[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:
a. 
Design storm used.
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:
(1) 
Impervious surfaces.
(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.