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Gunner Sub-CS 980129Halff Associates ENGINEERS * ARCHITECTS * SCIENTISTS PLANNERS · SURVEYORS $$16 NORTHWEb~l' pLAZA DRIVE DAIJ. AS. TEXAS 75225 (214) 73~X~4 FAX (214) 739-0095 January 29, 1998 AVO 16248 Carson-Salcedo-McWilliams 1201 Main Street Dallas. Texas 75202 Attn: Mr. Michael Gonzales Re: 37.77-acre Gunner Subdivision Dear Mr. Gonzales: The City of Coppell detail included in your 1/28/98 FAX is adequate for the 24-inch and 12-inch outfalls. The detail needs to be modified for the 48-inch and 60-inch ouffalls to provide a 10-foot long apron as shown in Exhibit "C" of the previously provided District Order. All storm drains must enter at the toe of slope. The 12-inch pipe is shown outfalling at mid-slope; this is unacceptable due to potential side slope erosion. Please call if you have any questions. Sincerely, HALFF ASSOCIATES, INC. Don O. Brock, P. E. Vice President cc: Paul Phy DALLAS · FORT WORTH · HOUSTON · McALLEN TRANSPORTATION · WATER RESOURCES -° LAND DEVELOPMENT o MUNICIPAL · ENVIRONMENTAL · STRUCTURAL MECHANICAL ° ELECTRICAL * SURVEYING · GEOGRAPHIC INFORMATION SYSTEMS ARCHITECTURE ° LANOSCAPE ARCHITECTURE ° PLANNING EXI-IIBIT C p. 5o£5 EXHIBIT p. 4o£S acceptable development and use of the District's easement area is sho~n in Exhibit "C" attached hereto and made a part hereof for all purposes· R[gh t-of-Way Easement Generally, development within the District's right-of-way easement is strongly discouraged. Hovever, the District rill consider proposals which meet the following minimum guidelines for use on a case-by-case basis. No proposed improvements within the District*s maintenance and access easement may threaten or reduce the integrity of the levee, sump, canals, channels or storm severs. A tvelve (12) foot vide by sixteen (16) foot high corridor must be maintained for access. ADOPTED AND EFFECTIVE JANUARY 9, 1986. p. $of5 In addition to the foregoing, the drainage of property adjacent to District facilities shall not alter the District's facilities in any way. Any District's facility, or the access easements adjacent thereto, which are disturbed by development construction must be regraded and re. grassed at the expense of the de~Veloper'~ The dew,lover must also regrade the side slopes of any D/strict lra.cility which has been disturbed and remove all construction debris at his expense. All developers of property adjacent to the District's facilities shall submit their proposal and/or requests in writing accompanied with such plans and spec/f/cations as are necessary to demonstrate compliance with the provisions of these Cuidel£nes. Said submission shall be reviewed by the District's engineers to determine compliance h~rewith and written approval issued by said engineers prior to the construction of any improvements adjacent to the District's facilities. Provided, however, that if in the opinion of the engineers a different or higher level of storm sewer facilities are required to protect the District's interests, then the developer shall be so notified and ah'all comply therewith unless a variance shall be granted by the Board of Directors. Except in' this instance, the .determination of the engineers shall be final and require no further action by the Board of Directors. Upon completion of the required construction by the developer, the engineers shall so advise the Board of Directors that the same has been completed in a satisfactory manner or that the construction is deficient. If deficient, the authority to drain into the District's facilities and/or use District easements is terminated until the deficiencies are cured. The District reserves the right to require all construction and the repair of District ~acilities and removal of debris to be bonded as a condition precedent to commencing construction. Maintenance & Access Easement No proposed improvement within the District's right-of-way easement may threaten the integrity of the levee, sump, canals, channels, or storm sewers. No above-$round development will be alloyed unless the developer makes provisions for an acceptable alternate maintenance and access easement. Streets and parking lot access lanes, and fire lanes are generally acceptable uses of the Irving Flood Controt District, Section III maintenance and access easement. The developer may not alloy parkinq within the maintenance and access easement unless an alternate maintenance and access easement is provided. A full and complete description of the intended use shall be submitted to the District, and if consent is given for the developer to use said easement, the developer will be required to clean, regrade and regrass the facility adjacent to the subject site· A typical section of p. 2of5 EXHIBIT A IRVING FLOOD CONTROL DISTRICT SECTION III STANDARDS FOR THE USE OF DISTRICT EASE~ZNTS AND DRAINAGE OF DEVELOPMENT ADJACENT TO TI[E DISTRICT'S FACILITIES Introduction The Irving Flood Control District, Section III has the responsibility of providing, flood pr6tection within the confines of the District. In this light, no development which threatens the safety, integrity, serviceability. or maintainability of the District's facilities is permissible. Criteria for Storm Drainage All development of property adjacent to any s,~p or drainageway of the District must provide drainage facilities which will convey runoff water from the property into the bottom of the District's sump or drainageway. All storm water must be collected in storm sewer inlets prior to entering the sump and drainageways. Storm sewer pipes discharging laterally into District facilities must be cut flush with the slope, and a reinforced concrete.headwall must be installed flush with the slope and must be adequate to support tractor/mowers. Storm sewer pipes shall be sized so that water velocities when flowing full do not exceed 10 feet per second for the design' frequency of the system. When possible, the end of the storm sewer pipe must be lald on a grade less than 0.5 percent for a distance of at least 12 feet. The developer.must include provision to prevent erosion at the storm sewer outfalI. Along sumps and drainageways which are designed to retain water at a normal water surface elevation, storm water must be conveyed into the District's facility in an enclosed storm sewer system entering the District facility at a flow line elevation us lower than 3 feet below and no higher than 1 foot below the normal water surface. For aesthetic reasons, it is desireable that the flow line of smaller pipes be established so that no portion of the pipe or headwall be above 417.5 feet msl. This is not a requirement of the District, but it may be a development restriction e~tablished by the Valley Ranch. Flumes or open drainage into the District facility is prohibited, A typical acceptable installation is shown in Exhibit "B" attached hereto and made a part hereof for all purposes. Along Grapevine Creek, all storm water must be collected in storm .sewer inlets and then conveyed into the District's facility in an enclosed storm sewer system. Flumes or open drainage into the District facility is prohibited. The' outfall flow line of the storm sever entering the District facility must be not less than 6" nor more than 18" above the flow line of the District facility. Where the District facility has a pilot channel, a paved flume must be installed into the pilot channel. A typical acceptable installation is shown in Exhibit "C" attached hereto and made a part hereof for ail purposes. p. lofS lin . · .- Halff Associates ENGINEERS * ARCHITECTS * SCIENTISTS PLANNERS · SURVEYORS 8616 NORTHWEST PLAZA DRIVE DALLAS, TEXAS 75225 (214) 73~.(X)94 FAX (214) 739OO95 January 27, 1998 AVO 9786 Irving Flood Control District - Section III 8300 Douglas Avenue, Suite 800 Dallas, Texas 75225 Attn: Mr. Paul Phy Re: Grinner Subdivision - Designed by Carson-Salcedo-McWilliams Dear Paul: The referenced 37.77-acre subdivision is located within Irving Flood Control District - Section III, in Coppell, on the south side of Belt Line Road, at the east end of the large fill area. The engineer on the project has requested permission from the District to discharge storm drainage into District facilities at several locations. The storm sewers will outfall into the Grapevine Creek channel on the south side of the development and into the Trinity River overflow swale on the east side of the development. I have reviewed the proposed storm drain plans, and I have no objection to the plans except that the headwall details should comply with the attached "Order" from the District and the detail presented in Exhibit "C" of said Order. By copy of this letter to Carson-Salcedo-McWilliams, I am, on behalf of the Irving Flood Control District - Section III, authorizing the developer of the tract described herein to discharge his storm water nmoffinto the Dislrict's facilities, so long as the improvements within the District's right-of-way comply with the attached Order, and so long as said discharges contain no illegal contaminants. The District assumes no responsibility nor liability for the repair or maintenance of any improvements constructed as part of this or subsequent projects. HalffAssociates does not assume any liability for the engineering design, nor does approval by the Irving Flood Control District - Section III or Halff Associates, Inc. release the Design Engineer from liability for correcting .errors or omissions in his design both during and after construction. Please call if you have any questions. CC' Sincerely, [IALFF ASSOCIATES, INC. Don O. Brock, P. E. Vice President Carson-Salcedo-McWilliams DALLAS · FORT WORTH · HOUSTON ' McALLEN TRANSPORTATION · WATER RESOURCES o' LAND DEVELOPMENT · MUNICIPAL ° ENVIRONMENTAL ° STRUCTURAL MECHANICAL · ELECTRICAL ° SURVEYING ° GEOGRAPHIC INFORMATION SYSTEMS ARCHITECTURE ° LANDSCAPE ARCHITECTURE · PLANNING