The Planning Commission shall not recommend approval of any Final Plat which does not make adequate provision for storm water for both flood water runoff control and water quality control including, but not limited to channels, catch basins, drywells detention ponds, retention facilities, low impact development and surface water treatment. Plans shall be reviewed for compliance with the Hooper City Development Standards and Specifications, or other standards as may be adopted. The storm water drainage system shall be separate and independent of the sanitary sewer system, the land drain system, and any other system. Storm drains, where required, shall be designed in accordance with the criteria provided below and a copy of design computations and water quality report in accordance with the City’s Low Impact Development Handbook shall be submitted along with Construction Drawings. Inlets shall be provided so that surface water is not carried across or around any intersection, nor for a distance of more than four hundred (400) feet in gutters, regardless of the calculated gutter capacity. When calculations indicate that gutter capability is exceeded, catch basins shall be used to intercept flow. Catch basin shall be used to collect and convey storm water at intersections. Surface water drainage patterns of the project site shall be shown on a Grading and Drainage Plan defined later in this chapter. In conjunction with the preparation of the Grading and Drainage Plan, the City Staff may require the applicant to meet with the Hooper City Public Works Director and others as needed in order to gain an understanding of existing upstream and downstream storm drainage, field drainage, and irrigation run-off issues so that these important considerations can be incorporated into the Plan. If the meeting is required, the Planning Commission shall not recommend Final Plat approval if this meeting has not occurred. The applicant may be required by the Planning Commission, upon the recommendation of the City Staff, to carry away by pipe or open channel (Hooper or Howard Sloughs) any spring or surface water that may exist either previously to, or as a result of the development. Such drainage facilities shall be located in the road right-of-way where feasible, or in approved perpetual unobstructed easements of appropriate width and length, and shall be constructed in accordance with the development standards and specifications. Hooper City will not maintain storm drain facilities located on private property or beyond the City’s right-of-way, including rear-lot drainage facilities, even those located within public utility easements. Underground storm drain systems shall be constructed throughout the development and be connected to an approved out-fall. No outfall will be approved which does not allow for gravity flow to a discharge point that is high enough in elevation to prevent surcharging into the development’s drainage system. In addition, the City reserves the right to dictate flowline elevations in the storm drain system that allow for an appropriate level of “freeboard” in the storm drain system or to pass “nuisance” water at a control structure. Inspection of facilities within the City’s right-of-way shall be conducted by the City. If a future connection to a public storm drain will be provided, as determined by the City Staff, the developer shall make arrangements for future storm water at the time the plat receives final approval. Provision for such connection shall be incorporated into the development plans. No development shall be approved unless adequate drainage will be provided to an approved drainage watercourse or facility as determined by the City Staff based upon approved pipeline slopes and flowline elevations

1. Accommodation of Upstream Drainage Areas Culverts or other drainage facilities shall be large enough to accommodate potential runoff from the entire upstream drainage area, whether inside or outside the development. The proposed drainage facilities shall be designed so that there is no negative impact on the upstream drainage through pipe size restrictions, abrupt grade changes, reverse grade, and so forth. The developer shall hire a qualified engineer to determine the necessary size of the facility, based on the provisions of the development standards and specifications assuming conditions of a ten-year year storm event for pipeline design and a one-hundred year storm event for detention basin design. The pipeline design shall also include capacity for other water from other sources besides storm events. The City Staff shall review and approve the design. Offsite drainage improvements, completed at the developer’s expense, may be required in order to preserve the integrity of the existing drainage system.
2. Effect on Downstream Drainage Areas To determine the effect the development will have on existing downstream drainage facilities outside the project area, the developer shall submit a storm water drainage study prepared by a qualified engineer. City and County storm drainage studies, together with the City’s Storm Drain Master Plan, may serve as a guide to determine needed improvements. Where it is anticipated that the additional runoff will overload an existing downstream drainage facility, the Planning Commission may require the applicant to improve the facility in order to serve the development or provide additional on-site drainage facilities.
3. Flood Plain and Low Elevation Areas The Planning Commission may, upon recommendation of the City Staff when determined necessary for the health, safety, or welfare of the present and future population of the area and for the conservation of water, drainage, and sanitary facilities, prohibit the development of any portion of the property which lies within the flood plain of any stream, lake or drainage course, or areas low in elevation having evidence of standing water or high groundwater. These flood plain and low-lying areas should be preserved from any and all disturbance or damage resulting from clearing, grading, or dumping of earth, waste material, or vegetative debris.
4. Dedication of Drainage Easements Where a development is traversed by a watercourse, drainage way, or channel, , there shall be provided a storm water easement or drainage right-of-way conforming substantially to the historic high water lines of such watercourse, as determined by the City Staff. Watercourses, drainageways, and channels shall be piped, with the exception of the Hooper and Howard Sloughs, it is desirable that these sloughs be maintained by an open channel with landscaped banks. Where topography or other conditions make the inclusion of drainage facilities within road rights-of-way impractical, perpetual unobstructed easements at least twenty (20) feet in width for such drainage facilities shall be provided across property outside the road right-of-way lines. This requirement applies to piped drainage channels as well, with the final width, length, access surface, and location of the easement to be approved on a case-by-case basis. Such easements shall include satisfactory access to the road. Easements shall be indicated on the Final Plat and be dedicated to Hooper City, or other applicable entity. Drainage shall be carried from the road to a natural watercourse or to other approved City drainage facilities. When a proposed drainage system will carry water across private land outside the development or to a private drainage facility, appropriate drainage easements and agreements must be secured during the Preliminary Plat phase of development and indicated on the plat. The applicant shall dedicate to the City or other appropriate agency, by drainage or conservation easement of land on both sides of existing watercourses, to a distance to be determined by the Planning Commission and City Staff.
5. Drainage Ways and Irrigation Ditches All existing drainage ditches within, abutting or adjacent to subdivisions or development, or impacted by new development, shall be piped in accordance with development standards and specifications. Notification and approval from irrigation companies for development may be required in certain circumstances as determined by the City if the development impacts irrigation works uses or access.
6. Drainage Facilities All drainage facilities as herein required shall include considerations for both flood control and water quality control.
   1. Flood control facilities shall be based upon estimates of peak and total discharges. Flood control facilities shall be designed by the Rational Method, or other methods as approved by the City Engineer. Flood control plans are to facilitate a 10-year, 1-hour storm event for pipeline design and a 100-year storm event for detention basin design. An off-site discharge rate to an approved storm drain outfall of 0.15 cfs per acre is the maximum allowed.
   2. Detention basins are flood control facilities, and the design shall incorporate “bypass” or “short circuit” control boxes in lieu of “pass through” detention basin which shall not be approved. The control box will allow design storm flows and “nuisance” water to pass and will only fill the detention basin if the design storm is exceeded. An overflow shall also be included in the control box to prevent overtopping of the detention basin. Detention basin shall be landscaped in accordance with City landscaping standards and specifications.
   3. Water quality control facilities shall be designed and constructed in accordance with the Hooper City Low Impact Development Handbook (handbook) and will consider both retention and water quality treatment methods as prescribed in the handbook.
   4. Retention facilities are water quality facilities, and the design shall include measures targeted at mimicking predevelopment hydrologic discharge conditions.
7. Grading and Drainage Plan
   1. The applicant shall submit a drainage plan to the City Staff prior to preliminary plat approval.
      1. Upon review and acceptance of the drainage plan, the City may approve the final plat.
      2. No grading, filling, clearing, or excavation of any kind shall be initiated until the City approves the drainage plan and an excavation permit, if required, is obtained from the Hooper City Public Works Director.
   2. The drainage plan shall be drawn to scale and shall include, but not be limited to, the following:
      1. Topography at 2-foot intervals. The proposed grading shall be indicated by solid-line contours superimposed on dashed-line contours of existing topography. In case of predominantly level topography throughout a development, one-foot (1’) contour intervals may be required.
      2. North arrow, road and lot layout, and development name.
      3. Location of all existing water courses, canals, ditches, land drains, springs, wells, culverts and storm drains.
      4. The flood hazard zone(s) if the development is in an area of special flood hazard.
      5. Wetlands delineation, if applicable.
      6. Essential elements, alignments, and functions of the proposed drainage system including, but not limited to, inlets, outlets, catch basins, manholes, , culverts, detention basins orifice plates, pumps, water quality features, retention and infiltration facilities necessary, outlets to off-site facilities, and off-site facilities planned to accommodate the project drainage.
      7. The drainage plan shall indicate by flow arrows, contours, spot elevations, or some other acceptable manner, where storm water will be routed for the property. It must show the location and size of any flows onto the site from outside the property boundaries as well as any discharges leaving the site. The drainage plan must be prepared in a way that prevents run-off onto adjacent properties. Rear-lot drainage facilities may be approved as an option but is rarely an acceptable alternative to grading with imported fill and/or retaining structures. The City does not maintain private rear-lot drainage facilities.
      8. When drainage courses and irrigation facilities exist on-site, the owner and/or applicant shall provide documentary evidence of consent to re-routings by all interested landowners and drainage and irrigation entities affected and having rights to, and in, such facilities; and
      9. Other supplemental data as may be required by the City Staff.