NDCFCD 2012 status reviewTable of Contents
SectionPage
I. EXECUTIVE SUMMARY....................................................................................2
II. SCOPE OF SERVICES..........................................................................................2
III. LIMITATION.........................................................................................................2
IV. OBSERVATIONS..................................................................................................2
A. Sumps...........................................................................................................2
B. Box Culverts under Riverchase Drive.......................................................13
C. Glory Holes................................................................................................13
D. Spillways....................................................................................................15
E. Outfall to the Elm Fork of the Trinity River..............................................20
F. General Observations.................................................................................22
V. RECOMMENDATIONS......................................................................................24
Appendix A Facility and Maintenance Summary.........................................................25
Appendix B Site Map....................................................................................................28
Appendix C Projected Maintenance, Engineering and NPDES/TPDES Costs.............30
1
I.EXECUTIVE SUMMARY
Nathan D. Maier Consulting Engineers, Inc. (NDM) was retained by the Northwest Dallas
County Flood Control District (District) to perform a status review of the District’s facilities
and structures. The District is generally located in and around the Riverchase Golf Course in
the City of Coppell, Texas (see Appendix B “Site Map”).
In general, all of the District’s facilities are functioning properly and are in good condition.
NDM visually reviewed the status of all above ground facilities within the District (intake
structure, spillway structures, glory hole intakes, sump banks, swales and outfall structure).
Observation of the performance of below grade structures was noted, but the facilities below
grade (box culverts, headwalls and storm sewer piping between sumps) were not visually
reviewed for this report because they are either submerged or buried and are not accessible.
Silt was previously probed in Sumps 2, 9, 10, 11 and 14 to evaluate sedimentation build-up
rates since those sumps and associated box culverts were cleaned in 2004 through 2006.
Negligible sediment accumulation was noted and therefore silt was not probed for this
review. Silt will be probed periodically for future reviews.
II.SCOPE OF SERVICES
NDM is providing engineering services to the District. These services include:
1.Performing a site reconnaissance of the District’s structures and facilities.
2.Preparing a report identifying the condition of the District’s structures and facilities.
3.Updating the 5 year maintenance schedule.
4.Attending a board meeting to answer any questions the District has concerning this
report.
III.LIMITATION
This report was prepared for the District. All information within this report is confidential
and may not be reproduced or conveyed in any fashion without the expressed written consent
of the District, and NDM. This report was prepared using generally accepted engineering
practices and no other warranty is expressed or implied.
IV.OBSERVATIONS
The following are photographs and comments from NDM's observations. Refer to
Appendix B, Site Map, for locations of photographs and facilities described.
A.Sumps
Sumps determined to have an impact on the hydraulic performance of the District’s facilities
have had sediment removed. Sediment was removed from Sump 11 in 2004. Sediment was
removed from Sumps 9 and 10 in 2006. Work to remove sediment from Sumps 2 and 14 was
completed in 2007.
2
Although some sediment accumulation has previously been noted in all of the recently
dredged sumps, sediment levels are minor and pose no concern at this time. Some minor
erosion was noted along the banks of the sumps but does not appear to be a significant
contributor to sediment accumulation at this time.
Erosion along the banks of sumps was evident at headwalls outfalling into sumps as well
as at the intake structure in Sump 3A. Vegetation growth prevented observation of these
areas in detail for this review, but no signs were evident that this condition has worsened.
Storm water levels were very high in 2007. Minor slope failures were noted along the
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 condition has worsened.
A sinkhole over the box culvert outfalling into Sump 11 was noted. It was also noted in
our reports 2006, 2007, 2008, 2009, 2010 and 2011. It did not appear to grow in size
since the last observation, but is likely the result of some type of void in the box culvert
allowing the infiltration of soil and water.
Aquatic vegetation is currently being addressed in Sump 14 near the box culvert under
Riverchase Drive.
A golf course retaining wall failure along the banks of Sump 10 was under repair at the
time of this review.
Photograph 1
Sloughing along South and West Bank of Sump 1A
3
Photograph 2
Erosion at Headwall at Sump 1A
Photograph 3
Sloughing along East and South Banks of Sump 1A
4
Photograph 4
Sloughing along West Bank of Sump 2A
Photograph 5
Sloughing along Northwest Corner of Sump 2A
5
Photograph 6
Erosion and Slope Failure South Bank of Sump 3A
Photograph 7
New Gabion Mattress on East Bank of Sump 3A
6
Photograph 8
Sloughing along South Bank of Sump 9
Photograph 9
Retaining Wall Failure being Repaired along South Bank of Sump 10
7
Photograph 10
Sloughing along East Bank of Sump 18
Photograph 11
Box Culvert Intake for Culvert under MacArthur Blvd
8
Photograph 12
Sinkhole over Box Culvert that Outfalls into Sump 11
Photograph 13
Box Culvert Outfall in Sump 11
9
Photograph 14
Sump 11
Photograph 15
Erosion at RCP Headwall in Sump 11
10
Photograph 16
Sloughing on Banks at Sump 9
Photograph 17
Sloughing on Bank at Northeast Corner of Sump 13
11
Photograph 18
Ongoing Treatment of Aquatic Vegetation at Sump 14
Photograph 19
Sloughing at Northeast Corner of Sump 14
12
Photograph 20
Erosion at Southeast Corner of Sump 2
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 were made as to the
overall condition of the structures. Sediment accumulations along the intakes and outfalls
of the box culverts were probed previously during surveys of sediment accumulation in
the adjacent sumps. Based on that information, sediment accumulation 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 condition. The grate at the
Glory Hole on Sump 18 needs to be re-positioned.
The Glory Hole on Sump 13 has significant vegetation growth and requires cleaning.
The Glory Hole on Sump 2 has collected debris and requires cleaning.
13
Photograph 21
Glory Hole at Sump 2
Photograph 22
Glory Hole at Sump 13
14
Photograph 23
Glory Hole at Sump 18
D.Spillways
All spillway structures were replaced in 2002 and 2004. No significant concerns were
noted during this observation and the structures appear to be in good condition. Golf course
maintenance has been performed at Spillways 5 and 6. The condition is improved at both
locations. Vegetation was noted growing in close proximity to Spillways 1, 2, 3, 5 and 6.
Minor cracking was observed in the concrete cap on Spillway 1. Erosion was noted behind
gabion Spillway 6.
15
Photograph 24
Gabion Spillway 1 at Sump 1A
Photograph 25
Crack in Concrete Cap on Gabion Spillway 1 at Sump 1A
16
Photograph 26
Gabion Spillway 2 at Sump 14
Photograph 27
Gabion Spillway 3 at Sump 13
17
Photograph 28
Gabion Spillway 4 at Sump 3A
Photograph 29
Gabion Spillway 5 at Sump 10
18
Photograph 30
Gabion Spillway 6 at Sump 18
Photograph 31
Erosion Behind Gabion Spillway 6 at Sump 18
19
Photograph 32
Erosion Behind Gabion Spillway 6 at Sump 18
E.Outfall to the Elm Fork of the Trinity River
The damaged gabion mattress at the inlet structure was replaced as a part of the 2010
Miscellaneous Repairs project. Areas of erosion were also repaired.
The visible portions of the inlet structure appear to be in generally good condition.
The outfall structure shows signs of some minor damage, but continues to perform its
intended function. Minor cracking is evident in the headwall structure. Some erosion was
previously observed at the bottom of the spillway as it enters the river; however the
bottom of the structure was submerged at the time of the review. The eroded area was not
visible, but there were no visible signs of damage to the structure.
The noted issues appear to be unchanged from the 2011 review.
20
Photograph 33
Gabion Mattress Apron and Inlet Structure at Sump 3A
Photograph 34
Outfall Structure at the Elm Fork of the Trinity River
21
Photograph 35
Outfall Structure at the Elm Fork of the Trinity River
F.General Observations
Stockpiled wood mulch and sand have been observed previously in the golf course
parking lot. These materials can wash into the storm sewer system if not contained. No
material stockpiles as noted in previous reports were observed at the time of this review.
A previous problem with standing water in the TXU Right of Way adjacent to the
District’s facilities has been reported. At the time of our observations, water levels were
elevated in this area. This area is within the District boundary but is not owned by the
District. It is our understanding that the Riverchase Owners Association, Oncor and the
City are ultimately responsible for maintenance of this area. The City has proposed a trail
project that will include improvements to the affected property. NDM is currently
performing a trail alignment study for the City.
Vegetation along the banks of the Sumps did not appear to have been maintained for
some time in many areas. While vegetation may have an adverse impact on the District’s
structures, the vegetation may help to deter bank erosion that has been noted.
22
Photograph 36
Vegetation and Standing Water in TXU ROW behind Gabion Spillway 3
Photograph 37
Vegetation Typical along Banks of Sumps
23
V.RECOMMENDATIONS
In general, the District's facilities are in good condition. However both 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 District in order to
address erosion and sloughing which will likely contribute to sedimentation of District
facilities; however this does not appear to have a great impact at this time. It is our
understanding that the golf course is responsible for the maintenance of the slopes and
sump edges.
In addition, vegetation growth along the sump banks obstructs the view of the slope
conditions.
It is our understanding that Riverchase Golf Course has expressed an intention to
maintain the sump banks over the upcoming winter months.
2.Sinkhole over City Box Culvert west of MacArthur:
While this box culvert is not
owned by the District, the District should notify the City of Coppell again as a courtesy
regarding the sinkhole over the box culvert upstream of Sump 11. The void is located
west of the commercial development west of MacArthur Boulevard. This void has been
noted previously and has also been repaired previously by the City. No significant visible
difference in the void was visible in comparing photographs of the current condition
against photographs from a year ago.
3.Vegetation Growing near District Structures:
Vegetation growing near District
structures should be monitored and removed if necessary.
4.Erosion behind Gabion Spillway 6:
Erosion needs to be filled and stabilized.
5.Glory Holes
: Glory holes should be cleaned and maintained.
24
APPENDIX A
FACILITY AND MAINTENANCE SUMMARY
25
Northwest Dallas County Flood Control District
Facility Maintenance Inspection Summary
September 2012
Sump2012 CommentsRecommendationsctivitction Taken
AyA
1ASloughing noted.Monitor progress of bank erosionNone.
Sediment accumulation noted in 2004 Annual
Sloughing noted.Review. Sediment removed in 2007.
2Monitor progress of bank erosion
2ASloughing noted.Monitor progress of bank erosionNone.
3ASloughing noted.Monitor progress of bank erosionNone.
9Sloughing noted.Monitor progress of bank erosionNone.
10Sloughing noted.Monitor progress of bank erosionNone.
Sediment accumulation noted in 2004 Annual Sediment removed in 2007. Debris
Sloughing noted. Review. Debris noted at outfall in 2009.removed in 2011.
11Monitor progress of bank erosion
13Sloughing noted. Monitor progress of bank erosionNone.
Sediment accumulation noted in 2004 Annual
Sloughing noted. Review. Sediment removed in 2007.
14Monitor progress of bank erosion
18Sloughing noted.Monitor progress of bank erosionNone.
Box Culvert
Sediment accumulation noted in 2004 Annual
Review.Sediment removed in 2006.
4-8x4Submerged. No comments.None
Sediment accumulation noted in 2004 Annual
Review.Sediment removed in 2006.
5-8x4Submerged. No comments.None
Glory Hole
Addition of grate recommended in 2003 Annual Grate installed in 2004. Grate
Review. Grate cleaning recommended in 2009.cleaning addressed in 2011.
Sump 2Grate is displaced.Re-place grate
Addition of grate recommended in 2003 Annual Grate installed in 2004. Grate
Review. Grate cleaning recommended in 2009.cleaning addressed in 2011.
Sump 13Overgrown with vegetation.Clean glory hole
Addition of grate recommended in 2003 Annual Grate installed in 2004. Grate
Review. Grate cleaning recommended in 2009.cleaning addressed in 2011.
Sump 18Debris collected on grate.Clean grate
Spillway
Damage noted in 2003 Annual Review.Structure replaced in 2004.
1Minor cracking noted. Vegetation growing near face of structure.Monitor vegetation
Damage noted in 2003 Annual Review.Structure replaced in 2004.
2No damage noted. Vegetation growing near face of structure.Monitor vegetation
Damage noted in 2001 Annual Review.Structure replaced in 2002.
3No damage noted. Vegetation growing near face of structure.Monitor vegetation
Damage noted in 2003 Annual Review.Structure replaced in 2004.
4No damage noted.Monitor vegetation
5No damage noted. Vegetation growing near face of structure.Damage noted in 2001 Annual Review.Structure replaced in 2002. Hole
filled and grading performed by
Riverchase Golf in 2010.
Monitor vegetation
6Erosion noted behind structure. No damage noted. Vegetation Damage noted in 2001 Annual Review.Structure replaced in 2002.
growing near face of structure.
Monitor vegetation
Outfall to the East Fork of the Trinity River
Gabion deterioration and erosion noted in 2009 Gabion and erosion repairs
No comments.review.addressed in 2011.
IntakeNone
Outfall Minor cracking at headwall/minor erosion.Monitor condition of outfallNone.
9/28/2012
Northwest Dallas County Flood Control District
Maintenance Summary*
September 2012
Construction Cost
YearProject
Annual Status Review
2002*2002 Gabion Spillway RepairsReplaced Spillway Structures 3, 5, and 6$76,100.00
2003No Maintenance Projects$0.00
20042003 Drainage Structure RepairsReplaced Spillway Structures 1, 2, and 4 and added grates to glory holes at Sumps 2, 13, and 18$138,400.00
Removed sediment from Sump 11 and cleaned box culvert under MacArthur Blvd.**
20052004 Sump #11 Sediment Removal Project$224,104.00
Removed sediment from Sumps 9 and 10 and cleaned box culverts under Riverchase Dr. ***
20062005 Sediment Removal Project****$197,407.40
Removed sediment form Sumps 2 and 14
20072005 Sediment Removal Project****$91,876.50
2008No Maintenance Projects$0.00
2009No Maintenance Projects$0.00
Removed debris in Sump 11; cleaned grates at Glory Holes in Sumps 2, 13 and 18; repaired
gabions and erosion at Intake to Outfall to the East Fork of the Trinity River
20102010 Miscellaneous Repairs Project Initiated$0.00
20112010 Miscellaneous Repairs Project Completed$172,392.00
2012No Maintenance Projects$0.00
Total$900,279.90
* NDMCE has no records of any maintenance projects prior to 2002.
** City of Coppell contributed $17,964.00 for box culvert cleaning.
*** City of Coppell contributed $82,692.90 for box culvert cleaning.
**** Split construction contract into two areas of work.
9/28/2012
APPENDIX B
SITE MAP
28
APPENDIX C
PROJECTED MAINTENANCE, ENGINEERING
AND NPDES/TPDES COSTS
30
Northwest Dallas County Flood Control District
5 Year Maintenance Schedule
2012-2017
(October through September)
Fiscal YearRecommended MaintenanceProjected Construction CostProjected Engineering FeesCombined Total
2012-2013Annual Status Review$0$7,700
Miscellaneous Repairs$3,500$6,000
NPDES/TPDES Requirements*$500$5,000
Totals$4,000$18,7002012 to 2013 Combined Total$22,700
2013-2014Annual Status Review w/Survey$0$15,250
Miscellaneous Repairs$3,500$1,000
NPDES/TPDES Requirements$500$2,500
Totals$4,000$18,7502013 to 2014 Combined Total$22,750
2014-2015Annual Status Review$0$8,240
Miscellaneous Repairs$3,500$1,000
NPDES/TPDES Requirements$500$2,500
Totals$4,000$11,7402014 to 2015 Combined Total$15,740
2015-2016Annual Status Review$0$8,450
Miscellaneous Repairs$3,500$1,000
NPDES/TPDES Requirements$500$2,500
Totals$4,000$11,9502015 to 2016 Combined Total$15,950
2016-2017Annual Status Review$0$8,750
Miscellaneous Repairs$3,500$1,000
NPDES/TPDES Requirements$500$2,500
Totals$4,000$12,2502016 to 2017 Combined Total$16,250
$20,000$73,390$93,390
5 Year Estimate
Engineering and NPDES/TPDES Costs
* TCEQ Permit will be renewed in 2013 with possible changes in requirements for MS4's.
9/28/2012
8080 Park Lane, Suite 600
Dallas, TX 75231
(P) 214.739.4741
(F) 214.739.5961