Hydraulics_Report_SD FTNP BADL 10(9).pdf

Final Hydraulic Report Dillon Pass

SD FTNP BADL 10(9)

Prepared by Brian Campbell

Technical Services Hydraulic Engineer Central Federal Lands Highway Division

Lakewood, Colorado December 2018

Contents Summary

Introduction

Location

Design Criteria

Cross Culverts

Storm Drain

Pavement Drianage

Hydrology

Dillon Pass

Existing Conditions for Dillon Pass

Proposed Conditions

Material

Pond

Rundowns and Energy Dissipator

Embankment Repair

Hydraulic Analysis

Bigfoot Pass

Existing Conditions for Bigfoot Pass

Proposed Conditions

Hydraulic Analysis

Inlet Retrofit

Inlet Discussion

Inspection summary

Inspection Discussion

References

Appendix A: Inlet Capacity Analysis:

Summary The following report provides hydraulic recommendations for SD FTNP BADL 10(9) Badlands Dillon and Bigfoot pass improvements.

The recommendations include:

- Bigfoot Pass o Retrofit existing storm drain inlets o Replace 2 CMP pipes along the storm drain alignment o Replace 2 CMP pipes within the Bigfoot Pass parking area

- Dillion Pass o Slip line pond outlet o Replace existing cross culverts and rundowns o Replace outlet with modified stilling well dissipator

Introduction The following report summarizes the proposed drainage improvements to incorporate into Badlands Loop Road at Dillon Pass and Bigfoot Pass. The project includes reconstructing the two roadway sections of the Badlands Loop Road, see Figure 1.

Existing drainage conditions at Dillon Pass include 2,600-feet of roadway which has been impacted by: clogged pond inlet, piping action around an existing culvert, failing energy dissipation devices located at culvert rundowns, and pipe material not suitable for the physical conditions of the site.

Existing drainage conditions at Bigfoot Pass consist of inefficient curb and gutter inlets and minor scour at storm drain outlets.

Location Dillon and Bigfoot Pass are located on Badlands Loop Road. The project is approximately 12 miles and 22 miles south of Wall, SD respectively.

Figure 1: Badlands National Park Boundary Map

Bigfoot Pass, see Figure 23

Dillon Pass, see Figure 7

Design Criteria The roadway is designated as a high standard road with a design ADT of 3874.

Chapter 7 of the Project Development and Design Manual (PDDM) published by the FHWA (2012) provides guidance for sizing drainage facilities on high standard road. The following standards are applied to this project:

Cross Culverts

- Cross culverts will convey runoff from the 50-year flood event

- The maximum Headwater to Diameter Ratio (HW/D) is 1.5 for culverts equal to or less than 48 inches and 1.2 for culverts greater than 48 inches.

- The minimum culvert diameter is 24 inches

Storm Drain

- Storm drain on grade will convey runoff from the 10-year flood event

Pavement Drainage

- On high standard roads, limit the spread width of surface drainage to 3 feet of one travel lane. The depth of flow should not exceed the curb height.

Hydrology The Watershed Modeling System (WMS vs 10.1) was used to delineate drainage areas from the tributaries. None of the drainage basins were gaged. However, all of the drainage areas were less than 160 acres. Criterial was met for using the rational method to identify peak flood-frequency values. For more information on the rational method and the variables required, see Federal Highway Administration HDS-2, Highway Hydrology, Second Edition, October 2002.

A minimum time of concentration (most conservative assumption) of 5 minutes was used for the storm drain analysis. In areas where the drainage basin was large enough the minimum time of concentration could not be used (cross culverts), the NRCS method was used to calculate the time of concentration. Values for the 10-year and 50-year intensities were gathered from NOAA Atlas 14.

The runoff coefficient for paved areas and undeveloped areas were given C values of 0.95, and 0.40 respectively. Mixed use areas (1/2 paved, 1/2 undeveloped) were given a weighted C value of 0.68.

Basins for the project limits can be seen in Figures 2-6. A summary of flow values are listed in Table 1.

Figure 2: Drainage Basins for Bigfoot Pass

Figure 3: Inlet locations for Bigfoot Pass East

North

Figure 4: Inlet locations for Bigfoot Pass West

Figure 5: Drainage Basins for Dillion Pass

Figure 6: Culvert and rundown locations for Dillon Pass

Table 1: Hydrology Summary

Basin ID Description Design Storm (Year Event)

Time of Concentration

(minutes)

Runoff Coefficient

Area (Acres)

10-year Intensity

(Inches/Hour)

50-year Intensity

(Inches/Hour)

10-year Runoff

(cfs)

50-year Runoff

(cfs)

114 Bigfoot Pass Overlook parking lot

10 5 0.8 1.25 6.53 6.53

115 Bigfoot Pass Overlook parking lot

10 5 0.40 1.25 6.53 3.27

116 US drop inlet 10 5 0.95 0.84 6.53 5.21

116 drop inlet 10 5 0.95 0.06 6.53 0.37

118 drop inlet 10 5 0.95 0.11 6.53 0.68

119 drop inlet 10 5 0.95 0.18 6.53 1.12

120 drop inlet 10 5 0.95 0.05 6.53 0.31

121 drop inlet 10 5 0.95 0.26 6.53 1.61

122 drop inlet 10 5 0.95 0.15 6.53 0.93

124 drop inlet 10 5 0.95 0.13 6.53 0.81

125 drop inlet 10 5 0.95 0.34 6.53 2.11

126 culvert with headwall

50 36 0.40 91.29 2.62 3.78 138.03

129 culvert with headwall

50 21 0.40 21.86 3.88 5.62 49.14

131 culvert with headwall

50 37 0.40 52.95 2.62 3.78 80.06

133 drop inlet 10 5 0.95 0.23 6.53 1.43

134 drop inlet 10 5 0.95 0.17 6.53 1.05

135 drop inlet 10 5 0.95 0.12 6.53 0.74

137 drop inlet 10 5 0.95 0.19 6.53 1.18

138 drop inlet 10 5 0.95 0.10 6.53 0.62

139 drop inlet 10 5 0.95 0.05 6.53 0.31

140 drop inlet 10 5 0.95 0.16 6.53 0.99

141 drop inlet 10 5 0.95 0.18 6.53 1.12

142 drop inlet 10 5 0.95 0.15 6.53 0.93

143 drop inlet 10 5 0.95 0.19 6.53 1.18

144 drop inlet 10 5 0.95 0.27 6.53 1.67

145 drop inlet 10 5 0.95 0.26 6.53 1.61

Basin ID Description Design Storm (Year Event)

Time of Concentration

(minutes)

Runoff Coefficient

Area (Acres)

10-year Intensity

(Inches/Hour)

50-year Intensity

(Inches/Hour)

10-year Runoff

(cfs)

50-year Runoff

(cfs)

West Fill Slope West

Channel 50 36 0.40 54.54 3.78 82.46

301 culvert with headwall

50 5 0.68 1.66 6.53 9.43 10.57

302 drop inlet 10 5 0.95 0.58 6.53 3.60

303 culvert with headwall

50 5 0.68 1.14 6.53 9.43 7.26

304 drop inlet 10 5 0.95 0.26 6.53 1.61

305 culvert with headwall

50 10 0.68 5.86 6.53 6.91 27.33

Dillon Pass Existing Conditions for Dillon Pass The existing conditions for Dillon Pass include:

- Pond area at ≈ station 1341+60. Pond area includes a 24-inch outlet pipe.

- 24-inch cross culverts at approximately the following stations: 1326+30 and 1331+51

- Drop inlets at the following stations: 1337+72, 1331+57, and 1330+67

- Rundowns are connected to the features listed above and outlet in various locations along the toe of the embankment.

Figure 7: Dillon Pass project limits

Proposed Conditions Material Previously, plastic pipe had been used throughout the park for various drainage features. In many locations, the pipe was not buried or insulated, but installed on the surface and staked to the embankment in steep areas. Plastic pipe has a large temperature expansion/contraction coefficient. When exposed to temperature differentials, the pipe can elongate and contract significantly.

Evidence of this was seen in many locations where the pipe was not buried or insulated from temperature fluctuations.

When this happens, the pipe can detach at the joints and ultimately lead to failure, see Figure 8. In instances where the pipe is fixed and unable to move, it can fail in compression or tension. There are instances where headwalls have become compromised due to the expanding and contracting of plastic pipes.

Pond Improvement

Surface Drainage, Cross Drainage, and Rundown Improvements

Existing Rundowns

Figure 8: Plastic pipe failure due to thermal expansion/contraction

Material Recommendation If plastic pipe is to be used, it is recommended the material is completely buried or insulated from temperature fluctuations. Per the Park’s request, reinforced concrete pipe, as opposed to corrugated metal pipe, is recommended in areas where the conduit daylights through embankments and is exposed to sunlight.

Pond At approximate station 1341+60, a pond formed on the north side of the road. The area was previously drained with a 24-inch CMP as shown in as-builts dated 1995 from South Dakota PRA-BADL 10(1). It was unclear to Park staff why the pond formed.

Near this location, a gabion retaining structure had been installed to support the roadway shoulder. During the investigation of this location, it appears this gabion structure failed and the gabion fill material was transported into the pipe causing an obstruction to flow.

After a storm event around April 2018, the obstruction was cleared and the pond drained.

The Park and project team discussed replacing this pipe due to the age of the conduit (≈ 23 years from 1995) and increasing the size.

The pipe is under approximately 20 feet of fill. To minimize traffic delays and user cost impact, replacement would typically include flow filling the old pipe, abandoning in place, and exploring options to jack a pipe through the embankment without the need to excavate into the 20 feet of fill.

However, the Park specifically requested any effort to replace the pipe include removing the old pipe and not abandoning it in place.

To remove the old pipe, it is likely a temporary detour (shoo-fly) would need to be constructed to facilitate the excavation without closing the road. An alternate approach was pursued.

The existing condition of the pipe was inspected using video recording and monitoring with a robotic crawler, see Figure 27. Gabion material was found in the pipe near the inlet, however, the pipe was free of obstructions for the remainder of the length. The video inspection process showed the pipe was in Good condition, free of penetrations or protrusions. In most areas, the protective lining the pipe was initially installed with was intact.

Pond Area Recommendation To improve the longevity of this culvert, it is recommended to clean the culvert for the entire length and retrofit with a slip line. It is recommended to use either a close-fit lining or a cured-in-place lining. Due to the time the inlet was clogged, material has settled in the pond increasing the elevation. Inlet grading and a pipe extension will be required to adjust to the new elevation.

Figure 9: Pond at approximate station 1340+00

Figure 10: Failed gabion wall located at the west side of the pond. The 18-inch CMP rundown can be seen at the top of the photo

Figure 11: Image after pond drained, April 2018

Figure 12: Existing 24" CMP with approximately 5 feet of aggradation

Figure 13: Gabion material could be seen near the inlet

Figure 14: The pipe is considered Good condition

Rundowns and Energy Dissipator Four rundowns currently exist within the project limits. The rundowns were installed to remove runoff from the roadway prism to the existing drainage waterway. The rundowns were constructed of black plastic storm pipe and were installed on the surface of embankment. The termination detail included a Tee dissipator system on an erosion mat.

Thermal expansion and contraction of the plastic pipe caused separation at many of the joints. The points of separation were a conduit for high energy flow to exist the rundown system. The embankment was exposed to high shear stresses causing significant erosion and failure of the rundown system. The effectiveness of the Tee dissipator is also suspect due to the thermal expansion and contraction as well as undermining from erosion. The Tee dissipator did not have properly sized relief holes to pass sediment. The result was sediment partially clogged the outlet and created a nozzle effect. This accelerated erosion in the vicinity of the outlet.

Figure 15:Tee dissipator with erosion encroaching

Figure 16: Failed rundown

Figure 17:Erosion encroaching on Tee

Figure 18: Failed rundown and resulting severe erosion

Modified Stilling Well, Energy Dissipator Recommendation

The design of the US Army Corps of Engineers’ stilling well energy dissipator is based on model tests conducted by the US Army Corps of Engineers (USACE, 1963; Grace and Pickering, 1971). It is illustrated in Figure 19. The stilling well can be used in channels with moderate to high concentrations of sand or silt and where debris is not a serious problem. The stilling well should not be used in areas where large floating or rolling debris is expected unless suitable debris-control structures are used. The highway uses of stilling wells are at the outfalls of storm drains, median, and pipe down drains where little debris is expected.

Figure 19: USACE Stilling Well

To minimize maintenance challenges a modified design is proposed. The diameter of the modified stilling well is 5-feet. The modified design uses the energy dissipation function of the expansion and change of direction in flow while (3) 6 -inch vent holes in the base provide relief for sediment that may be transported through the system. The vent holes of the system are placed even with the elevation of the surrounding grade. To prevent from failure due to thrust, overturning or translation, the base is suppressed into the ground (minimum 3-feet) and filled with concrete (per geotech recommendation). The base is sloped towards the vent holes to promote self-cleaning, see Figure 20.

When larger events occur, the water will exit the well from the top and spill to the sides to drain.

Figure 20: Modified Stilling Well

Embankment Repair A mass failure occurred at approximate station 1331+00 which resulted in an emergency repair. Approximately 300 cubic yards of slurry fill was imported to rebuild the embankment. The failure is suspected to have occurred due to piping around the existing culvert. The rate at which this failure propagated is not known. However, during the scoping site visit, it was evident this area also transmits groundwater through the prism.

Embankment Repair Recommendations From conversations with the Park, it is requested the slurry fill be removed and the embankment be reconstructed. It is recommended to replace the existing culvert with a 24-inch RCP and headwall. Although the hydraulic analysis shows the area is within the HW/D ratios of the design criteria, a headwall will further assist with resisting piping along the culvert wall if ponding occurs. Additionally, subsurface drains are proposed to relieve groundwater from the roadway prism.

Figure 21: The area at approximate station 1331+00 is suspected to have failed due to piping of flow around the culvert. The image is of the inlet after an emergency repair was installed.

Hydraulic Analysis Table 2: Hydraulic Analysis Summary for Dillon Pass Pipes

Station Q50 (cfs)

Proposed HW/D ratio

1340+00 (Pond) 30 24” RCP with Drop Inlet

3.1*

1331+50 (Embankment Failure)

10 24” RCP with Headwall

0.88

1349+00 (cross drainage)

11 24” RCP with Headwall

1.00

*The headwater to depth ratio at the pond location will be addressed by constructing an inlet basin at the entrance. All other proposed pipes meet the design criteria. Additionally, the pond area has large storage upstream. The stage-discharge relationship of the culvert can be significantly influenced by storage within a watershed. Sufficient topographic data is not available to accurately model the storage capacity upstream of the pond. However, it is anticipated the 50-year peak culvert discharge within the pond may be significantly reduced.

Bigfoot Pass Existing Conditions for Bigfoot Pass The project footprint for Bigfoot Pass includes:

- Parking area drainage consisting of (2) 12-inch CMP culverts.

- Storm drain consisting of (2) separate systems. The east system (1,500 feet) and the west system (3,500 feet).

- (3) cross culverts o (2) 30-inch RCP o (1) 48-inch RCP

Figure 22: Bigfoot Pass project limits

Proposed Conditions Hydraulic Analysis Table 3: Hydraulic Analysis Summary for Bigfoot Pass Pipes

Station Q50 (cfs)

Q 50 with Storage (cfs)*

Existing HW/D ratio

699+00 (126) 126 40 24” RCP with Headwall

1.22

702+00 (129) 50 26 24” RCP with Headwall

1.08

708+00 (131) 80 80 48” RCP with Headwall

1.4

Each of these areas has large storage upstream. The stage-discharge relationship of the culvert can be significantly influenced by storage within a watershed. Sufficient topographic data is not available to accurately model the storage capacity upstream of these areas. 10-meter digital elevation data was used to estimate the stage/storage relationship. A hydrograph was estimated using the Rational Method and routed through the culverts in this area. Figure 23 shows the reduced peak through the area. The existing pipes meet the design criteria for the corridor.

Bigfoot Parking Lot

Surface Drainage, Cross Drainage, and Rundown Improvements for Extent of Roadway

Approximately 3500 feet of storm drain

Approximately 1500 feet of storm drain

Figure 23: Routed Hydrographs through 699+00 (left) and 702+00 (right)

Inlet Retrofit Areas along Bigfoot Pass include steep longitudinal roadway slopes with minimal gutter sections. This geometrical configuration makes the existing inlets very inefficient. The Park staff expressed concern of water overtopping the curb and causing erosion of embankment slopes. In addition to erosion problems, spread on the roadway becomes an issue with large rain events.

Additionally, due to the mass failure at Dillon Pass station 1331+00, the Park staff requested storm drain inspections. Information from the inspection effort is summarized in the sections below.

Figure 24: Storm drain on steep slopes without a gutter section

Figure 25: Inlets with two grates on steep slopes

In many spots along Bigfoot Pass, the gutter and shoulder are 10 feet wide. These wide shoulders become a safety hazard during peak visitation because users park their vehicles in non-designated parking areas along the shoulder. Part of the Roadway upgrades in the area include obliterating portions of this shoulder and reducing the width to 6 feet.

This geometric change provides an opportunity to retrofit many of the inlets with an inlet settling basin. The basin is designed to capture the runoff from the roadway and provide minor detention for the inlet. The detention is modeled as a sump condition as opposed to an inlet on grade. This retrofit results in significant improvements to the inlet efficiency, see Figure 26.

Figure 26: Inlet Settling Basin Detail

The installed grates are manufactured from Neenah Foundry and are models R3067, R3067-V, and R3067-L. The Neenah Foundry have tested each of these grates and provide performance equations, unique to each grate, on their website. Additionally, the website, https://www.nfco.com/municipal/resources/manning-equation-calculator, includes a calculation tool to estimate the performance of each grate. This tool was used to compute the capacity of each grate, using the 10-year runoff values, as well as the spread width into the traveled lane at each site. Modifications will be made to the inlet at station 692+00 and 695+50. These modifications have been incorporated into the computed values. The output from the calculation tool can be seen in Appendix A.

The results are summarized in Table 3.

Table 4: Inlet Analysis Results

ID Station Neenah Inlet Type Sump Basin Hydology

(cfs)

Basin Hydrology

+ Bypass (cfs)

Capacity

(cfs)

Bypass

(cfs)

Width of Flow in Gutter (ft)

Width of

Shoulder (ft)

Spread into

Lane (ft)

116 US 686+00 R3067 Yes 5.21 5.21 2.30 2.91 4.57 6.00 0.00

118 689+00 R3067 Yes 0.68 3.59 2.00 1.59 4.26 6.00 0.00

120 692+00 DOT 604-A Yes 0.31 1.90 5.00 0.00 4.83 6.00 0.00

124 695+50 R3067 No 0.81 0.81 1.00 0.00 4.64 3.00 1.64

System 1

ID Station Neenah Inlet Type Sump Basin Hydology

(cfs)

Basin Hydrology

+ Bypass (cfs)

Capacity

(cfs)

Bypass

(cfs)

Width of Flow in Gutter (ft)

Width of

Shoulder (ft)

Spread into

Lane (ft)

116 686+00 R3067 Yes 0.37 0.37 2.30 0.00 1.67 6.00 0.00

119 689+00 R3067 Yes 1.12 1.12 3.50 0.00 2.50 6.00 0.00

121 692+00 R3067 Yes 1.61 1.61 1.90 0.00 2.83 6.00 0.00

122 694+50 R3067-V (x2) No 0.93 0.93 1.82 0.00 2.50 3.00 0.00

125 699+00 R3067 No 2.11 2.11 1.51 0.60 3.53 3.00 0.53

Runout 0.60 2.17 3.00 0.00

System 2 https://www.nfco.com/municipal/resources/manning-equation-calculator

Inlet Discussion The inlet analysis does not consider clogging. If the inlets become clogged, it is likely more flow will be bypassed. The result can include increased spread width into the traveled lane. Similar to most infrastructure, the operation of the storm drain system will be dependent on continued maintenance intervals to keep inlets free of debris and clogging.

Inspection summary The storm drain system on Bigfoot Pass was installed around 1995, approximating the age of the system at 23 years. The majority of the storm drain system consisted of reinforced concrete pipe (RCP) 18 inches to 36 inches in diameter. Two locations consisted of corrugated metal pipe (CMP). It is recommended to replace these 2 CMP pipes with RCP. The overall condition of the system is classified as Good to Fair.

The system was inspected using video recording and monitoring with a robotic crawler, see Figure 25. The device was powered by a cable attached to a truck mounted generator. The cable length was 500 feet. This length limited the distance the device could travel, requiring a set up at each storm drain access. The inspection was conducted almost immediately after a storm event. This was a benefit as most pipes were free of debris or visual obstructions.

The Federal Highway Administration, “Culvert Assessment and Decision Making Procedures Manual (2010)” was referenced for the inspection procedure. Examples of RCP in good, fair, and poor condition from the manual are shown in Figures 28-31. Field notes from the inspection are listed in Table 4.

Figure 27: Robotic Crawler with Camera

ID Station Neenah Inlet Type Sump Basin Hydology

(cfs)

Basin Hydrology

+ Bypass (cfs)

Capacity

(cfs)

Bypass

(cfs)

Width of Flow in Gutter (ft)

Width of

Shoulder (ft)

Spread into

Lane (ft)

145 730+00 R3067-L (x2) No 1.61 1.61 2.38 0.00 4.13 10.00 0.00

143 726+50 R3067-L (x2) No 1.18 1.18 1.74 0.00 4.03 6.00 0.00

139 722+50 R3067-L (x2) Yes 0.31 0.31 0.60 0.00 1.67 6.00 0.00

138 719+50 R3067 Yes 0.62 0.62 0.90 0.00 1.67 6.00 0.00

135 716+50 R3067 No 0.74 0.74 0.71 0.03 2.73 3.00 0.00

134 713+00 R3067 No 1.05 1.09 0.99 0.10 2.75 3.00 0.00

133 709+50 R3067 No 1.43 1.53 1.22 0.31 3.12 3.00 0.12

Runout 0.31 5.00 3.00 2.00

System 3

ID Station Neenah Inlet Type Sump Basin Hydology

(cfs)

Basin Hydrology

+ Bypass (cfs)

Capacity

(cfs)

Bypass

(cfs)

Width of Flow in Gutter (ft)

Width of

Shoulder (ft)

Spread into

Lane (ft)

144 730+00 R3067-L (x2) Yes 1.67 1.67 7.00 0.00 3.33 3.00 0.33

142 726+50 R3067 Yes 0.93 0.93 4.20 0.00 2.50 3.00 0.00

141 725+00 R3067-V (x2) Yes 1.12 1.12 7.00 0.00 2.80 3.00 0.00

140 722+50 R3067 Yes 0.99 0.99 2.70 0.00 2.50 3.00 0.00

137 718+00 R3067-V (x2) Yes 1.18 1.18 1.20 0.00 5.50 3.00 2.50

System 4

Table 5: Storm Drain Inspection Notes. Numerical values under "Notes" column are distance from inlet to location of interest.

Inlet Outlet DescriptionSize Material Notes

145 144 minor 18" Conc

- Road subsurface drain penetrates pipe. Some minor cracks at penetration

- Top of basin, minor water collection

- 35.8 ft Material in pipe. Unclear if coming in through joint

- 56.4 ft slight separation of joint. Moisture present

- 64.4 ft minor separation and minor cracking

144 142 main 18" Conc

- All joints minor leaking

- Minor joint separation 28.8, 75.4, 240.5

- Minor cracking 61.2, 93.5, 115.6, 147.2

- 160.5 penetrations begin

- 188.4, 194, 194.4, 198.6, 201, 206.6, 210, 214 (cracking at penetration), 223, 230, 242.3, 249.1, 261.9, 266.3, 273.7, 278, 281.5, 286, 289, 294, 294.5 (cracking at penetration), 297.4, 302.2, 321 (crack migrated from hole to joint), 325, 328

(cracking at penetration), 335, 340, 341 (vegetation in joint)

143 142 minor 18" Conc - Visual inspection, Good

142 141 main 18" Conc

- 11.6 Penetrations begin

- 14.6, 22.5, 25.2, 53.8 (cracking at penetration), 77.9 (drilled holes at invert, leak),

103.6 (drilled holes at invert, leak)

- 15.5 minor joint cracking and separating

141 139 main 18" Conc

- Minor cracking at joint 142.2, 164.7, 178.9 (bigger crack), 244, 259, 269.3, 315.9, 357

- Joint material showing 223

- Pipe penetration 368

140 139 minor 18" Conc - Visual inspection, Good

139 138 main 24" Conc

- Minor cracking 72.5, 111.7, 1999.9, 215.1, 238.9, 259.3, 269.6

- Minor joint separation 40.8,58.1, 175.9, 183.1

138 135 main 24" Conc

- Minor joint separation 17.7, 25.4, 32.6, 135.6 218.9, 290.1

- Penetration 248.2, 259.6, 273.6, 303.9

- Minor cracking 234, 218.9, 135 134 main 30" Conc

- Minor cracking 101.3, 132.9, 156.1, 164.4, 232.1, 252.3, 266.3, 270.1, 277.2, 309.5, 321.4, 354.1

- Settling 101.3, 277.2

134 133 main 30" Conc

- Minor cracking 29.1, 34.6, 50.8, 68, 106.8 (bigger crack), 126.4, 167.8, 190, 197.4, 207.3, 228.3, 229.5, 304 (bigger crack)

133 Area Inlet

Area Inlet Outlet main 30" CMP Replace

Bigfoot West

116 US 116 minor 18" Conc - Visual inspection, Good

116 119 main 30" Conc - Minor cracking 21.2, 22.5, 29.1, 44.6, 58.6, 112.6, 145.3, 152.2

118 119 minor 18" Conc - Visual inspection, Good

119 121 main 30" Conc - Minor cracking 21, 86.9, 161.7

120 121 minor 18" Conc - Visual inspection, Good

121 122 main 30" Conc - Minor cracking 51.5, 68.7, 89, 195, 265.3

122 Outlet main CMP Replace

124 Outlet main CMP Replace

Bigfoot East

Figure 28: Condition Assessment Rating Codes from FHWA “Culvert Assessment and Decision Making Procedures Manual (2010)”

Figure 29: RCP ratings from FHWA “Culvert Assessment and Decision Making Procedures Manual (2010)”

Figure 30: Examples from FHWA “Culvert Assessment and Decision Making Procedures Manual (2010)”

Figure 31: Examples from FHWA “Culvert Assessment and Decision Making Procedures Manual (2010)”

Inspection Discussion There are few areas of concern that were noticeable, discussed below. However, the majority of the storm drain was in Good condition.

There were areas of interest where penetrations were visible. The penetrations were mostly symmetrical and grout sealed.

Conversations with Central Federal Land construction staff identified these as holes used to transport the pipe into place, see Figure 32.

There were areas where joint displacement could be seen, see Figure 33. This displacement was similar to Figure 30, RCP Fair condition. Although this is considered “Fair” no cracks or settling was noticeable on the surface.

In few areas, compression cracks were identified. These were noticed at the joint between two pipes, see Figure 34. The cracks likely manifested during construction, from post construction settling, or impact from debris. If cobbles had entered the storm drain system and were transported through with a high velocity, the impact of the cobbles could cause cracking seen in the images. These cracks are similar to Figure 30, “Isolated joint deterioration”, Fair.

Inspection Recommendation The overall condition of the storm drain is classified as Good to Fair. Despite being 23 years old, it is anticipated the storm drain still has many years of service life. It is recommended to re-inspect the storm drain after a 5-year period for the following reasons:

- It is challenging to identify remaining service life with a single snapshot in time. Re-inspecting the storm drain will enable measurements to be made to estimate the rate in which the identified locations change. This rate can be used to estimate a projected remaining service life.

- 5-years is estimated as a period in which a few larger event (2-year) storms could occur. Measuring the difference in condition of the storm drain at this time and after a few large events will provide data to estimate a projected remaining service life.

Figure 32: Penetrations were noticed throughout the storm drain alignment. The penetrations were grout filled. These were likely used to transport the pipe during installation.

Figure 33: In few areas, joint displacement could be seen. The image shown is considered "Fair".

Figure 34: Compression cracks were noticed in few areas. The top left image is likely a compression crack due to settling. The top right and bottom image could be cracks due to debris or installation. The crack in the bottom image is on the roof of the pipe.

References Aquaveo (2016) “Watershed Modeling System (WMS)” Software version 10.1.11

Federal Highway Administration (FHWA)(2016) “Hydraulic Toolbox” Software Version 4.3

Federal Highway Administration (FHWA)(2016) “HY-8” Software Version 7.4

Federal Highway Administration, Culvert Assessment and Decision Making Procedures Manual, September 2010

Federal Highway Administration (FHWA)(2012) “Project Development and Design Manual” Chp. 7. Hydrology and Hydraulics. Federal Lands Highway Division. Federal Highway Administration. Dept. of Transportation. Washington, DC.

Park Imagery

Federal Highway Administration HEC-23, Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design guidance-third Edition, Volume2, September 2009.

Federal Highway Administration HEC-15, Design of Roadside Channels with Flexible Linings, September 2005.

Federal Highway Administration HDS-5, Hydraulic Design of Highway Culverts, Third Edition, April 2012.

Federal Highway Administration HDS-2, Highway Hydrology, Second Edition, October 2002.

Google Earth Imagery

Appendix A: Inlet Capacity Analysis:

System 1

116 US

120 124

Runout

System 2

686+00 689+00

692+00 694+50

699+00 Runout

System 3

730+00 726+50

722+50 719+50

716+50 713+00

709+50 Runout

System 4

730+00 726+50

725+00 722+50

718+00