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NDCFCD 2013 status review Northwest Dallas County Flood Control District Table of Contents SectionPage I.EXECUTIVE SUMMARY ................................................................ 2 II.SCOPE OF SERVICES ................................................................ 2 III.LIMITATION ................................................................ 2 IV.OBSERVATIONS ................................................................ 2 A.Sumps ................................................................ 3 B.Box Culverts under Riverchase Drive ................................................................ 18 C.Glory Holes ................................................................ 18 D.Spillways ................................................................ 20 E.Outfall to the Elm Fork of the Trinity River ........................................................... 25 F.General Observations ................................................................ 27 V.RECOMMENDATIONS ................................................................. 28 Appendix A Facility and Maintenance Summary ......................................................... 29 Appendix B Site Map ................................................................ 32 Appendix C Outfall Exhibit ................................................................ 34 Appendix D Projected Maintenance, Engineering and NPDES/TPDES Costs ............... 36 1 Northwest Dallas County Flood Control District I.EXECUTIVE SUMMARY Nathan D. Maier Consulting Engineers, Inc. (NDM) was retained by County Flood and structures. The District is generally located in and around the C In general, all of th NDM visually reviewed the status of all above ground facilities structure, spillway structures, glory hole intakes, sump banks, . Visible storm sewer outfalls along sump banks were also reviewed performance of below grade structures was noted, but the facilit culverts, headwalls and storm sewer piping between sumps) were n this report because they are either submerged or buried and are sewer outfalls flowing into district sumps were surveyed as a pa previously probed in Sumps 2, 9, 10, 11 and 14 to evaluate sedim since those sumps and associated box culverts were cleaned in 20 Negligible sediment accumulation was noted and therefore silt wa review. Silt will be probed periodically for future reviews. II.SCOPE OF SERVICES NDM is providing engineering services to the District. These ser 1. Preparing 2. Updating the 5 year maintenance schedule. 3. Attending a board meeting to answer any questions the District h 4. report. III.LIMITATION This report was prepared for the District. All information withi and may not be reproduced or conveyed in any fashion without the consent of the District, and NDM. This report was prepared using engineering practices and no other warranty is expressed or impl IV.OBSERVATIONS The following are photographs and comments from NDM's observatio Appendix B, Site Map, for locations of photographs and facilitie 2 Northwest Dallas County Flood Control District A.Sumps Sumps determined to have an impa facilities have had sediment removed. Sediment was removed from Sediment was removed from Sumps 9 and 10 in 2006. Work to remove Sumps 2 and 14 was completed in 2007. Although some sediment accumulation has previously been noted in dredged sumps, sediment levels are minor and pose no concern at minor erosion was noted along the banks of the sumps but does no significant contributor to sediment accumulation at this time. Erosion along the banks of sumps was evident at headwalls outfal the sumps as well as at the intake structure in Sump 3A. Vegetat observation of these areas in detail for this review, but no sig condition has worsened. Storm water levels were very high in 2007. Minor slope failures banks of Sump 3A in the 2007 report. Vegetation growth prevented observation of these areas in detail for this review, but no signs were evident that this cond worsened. Storm sewer outfalls into the sumps were observed. Visual observ performed where outfalls were found and were accessible at the t Vegetation growth along the sump banks limited access and obscur observations. Some erosion around storm sewer headwalls was obse sediment accumulation was noted in some areas. A number of storm shown on record drawings were not found in the field. See Attach Exhibit. 3 Northwest Dallas County Flood Control District Photograph 1 Sloughing along South and West Bank of Sump 1A Photograph 2 Erosion at Storm Sewer Outfall Headwall at Sump 1A 4 Northwest Dallas County Flood Control District Photograph 3 Sloughing along East and South Banks of Sump 1A Photograph 4 Sloughing along West Bank of Sump 2A 5 Northwest Dallas County Flood Control District Photograph 5 Sloughing along Northwest Corner of Sump 2A Photograph 6 Erosion behind Storm Sewer Outfall Headwall in Sump 2A 6 Northwest Dallas County Flood Control District Photograph 7 Erosion behind Storm Sewer Outfall Headwall in Sump 2A Photograph 8 Erosion and Slope Failure South Bank of Sump 3A 7 Northwest Dallas County Flood Control District Photograph 9 New Gabion Mattress on East Bank of Sump 3A Photograph 10 Headwall on Bank of Sump 8 8 Northwest Dallas County Flood Control District Photograph 11 Sloughing along South Bank of Sump 9 Photograph 12 Retaining Wall Repair along South Bank of Sump 10 9 Northwest Dallas County Flood Control District Photograph 13 Erosion at Storm Sewer Outfall Headwall in Sump 10 Photograph 14 Box Culvert Intake for Culvert under MacArthur Blvd 10 Northwest Dallas County Flood Control District Photograph 15 Storm Sewer Outfall Headwall on Bank of Sump 11 Condition not Observed Photograph 16 Box Culvert Outfall in Sump 11 11 Northwest Dallas County Flood Control District Photograph 17 Sump 11 Overview Photograph 18 Erosion at Storm Sewer Outfall Headwall in Sump 11 12 Northwest Dallas County Flood Control District Photograph 19 Sloughing on Banks at Sump 9 Photograph 20 Storm Sewer Outfall Headwall on Bank of Sump 14 Condition not Observed 13 Northwest Dallas County Flood Control District Photograph 21 Storm Sewer Outfall Headwall on Bank of Sump 14 Condition not Observed Photograph 22 Storm Sewer Outfall Headwall on Bank of Sump 11 Condition not Observed 14 Northwest Dallas County Flood Control District Photograph 23 Box Culvert Headwall at Sump 14 Photograph 24 Debris at Headwall of Sump 14 15 Northwest Dallas County Flood Control District Photograph 25 Sloughing at Northeast Corner of Sump 14 Photograph 26 Storm Sewer Outfall Headwall at Southeast Corner of Sump 2 16 Northwest Dallas County Flood Control District Photograph 27 Storm Sewer Outfall Erosion behind Headwall in Sump 2 Photograph 28 Storm Sewer Outfall Erosion behind Headwall in Sump 2 17 Northwest Dallas County Flood Control District B.Box Culverts under Riverchase Drive Sediment accumulation was removed from both the 5-84 box culverts (Line A, between Sumps 2 and 14) and the 4-84 box culverts (Line B, between Sumps 9 and 10) in 2005-2006. Since the box culverts are submerged, no additional observations overall condition of the structures. Sediment accumulations alon outfalls of the box culverts were probed previously during surve accumulation in the adjacent sumps. Based on that information, s in the box culverts does not appear to be a concern at this time C.Glory Holes Visible portions of Glory Holes appear to be in generally good c Glory Hole on Sump 18 needs to be re-positioned. The Glory Hole on Sump 13 has significant vegetation growth and The Glory Hole on Sump 2 has collected debris and requires clean 18 Northwest Dallas County Flood Control District Photograph 29 Glory Hole at Sump 2 Photograph 30 Glory Hole at Sump 13 19 Northwest Dallas County Flood Control District Photograph 31 Glory Hole at Sump 18 D.Spillways All spillway structures were replaced in 2002 and 2004. No signi noted during this observation and the structures appear to be in course maintenance has been performed at Spillways 5 and 6. The at both locations. Vegetation was noted growing in close proximi and 6. Minor cracking was observed in the concrete cap on Spillw behind gabion Spillway 6. Erosion behind Spillway 6 appears to b previous observations. 20 Northwest Dallas County Flood Control District Photograph 32 Gabion Spillway 1 at Sump 1A Photograph 33 Crack in Concrete Cap on Gabion Spillway 1 at Sump 1A 21 Northwest Dallas County Flood Control District Photograph 34 Gabion Spillway 2 at Sump 14 Photograph 35 Gabion Spillway 3 at Sump 13 22 Northwest Dallas County Flood Control District Photograph 36 Gabion Spillway 4 at Sump 3A Photograph 37 Gabion Spillway 5 at Sump 10 23 Northwest Dallas County Flood Control District Photograph 38 Gabion Spillway 6 at Sump 18 Photograph 39 Erosion Behind Gabion Spillway 6 at Sump 18 24 Northwest Dallas County Flood Control District E.Outfall to the Elm Fork of the Trinity River The damaged gabion mattress at the inlet structure was replaced Miscellaneous Repairs project. Areas of erosion were also repair The visible portions of the inlet structure appear to be in gene The outfall structure shows signs of some minor damage, but cont intended function. Minor cracking is evident in the headwall str was previously observed at the bottom of the spillway as it ente the bottom of the structure was submerged at the time of the rev was not visible, but there were no visible signs of damage to th The noted issues appear to be unchanged from the 2012 review. Photograph 40 Gabion Mattress Apron and Inlet Structure at Sump 3A 25 Northwest Dallas County Flood Control District Photograph 41 Outfall Structure at the Elm Fork of the Trinity River Photograph 42 Outfall Structure at the Elm Fork of the Trinity River 26 Northwest Dallas County Flood Control District F.General Observations Stockpiled wood mulch and sand have been observed previously in parking lot. These materials can wash into the storm sewer syste material stockpiles as noted in previous reports were observed a review. A previous problem with standing water in the TXU Right of Way a s been reported. At the time of our observations, water levels w elevated in this area. This area is within the District boundary District. It is our understanding that the Riverchase Owners Ass City are ultimately responsible for maintenance of this area. Th trail project that will include improvements to the affected pro contacted by the City to provide a concept for drainage improvem NDM is waiting for direction from the City. Vegetation along the banks of the Sumps did not appear to have b some time in many areas. While vegetation may have an adverse im Photograph 43 Vegetation and Standing Water in TXU ROW behind Gabion Spillway 27 Northwest Dallas County Flood Control District Photograph 44 Vegetation Typical along Banks of Sumps V.RECOMMENDATIONS In general, the District's facilities are in good condition. How maintenance and monitoring are advisable. 1.Sump Bank Maintenance: The District should contact Riverchase Golf Course again regarding the maintenance of the banks of all sumps within the D address erosion and sloughing which will likely contribute to se facilities; however this does not appear to have a great impact understanding that the golf course is responsible for the mainte sump edges. In addition, vegetation growth along the sump banks obstructs th condition of the slope and storm sewer outfall conditions. 2.Vegetation Growing near District Structures: Vegetation growing near District structures should be monitored and removed if necessary. 3.Erosion behind Gabion Spillway 6: Eroded areas need to be filled and stabilized. 4.Glory Holes: Glory holes should be cleaned and maintained. 28 Northwest Dallas County Flood Control District APPENDIX A FACILITY AND MAINTENANCE SUMMARY 29 Northwest Dallas County Flood Control District APPENDIX B SITE MAP 32 Northwest Dallas County Flood Control District APPENDIX C OUTFALL EXHIBIT 34 Northwest Dallas County Flood Control District APPENDIX D PROJECTED MAINTENANCE, ENGINEERING AND NPDES/TPDES COSTS 36