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Gateway BP(1.1)-CS 921005 ALBERT H. HALFF ASSOCIATES, INC. ENGINEERS · SCIENTISTS · SURVEYORS DALLAS · ARLINGTON · CHICAGO · FORT WORTH 8~.~6 NO~ThWr-~T ~'LAZ& ~iVE · Dg.b&S T~×A~ 7£2~5 214 739-0094 · F~X 214 739-0095 October 5, 1992 AVO 11978 City of Copper Dept. of Public Works .... P.O. Box 478 Coppell, Texas 75019 Att: Mr. Kenneth M. Griffin, P.E. City Engineer Rc: "~ .... ~ ---' Dear Mr. Griffin: Please find attached two blueline sets of the above referenced construction drawings for your approval. The drawings will be sealed upon your preliminary approval. As per your letter dated March 23, 1992 we have made the following revisions have been made to the above referenced plans. 1. As stated on the' approved final plat, landscaping will be done as individual lots are developed, although PVC conduit has been provided under roadways for future irrigation. 2. The plans have been revised to indicate recessed inlets. 3. To provide positive drainage. The site is on a 0.25% slope. The minimum slope on the proposed streets is 0.6% therefore requiring low spots. 4. The Owner (Catellus Development Corporation) is in the process of obtaining the offsite easement. This work has been incorporated into these construction drawings. 5. The drainage area for the inlet in question has been broken down to smaller drainage areas and is being partially redirected to inlets in proposed Southwestern drive. The drainage areas have been designed such that each inlet has a design flow of 11.7 els or less. See attached drainage area map. 6. The plans have been revised accordingly. TRANSPCq-A-iON WATE~ RESOuI:¢E.~ · _AN",?.- DE'.'ELCPMENT M.~.%i:Cip-*_ · EN'."RC%ME".-A_ · ST~L~-;..:.:._ SURVEYING LANDSCAPE ARC~:-ECT...F E · = _ A~':I'. :.".G ALBERT H. HALFF ASSOCIATES, INC. ENGINEERS · SCIENTISTS · SURVEYORS Ci~ of Coppell October 5, 1992 Page 2 7. The plans have been revised accordingly. 8. The offsite drainage area map has been provided. See Sheet DA-IA 9. A ditch and Y inlet have been added onsite to direct the water to Southwestern Drive. 10. A typical ditch section has been provided under existing conditions the total flow to this ditch has been reduced. Under improved conditions a storm sewer system consisting of ditch improvements and/or pipe system will be required to the existing 54-inch stubout at the southwest corner of the railroad and Freeport Parkway. These improvements will be made in conjunction with the development of Block 2 of this project. 11. All discrepancies within the inlet and pipe design chart have been corrected. 12. The time of concentration has been changed to 11.5 min. 13. Access to the storm sewer system has been provided by adding manholes at stations 19+60.9 and 30+18.14 and by increasing lateral 1.1:.-14 to 30" in Southwestern Drive. Laterals LF-2 in Exchange Drive, and LG-3 in Sterling Drive have also been increased to 30". 14. A proffie view has been provided for all laterals. See Sheets D-7 thru D-9. 15. A direct traffic box with 1.5' cover will be provided. The system can not be lowered due to the existing sanitary sewer in Freeport Parkway. We have shifted the low point at storm sewer Sta. 24+00 to Sta. 26+00 to increase the cover over the box and improve the hydraulic grade. 16. We have discussed the option of providing a fabricated opening for a manhole in the top of the box with Gifford Hill engineers. The plans now call out a 3'x3' prefabricated opening at the centerline of the box and the contractor is to construct the top portion of a type B manhole. (See Item 13 above) 17. The plans have been revised accordingly. ALBERT H. HALFF ASSOCIATES, INC. ENGINEERS * SCIENTISTS · SURVEYORS City of Coppell October 5, 1992 '" Page 3 18 ..... Plans now call out a type B manhole to be constructed at this location. (See Items 13 and 16 above) 19. Drainage area E-1 has a y-inlet (11 cfs) and has been graded to drain. (See Item 9 above) 20. The water and sanitary sewer where extended along Gateway Boulevard under the Phase I construction to the southwest comer of the Thompson property. In addition we believe water and sewer services was extended to the northwest comer of the property with the Royal Lane construction. On behalf of the Owner we would request that these lines not be extended on this project. 21. The hydraulic grade is 1.0 feet below the top of curb at this point. 22. These items have been corrected. 23. These details have been included. Please call if you have any questions. Very truly yours, ALBERT 1~. I~LFF ASSOCIATES, INC. Z~~ck~er, p.E~.,~R.p.L.S. cc: Mr. Wayland Threadgill, Catellus Development Corp. Ms. Taryon Bowman, City of Coppell I:~AVO~11978~WI~LTR10-5 Coppell, Texas 75019 ~~ The City With A Beautiful FutureMarch 23, 1992 214-462-0022 Mr. Pat Acker Albert H. Half~ Associates Three Northpark ....... 8800 N. Central Expressway, Suite 300 Dallas, TX 75231 Re: Gateway Business Park Dear Mr. Acker: The City of Coppe!l has reviewed the referenced plans and has the following com~ments to offer: i) irrigation and landscape plans should be provided. 2) Recessed inlets should be used in lieu of curb ~ 3} Please explain why ail the~ow~ · points~ were des~__.__cn~~ for Sothwestern Drive. 4) As discussed at our meeting, the proposed $ X 6 offsite storm drainaae system should be constructed by the dev__c Gateway Business Park. 5) Will the removal of the inlet at the intersection of Southwestern Drive and Freeport Parkway have any afl_ct ~n the drainage in Freeport Parkway? 6) The length of the transition for the left-turn lane skouZ~ be skown. 7) The p T ~l~V~mn should be provided for intersections. 8) An offsite drainage area map should be provided. 9) Please explain how drainage area E-i will drain througk 5his site. Based on the contours, it appears as though some ef it should drain through drainage area F-1. However, your plans show it all going do-,~ Southwestern Drive. Will there ke any offsite grading needed to accomplish this? 10) A typical ditch section should be provided for the existing/proposed ditch along the north side of this development. Letter to Mr. Pat Acker March 23, 1992 Page 2 11) There are several discrepancies in the drainage areas contained in the Inlet and Pipe Design Chart. 12) The time of concentration for drainage area E-! appears to be too high. You might want to consider using !0 minutes as opposed to 14.! minutes. 13) Some type of junction box or upsized~- lateral should be periodically provided for access to the system. If you choose the upsized laterals, they should be at least 30" diameter. 14) Profile view should be provided for ali the laterals. !5) At several places throughout this design, there is inadequate cover over the pro~o~ed. ~ storm drainaGe~ system. I~ is Gui possible that a direct traffic box may be required. However, my opinion is that the system should either be lowered or the streets should be raised to provide adequate cover over the box. A'so,.~ there appears to be a problem hydraulically with the system about Station 24 + 00. The hydraulic grade line is above the street and the inlets may not function as designed. i6) A .... ~ ~ ~ be ~ ~un~_on box~.ou~.~ constructed at Station 19 + ~ cf £ with its intersection at Station 0 + 00 of Line G. i7) Am.y utilities within 2 feet of the proposed storm drainage system should be concrete encased. 18) A junction box should be provided at Station 30 + 10..44 cf -"_:-= E with its intersection at Station 0 + 00 of Line ~. !9] T:-~ proposed storm drainage system to the west .of -~his development should not be plugged. A headwall and a grade drain should Be provided so that drainage area E-! wi!! have place to drain. 20) Both the water and the sewer should be extended to tko western property ~ ~ . . ..n~ of this develooment 21) At Station 2 + 00 of Line G, the hydraulic grade line is abc.::e the street and the inlets may not f~unction as desicn=d Letter to Mr. Pat Acker March 23, !992 Page 3 22) The minim~ manhole depth is 4 feet. Your proposed manhole at Station 9 + 53.1i of Line B is just a little bit over 2 f_e~ deep. Please com.ment as to how you will accomplish a manhole depth of at least .4 feet. Also, along Line B of the sanitary sewer, the flow line elevations from Station 5 + 03.1i up through Station 9 + 64.6! are incorrect. These should be corrected. 23) All appropriate details should be provided when the plans are resubmitted. Once all re~uested~ chanaes~ have been made, the revised set of -~-~=ns plus these markup =e+ of plans should be resubmitted to the City for =v~'' if you should have any questions or comments concerning this review, oiease, feel fr~ to contact me at your convenience. Sincerely~_~ K~nnerh }:.iGri~fin, P.E. ~ty Encineer ~.!G/bd GATEB?