Loading...
HomeMy Public PortalAboutOrdinance No. 481-83 01-17-1983 ORDINANCE N0. 481 BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY OF RICHLAND HILLS, TEXAS, that: I. This Ordinance is passed by this city council in order to protect the City and its inhabitants from flooding and drainage problems. II. Any person, firm or corporation wishing to develop real estate or accomplish landscape disturbing activities within the city limits of this city must make application for and procure a permit from the city which agrees to compliance with this ordinance. Such application shall be accompanied by plans for water detention facilities and all other plans called for by this ordinance. The plans shall be drawn and signed by a Registered Professional Engineer. The application shall be on a form provided by the City Administrator and accompanied by a fee of $ 100.00 III. 1. Landscape disturbing activities which increase the danger of excessive erosion and sedimentation shall be subject to the terms of this ordinance, and a permit shall be required of all such activities which: a. Alter floodway storage or conveyance capacity of a floodway. Where floodways are not determined, the entire area inundated by the 100 year flood shall be considered to be a floodway. b. Alter existing floodwater or stormwater drainage or storage in a manner which would divert or direct stormwaters or flood waters onto another property so as to cause damage; c. Produce a high risk of excessive erosion, sediment transport, or deposition. 2. A permit shall not be issued unless it can be demonstrated through competent hydraulic analysis that alteration will not increase flood stages and/or flood damage to adjacent upstream or downstream properties. 3. To secure a permit, the applicant shall submit for approval to the City, all plans, materials, or calculations which are required to demon- strate conformity with the general requirements of this ordinance. 4. In regulating landscape disturbing activities, the City shall have the authority to: a. Require modification of submitted plans where necessary to prevent damage to other properties and where said modifications are reasonable and economically feasible; b. Issue a stop-work order with regard to the landscape disturbing activity where such activity is in violation of this ordinance or not in compliance with authorized plans and schedules. c. Issue orders requiring corrective measures to be undertaken to bring landscape disturbing activities in compliance with this ordinance and any authorized plans and schedules; d. Orders issued by the City shall be serviced or posted at the location of the landscape disturbing activity. IV. Developments which increase the amount of impermeable area, such as the construction of roof structures, paved areas, or compacted areas, shall be subject to the terms of this ordinance. A. The following, however, shall not be included: 1. Modification of single-family dwellings which will continue to be used as single-family dwellings; 2. Improvement of existing roadways which does not increase the number of traffic lanes in the typical cross-section of the roadway: Ord. 4~ X81 Page two B. The maximum controlled stormwater runoff release rate shall not exceed the natural safe stormwater drainage capacity of the downstream system, which • has been determined by Storm Drainage System Evaluation, dated July 1982 by Owen Ayres & Associates Inc. which is on file in the office of the City Secretary. Pipe outlets of less than twelve inches in diameter shall not be allowed. Multiple outlets from a storm water storage area shall be avoided if they are designed to be less than 12 inches in diameter. Removable orifice plates shall be employed when these pipe size requirements cannot be met. C. When the maximum controlled stormwater runoff release rate shall be ex- ceeded, any or all of the following stormwater storage methods shall be pro- vided and constructed: 1. Dry Bottom Storm Water Storage a. Dry bottom storm water storage areas must be designated to serve a secondary purpose for recreation, open space, or similar type of use, which will not be adversely affected by occasional intermittent flooding. b. The combination of storage of major flood water runoff from a 100-year return frequency storm and the allowable release rate shall not result in a storage duration in excess of 48 hours. c. Minimum grades for turf areas shall be z percent (200 units horizontal to one vertical) and maximum side slopes shall be 30 percent (three units horizontal to one unit vertical). Storage area side slopes shall follow the natural land contours • as closely as practicable, and a minimum of earth excavation shall be used to create the storage facility. d. Temporary seeding or other soil stabilization measures shall be established in the stormwater storage area and major flood water passageway immediately following the construction or reconstruc- tion of the of these areas. During the construction of the overall development, it is recognized that a limited amount of sediment buildup may occur in the. storm water storage area due to erosion. In no case shall the volume of the storage-area be reduced to less than three-quarters of the required volume during the construction phase of the development. e. Permanent erosion control measures such as mulching, hydro- seeding, conventional seeding, nurse crops, fertilizing, or sod installation shall be utilized to control soil movement and erosion within the storage area and major flood water passageway. These measures shall meet or exceed the standards established by the Soil and Water Conservation District. The installation of these permanent measures shall take place only after the major- ity of construction and other silt and sediment producing activ- ities have been completed. Prior to the establishemnt of the permanent erosion control measures, the required capacity of the storm water storage area and the excess storm water passageway shall be restored. f. The control structure shall be provided with an interceptor for trash and debris and it shall be designed and constructed to prevent soil erosion and not to require manual adjustments for its proper operation. An inlet design that will produce turbu- lent flow conditions during any portion of the storm water stor- age cycle will not be acceptable. g. Adequate impact stilling basins shall be provided to ensure that downstream soil erosion is alleviated and the regime of the down- stream drainage facility is not disturbed. h. Each stormwater storage area shall be provided with a method of overflow in the event a storm in excess of the design capacity occurs. This overflow facility shall be constructed to function without specific attention and can become a part of the excess stormwater passageway described in this section. i. The entire stormwater storage area shall be designed and construct- ed to fully protect the public health, safety, and welfare. If a condition occurs in the stormwater storage area which is hazard- ous to the public health, safety, or welfare, the person responsible for the condition will be required to provide approved corrective Ord . 481 Page three measures.. In the event these corrective measures are not provided, the City may eliminate the hazard at the expense of the person respon- sible. j. Low flow conduits or channels shall be provided in storm water storage areas; these conduits or channels shall be so constructed that they will not interfere with the secondary usage of the storage area and and will reduce the frequency of time that the storage area will be covered with water. 2. Wet Bottom Storm Water Storage. Wet bottom storm water storage areas shall be designed in compliance with all of the regulations which are applicable and govern the construction of dry bottom storm water storage areas. The follow- ing additional regulations shall apply: a. The water surface area of the permanent pool shall not exceed one-tenth of the area of the tributary watershed.. b. Protection of the shoreline must be provided to alleviate soil erosion due to wave action. c. Minimum normal water depth shall be four feet. d. Facilities shall be provided to lower the pond elevation by gravity flow for cleaning pruposes and shoreline maintenance. e. The control structure for stormwater release shall be designed to operate at full design release rate with only a minor increase in the water depth in order to minimize the land surface wetted by frequent minor stormwater runoff conditions. f. Measures shall be included in the design to prevent pond stagna- tion. This may be accomplished by fountain aeration or some other method used to ensure aerobic pond conditions. g. The volume of water permanently stored shall not be considered to be part of the required excess stormwater storage volume. 3. Paved Storm Water Storage. Design and construction of the pavement base must insure that there is not pavement damage due to flooding. Control struc- tures in paved areas must be readily accessible for maintenance and cleaning. Vortex control devices will be required. 4. Rooftop Storm Water Storage. Rooftop storage of excess water shall be designed and constructed to provide permanent control inlets and parapet walls to contain excess storm water. Adequate structural roof design must be provided to ensure that roof deflection does not occur which could cause the roofing material to fail and result in leakage. Overflow areas must be provided to en- sure that the weight of stored storm water will never exceed the structural capacity of the roof. 5. Automobile Parking Storm Water Storage Areas. Automobile parking facilities used to store excess water must be constructed having a maximum depth of stored storm water of 1.5 feet; and these areas shall be located in the most remote, least used areas of the parking facility. 6. Underground Storm Water Storage. Underground storm water storage facilities must be designed for easy access in order to remove accumulated sedi- ment and debris. These facilities must be provided with a positive gravity outlet. V. ~ 1. The volume of required storm water storage shall be calculated on the basis of the maximum value achieved from the runoff of a 100-year return frequency storm less the volume of water released through the outlet structure. Any gen- erally recognized and substantiated method acceptable to the City may be used for these calculations. The release rate of the outlet structure when only half of the storage area is filled may be used in lieu of rouing techniques in small drainage areas. The control structure shall be designed to maintain as uniform a flow as possible, independent of the storm water storage volume. Where the proposed structure, project, or land development forms only a portion of a water- shed or contains portions of several watersheds, the storage volume calculations shall be based upon the area of the entire project, development, or land use change. The maximum release rate shall not exceed that computed in the Drainage System Evaluation Report, July, 1982, on file in the office of the City Secretary. Ord . 481 Page Four 2. Storm water storage areas which will be filled to capacity by high frequency storms shall be designed in a manner that will protect immediate downstream properties, and all overflow structures shall be designed to function properly and effectively without the necessity of making manual adjustments. A larger outlet for a storm water storage area may be permitted by the City for the orderly management of storm water runoff where large tributary areas are develop- ed without detention. 3. If the orderly management of the storm water runoff cannot be achieved by passing the entire tributary area runoff through the storm water storage area, then the storm water storage area shall be constructed to exclude the runoff from the tributary area originating outside the area to be developed. E. Application. 1. Storm water detention facilities shall be designed by and their construction supervised by a Registered Professional Engineer. 2. Compliance with this Section shall be as provided for in Section II- Permit Applications. In addition, the following shall be required by the City: a. Upon completion of construction, a set of as-built drawings cert- ified by a Registered Professional Engineer; and b. An estimated schedule of development phases. 3. All applications for building permits shall contain a statement • that such buildings or structures and appurtenances connected therewith include facilities for the orderly runoff or retention of rain. Plans submitted with said application shall include a signed statement issued by a Texas Registered Professional Engineer that the plans include fac- ilities adequate to prevent harmful runoff. For single-family dwellings to be located in a subdivision meeting the requirements of this ordinance, the signed statement may, in lieu of the above, be placed on the face of the final plat.. VI. Administration of this ordinance shall be the responsibility of the City Administrator or his designated representative. The City shall not issue a permit with respect to this ordinance until clearances necessary from the res- pective State and Federal agencies are obtained. A. No development or activity regulated by this ordinance shall commence in any area known or suspected to be inundated by the base flood (100-year return frequency storm) without prior written approval from the City in accordance with the requirements of this ordinance. B. After the effective date of this ordinance, no zoning clearance, building permit, or plat or subdivision approval shall be issued for development activity or land subdivision in a known or suspected base flood area until the proposed use, structure, development, subdivision, or activity is approved by the City. C. The City Administrator shall enforce the provisions of this ordinance, and for that purpose shall have the following additional powers and duties to: 1. The City Administrator shall or shall request a Registered Professional Engineer to review and examine all applications for said permits to assure compliance with the provisions of this ordinance; 2. Issue permits and keep permanent records thereof; 3. Issue certificates indicating compliance with this ordinance and keep permanent records thereof; 4. Conduct inspections of buildings, structures, lands and uses as are necessary to determine compliance with this ordinance. Said inspec- tions may be made by the building official or inspector in conjunction with normal building or construction inspections; 5. Receive, file, and forward as necessary all applications pertaining to this ordinance. Ord. 481 Page Five 6. Initiate, direct, and review from time to time the provisions of this ordinance and make recommendations to the Council as necessary; 7. Initiate amendments to this chapter as may be necessary to comply with changes in the National Flood Insurance Program; 8. Revoke permits, certificates of compliance, and post stop-work orders where the provisions of this ordinance are being violated; 9. ~ quire or conduct elevation surveys and monumentation as necessary to assure compliance; 10. Issue notices of violation where necessary and take further action as specified in this ordinance to obtain compliance; 11. Provide and maintain public information relative to all matters arising out of this ordinance. VII. Any person, firm, or corporation violating any portion of this ordinance sYiall be deemed guilty of a misdemeanor and fined not in excess of $200.00. Each days violation shall be a separate offense. The City shall also be entitled to enforcement in Civil Court. PASSED AND APPROVED at a Regular Meeting of the City Council of the City of Ric bland Hills Texas, this the 17th day of January , 1983. ayor AT EST: City Secretary