Annual Report 150130
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 ........................................................... 27
F.General Observations ........................................................................................... 29
V.RECOMMENDATIONS ................................................................................................. 30
Appendix A Facility and Maintenance Summary ......................................................... 31
Appendix B Site Map .................................................................................................... 35
Appendix C Sediment Accumulation Exhibits .............................................................. 37
Appendix D Projected Maintenance, Engineering and NPDES/TPDES Costs ............... 43
1
Northwest Dallas County
Flood Control District
I.EXECUTIVE SUMMARY
Nathan D. Maier Consulting Engineers, Inc. (NDM) was retained by the Northwest Dallas
and structures. The District is generally located in and around the Riverchase Golf Course in
the C
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).
Visible storm sewer outfalls along sump banks were also reviewed. Observation of the
performance of below grade structures was noted. However, 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. Storm
sewer outfalls flowing into District sumps were surveyed as a part of this review. 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. The sediment accumulations are documented
in Appendix D.
II.SCOPE OF SERVICES
NDM is providing engineering services to the District. These services include:
1.
2.Preparing
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.
2
Northwest Dallas County
Flood Control District
A.Sumps
Sumps determined to have an impact
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.
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.
Soughing along the banks of sumps was evident at headwalls outfalling into a number of
the 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.
Storm sewer outfalls into the sumps were observed. Visual observation and survey were
performed where outfalls were found and were accessible at the time of the review.
Vegetation growth along the sump banks limited access and obscured visual
observations. Some erosion around storm sewer headwalls was observed. Minor
sediment accumulation was noted in some areas. A number of storm sewer outfalls
shown on record drawings were not found in the field. See Attachment C - Outfall
Exhibit.
Significant aquatic vegetation was noted in Sump 13 during this review.
Sumps 10, 18, 11, 13, 14 and 2 were observed in April of this year. At that time, mowing
had been performed on the banks of these sumps. Mowing had not been performed on
sumps 1A, 2A, 3A and 9. At that time, there were no signs that erosion or slope failures
had worsened from previous reviews.
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 of 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 of Sump 2A
6
Northwest Dallas County
Flood Control District
Photograph 7
Erosion behind Storm Sewer Outfall Headwall of Sump 2A
Photograph 8
Erosion and Slope Failure along South Bank of Sump 3A
7
Northwest Dallas County
Flood Control District
Photograph 9
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 (by others) along South Bank of Sump 10
9
Northwest Dallas County
Flood Control District
Photograph 13
Erosion at Storm Sewer Outfall Headwall of Sump 10
Photograph 14
Excessive Aquatic Vegetation in Sump 13
10
Northwest Dallas County
Flood Control District
Photograph 15
Box Culvert Intake for Culvert under MacArthur Blvd.
Photograph 16
Storm Sewer Outfall Headwall on Bank of Sump 11 Condition not Observed
11
Northwest Dallas County
Flood Control District
Photograph 17
Box Culvert Outfall of Sump 11
Photograph 18
Sump 11 Overview
12
Northwest Dallas County
Flood Control District
Photograph 19
Erosion at Storm Sewer Outfall Headwall in Sump 11
Photograph 20
Sloughing on Banks of Sump 9 (Obscured by Vegetation)
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 14 Condition not Observed
14
Northwest Dallas County
Flood Control District
Photograph 23
Storm Sewer Outfall Headwall on Bank of Sump 11 Condition not Observed
15
Northwest Dallas County
Flood Control District
Photograph 24
Box Culvert Headwall of Sump 14
Photograph 25
Sloughing at Northeast Corner of Sump 14 (Obscured by Vegetation)
16
Northwest Dallas County
Flood Control District
Photograph 26
Storm Sewer Outfall Headwall at Southeast Corner of Sump 2
Photograph 27
Storm Sewer Outfall Erosion behind Headwall of Sump 2
17
Northwest Dallas County
Flood Control District
Photograph 28
Storm Sewer Outfall Erosion behind Headwall 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 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 Glory Hole
on Sump 2 has collected debris and requires cleaning. The Glory Hole on Sump 13 has
significant vegetation growth and requires cleaning. The grate at the Glory Hole on
Sump 18 needs to be re-positioned.
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 significant concerns were
noted during this observation and the structures appear to be in good condition.
Vegetation was noted growing in close proximity to Spillways 1, 2, 3, 5 and 6. Minor
cracking was observed in the concrete cap on Spillways 1, 2, 4 and 6. Erosion was noted
behind gabion Spillway 6. Erosion behind Spillway 6 appears to be unchanged from
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
Crack in Concrete Cap on Gabion Spillway 2 at Sump 14
22
Northwest Dallas County
Flood Control District
Photograph 35
Crack in Concrete Cap on Gabion Spillway 4 at Sump 3A
Photograph 36
Crack in Concrete Cap on Gabion Spillway 6 at Sump 18
23
Northwest Dallas County
Flood Control District
Photograph 37
Gabion Spillway 2 at Sump 14
Photograph 38
Gabion Spillway 3 at Sump 13
24
Northwest Dallas County
Flood Control District
Photograph 39
Gabion Spillway 4 at Sump 3A
Photograph 40
Gabion Spillway 5 at Sump 10
25
Northwest Dallas County
Flood Control District
Photograph 41
Gabion Spillway 6 at Sump 18
Photograph 42
Erosion Behind Gabion Spillway 6 at Sump 18
26
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 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 2013 review.
Photograph 43
Gabion Mattress Apron and Inlet Structure at Sump 3A
27
Northwest Dallas County
Flood Control District
Photograph 44
Outfall Structure at the Elm Fork of the Trinity River
Photograph 45
Outfall Structure at the Elm Fork of the Trinity River
28
Northwest Dallas County
Flood Control District
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
s 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 was
contacted by the City to provide a concept for drainage improvements in this area.
NDM is waiting for direction from 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
Photograph 46
Vegetation and Standing Water in TXU ROW behind Gabion Spillway 3
29
Northwest Dallas County
Flood Control District
Photograph 47
Vegetation Typical along Banks of Sumps
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 ability to observe the
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.
3.Erosion behind Gabion Spillway 6: Eroded areas need to be filled and stabilized.
4.Glory Holes: Glory holes should be cleaned and maintained.
5.Aquatic Vegetation in Sump 13 should be monitored.
6.Cracking in Spillway Concrete Caps should be monitored.
30
Northwest Dallas County
Flood Control District
APPENDIX A
FACILITY AND MAINTENANCE SUMMARY
31
9/29/2014
Sediment removed in 2007. Debris
Structure replaced in 2002. Hole
filled and grading performed by
Grate installed in 2004. Grate Grate installed in 2004. Grate Grate installed in 2004. Grate
cleaning addressed in 2011.cleaning addressed in 2011.cleaning addressed in 2011.
Structure replaced in 2004. Structure replaced in 2004. Structure replaced in 2004.
Sediment removed in 2007.Sediment removed in 2007.Sediment removed in 2006.Sediment removed in 2006.
Structure replaced in 2002.Structure replaced in 2002.
Riverchase Golf in 2010.
removed in 2011.
Action Taken
Addition of grate recommended in 2003 Annual Review. Grate cleaning recommended in 2009.Addition of grate recommended in 2003 Annual Review. Grate cleaning recommended in 2009.Addition
of grate recommended in 2003 Annual Review. Grate cleaning recommended in 2009.
Sediment accumulation noted in 2004 Annual Sediment accumulation noted in 2004 Annual Sediment accumulation noted in 2004 Annual Sediment accumulation noted in 2004 Annual Sediment accumulation
noted in 2004 Annual
Review. Debris noted at outfall in 2009.
Damage noted in 2003 Annual Review.Damage noted in 2003 Annual Review.Damage noted in 2001 Annual Review.Damage noted in 2003 Annual Review.Damage noted in 2001 Annual Review.Damage
noted in 2001 Annual Review.
Northwest Dallas County Flood Control District
Facility Maintenance Inspection Summary
Review. Review.
Review.Review.
Activity
None.None.None.None.None.None.None.
Monitor cracking; Monitor vegetation
Monitor cracking; Monitor vegetation;
September 2014
Monitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank
erosionMonitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank erosionMonitor progress of bank erosion
Recommendations
Monitor vegetation
Monitor crackingMonitor cracking
Clean glory hole
Monitor erosion
Re-place grate
Clean grate
NoneNoneNone
Erosion noted behind structure. Minor cracking noted. Vegetation
Minor cracking noted. Vegetation growing near face of structure.
No damage noted. Vegetation growing near face of structure.
growing near face of structure.
Submerged. No comments.Submerged. No comments.Overgrown with vegetation.
Debris collected on grate.
Minor cracking noted. Minor cracking noted.
Grate is displaced.
No damage noted.
Sloughing noted. Sloughing noted. Sloughing noted.
Sloughing noted.Sloughing noted.Sloughing noted.Sloughing noted.Sloughing noted.Sloughing noted.Sloughing noted.
2014 Comments
Box Culvert
Glory Hole
Sump 13Sump 18
Sump 2
Spillway
4-8x45-8x4
1011131418
1A2A3A
29123456
Sump
9/29/2014
Gabion and erosion repairs
addressed in 2011.
Action Taken
NANANANANANANANANANANANANANANANANANANANANANA
Gabion deterioration and erosion noted in 2009
Northwest Dallas County Flood Control District
Facility Maintenance Inspection Summary
Activity
review.
None.
NANANANANANANANANANANANANANANANANANANANANANA
2. Listing includes all storm sewer outfalls identified from record drawing investigations. Not all storm sewer outfalls were found in the field.
September 2014
Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued
visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.Contin
ued visual observation.Continued visual observation.Continued visual observation.Continued visual observation.
Monitor condition of outfall
Recommendations
None
Apparent erosion at flowline. Minor erosion visible around headwall.
Minor sediment accumulation at flowline. Visible erosion around headwall.Minor sediment accumulation at flowline. Visible erosion around headwall.Minor sediment accumulation at flowline.
Visible erosion around headwall.
Apparent erosion at flowline. Visible erosion around headwall.Apparent erosion at flowline. Visible erosion around headwall.Apparent erosion at flowline. Visible erosion around headwall.Apparent
erosion at flowline. Visible erosion around headwall.
1. Not all headwalls visible or accessible at time of observations.
Minor cracking at headwall/minor erosion.
Minor sediment accumulation at flowline.Minor sediment accumulation at flowline.
Minor erosion visible around headwall.
Outfall to the East Fork of the Trinity River
Visible erosion around headwall.Visible erosion around headwall.Visible erosion around headwall.Visible erosion around headwall.
Apparent erosion at flowline.Apparent erosion at flowline.
1,2
Storm Sewer Outfalls to Sumps
No comments.
Not Found.Not Found.Not Found.Not Found.Not Found.
Outfall
Intake
1A-A2A-A2A-B
10-A10-B11-A11-B11-E13-A13-B14-A14-B18-A18-B
11-C11-D13-C13-D14-C
2-A2-B8-A
Notes:
9/29/2014
$76,100.00$0.00$138,400.00$224,104.00$197,407.40$91,876.50$0.00$0.00$0.00$172,392.00$0.00$0.00$0.00$900,279.90
Construction Cost
Replaced Spillway Structures 1, 2, and 4 and added grates to glory holes at Sumps 2, 13, and 18
Removed debris in Sump 11; cleaned grates at Glory Holes in Sumps 2, 13 and 18; repaired
Removed sediment from Sumps 9 and 10 and cleaned box culverts under Riverchase Dr. ***
Removed sediment from Sump 11 and cleaned box culvert under MacArthur Blvd.**
gabions and erosion at Intake to Outfall to the East Fork of the Trinity River
Northwest Dallas County Flood Control District
Removed sediment form Sumps 2 and 14
Maintenance Summary*
Replaced Spillway Structures 3, 5, and 6
September 2014
Annual Status Review
2010 Miscellaneous Repairs Project Completed
2010 Miscellaneous Repairs Project Initiated
2004 Sump #11 Sediment Removal Project
2005 Sediment Removal Project****2005 Sediment Removal Project****
* NDMCE has no records of any maintenance projects prior to 2002.
2003 Drainage Structure Repairs
*** City of Coppell contributed $82,692.90 for box culvert cleaning.
** City of Coppell contributed $17,964.00 for box culvert cleaning.
2002 Gabion Spillway Repairs
No Maintenance ProjectsNo Maintenance ProjectsNo Maintenance ProjectsNo Maintenance ProjectsNo Maintenance ProjectsNo Maintenance Projects
**** Split construction contract into two areas of work.
Project
2002*
Total
200320042005200620072008200920102011201220132014
Year
Northwest Dallas County
Flood Control District
APPENDIX B
SITE MAP
35
Northwest Dallas County
Flood Control District
APPENDIX C
SEDIMENT ACCUMULATION EXHIBITS
37
Northwest Dallas County
Flood Control District
APPENDIX D
PROJECTED MAINTENANCE, ENGINEERING
AND NPDES/TPDES COSTS
43
9/29/2014
$24,500$24,965$25,444$25,937$39,000$139,846
Combined Total
Combined TotalCombined TotalCombined TotalCombined TotalCombined Total
$13,000$5,000$2,500$20,500$13,390$5,000$2,575$20,965$13,792$5,000$2,652$21,444$14,205$5,000$2,732$21,937$25,000$5,000$5,000$35,000
$119,846
Projected Engineering Fees
Northwest Dallas County Flood Control District
(October through September)
5 Year Maintenance Schedule
2014-2019
Projected Construction Cost
$0$3,500$500$4,000$0$3,500$500$4,000$0$3,500$500$4,000$0$3,500$500$4,000$0$3,500$500$4,000
$20,000
NPDES/TPDES Requirements (Current
projected SWMP renewal in December
Annual Status Review (Includes Storm
Outfall Survey and Sediment Survey)
Recommended Maintenance
NPDES/TPDES RequirementsNPDES/TPDES RequirementsNPDES/TPDES RequirementsNPDES/TPDES Requirements
5 Year Projected Costs
Miscellaneous RepairsMiscellaneous RepairsMiscellaneous RepairsMiscellaneous RepairsMiscellaneous Repairs
Annual Status ReviewAnnual Status ReviewAnnual Status ReviewAnnual Status Review
2013)TotalsTotalsTotalsTotalsTotals
Fiscal Year
2014-20152015-20162016-20172017-20182018-2019