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Northpoint Dr-CS020212 T H ir . C I T Y · 0 F COPPE L February 12, 2002 Marry Paris, P. E. Halff Associates, Inc. 8616 Northwest Plaza Drive Dallas, TX 75225 RE: Amberpoint Business Park at Coppell, Northpoint Drive Construction Plan Review Comments Dear Mr. Paris: The City of Coppell has reviewed the plans for the referenced project and has the following comments to offer: Plat - The detention area labeled drainage easement should be called out as Private Maintenance, and appropriate notes and dedications should be included. Sheet CPP01 - 1. Review general note #6, which states that lime stabilization shall be utilized. A minimum of 30 lbs. per square yards is required. Also, a geotechnical report may show that cement stabilization is more appropriate than lime stabilization for this area. Make all necessary changes and submit any supporting information. 2. Regarding the entrance to the water tower and park, there are several concerns: a) Midpoints of the drive should be raised to force the water to continue to flow down Northpoint rather than cut through the water tower drive. b) Return radii of this area should be increased to serve the various trucks that will be bringing material in and out of the city yard. c) Provide turning template feedback as previously discussed with this department. d) Access should be maintained to the water tower at all times. 3. There are water valves for the 24" and 12" waterlines at approximately station 1+40 that will need to be taken into account in the design and adjustments should be made accordingly. 4. Complete the flair at the western end of this project to improve the alignment with the existing roadway. 5. Minimum street grade is 0.5% 6. Correct all typos and add vertical scales throughout the plans. Sheet CPP02 - 1. Extend the 18" stormwater pipe at station 14+20. 2. The vertical curves of 73' and 113' (as well as 122' from the next sheet) are unusual. Consider modifying to typical dimensions. Avoid ponding at the top of a crest. The K values of 70 and 80 may be excessive. Sheet CPP03 - 1. Show both the 24" waterline and proposed culvert in profile. 2. The roadway from 28+20 to Sandy Lake Road should be constructed as a temporary roadway. Our recommendation is that this roadway be constructed with 6" HMAC and that the curb end at 28+50. Sheet CPP04 - Ensure that no drainage will be blocked behind the right-of-way line and/or trapped by any drive approaches. Sheet CPP05 - Reflect the limits of the grading plan fi'om CGP01 on all extended cross- sections. Sheet CGP01 - Make all necessary drafting changes and use the most recent version of this sheet showing existing and proposed contours. Sheet CGP02 - I. The low flow pilot channel will handle little more than irrigation runoff. You may want to consider a design that can handle a 2 or 5 year storm, bearing in mind that maintenance will reside with this business park developer and owners. 2. Add a note which states, "Maintenance for the detention pond and its outlet will be the responsibility of Amberpoint Business Park owners and developers." 3. Add appropriate notes regarding the compaction and material requirements for the embankment. Field observations indicate that materials in this area may be of low PI and may require modification to be adequate for the proposed use. 4. Address all erosion control concerns, both during construction and long-term viability of the detention facility. 5. The proposed location of the emergency overflow raises some concerns with regard to State Road, and homes on the other side of State Road. Reconsider your design for an emergency overflow. 6. You may want to consider providing a pipe to the west for the future parking lot. 7. Has the revised outlet pipe been analyzed with regard to the forces in the pipe at the bend, and the stability with the proposed design? 8. Show the limits of this contract as per the latest revisions. Sheet CDAA-1 - 1. Add a legend showing what the drainage symbol indicates. 2. Show the contract limits as per the latest revision. 3. There is an arrow on the east side of State Road. Make all necessary corrections. Sheet CDA-2 - Areas A3, E3 and E2 are inconsistent with the building plans. Please coordinate with those plans. Sheet CDA-3 - The detention calculations only show the required storage volume and the preliminary calculations to obtain that information. Add the area provided to this information. Also, add the stage/storage/discharge table and the routing table. Sheet CSD01 - 1. Add a note requiring ductile iron where all waterlines cross under storm drains, sewers, etc. 2. Provide for adequate protection of the sanitary sewer and waterlines that cross under the storm drain. 3 3. Several storm pipes are stubbed out to future development areas. Note whether they are to receive a grate inlet, a wye inlet or to be plugged. Sheet CSD02 - Add appropriate note or notes to require prefab wyes and bends. Sheet CSD03 - 1. Provide additional information for the wye inlet at approximately 4+00. Include size, reference to detail sheet, rip rap, etc. 2. Correct labeling errors between profile and plan view. 3. On lateral A-lb: a) Why is the waterline so deep at this location? b) Include the fire hydrant lead in the profile. c) Any waterline crossing shall be ductile iron. Sheet CSD04 - 1. Extend lateral A-2c to get it out fiom under the proposed drive approach. 2. Show waterline and fire hydrant lead crossings at the storm pipe in the profile view and label as ductile iron if they are below the pipe. Sheet CSD05 - 1. As requested on previous sheets, add appropriate notes for prefabricated wyes and bends. 2. The storm pipe should be at or near the flowline of the creek at the outlet of line B, or an adequate channel should be provided for the conveyance. Adequate slope and erosion control should be provided. 3. In the profile for storm sewer line B, two feet of cover should be provided over the pipe as was requested for the 54" and 72" pipes. 4. Profile for storm lateral B-l: a) Show the 12" waterline in profile as well. Addressing all ductile iron and line protection issues as requested in previous sheets. b) The HGL is well above the proposed grade. Modify the storm drain design to eliminate this condition. c) Show the fire hydrant lead crossing at approximately 3+20. d) Add an elevation for the 24" storm pipe at both the 24" and 12" waterline crossings. 5. For laterals B-lb and B-lc the HGL is also of concern. Address the HGL problems for these lines while addressing lateral B-1. Sheet CSD06 - 1. Add a note referencing the Standard Street Header on SD2. 2. Change the Sloped End Section to Safety End Treatment at both ends of the 18" pipe at Sandy Lake Road. 3. Provide a minimum of 1 foot of earth between the pavement and top of pipe at Sandy Lake Road and Northpoint Drive. An alternate design may be acceptable with the use of Class IV RCP. 4. Address the potential for piping around the 54" RCP outlet fiom the detention pond. 5. Label both bends as prefab. 6. Release of the stormwater pipe should be at or near the flowline of the creek or a channel with adequate conveyance should be provided. Address slope and erosion control concerns. 7. Line D as proposed raises concerns with regard to the movement of the pipe and thus future maintenance problems at the outlet end. Also address cover concerns for the pipe. 4 Sheet CWW01 - 1. Show the existing 12"x 8" stub and valve to the north at approximately 0-15 for the waterline. 2. Add an air-relief valve at the western end of the waterline. This is a localized peak on the waterline. 3. Where is the transition fi:om 4.1 feet to 4.5 feet? 4. Add a fire hydrant near 3+00 to maintain the required fire hydrant spacing. 5. Add a 90-degree bend to the list of fittings for the fire hydrant at 6+00. 6. Consider relocating the irrigation connection that is currently under a proposed drive approach. 7. Add a blow-offvalve at the localized low spot at approximately 9+50. Sheet CWW02 - 1. Add a 90-degree bend to the list of fittings for the fire hydrants at 12+00 and at 18+40. 2. Add a note stating, "Proposed fire hydrants to be set three feet off'back of curb." 3. Note that waterline and fire hydrant leads crossing under storm sewers shall be ductile iron. 4. Dimension spacing between the 8" waterline and 8" sanitary sewer line at approximately 17+25. Maintain spacing as required by TNRCC regulations. 5. Dimension the waterline from back of curb. 6. There appears to be a potential conflict for the waterline and storm sewer at 14+30. Show the storm sewer in the profile and make any necessary modifications. 7. Regarding the lowered section of waterline at 16+00 to 16+15: a) The difference in stationing for the lowest section is only 10 feet and noted at the bottom as 18 linear feet. Resolve this discrepancy. b) Consider a blow-off valve at this location. c) Does this line need to be this deep? Our requirement is for a minimum of two feet of separation. 8. There is a localized high spot at station 19+90. Provide an air relief valve. Sheet CWW03 - 1. Dimension the waterline to the back of curb. 2. Add sufficient pipe length to provide for 20' of pipe fi:om the gate valve at all locations. 3. Add ductile pipe where waterlines cross under other utilities or storm drains. 4. Add a note at 28+31 stating, "Field verify location of the 12" waterline." 5. Add a blow-off valve at 24+90. Sheet CWW04 - 1. The irrigation meter and double check valve at approximately 7+00 should be relocated to the location shown on CWW05 where the 2" waterline departs from the 8" main. 2. The manhole at 0+00 should be a 5-foot diameter drop manhole. 3. Provide top of rim information on this and subsequent sheets. Sheet CWW05 - 1. Adjust the waterline location in order to provide appropriate separation between waterline and sanitary sewer line, typically 10' centerline to centedine. Provide additional easement to allow at least 10' on either side of the outer lines. 2. The waterline stub, 8-inch plug and blow-off valve shown at the far east end should also be contained within an easement. 3. The sanitary sewer from approximately 10+25 to 17+30 is still too deep. Raise the sanitary sewer to a more reasonable depth. 5 4. Show the waterline crossing at 8+40. Sheet CEC02 - Add dimensions and notes for the stabilized construction entrance as per previous releases. Sheet CSC01 - Consider also providing irrigation sleeves in order to minimize the number of bores that will be required after construction of the roadway. Sheet CPM01 - 1. Provide breaks in the median striping at both driveways (0-30 and 2+60). 2. Add a legend for all symbols appearing on this sheet. Sheet CPM02 - 1. Provide appropriate pavement arrows for the T-intersection at Sandy Lake Road. 2. Place the stop sign and stop bar as close as reasonably possible. 3. Pavement markings should be accomplished with thermal plastic tape and not paint. Add a note. There are other minor comments throughout the plans that should be addressed. Please make the necessary changes and re-submit these marked-up plans and two sets of revised plans to the City for review and/or approval. If you have any questions, please contact me at (972) 304- 3679. Sincerely, Assistant City Engineer cc: Project File P.O. 8~x 478 2~ ~ B~d C,o~Od. TX 75019 phone: (972)3043679 F=: (972)304-3570 ENGINEERING DEPARTMENT FAX COVER SHEET [] Urgent //~For Review [] Please Comment (including cover sheet) [] Please Reply [] As Requested IF YOU DO NOT RECEIVE.412, OF THE PAGES PLEASE CAZ.L (972} 304-3679 "City of Coppell Engineering- Excellence By Design"