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Pecan Hollow-CS 900827 Jerry Parchd Consulting Engineers August 1990 Ms. Mary Hicks ...... ABQ Federal Savings Bank P O Box 25625 Albuquerque, NM 98125 505/242-3330 RE: JP No. 88009; Parks of Coppell; Pecan Hollow Drainage Channel; Coppell, Texas Dear Mary: By ABQ's letter to Mr. Doyle Cameron of May 21, 1990, information was requested from Pecan Hollow Joint Venture necessary to evaluate requested easements and proposed construction on ABQ's property to serve the Pecan Hollow Addition. The information requested generally consisted of written confirmation from Pecan Hollow that the developer will construct the channel improvements, as agreed to previously and described as Alternative No. 1 in the aforementioned letter, and channel improvements plans. Once this information is accepted by ABQ the process of preparing easements and an agreement that would permit the proposed construction by Pecan Hollow could proceed. On August 21, 1990, the following information was received from Mr. Cameron: 1. Three documents on State of Texas forms for the Granting of drainage easements on ABQ's property to the City of Coppell. These three easements would permit construction and maintenance of storm drain discharge facilities on ABQ's property serving Pecan Hollow. 2. Six drawings by Dan M. Dowdey & Associates described as follows: A. Drainage area map showing proposed facilities to handle storm water through Pecan Hollow. B. Lot grading plan of the northwesterly portion of Pecan Hollow. C. Storm Sewer Line A plan and profile. D. Storm Sewer Line B, station - 0+03.10 to station 11+00, plan and profile. E. Storm sewer lines C and C-1 plan and profile. F. Three channel improvement cross sections. 320 VC/estway Place, Suite 501 * Arlington, Texas 76018 * Metro (817) 467-2418 · (817) 465-0259 Ms. Mary Hicks August 27, 1990 JP No. 88009 Page 2 of 4 We have reviewed the information submitted by Mr. Cameron and offer the following comments. 1. To my knowledge Pecan Hollow has not yet provided written confirmation that the developer (Pecan Hollow Joint Venture) will construct the channel improvements in conjunction with fillin~ for lot pads in Lots 1-10, Block C as requested in ABQ's letter of May 21, 1990. 2. To avoid confusion by subsequent developers of property on the north side of the channel, the water surface elevations shown on the cross sections and in the Lot Grading Plan should agree and should be in accordance with results of the proposed channel hydraulic model containin~ 4:1 sideslopes (Model PEHOP14.DAT). This channel improvement model generally resulted in the higher water surface elevations. 3. There are slight variations in the channel bottom elevation shown at sections 19+50 and 24+50 between those shown on the cross sections and elevations at these sections contained on the most recent HEC II model, PEHOP14.DAT, submitted to us on May 4, 1990. The channel bottom slope of 0.10~ indicated on the Lot Gradin~ Plan varies from the 0.1444 Grade shown on Sheet No. 26 of the Heartz Road plans prepared by our firm. If the model has been revised, an updated copy should be submitted to us for record purposes. 4. The fifteen foot drainage easement required by the City in the rear of Lots 1 through 10, Block C is not shown on the plans submitted to us. However, I recall seein~ this easement on a copy of the Pecan Hollow Final Plat at the City. This easement should be shown on the storm drain plan and profile sheets for future reference. 5. If the 4:1 slope on the south bank of the channel is extended above 100-year flood elevations on Lots 1-10, Block C, the design flood will inundate approximately 20-23 feet of the back of these lots. Floodin~ will therefore extend outside of the 15 foot drainage easement. A~reements between ABQ and Pecan Hollow should preserve the flood carrying capability of the lot area outside of the drainage easements, as well as within the drainage easements, by prohibiting fences or fillin~ in the channel slope area below the design flood elevations. If the ~radin~ scheme indicated as Alternate 1, on the cross sections (Alternate 2 in the ABQ letter of May 21, 1990) is implemented, then fences can be constructed anywhere outside of the drainage easement unless other restrictions apply. Ms. Mary Hicks August 27, 1990 JP No. 88009 Page 3 of 4 6. Permissible grading schemes in the flood carrying areas of lots backing onto the drainage channel should be emphasized in agreements between ABQ and Pecan Hollow, and in the Pecan Hollow Homeowners Association Agreement or deed restrictions. It should be clear that construction of a vertical wall on the south easement limits must include excavation of the channel sideslope on the north side of this wall in accordance with the grading shown on the cross sections. 7. The City of Coppell has advised us that the Pecan Hollow Construction Plans have been approved. I am not aware if the plans sent to us by Mr. Cameron are similar to the approved plans of record at the City. 8. The curve requested by ABQ in Beechwood Lane is shown on the plans submitted to us. By cody of this letter I am requested that Pecan Hollow Joint Venture provide an updated copy of the Final Plat to us and ABQ. 9. The proposed headwalls at storm drain discharge points should conform to or be slightly recessed into the proposed south channel sideslope to avoid presenting an obstacle to flow in the channel. Engineers for Pecan Hollow should consider whether the flow line of Storm Sewer Line A at the point of discharge should be lowered, since the proposed elevation shown in profile is approximately 1.5 feet above the proposed channel bottom. A copy of detail sheet SD-14 is requested by copy of this letter to Mr. Cameron. 10. The State of Texas easement forms submitted to us are very general and do not specify rights of affected parties in the easement areas. Certain responsibilities and acceptable activities should be specified in the instrument. A copy of a drainage easement executed by ABQ on behalf of the Coppell Independent School District is enclosed. You may wish to request that Pecan Hollow Joint Venture submit requested easements to you in a form similar to those executed for C.I.S.D. A copy of this easement is being provided to Mr. Cameron with a copy of this letter, however, your attorney should advise ABQ whether this easement form is appropriate for the Pecan Hollow easements. 11. The channel improvement plans are generally in compliance with the proposed channel included in hydraulic models reviewed in May. Additional clarification of the design of the downstream transition of the south bank of the proposed channel to the existing south bank should be shown on the Lot Grading Plan. This transition should begin approximately 80 feet east of Section 19+50. Ms. Mary Hicks August 27, 1990 dP No. 88009 Page 4 of 4 Our review of the Pecan Hollow Channel Improvements plans was performed in the interest of maintaining sufficient flow area in the channel such that water surface levels in the drainage channel between the Parks of Coppell and Pecan Hollow will not be increased due to the filling proposed by Pecan Hollow. Jerry Parche' Consulting Engineers and ABQ Federal Savings Bank accept no responsibility for the design or impacts of proposed storm drains designed and constructed to serve the Pecan Hollow Addition. If you have any questions, please call. Sincerely, Parche ' P E. JP:ch Enclosure: Drainage Easement executed on behalf of C.I.S.D. cc: Mr. Doyle Cameron/Pecan Hollow Joint Venture w/encl. Ms. Shohre Daneshmand/City of Coppell Mr. Bill Anderson, P.E./Dowdey & Associates Mr. Jim Schell/Law, Snakard & Gambill Mr. Wayne Ginn, P.E/Ginn, Inc.