[Ord. No. 01-35, 8-2-2001; Ord. No. 03-14, 4-3-2003]
A. Adequate
surface and subsurface drainage plans for the transport and detention
of storm water shall be provided by the developer. The extent to which
storm drainage facilities shall be required shall be based upon an
analysis of need prepared by a Missouri registered professional engineer.
Times of concentration, soil infiltration rates and other variable
factors to be used in the analysis shall be discussed with and approved
by the Building Department of the City of Hollister during the preliminary
consideration of the development.
1. The detention facility shall provide post development peak discharge
rates that are equal to or less than pre-development peak runoff rates
during 2-, 25- and 100-year frequency 24-hour duration storms and
an SCS type II distribution.
B. The
developer shall provide in all cases where curb and gutter is installed,
a storm water drainage system, which shall be separate and independent
of the sanitary sewer system, with surface inlets. Curb inlets shall
be sized and located to prevent gutter spread from extending beyond
the crown of the street in a 2-year frequency storm. All other drainage
system components shall be sized to convey peak flow rates for a 25-year
storm.
C. Distance From Streams. Any person proposing to locate a
structure or a use within one hundred (100) feet of the top of any
stream bank shall include a statement by a competent engineer, based
on a study of the water shed area and the probable runoff, that the
structure or use in the location proposed will leave adequate space
for the flow of floodwater, provided however, that no building shall
be permitted within fifty (50) feet of the top of the stream bank.
D. Any
development that creates a land disturbance of one (1) acre or more
in size must present proof that all required permits from the Missouri
Department of Natural Resources and the Corps of Engineers have been
obtained.
E. The
storm water control system must be designed to accept, control, detain
and discharge the post development storm water for the development,
including any other runoff that may be contributing to the discharge
of the development and meets the standards of the needs analysis.
[Ord. No. 01-35, 8-2-2001]
A. The storm water control plan must meet the criteria listed in Section
401.040 and contain adequate information to show that the design standards listed in this Section will be met.
1. Maximum allowable impervious surface coverage for development is to be considered eighty percent (80%) (see Chapter
400 for individual zoning districts).
2. The peak rate of storm water runoff at predevelopment shall be determined by a site analysis and be included as part of the control plan. The detention basin must be designed to discharge the storm water post development at a rate equal to or less than the predevelopment rate in accordance with Section
401.040(A)(1).
3. The detention basin must have adequate capacity to meet the requirements of Section
401.040(A)(1) whether it is a dry bottom basin or a wet bottom basin.
a. Wet bottom detention basins must have the required storm water holding
capacity while at normal pool.
b. Wet bottom basins will be required to have fences around them (such
as are required around swimming pools).
c. Dry bottom detention basins shall have the entire reservoir seeded,
fertilized and mulched, sodded or paved.
d. The bottom of dry bottom detention basins shall be sloped at a grade
not less than one percent (1%) toward the outlet structure.
e. Maximum berm slopes for grass-lined reservoirs shall not exceed three
(3) feet horizontal to one (1) foot vertical for maintenance reasons.
f. Detention basin berms shall have a top width of not less than three
(3) feet.
4. Parking lots may be used (if designed to do so) as dry bottom detention
basins. Maximum depth of detained water is to be eight (8) inches
or less. The detained storm water can be no closer than ten (10) feet
from any building.
5. The discharge features of the detention basins must have energy dissipaters
placed to prevent the discharge water from causing downstream erosion.
a. Low-flow pipes shall not be smaller than four (4) inches in diameter
to minimize maintenance problems, except in parking lot detention
where minimum size of opening shall be designed specifically for each
condition. The low-flow pipe shall be provided with a bar-screen to
reduce blockage by debris.
b. Sizing of the system below the control structure shall be adequate
to convey the peak design discharge from the control structure.
6. Surface storm water facilities shall be landscaped to enhance the
function and appearance of the facility. The landscaping shall be
in the form of seeded or sodded grass, ground cover, low walls, earth
berms, and/or trees and shrubs.
7. Storm drainage and detention facilities required in this Chapter
shall be maintained by the owners of the property on which the storm
drainage and detention facilities are located.
[Ord. No. 01-35, 8-2-2001]
A. A storm water control plan must meet the criteria and standards set forth in Sections
401.040 and
401.050. The actual plan maps submitted must be a minimum scale of one (1) inch equals two hundred (200) feet, show the basis of computation, and the following:
1. Required predevelopment information:
a. Detailed location sketch showing the parcel and major adjacent roads.
b. Topographic map of the site with maximum five (5) foot contour intervals.
c. Location of streams and other floodwater channels, their normal channels,
and the extent of the floodplain at the established high-water elevations,
and the limits of the floodway.
d. Location of lakes, ponds, wetlands and detention basins indicating
their normal shoreline and lines of inflow and outflow mapped to scale.
e. Location of storm, sanitary and combined sewers and outfalls, septic
tank systems, seeps, springs and wells.
f. Location and description of nearby existing off-site water management
facilities (wells, lakes, drainage ways) that are potentially directly
affected by the proposed development.
2. Show all existing drainage facilities that are to be maintained,
altered or enlarged as part of the storm water control system; provide
sizes, slopes, depths, outfalls, receiving waters, elevations, cross
sections, profiles, materials and other applicable design details.
3. Location of new storm water control facilities, including detention
basins, to be constructed. Provide design details.
4. Provide grading and paving plans and specifications including the
proposed impervious surfaces and elevations.
5. Location and extent of right-of-ways and easements for the storm
water control system.
6. List any special or required maintenance procedures to keep the project
functioning as designed.
7. Provide storm water control system calculations as follows:
b. Inflow and outflow of design storm runoff for the predevelopment
watershed.
c. Runoff from the site post-development.
d. Detention basins' storage volume, water surface elevation, and outflow
rates for those water elevations.
e. Acreages and percentage of property proposed as:
(2)
Green space (pervious surface).
(a)
Detention basins, canals, ponds, etc.
(b)
Total acreage of the project.
f. Minimum building and road elevation.
8. List the entity responsible for maintenance of the storm water control
system.
9. The Building Director and the Public Works Director will review and
determine the completeness of the submitted storm water control plans.
The permit may be approved, approved with conditions, or denied. If
the permit is denied or approved with conditions, the reason for denial
or specific conditions shall be stated in writing. If the applicant
is denied a permit, they may file a request for variance from the
required specification. The Board of Adjustment shall hear this request.