the 100-year storm event shall also
be analyzed to ensure no property damage or dangerous conditions result.
Inlets located on continuous grades may be designed to permit a portion
of flow to bypass the structure; however, calculations for the downstream
structure must consider the bypass.
7.
Plans And Calculations.
a.
A drainage map shall be developed
from a base reproduction of the site plan or grading plan. The existing
and proposed contours shall be shown, normally at two-foot intervals,
for the subject property, extending off-site one hundred (100) feet
or less as determined by the Department for proper design of the proposed
improvements. Contour intervals other than the above shall be used
as determined by the site topography. Only United State Geological
Survey datum shall be used. Locations and elevations of bench mark
references are available from the Engineering Department.
b.
The location of existing and proposed
property lines, streets, sinkholes, railroads, areas within the tract
subject to inundation by stormwater and other significant natural
features, such as wooded areas and rock formations, etc., shall be
included on the map. All existing and proposed stormwater facilities,
such as inlets, manholes, pipes, culverts, bridges, channels, etc.,
and all existing and proposed improvements required for proper design
review, such as pavement, buildings, etc., shall be included on the
map.
c.
The runoff details shall be required,
showing individual flows for each existing and proposed structure
and cumulative flows in pipes and gutters, including "Q" and area.
The map shall show all bodies of water, such as ponds or lakes (including
surface area and elevation) and all waterways (including their names
or the names of creeks or rivers they flow into).
d.
Lots shall be laid out so as to provide
positive drainage away from all buildings. Individual lot drainage
shall be shown and coordinated with the drainage pattern for the area
and designed so that runoff from one (1) lot will not adversely affect
an adjoining lot. All necessary grading to direct stormwater runoff
shall be located within a drainage easement.
e.
All computations, plans and specifications
related to the implementation of this Section must be prepared and
sealed by a professional engineer registered in the State of Missouri.
E. Detention And Retention Facilities.
1.
Maintenance.
a.
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 for 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 goes to vested property owners within the subdivision.
b.
The final plat of the subdivision
shall contain language substantially as follows: "The owner of each
lot within this subdivision shall maintain the stormwater management
system serving this subdivision unless the stormwater management system
has been accepted for maintenance by the City of Washington, Missouri.
The maintenance costs shall be shared equally with each owner of any
lot served by the stormwater management system." There shall also
be recorded with the final plat of the subdivision deed restrictions
containing the same language.
c.
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.
d.
All such privately owned and maintained
systems shall be subject to periodic inspection by the City Engineer
or his/her representative. The City of Washington, Missouri, may,
upon failure of the responsible party to maintain the systems, maintain
the system and charge the cost thereof against the responsible party.
The costs shall be certified to the City Clerk who shall cause a special
tax bill therefor against the property to be prepared and to be collected
by the Collector with other taxes assessed against the property. The
special tax bill from the date of its issuance shall be a first lien
on the property until paid and shall be prima facie evidence of the
recitals therein and of its validity and no mere clerical error, informality
in the same or in the proceeding leading up the issuance shall be
a defense thereto. Such tax bills if not paid when due shall bear
interest at the rate of eight percent (8%) per annum.
e.
A proper access easement to such
stormwater management systems shall be provided, and a minimum ten-foot
wide hard surface designed to support construction traffic with a
maximum twelve percent (12%) grade shall be provided within such easement.
A permeable, flexible plantable concrete block pavement system is
preferred in residential areas.
2.
Storage Capacity.
a.
The rates (pre-developed and post-developed)
of runoff shall be determined for the two-, twenty- and 100-year rainfall
frequencies. The storm duration shall be the twenty-four-hour event
when the SCS TR-55 method is utilized and a minimum twenty-minute
event when the Rational Method is utilized. Rainfall data shall be
determined using the most current twenty-four-hour rainfall data published
by the National Weather Service (NWS) Technical Paper 40 (TP40).
b.
Stormwater shall be detained on site or adjacent property under agreement and metered out at the rate of an undeveloped site for the above frequencies and minimum duration to prevent possible flooding and erosion downstream. Design criteria to establish this differential runoff rate shall be as provided in Subsection
(B), Design Criteria. Note that stormwater pipes shall be sized to carry the total developed tributary upstream water shed. No reduction in pipe size shall be permitted because of detention.
c.
Detention basin volume will be based
on providing adequate storage for the 100-year storm event of the
required duration. Each post-developed runoff hydrograph (two- and
100-year) shall be routed through the detention facility while satisfying
the appropriate allowable release rate. The routing computation shall
be based on an application of the continuity principle. The discharge
rate shall be based on the maximum head conditions in the detention
facility.
3.
Shared Facilities And Regional Detention.
The City retains the right to require on-site detention storage in
all cases in which the proposed development will generate excess runoff
that adversely affects the carrying capacity of the receiving watercourse
and/or adversely affects adjoining property owners. In certain cases
the applicant may make use of off-site or regional detention facilities,
in lieu of on-site facilities, as described below:
a.
Off-Site facility, two (2) or more
developments: if two (2) or more developments, including that of the
applicant, have provided for a common system.
b.
Off-site facility by City: if an off-site stormwater management system has been either constructed or programmed or identified for construction by the City and the applicant has agreed to contribute to or participate in the construction thereof. Such contribution shall be determined per the following Subsection
(E)(3)(b)(1).
(1) Stormwater Management
Fund.
(a) Eligibility. It is determined that no immediate adverse effects will result to adjacent property and a contribution is made to the Stormwater Management Improvements Fund. Such fund is described in Subsection
(E)(3)(b)(1)(c), Establishment Of Fund, below. Developments which have a differential runoff of three (3) cfs or less for the ten-year, twenty-minute event utilizing the Rational Method will be considered as prime candidates for a contribution in lieu of on-site detention. It is the City's intention to provide regional detention storage to accommodate these smaller developments. The City Council will render all decisions concerning participation in the Stormwater Management Fund.
(b) Contribution. The contribution
shall be an amount equal to a cost estimate prepared by a professional
engineer for site specific improvements necessary to provide detention
as provided herein. Such estimate shall not include the cost of any
land necessary for detention purposes. All cost estimates for site
specific detention facilities shall be subject to review and approval
by the City Engineer. The developer may request that the City Engineer
provide the necessary cost estimate.
(c) Establishment Of Fund. The Stormwater Management Improvements Fund shall be and is hereby created. Said fund shall be reserved for funding improvements to stormwater systems owned and maintained by the City and for no other purposes unless authorized in the ordinance. All contributions made by parties developing within the City in accordance with Subsection
(E)(3) of this Section shall be deposited to said fund. Said fund shall be deposited in an interest-bearing account.
c.
Other Management Techniques. Management
techniques other than detention facilities may be utilized by the
development, provided that the techniques proposed meet the intent
of this Section and provide a benefit to the watershed that equals
or exceeds the benefit that a detention facility would provide. Such
techniques would include pervious pavement systems and improved vegetation
conditions.
4.
General Design Features.
a.
Dry Bottom Basins. A stormwater detention
facility, natural or artificial, which normally drains completely
between spaced runoff events, 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. The following features shall
be incorporated into the design of any detention basin:
(1) 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.
(2) 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.
(3) 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.
(4) Emergency Overflow/Spillway.
Emergency structures shall be provided to permit the safe passage
of runoff generated in excess of the 100-year design storm event.
Antivortex measures shall be provided.
(5) Maximum Depth. The maximum
planned depth of stormwaters stored shall not normally exceed five
(5) feet.
(6) Side Slopes. The maximum
side slopes for gassed basins shall not normally exceed one (1) foot
vertical for three (3) feet horizontal.
(7) Limits Of Ponding. In
no case shall the limits of maximum ponding be closer than thirty
(30) feet horizontally from any building and less than two (2) feet
vertically below the lowest sill elevation.
(8) Interior Drainage. The
basin should be designed to drain within a twenty-four-hour period.
Flows through the detention basin should be handled by paved ditch
from inflow structure to outflow structure to minimize erosion.
(9) Multipurpose Basin.
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.
(10) Aesthetics. Designs
should result in aesthetically pleasing configurations which will
enhance public acceptability.
b.
Wet bottom basin: a stormwater retention
facility, natural or artificial, which maintains a fixed minimum water
elevation between runoff events. Wet bottom basins may also be used
to temporarily detain the differential runoff from the development.
In addition to the general design features enumerated above for dry
bottom basins, the following features should also be incorporated
into the design of any wet bottom basin:
(1) Normal Pool Depth. In
order to minimize weed growth, the normal pool depth should be four
(4) feet minimum.
(2) Depth For Fish. If fish
are to be kept in the pond, at least one-fourth (1/4) of the area
of the permanent pool should have a minimum depth of ten (10) feet.
(3) Facilities For Emptying.
In order to ease cleaning of the pond or shoreline maintenance, the
pond design should include provisions for emptying the pond.
(4) Low Flow By-Pass. The
design of any pond may include a low flow by-pass channel or pipeline
to divert runoff that can be accommodated by downstream drainageways.
(5) Side Slopes Below Normal
Pool. The side slopes below the normal pool elevation may exceed the
maximum side slope permitted above normal pool (3:1 slope). The design
shall, however, include provisions for a safety ledge having a depth
of water not greater than three (3) feet immediately adjacent to the
shoreline.
(6) Forebay. In order to
minimize siltation of the pond, a forebay should be included in the
design. Calculations for sediment volume and forebay sizing shall
be submitted to the City Engineer.
c.
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 down drains, and elevations of overflow provisions. Direct connection
of roof drains to sanitary sewers is prohibited.
d.
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. Depth of storage shall be a
maximum of eight (8) inches.
e.
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. Emergency overflow conditions shall be considered in all methods.
5.
Plans And Calculations.
a.
The following must be submitted for
the design of a detention facility:
(1) Elevation versus discharge
relationship for the basin.
(2) Elevation versus storage
relationship for the basin.
(3) Inflow calculations
and data for all required frequencies.
(4) Hydraulic grade line
computations for pipes entering and leaving the basin for all required
frequencies.
(5) Site plan with two-foot
contours showing land to be developed and adjoining land whose topography
may affect the layout or drainage of a basin site and the location
of streams and other runoff channels.
(6) Basic information regarding
the receiving watercourse and affected downstream structures to a
distance of two hundred (200) feet from the site. Additional analysis
of the receiving stream of greater distances from the site shall be
performed if required by the City Engineer.
(7) A summary of routing
calculations for all required frequencies.
b.
All computations, plans and specifications
related to the implementation of this Section must be prepared and
sealed by a professional engineer registered in the State of Missouri.
F. Material And Construction Standards.
1.
Storm pipes shall be protected from
excessive bearing pressures by placing them outside the forty-five-degree
influence zone of building structures unless an engineering calculation
shows the pipe material or soil condition to be adequate for the subjected
load.
2.
Pipes on slopes of twenty percent
(20%) or greater shall be anchored securely with concrete anchors
or equal to prevent the pipe from creeping downhill.
3.
Pipes or structures constructed on
fill shall be stable and protected against settlement by compacting
fill material to ninety-five percent (95%) of the modified proctor
maximum dry density, per AASHTO T180 (ASTM D1557).
4.
Pipes thirty-six (36) inches or larger
may be placed on a curved alignment utilizing alignment radii established
by the pipe manufacturer.
5.
The receiving surface where pipes
discharge shall be protected from erosion by evaluating the discharge
velocity for the ten-year design storm. The use of energy-dissipating
devices may be necessary to reduce the velocity to acceptable levels
for the receiving surface. Grouted revetment used shall be a minimum
length of ten (10) times the diameter of the discharge pipe.
6.
A manhole, inlet or junction box
shall be located at changes in pipe size, grade, alignment or material.
7.
The angle between influent and effluent
pipes shall be not less than ninety degrees (90°) and the drop
between inverts shall be not less than one-tenth (0.1) foot.
8.
Manhole and inlet castings located
in travel ways shall be capable of withstanding traffic loads and
shall be constructed flush with the finished surface.
9.
All materials and appurtenances for
stormwater management systems shall conform to current standards of
the American Society for Testing and Materials (ASTM).
10.
Manholes shall be precast or cast-in-place
concrete, brick, concrete block, with concrete or brick risers and
approved manhole covers.
11.
A new drainage channel or pipe shall
intersect an existing drainage channel at a maximum angle of sixty
degrees (60°).
12.
All trenches under roadway pavement
shall be backfilled with Missouri Department of Transportation (MoDOT)
Type I aggregate in six-inch layers and compacted to ninety-five percent
(95%) of the modified proctor maximum dry density per AASHTO T180
(ASTM D1557).
13.
All piping shall be bedded per the
manufacturer's requirements.
14.
Grated inlets will not be allowed
without special approval by the City Engineer.
15.
All materials used in the construction
of storm sewers shall be subject to inspection and approval of the
City Engineer.
16.
Acceptable pipe material is as follows.
a.
Reinforced concrete pipe shall conform
to the requirements of the Specifications for Reinforced Concrete
Culvert, Storm Drain and Sewer Pipe, ASTM C76. Strength class or classes
shall be as required per design specifications of the latest edition
of the Concrete Pipe Handbook as published by the American Pipe Association.
b.
Corrugated metal pipe shall conform
to the requirements of AASHTO M36, Standard Specification for Zinc
Coated (Galvanized) Pipe, or the Standard Specifications for AASHTO
M196 Corrugated Aluminum Pipe. Structural design requirements shall
be per the latest edition of the Handbook of Steel Drainage and Highway
Construction Products, as published by the American Iron and Steel
Institute.
c.
Corrugated polyethylene pipe shall
conform to the requirements of AASHTO M294, Standard Specifications
for Corrugated Polyethylene Pipe. All polyethylene pipe should be
installed according to ASTM D2321, Standard Practice for Underground
Installation of Thermoplastic Pipe for Sewers and Other Gravity-Flow
Applications.
d.
Dual wall and triple wall polypropylene
pipe shall conform to the requirements of AASHTO M330 "Standard Specification
for Polypropylene Pipe" and ASTM F2881 for sizes 12" to 30" and ASTM
F2764 for sizes 30" to 60". All polypropylene pipe shall be installed
according to ASTM D2321 "Standard Practice for Underground Installation
of Thermoplastic Pipe for Sewers and Other Gravity-Flow Applications"
and shall meet MoDOT "Standard Specifications for Highway Construction"
Section 724 Pipe Culverts specifications.
[Ord. No. 22-13620, 9-19-2022]
17.
Reinforced concrete pipe and corrugated polypropylene complying with the provisions in Section
420.035(F)(16), above, shall be required under road pavement.
18.
A minimum pipe size of twelve (12)
inches is required to prevent blockage.
19.
All construction details pertaining
to stormwater drainage shall be in accordance with the Metropolitan
St. Louis Sewer District requirements and standards for construction
of sewers and drainage facilities, unless otherwise noted herein.
[R.O. 1992 § 420.040; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
A. Purpose And Intent: to provide erosion
control measures for disturbed areas in order to prevent sedimentation
that is carried by stormwater during construction activities.
B. Applicability. The standards and criteria
contained within this Section are deemed to be minimum standards and
shall apply where natural vegetation is removed during grading operations.
When grading operations are substantially complete or have been suspended
for thirty (30) days, revegetation shall occur. Such revegetation
shall meet the below criteria for either temporary or intermediate
seeding.
C. Enforcement. The provisions of this Section
shall be administered and enforced by the Director of Public Works
or authorized representative. If at any time after the issuance of
a grading permit, development plan approval or preliminary plat approval
the revegetation does not conform to the standards and criteria in
this Section, a notice shall be sent to the owner citing the violation
and describing what action is required to comply with this Section.
The owner shall have thirty (30) days from date of said notice to
restore vegetation as required. If the vegetation is not restored
within the allotted time, such person shall be in violation of this
Section. It is the responsibility of the owner of the property to
comply with these requirements.
D. Penalty. Failure to comply with the provisions within Section
420.035 shall be subject to penalties as outlined under Section
400.035 of the Washington Municipal Code.
E. Financial Assurance. No permit shall be
issued for grading, development plans or preliminary plat approval
for any site for which revegetation is required by this Section until
such sediment and erosion control plan has been submitted and approved
by the Director of Public Works or authorized representative. Financial
assurance must be given by the developer/property owner for one hundred
thirty percent (130%) of the estimated cost of the revegetation plan.
F. Sediment And Erosion Control Plan. Where
natural vegetation is removed during grading operations, it shall
be replaced as specified herein. The sediment and erosion control
plan shall indicate the proposed phasing of the project to include
conveyance systems, detention facilities, clearing, rough grading
and construction, final grading, landscaping. When grading operations
are substantially complete or have been suspended for thirty (30)
days, revegetation shall occur. Such revegetation shall meet the below
criteria for either temporary or intermediate seeding.
1.
Temporary Seeding. This is the establishment
of fast-growing annual vegetation to provide economical erosion control
for up to twelve (12) months and reduce the amount of sediment moving
off the site. This practice applies when the landscape is anticipated
to be disturbed within the next twelve (12) months. The required application
rates are as follows: one (1) bushel of wheat or oats per acre; 10-20-10
fertilizer at four hundred (400) pounds per acre; eighty (80) to one
hundred (100) bales of straw mulch per acre.
2.
Intermediate Seeding. This is the
establishment of perennial vegetation on disturbed areas for periods
longer than twelve (12) months. This type of vegetation provides economical
long-term erosion control and helps prevent sediment from leaving
the site. The required application rates are the same as for temporary
seeding with the addition of forty (40) to fifty (50) pounds per acre
of fescue grass seed. The application of fescue is not required during
the period of May 15 to August 15. However, it shall be applied as
soon as weather conditions permit following August 15.
G. Reseeding. Reseeding shall occur at any
time at the direction of the Director of Public Works if necessary
to obtain the desired erosion control benefits. Vegetation types other
than those specified herein may be utilized upon approval of the Director.
H. Minimum Requirements. The criteria established
herein are the minimum requirements for erosion and sediment control.
The owner may at any time establish permanent vegetation which exceeds
these requirements.