NM FLAP 159(1) Catwalk Access Road -Hydraulics Report.pdf

Final Hydraulic Report

Catwalk Access Road

NM FLAP 159(1)

Prepared by:

Brian Campbell

Technical Services Hydraulic Engineer

Central Federal Lands Highway Division

Lakewood, Colorado

January 2019

Summary NM 174/Catwalk Road is a 4.78‐mile‐long two‐lane road that provides access to the Catwalk National Recreation Area off US 180. The first mile provides access for multiple residents, businesses, and a fish hatchery. The existing roadway is narrow (9’ ‐ 11’ lanes and no shoulders). This roadway parallels the Whitewater Creek, and crosses the Whitewater

Creek in two locations using low water crossings. There are numerous side drainages that cross the roadway, including eight low water crossings and numerous large culverts. After storm events, NMDOT repairs edge drop‐offs due to scour, and removes heavy sediment loads that block the roadway.

The existing roadway alignment and profile is relatively fixed and relocating the roadway is not within the scope of work.

Bridges were considered for many of the low water crossings in the area during preliminary engineering phases but were ruled out due to funding constraints and community hesitation to support bridge options as a solution.

Recommendations:

The recommendations in this report include:

‐ Replacing the two Whitewater Creek crossings ‐ Modifying multiple tributary low water crossings ‐ Replacing all culverts between mile marker 1.0 and mile marker 4.8 ‐ Raising the portion of roadway between mile marker 4.4 and 4.8 to be out of the 100‐year flood inundation as defined by the US Army Corps of Engineers (2017) “Floodplain Mapping Study Whitewater Creek, Caltron County, New Mexico”

‐ Develop a sediment management plan that includes o Maintenance of drainage ditches o Sediment storage locations o Sediment removal plan.

The recommendations within this report will not eliminate the drainage challenges experienced within the corridor.

Given the geometric and budget constrictions, the design intent of the hydraulic scope of work has been defined to incorporate reasonable changes to the existing corridor that will improve the existing drainage condition, help maintenance manage drainage and sediment in the area, and replace the drop structure at mile marker 1.2 with a more robust system

Table of Contents

Summary

Recommendations:

Introduction

Project Location

Site Description and History

USACE (2017) Floodplain Mapping and Sediment Transport Analysis

Hydraulic Design Standards

Roadway Classifications

Hydrologic Analysis

Hydraulic Analysis

Proposed Culverts

Discussion

Low Water Crossings

Discussion

MP 1.2 Drop Structure Design

Existing Condition

Proposes Design

Fish Barrier Analysis

Aggradation

Mile Post 4.5 Grade Raise

Discussion

References

Appendix

Introduction The following report summarizes hydraulic recommendations for NM FLAP 159(1) Catwalk Access Road Repair.

NM 174/Catwalk Road is a 4.78‐mile‐long two‐lane road that provides access to the Catwalk National Recreation Area off US 180. The first mile provides access for multiple residents, businesses, and a fish hatchery. The existing roadway is narrow (9’ ‐ 11’ lanes and no shoulders). This roadway parallels the Whitewater Creek, and crosses Whitewater Creek in two locations using low water crossings. There are numerous side drainages that cross the roadway, including eight low water crossings and numerous large culverts. After storm events, NMDOT repairs edge drop‐offs due to scour, and removes heavy sediment loads that block the roadway.

In 2012, the Whitewater‐Baldy Complex Fire burned 25,000 acres of the Whitewater Creek watershed and was considered a high severity burn. High debris flows occurred shortly after in 2013 and caused severe impact to access.

More debris from the wildfire is expected to be transported downstream during rain events, increasing the need to protect the road and provide structures that can withstand the anticipated runoff events.

The existing roadway alignment and profile is relatively fixed and relocating the roadway is not within the scope of work.

Bridges were considered for many of the low water crossings in the area during preliminary engineering phases but were ruled out due to funding constraints and community hesitation to support bridge options as a solution.

The hydraulic scope of work extends from mile marker 1.0 to the Catwalk National Recreation Area parking lot at mile marker 4.8. Given the geometric and budget constrictions, the design intent of the hydraulic scope of work has been defined to incorporate reasonable changes to the existing corridor that will improve the existing drainage condition, help maintenance manage drainage and sediment in the area, and replace the drop structure at mile marker 1.2 with a more robust system.

Project Location The project is located in Catron County in the Town of Glenwood, New Mexico. The Catwalk Access Road, NM 174 begins at the intersection of US 180 in Glenwood, NM and extends to the parking area at the Catwalk National

Recreation Area. Current ADT for the area is 189 (NMDOT traffic count data). For most the alignment, the corridor is east and parallel to the Whitewater Creek. In many locations, the roadway is within 10 feet or less of the Whitewater

Creek.

Figure 1: Location Map (Image from Google Earth)

Site Description and History There are numerous tributaries to the east that cross NM 174 before reaching Whitewater Creek. These crossings are constructed with a low water crossing or culvert (see Hydrology section for tributary map). During and after storm events, the tributaries with low water crossings inundate the roadway with sediment and debris. At times, the inundation can cause the road to be impassable and needs to be cleared with heavy equipment. In some areas, the roadway has developed a sump condition and ponding occurs.

The roadway crosses Whitewater Creek in two locations, at approximately mile marker 1.2 and mile marker 4.8. Mile marker 4.8 is a low water crossing. Mile marker 1.2 is a low water crossing that also functions as a grade control and drop structure. Documentation provided by New Mexico Department of Transportation (NMDOT) reflects a history of maintenance challenges with scour downstream of the structure at mile marker 1.2.

Parking Area

Glenwood, NM

Whitewater Creek

North

Figure 2: Plan view example of existing low water crossing (Image from Google Earth)

Figure 3: Example of sump condition without relief

In May of 2012, the Whitewater Baldy Complex Wildfire burned approximately 510 acres of the Whitewater Creek watershed. In September of 2013, historic rainfall coupled with the burned watershed caused major flooding in the area. The flooding also transported large amounts of debris through the watershed. The event damaged the structure at mile marker 1.2 and left it in critical condition (see Figures 4, 5, and 6). Maintenance forces conducted an emergency repair that included a grouted riprap rundown downstream of the low water crossing, and reinstalled the stacked concrete barrier as toe protection. A site visit conducted in May of 2017 show the structure is at risk of failing and is currently threatened by local scour and erosion.

Figure 4: Mile marker 1.2 after 2013 flooding

Figure 5: Mile marker 1.2 after maintenance repair

Figure 6: Mile marker 1.2 as seen from the May 2017 site visit

USACE (2017) Floodplain Mapping and Sediment Transport Analysis After the 2012 Whitewater Baldy Complex Wildfire, the U.S Army Corp of Engineers (USACE) conducted a floodplain mapping study for the corridor which included a sediment transport analysis. The study identified the “delivery of sediment to Catwalk Recreation Area is expected to remain elevated for years to decades, depending on the flows and vegetation recovery”. Figure 7 shows the anticipated Whitewater Creek response to sedimentation due to debris flows by reaches (as defined by the USACE). The limits of the NM FLAP 159(1) Catwalk Access Road Repair project are within

Reach 1 and Reach 2 of Figure 7. Reach 1 extends from the Catwalk Recreational Area parking lot to just upstream of the mile marker 1.2 drop structure. Reach 2 extends from just downstream of the mile marker 1.2 drop structure to the

US 180 Whitewater Creek bridge crossing. Table 1 is a summary by reach:

Table 1: Sedimentation Summary by Reach

Reach 1 Reach 2

Near‐Term* Long‐Term* Near‐Term* Long‐Term*

‐ Channel Widening ‐ Localized Lateral

Erosion ‐ Aggradation ‐ Stable Bed Material

Gradation

‐ Channel Narrowing (Floodplain Creation)

‐ Incision ‐ Armor Development

‐ Localized Lateral Erosion

‐ Incision or Aggradation ‐ Stable Bed Material

Gradation

‐ Uncertain because of Excavation

‐ Inset Floodplain Creation Likely

*Near‐Term and Long‐Term are not specifically defined. They are dependent upon the watershed recovery rate from the fire and can vary.

Figure 7: Whitewater Creek response to sedimentation due to debris flows by reaches (as defined by the USACE)

Hydraulic Design Standards

Roadway Classifications The roadway is designated as a critical access road since it is the sole access to the community in the corridor and is labeled a High‐Standard Road.

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

‐ Culverts o Culverts will convey runoff form the 50‐year flood o 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 o The minimum culvert diameter is 24 inches

‐ Roadway o Roadside ditches will convey the 10‐year flood (up to 50 cfs) and have a minimum slope of 0.5% o The proposed typical section will have less than 3 feet of pavement width outside the travel lane. In areas of cut sections, allowable flow spread will be limited to half of one travel lane.

‐ Low Water Crossing o The low water crossings will be unvented. The PDDM does not have a capacity standard for unvented low water crossings as all flow must pass over the roadway. The crossing will be stabilized for a 25‐year event.

o The PDDM refers to the The U.S. Forest Service and U.S. Agency for International Development manual, Low Volume Roads Engineering‐Best Management Practices Field Guide, as a reference for the design of low‐water crossings. The maximum recommended depth of flow over the low water crossing that is passible by vehicle is limited to 6 inches. However, the site constraints include minimum changes to the existing roadway alignment and profile. The capacity of the existing structure is relatively fixed.

Improvements made to the low water crossings will contribute to maintenance efforts and stabilization measures. Warning signs will be incorporated at the crossings to improve the communication of safety to the public when crossing the low water crossing.

Hydrologic Analysis The Watershed Modeling System (WMS vs 10.1) was used to delineate drainage areas from the tributaries. The most recent New Mexico regional regression equations from USGS 2008 were used to calculate peak flood‐frequency values for tributary areas with a minimum area of 0.20 square miles. Of the tributary drainage areas, 5 areas were less than

0.20 square miles. These met criterial for using the rational method to identify peak flood‐frequency values. A time of concentration value of 10 minutes was used for the basins that met criterial for the rational method. This is minimum time of concentration value for rural drainage basins.

Hydrologic peak flow values from the USACE (2017) report were used for the crossings at mile marker 1.2 and 4.2.

Basins for mile markers 1.0 – 4.0 can be seen in Figure 8. Basins for mile markers 4.2 – 4.6 can be seen in Figure 9. A summary of flow values can be seen in Table 2.

Table 2: Summary of Peak Flow per site

MP Description Area (mi²) (*acres) 25 Year Flow Rate (cfs)

50 Year Flow Rate (cfs)

1 Low Water Crossing 0.7 462 578

1.2** Low Water Crossing/ Drop Structure 47.8 3580 4330

1.4A Low Water Crossing 0.4 367 457

1.4B Low Water Crossing 3.5 1019 1294

1.9 Sump, No Outlet 0.07 (*45) 78 88

2.1 Culvert Crossing 0.2 252 313

2.2 Culvert Crossing 0.37 340 425

2.4 Low Water Crossing 1.2 615 774

2.5 Culvert Crossing 0.02 (*13) 22 25

2.6 Low Water Crossing 0.3 322 401

2.9A Low Water Crossing 0.4 358 447

2.9B Culvert Crossing 0.12 (*77) 134 151

3.5A Culvert Crossing 0.9 517 649

3.5B Culvert Crossing 0.09 (*58) 100 113

4 Low Water Crossing 0.7 478 599

4.2 and 4.4 combined

Culvert Crossing 0.4 336 419

4.6 Culvert Crossing 0.08 (*51) 89 101

4.8** Low Water Crossing 36.8 2930 3530

** Values obtained for pre‐fire conditions from USACE (2017) 25 Year Flow Rate was used for the LWC stability design per PDDM 2012 50 Year Flow Rate was used for the culvert capacity design per PDDM 2012

Hydraulic Analysis

Proposed Culverts In total, there are 9 culvert locations within the project limits. Existing sizes range from 18 inches to 96 inches. Table 3 summarizes the proposed action at each location.

Table 3: Proposed Culvert Improvements

MP Existing Culverts

Proposed System 50 Year Peak Flow Rate (cfs)

Inlet Elevation (ft)

Outlet Elevation (ft)

50 Year HW Elevation (ft)

50 Year HW/D Ratio

Armor Size

1.0 None Install minor drainage relief N/A Per Design Per Design N/A N/A Per Design

1.2 None Install minor drainage relief N/A Per Design Per Design N/A N/A Per Design

2.1 (1) 48" x 72" Arch CMP

This is an abandoned pipe. Site will be converted to lwc.

2.2 (3) 48" x 72" Arch CMP

The existing (3) 48" x 72" Arch CMP's can stay in place. Clean existing culverts. Add inlet and outlet armor.

Layout armor per CFL standard detail C251‐50.

380 4895.60 4894.70 4900.57 1.24 Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

2.5 (1) 18" CMP Replace existing 18" CMP with 30" CMP. Add end sections. Add inlet and outlet armor. Layout armor per CFL standard detail C251‐50. Construct berm downstream to induce detention and promote drainage through culvert.

25 4930.50 4929.90 4933.57 1.23 Class I (D50 = 6 inch) 1.0' depth. Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

2.9B (3) 30" CMP The existing (3) 30" CMP's can stay in place. Clean existing culverts. Add end sections. Add inlet and outlet armor.

Layout armor per CFL standard detail C251‐50.

90 4970.20 4968.50 4973.46 1.30

Class I (D50 = 6 inch) 1.0' depth. Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

3.5A (4) 72" CMP The existing (4) 72" CMP system is damaged. Replace with (4) 72" equivalent RCP's. Add inlet and outlet armor. Layout armor per CFL standard detail C251‐50. Add headwall, wingwalls, and cutoff wall at inlet and outlet per standard.

650 5020.1 5018.5 5025.24 0.86

Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

MP Existing Culverts

Proposed System 50 Year Peak Flow Rate (cfs)

Inlet Elevation (ft)

Outlet Elevation (ft)

50 Year HW Elevation (ft)

50 Year HW/D Ratio

Armor Size

3.5B (1) 96" CMP The ends of the structure are damaged. Replace 30' of pipe on both ends for a total of 60'. The pipe can be cut, mitered to the slope, and anchored on headwall per standard 601‐1. Fill voids between pipe and backfill material with flowable fill. Add inlet and outlet armor. Layout armor per CFL standard detail C251‐50.

113 5022.10 5022.00 5026.18 0.51 Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

4.2 (1) 52" CMP Replace existing 52" CMP with (2) 48" RCP. Add inlet and outlet armor.

Layout armor per CFL standard detail C251‐50. Add headwall, wingwalls, and cutoff wall at inlet and outlet per standard.

210 5085.60 5085.10 5091.02 1.36 Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

4.4 (1) 48" CMP Replace existing 48" CMP with (2) 48" RCP. Add inlet and outlet armor.

Layout armor per CFL standard detail C251‐50. Add headwall, wingwalls, and cutoff wall at inlet and outlet per standard.

210 5105.80 5105.50 5110.47 1.17 Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

4.6 (1) 48" CMP Replace existing 48" CMP with (1) 48" RCP. Add inlet and outlet armor.

Layout armor per CFL standard detail C251‐50. Add headwall, wingwalls, and cutoff wall at inlet and outlet per standard.

100 5126.30 5125.10 5131.53 1.31 Class III (D50 = 12 inch), 2.0' depth. Line riprap with Non‐Woven, Class 1, Type A Geotextile

Discussion

Tailwater elevations for mile point 2.9B, 3.5A, 3.5B, 4.2, 4.4, and 4.6 were gathered from the USACE (2017) HECRAS model for the corridor. These structures discharge within the envelope of runoff influence from the Whitewater Creek during the 50‐year runoff event. It is assumed the tailwater for these structures is controlled by the Whitewater Creek.

Channel limits are not defined for areas downstream of all other culverts making it difficult to model the tailwater during a runoff event. For these crossings, the tailwater elevation was assumed to be at springline of the culvert. Because the downstream area of these culverts is so wide, a springline tailwater estimate is conservative.

MP 2.1

The drainage basin for mile point 2.1 terminates in a sump area drained by an existing 48” x 72” arch CMP. However, the basin yields large sediment loads during runoff events. The sediment fills in the sump and caused runoff to overtop the roadway in this area. The existing 48” x 72” CMP had been buried for an unknown amount of time (see Figure 10 and 11). Changes to the existing roadway alignment and profile in this area is not an option. To limit overtopping events, maintenance practices will need to include removing sediment in the area after runoff events.

Figure 8: Sump at MP 2.1. The 48" x 72" CMP has been buried for an unknown amount of time

Figure 9: Sump at MP 2.1. When the sump is filled with sediment, the roadway overtops

MP 2.9B

The area upstream of the existing culverts provides approximately 7 ac‐ft of storage. This storage attenuates the peak runoff of the 50‐year event from 151 cfs to 90 cfs. A storage‐discharge analysis was conducted using contours obtained from the USACE (2017) LIDAR data. The analysis considers the attenuation action and shows the existing system has capacity for the design storm with appropriate HW/D ratios. Additionally, this area is not a documented challenge area from field personnel. Site data collection also suggests this site’s performance is acceptable.

Figure 10: Aerial view of storage upstream of culvert crossing at MP 2.9B. The highlighted contours are the storage area.

Figure 11: Inflow‐Outflow hydrograph for storage at MP 2.9B. The dark blue line is the inflow hydrograph and the red line is the outflow hydrograph after considering attenuation.

MP 3.5A

Basin 3.5A transports large amounts of sediment and maintaining clear conduits is challenging. A sediment transport model for this basin is beyond the scope of work for the hydraulic analysis. However, the following results can be concluded based on data gathered in the field.

The existing (4) 72" CMP system is damaged and filled with sediment. The structures daylight in an area of the Whitewater Creek that has a lower thalweg slope. Aggradation in this area can be seen in the field. This aggradation limits capacity of the existing system. Aggradation continues to build until a sufficient runoff in the Whitewater Creek removes the aggradation build up. The runoff events do not occur often. Realigning the approach road to a higher elevation would provide aggradation relief downstream of the conduits and allow them to perform better under high sediment loads. However, changes to the existing roadway alignment and profile in this area is not an option. Two alternatives were reviewed:

‐ Replacing the system with concrete pipes. Include headwall, wingwalls, and toewall protection at both inlet and outlet.

‐ Replacing the system with a cast in place, dual 8’ x 6’ box structure. Include headwall, wingwalls, and toewall protection at both inlet and outlet.

Concrete Pipes The concrete pipes will be a lower cost option. The concrete material will be more robust to withstand abrasion from the sediment transport. Additionally, slight increase in sediment transport efficiencies may be realized with the smoother material. The headwall and wingwalls on the upstream side will increase inlet efficiency to pass material.

However, no changes in aggradation patterns downstream of the structure are anticipated. Maintenance is still expected for the conduits on intervals consistent with large runoff events to remove sediment build up to achieve performance. At the time of this analysis, costs for 72” RCP are estimated at $225/Lf for a total of $100,000, not including headwalls, wingwalls, or toewalls.

Box Structure

Culvert Inlet:

Approximately 7 ac‐ft of storage up stream

If a box structure is used to replace the existing system a 6’ rise is desired to access the structures with equipment to streamline the cleaning process. A minimum structure consisting of (2) 8’ x 6’ concrete boxes was analyzed for capacity.

Capacity is achieved for clear water conditions, however, no changes in aggradation patterns downstream of the structure are anticipated. Maintenance is still expected for the conduits on intervals consistent with large runoff events to remove sediment build up to achieve performance. At the time of this analysis, costs for 8’ x 6’ RCBC are estimated at $3,000/LF for a total of $600,000, not including headwalls, wingwalls, or toewalls.

The system is controlled by the downstream aggradation condition for either system installed. Both systems will require maintenance efforts after large runoff events to maintain function. Replacing the existing system with concrete pipes including headwall, wingwalls, and toewall protection at both inlet and outlet is recommended.

Figure 12: Downstream of MP3.5a. Note the aggradation depth.

Vegetation present in the aggradated sections suggests events large enough to remove the sedimentation do not occur often. This aggradation limits the capacity of the conduits upstream.

Maintenance practices should consider removing this aggradation after large events to help facilitate the culvert operation.

Figure 13: Aggradation within the existing conduits varies and is approximately at springline.

MP 3.5B

The existing pipe is a 96" CMP. It is unclear why this pipe is so large. It is possible the pipe functioned as an animal crossing at one time. The ends of the structure are damaged. Replace 30 feet of pipe on both ends for a total of 60 feet.

The pipe can be cut, mitered to the slope, and anchored on headwall per standard 601‐1. Fill voids between pipe and backfill material with flowable fill. Add riprap armor on inlet and outlet.

MP 4.2 and 4.4

Culverts at mile points 4.2 and 4.4 both receive runoff from the same 0.36 mi² basin. The basin is split at the toe (an alluvial fan is present) and it is unclear how much runoff is directed to each culvert. However, if the culvert at MP 4.4 overtops, runoff will go down the roadside ditch to MP 4.2. The system was analyzed anticipating MP 4.4 to overtop and spill ≈50 cfs to the roadside ditch. This will then be conveyed to MP 4.2.

Limited cover is a concern for both sites, therefore, it is recommended the replacement system is concrete pipe with headwall, wingwalls, and cutoff wall at inlet and outlet.

Figure 14: Assumed flow path for MP 4.2 and MP 4.4 culverts after site inspection

MP 4.6

MP 4.6 is in a portion of the project limits in which the roadway surface elevation is designed to be approximately 2 ft higher. The proposed increase in roadway surface will be discussed in following sections. The proposed design surface elevation was used to model the culvert inlet hydraulics.

MP 1.9 Sump without Relief

The roadway between MP 1.4 and 2.1 is narrow with limited right of way beyond the edge of traveled way. The roadway is crowned and the drainage basin flows from the east to the west. Private property is immediately to the west of the roadway in this area. At this time, two minor depressions (approximately 8” depth) sumps exist in this stretch on the east side of the roadway. During storm events, the sumps fill with water until the water elevation reaches the elevation of the center of the roadway. After this, water sheet flows to the west. After storm events, the depressions remain filled until water seeps into the ground or evaporates. Alligator cracking can be seen in the area and maintenance has patched the area multiple times (see Figure 17).

The most cost effective solution in this area is to reverse crown the east side of the roadway to promote sheet flow drainage for the entire section. The solution will require minor fill and geometric changes but will reduce maintenance effort in the area and promote positive drainage from the initiation of the storm.

MP 4.6: (1)

48” RCP

MP 4.4: (2)

48” RCP

MP 4.2: (2)

48” RCP

Figure 15: Example of patched sump area

Low Water Crossings In total, there are 8 existing locations within the project limits that function as low water crossings.

Table 4 summarizes the proposed action at each location.

Table 4: Proposed Low Water Crossing Improvements

Stationing Proposed System Image (All images are orientated with North pointing to top of page)

MP 1.0, MP ‐ Concrete surface, extent per roadway design ‐ Increase cross slope and include reverse crown ‐ Replace damaged gabion section upstream ‐ Include concrete barrier toewall upstream and downstream ‐ Armor channel width 10’ upstream and downstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Line riprap with Non‐Woven, Class 1, Type A Geotextile

MP 1.2 ‐ See report section “Drop Structure”

MP 1.4 ‐ Concrete surface, extent per roadway design ‐ Increase cross slope and include reverse crown ‐ Include concrete barrier toewall upstream and downstream ‐ Armor channel width 10’ upstream and downstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Establish roadside ditch. Maintain roadside ditch grade

Flow Direction

MP 2.4 ‐ Concrete surface, extent per roadway design ‐ Increase cross slope and include reverse crown ‐ Include concrete barrier toewall upstream and downstream ‐ Armor channel width 10’ upstream and downstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Grade and roadside ditch to MP 2.2 culvert crossing

MP 2.6 ‐ Concrete surface, extent per roadway design

‐ Replace damaged gabion section upstream ‐ Include concrete barrier toewall upstream ‐ Armor channel width 10’ upstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Pave concrete surface to top of channel drop ‐ Construct channel drop with gabion basket step wall (per Geotech) ‐ Extend gabion basket step wall minimum of 3 feet below channel bed ‐ Extend gabion basket armor, channel width, 10 feet downstream of gabion basket step wall. Depth 3 feet minimum

MP 2.9 A ‐ Concrete surface, extent per roadway design

‐ Include concrete barrier toewall upstream ‐ Armor channel width 10’ upstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Pave concrete surface to top of channel drop ‐ Construct channel drop with gabion basket step wall (per Geotech) ‐ Extend gabion basket step wall minimum of 3 feet below channel bed ‐ Extend gabion basket armor, channel width, 10 feet downstream of gabion basket step wall. Depth 3 feet minimum

MP 4.0 ‐ Concrete surface, extent per roadway design

‐ Include concrete barrier toewall upstream ‐ Armor channel width 10’ upstream with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Armor channel to top of channel drop with Class III riprap, D50 = 12 inches, Depth 2‐foot minimum ‐ Construct channel drop with gabion basket step wall (per Geotech) ‐ Extend gabion basket step wall minimum of 6 feet below channel bed elevation downstream of headcut ‐ Extend gabion basket armor, channel width, 10 feet downstream of gabion basket step wall.

Depth 3 feet minimum ‐ The crest of the gabion wall should be protected with a concrete cap (per Design).

MP 4.8 ‐ Concrete surface, extent per roadway design

‐ Include concrete barrier toewall upstream and downstream ‐ Armor channel width 10’ upstream and downstream with Class IV riprap, D50 = 15 inches, Depth 2.5‐foot minimum

Discussion

The existing roadway alignment and profile is relatively fixed and relocating the roadway is not within the scope of work.

Therefore, improvements to the low water crossing areas focus on incorporating reasonable changes to the structure that will help maintenance manage drainage and sediment in the area using current maintenance practices.

The roadway cross section for the low water crossing should be sloped in the downstream direction at the maximum slope acceptable for roadway design. This will help promote surface drainage and sheet flow in the downstream direction and will aid in preventing ponding. However, when storms produce sediment and debris flows, deposition of the sediment and debris is still expected on the roadway surface.

To date, the areas where the existing surface condition of low water crossings are asphalt, the surface has deteriorated in many places due in part to exposure to heavy maintenance equipment removing sediment. The application of a concrete surface will help maintenance crews maintain the integrity of the roadway surface when blading and removing sediment and debris.

Figure 16:Example of surface patching of damaged asphalt due to heavy blading

In addition to the improved surface, the drainage channel entry and exit to the low water crossing will be armored to stabilize the structure for flow rates corresponding to the 25‐year event.

The maximum depth of flow recommended to pass a low water crossing by a vehicle is limited to 6 inches. Of the 8 low water crossings, 5 are considered passable and 3 are considered vehicle barriers in frequent storm events. The 3 that are considered vehicle barriers have depths of 6 inches in runoff from storms less than the 2‐year event. The 5 that are considered passable are unique because if the water gets above 6 inches, the runoff will spill over the low water crossing and drains to the adjacent roadside ditch and continue to lower elevations. The analysis did not include sediment or debris barriers. It is possible that some of the low water crossings considered passible may become inundated with sediment to the point that they become barriers. Table 5 summarizes the low water crossing passage analysis.

Note: Surface patching from blading material off asphalt

Table 5: Summary of low water crossing passage

Mile Post Description Depth of water at 2 yr storm

MP 4.8 Barrier ≈ 1.97 feet*

MP 4 Barrier ≈ 1.10 feet

MP 2.9 Passable ≈ 0.50 feet

MP 2.6 Passable ≈ 0.50 feet

MP 2.4 Passable ≈ 0.50 feet

MP 1.4 Passable ≈ 0.50 feet

MP 1.2 Barrier ≈ 2.53 feet**

MP 1.1 Passable ≈ 0.50 feet

*Values from US Army Corps of Engineers (2017) “Floodplain Mapping Study Whitewater Creek, Caltron County, New Mexico” **Values from HECRAS Drop Structure Model

MP 4.8

Calculated values for MP 4.8 suggest the site is not safe to pass for frequent storms (less than the 2‐year event). The

Forest has an active emergency plan for the area and should continue to administer this plan.

Initially, bridges were considered for crossing the Whitewater Creek at MP 4.8. However, the expense of bridges in these locations excluded them from being feasible for the current project budget. Additionally, there was opposition to the bridges by project partners.

Box culverts and relief pipes were considered for low water crossing at MP 4.8. However, recall Table 1 of this report. It is anticipated that the near term response for this area is further aggradation. This further aggradation is expected to remain elevated for years to decades, depending on the flows and vegetation recovery in the basin. The large amount of sediment transported expected in the reach is a concern for clogging any type of conduit structure. Additionally, if the roadway elevation is raised to accommodate a box or culvert structure and the structure become clogged, it is possible for the aggradation upstream to raise the thalweg elevation to the new height of the roadway and possibly re‐ align the channel as sediments deposit during a storm event. If a bridge is not implemented, leaving the area as an open, low water crossing is the more efficient approach until the aggradation process is cycled.

Currently, maintenance at MP 4.8 consists of removing debris and sediment after large runoff events. It is recommended that this practice is continued until funding and support is available for a bridge structure or until the basin has recovered from the Whitewater‐Baldy Complex Fire.

Figure 17: Low water crossing at MP 4.8. Large amounts of sediment and debris inundate the area after significant storm events. Without bridging the area, leaving the area as an open, low water crossing is the more efficient approach until the aggradation process is cycled. This will require continued maintenance on the area as well as closure for storms approximately equal to the 2‐year event.

MP 4.0

The roadway elevation at MP 4.0 is acting as a hardpoint in the system controlling the channel elevation upstream. A box culvert system at this location would include a suppressed 12’ x 6’ box with large inlet and outlet works to shift the channel elevation control upstream of the proposed system. If the system was not suppressed, material deposition upstream could cause the tributary to breach its banks, a costly fix. Downstream of the bank boundary is a private residence. It is unclear if runoff would influence this area, however, breaching the channel bank should be avoided.

The expense of a suppressed culvert system in this location is not feasible for the project budget. It is recommended to continue the current maintenance practice of removing debris and sediment after large runoffs and improve the crossing with recommendations outlined in Table 4.

MP 1.2 Drop Structure Design Calculated values for MP 1.2 suggest the site is not safe to pass for frequent storms (less than the 2‐year event). The

Forest has an active emergency plan for the area and should continue to administer this plan. Initially, bridges were considered for crossing the Whitewater Creek at MP 1.2. However, the expense of bridges in these locations excluded them from being feasible for the current project budget. Additionally, there was opposition to the bridges by project partners.

Existing Condition

The current configuration of the drop structure at MP 1.2 consists of an instream hardened surface (1/2 shotcrete rock filled wire basket, 1/2 grouted riprap), approximately 120 feet wide, sloped at a 5H: 1V to a double stacked concrete barrier toe wall. There is a vertical drop height of 2 concrete barriers (6 feet) to the existing thalweg. The channel left is armored with a recent Reno Mattress installation (2014) which extends approximately 120 feet downstream. The channel right has no armor and is showing significant signs of bank erosion with 5 to 10 foot vertical banks.

Figure 18: Channel Left Reno Mattress

Figure 19: Center of drop showing recent grouted riprap patch by maintenance

Figure 20: Channel right bank (Image from Google Earth)

Documentation provided by New Mexico Department of Transportation (NMDOT) reflects a history of maintenance challenges with scour downstream of the structure at mile marker 1.2. Multiple site repairs have been conducted over the life of the structure. At this time, the structure is at risk of failing and is currently threatened by local scour and erosion. The downstream end of the structure has been undermined and the previously placed protection is fractured

(see Figures 23 and 24).

Figure 21: Image taken during 2017 site visit. The structure is at risk of failing and is currently threatened by local scour and erosion.

Figure 22: The downstream end of the structure has been undermined and the previously placed protection is fractured

Previous repairs were inadequate in depth below the stream and longitudinal length downstream to protect the structure from the scour potential at the site.

Proposes Design

In the pre‐planning stages, the following criteria were defined for the proposed site:

‐ No bridges ‐ Minimize costs, both materials and constructability ‐ Create a fish barrier (per Forest Service Request) ‐ Minimize right of way needs

Two structures were considered for this site and evaluated against the defined criteria:

‐ Sloping Sill as shown in HDS 6 (2001) (Figure 25) ‐ Concrete Vertical Drop as shown in HEC 14 (2006) (Figure 26)

Figure 23:Sloping Sill as shown in HDS 6 (2001) Figure 24: Vertical Drop as shown in HEC 14(2006)

A sloping sill, as shown in HDS 6 (2001), was selected as the appropriate structure for the site (see Figure 25). The preliminary cost estimate of the sloping sill (≈$475K) is significantly less than the preliminary cost estimate of the vertical drop ($755 K). The sloping sill conforms much better to the existing terrain and is designed to maximize the use of the existing terrain as the geometry of the drop.

Geometry of Sloping Sill

The clear zone from the edge of traveled way is 19’. The drop slope will be steepened from the existing 5H:1V to a 2H:1V beginning just beyond the clear zone and extending to the calculated scour depth below the channel (discussed below). By steepening the drop slope to a 2H:1V, costs are minimized, right of way needs are minimized, and calculations show that the structure is a fish barrier (see Fish Barrier section).

Armor

Typical permissible shear stress values for select linings are shown in Table 6:

Table 6:Typical shear stress values from HEC 15 (2005)

Calculated values for velocity and shear at the toe of the drop structure for the 25‐yr event are shown in Table 7. These values are recorded while flow is still on the slope prior to energy being dissipated in the downstream hydraulic jump.

Table 7:Calculated values for velocity and shear at the toe of the drop structure for the 25‐yr event

Velocity ft/sec Shear Stress lb/ft²

24.87 23.84

The high velocity and shear force is due to the steep slope of the drop structure. However, to minimize costs, minimize right of way, and provide a fish barrier, this feature was selected as the design structure. Riprap is the most common, economical, and available material used for erosion and scour protection. Placed riprap was evaluated as a potential solution for the drop structure, but the results indicated that rock sizes greater than Class X riprap (84” D100) would be necessary to sustain the hydraulic conditions associated with a 25‐yr event. Riprap greater than Class VII, becomes impractical to deliver to the site and difficult to place. An alternative solution was necessary.

Rigid linings are useful in flow zones where high shear stress or non‐uniform flow conditions exist, such as at transitions in channel shape or at an energy dissipation structure. Since rigid linings are more robust, any channel shape that is necessary to convey the flow can be used. This is helpful where right‐of‐way constrains the channel width.

Grouted riprap was selected for the drop face from the top of the drop to the toe at the calculated scour depth (see below). Using methods outlined in HEC 11 (1989), a grouted riprap blanket thickness of 3 feet was calculated. A modified Class V (D100 = 36 inches) is specified for riprap material. A 10‐foot‐wide low flow channel will be included in the center of the drop face.

Beyond the toe of the drop structure, the channel bottom is lined with a launchable riprap apron for 16 feet (a distance equal to 2 x the depth) with Class III (D50 = 12 inches, thickness = 2 feet). The channel right bank is protected with a revetment mattress for a distance of 75 feet (approximately equal to one channel width and the length of coverage of the existing Reno mattress on the channel left). The revetment mattress is built with Class III (D50 = 12 inches, thickness = 2 feet) to the calculated scour depth of the drop structure, 10 feet below the channel thalweg.

The grouted drop face and the apron at the toe will tie into the existing Reno mattress on the channel left.

Outlet Protection and Erosion Control Aside from aesthetics, scour holes are not necessarily detrimental unless structural damage due to undermining occurs.

Scour holes provide efficient energy dissipation. External energy dissipation (baffles, stilling basins, etc.) are considered where the scour hole depth computations indicate:

‐ the scour hole will undermine the structure ‐ the expected scour hole may cause costly property damage, ‐ the scour hole causes a nuisance effect (most common in urban areas), ‐ the scour hole will restrict land‐use requirements.

By extending the 2H:1V slope to the calculated scour depth, the structure is protected from the local scour and the anticipated scour hole will function as an appropriate energy dissipator for the site.

Calculated Scour Depth

Equation 3.1 and 3.2 in FHWA’s Hydraulic Engineering Circular 23 Volume 2 (HEC 23 V2) was used with values calculated from HECRAS to calculate the maximum theoretical bed scour for vertical drops. The most conservative estimate of scour downstream of channel drop structures is for vertical drops with unsubmerged flow conditions. For design purposes, the maximum expected scour can be assumed to be equal to the scour for a vertical, unsubmerged drop, regardless of whether the drop is actually sloped or is submerged. The MP 1.2 drop structure will be sloped and the HECRAS model suggests the outlet will be submerged for the design event. The calculated scour is shown in Table 9 and is considered conservative.

Recall Table 1 shown below:

Table 1: Sedimentation Summary by Reach

Reach 1 Reach 2

Near‐Term* Long‐Term* Near‐Term* Long‐Term*

Channel Widening Localized Lateral Erosion Aggradation Stable Bed Material Gradation

Channel Narrowing (Floodplain Creation) Incision Armor Development

Localized Lateral Erosion Incision or Aggradation Stable Bed Material Gradation

Uncertain because of Excavation Inset Floodplain Creation Likely

*Near‐Term and Long‐Term are not specifically defined. They are dependent upon the watershed recovery rate from

The drop structure at MP 1.2 is the beginning of Reach 2. Per USACE (2017), it is uncertain if aggradation or degradation will occur in the short term time frame as well as the long term time frame. Two feet of degradation was assumed for long term degradation at the site. Table 9 shows the calculated scour values:

Table 8: Calculated Scour Values

*Channel Bed Elevation

Long‐term Degradation

Local Scour (Bed Scour for Vertical

Drop)

Total Scour Depth

Scour Elevation

(ft) (ft) (ft) (ft) (ft)

4807.36 2 8.5 10.5 4796.86

*At time of survey in 2016.

A summary of the recommended design features, dimensions, and specifications is as follows:

‐ Grouted Riprap Drop Face o Class V (special) (D100 = 36 inches, D minimum = 17 inches) (Grout thickness = 36 inches) o Weep Holes (per geotech), placed at 5 foot intervals both horizontally and vertically o Thickened edges to 6 feet o Subsurface per Geotech Design o Geotextile, Class 1, Type A, Nonwoven

‐ Apron at Toe o Class III (D50 = 12 inches) (Thickness = 24 inches) o Longitudinal distance = 16 feet o Width = 75 feet (to be verified with survey, width of channel bottom at scour depth) o Geotextile, Class 1, Type A, Nonwoven

‐ Channel Right Revetment o Class III (D50 = 12 inches) (Thickness = 24 inches) o Slope of Revetment = 2H : 1V o From top of Channel bank to 10 feet below thalweg o Longitudinal distance = 75 feet o Geotextile, Class 1, Type A, Nonwoven

Figure 25:Channel centerline profile at MP 1.2 drop

Figure 26: Revetment protection for channel right beyond toe of drop

Fish Barrier Analysis Project partner with Forest Service requested the design criteria for the drop structure at MP 1.2 to consider including criteria for fish barrier applications. The Forest provided a technical memorandum prepared by Pioneer Technical

Services, Inc. as an example of design criteria to evaluate performance against. The technical memorandum was specific to evaluation of the West Fork Gila River fish barrier performance.

Specifically, the Forest is trying to prevent Rainbow and Brown Trout from passing the structure at MP 1.2.

Per the technical memorandum provided by the Forest, “In‐stream drops can function as an upstream barrier to fish in two primary ways:

1. Height Barrier: The structure provides a vertical distance between the downstream water surface and the upstream water surface greater than the vertical distance a fish can leap; and

2. Velocity Barrier: A velocity barrier is formed when the stream flow velocity is greater than the burst speed velocity of the fish or the stream flow velocity is less than the fish burst velocity but is sustained over a distance greater than the fish can maintain its burst velocity”

Using the information provided by USFS, the following table was used as barrier criteria:

Table 9: Summary of Criteria Provided by USFS

Height Barrier* Velocity Barrier

Browns Rainbow Browns Rainbow

4.1 feet 4.1 feet 13 feet/second 9 feet/second

*The height barrier was based on a Cutthroat Trout. The height listed is the maximum height for a horizontal travel distance of 2 feet. Using 4.1 feet as a barrier for Browns and Rainbows is conservative as they do not have the same leaping capabilities of Cutthroat Trout.

The maximum vertical height of 4.1 feet is obtained for a horizontal travel distance of 2 feet. After 2 feet, the fish will begin to come back down. If the proposed drop was a vertical drop, a fish may be able to make the leap. However, since the drop is sloped at a 2H : 1V, this adds horizontal distance barrier to the fish leap, see Figure 1 through 4.

Figure 27: Leaping Capabilities of a Cutthroat Trout from Pioneer Technical Services, Inc.

Table 2 summarizes the HECRAS modeling calculations for the drop structure. Figures 2 through 4 are a graphical summary of the projected leap of the Rainbow and Brown Trout.

Table 10: HECRAS Output

2 yr Storm 25 yr Storm 100 yr Storm

Roadway Surface El (ft) 4821.34 4821.34 4821.34

Depth Downstream of Drop as Modeled from HECRAS (ft)

3.93 7.68 8.96

Downstream Water Elevation (ft) 4811.54 4815.28 4816.54

4.1 feet (jump height) Above Downstream Water Elevation (ft)

4815.64 4819.38 4820.64

Distance below Roadway Elevation (ft) 5.7 1.96 0.7

Velocity 4' above TW elevation on Drop (ft/s) 13.51 16.49 16.97

Grade of Drop (%) 50% (≈2H : 1V) 50% (≈2H : 1V) 50% (≈2H : 1V)

It is important to note; the calculations assume the hydraulic jump at the toe of the structure is submerged. This assumes the fish can swim to the toe of the structure before beginning the barrier passage. It is likely the toe will not be submerged and a form of hydraulic jump will exist as being shown in Figures 2 through 4. This will start the fish barrier passage hydraulics further away from the toe and force the fish to use its bursting energy sooner and making it harder for the fish to swim to the toe and begin the climb. The assumption the hydraulic jump is submerged is conservative for the fish barrier calculation.

Figure 28: 2‐Year Water Surface Profile and Results

Figure 29: 25‐Year Water Surface Profile and Results

Velocity of Water at 4.1’ high is 13.51 ft/s.

This is greater than 13ft/s. An additional vertical 5.7’ still needs to be gained.

2‐yr flow over structure is considered a barrier.

Fish projectile path for 4.1 ‘leap

Assume no hydraulic jump.

Velocity of Water at 4.1’ high is 16.49 ft/s.

This is greater than 13ft/s. An additional vertical 1.96’ still needs to be gained.

25‐yr flow over structure is considered a barrier.

Fish projectile path for 4.1 ‘leap

Assume no hydraulic jump.

Figure 30:100‐Year Water Surface Profile and Results

Aggradation

After the 2012 Whitewater Baldy Complex Wildfire, the U.S Army Corp of Engineers (USACE) conducted a floodplain mapping study for the corridor which included a sediment transport analysis. The study identified the “delivery of sediment to Catwalk Recreation Area is expected to remain elevated for years to decades, depending on the flows and vegetation recovery”. Figure 4 shows the anticipated Whitewater Creek response to sedimentation due to debris flows by reaches (as defined by the USACE (2017)). The limits of the NM FLAP 159(1) Catwalk Access Road Repair project are within Reach 1 and Reach 2 of Figure 4. Reach 1 extends from the Catwalk Recreational Area parking lot to just upstream of the mile marker 1.2 drop structure. Reach 2 extends from just downstream of the mile marker 1.2 drop structure to the US 180 Whitewater Creek bridge crossing. Table 3 is a sediment analysis summary by reach:

Table 11: Sedimentation Summary by Reach

Reach 1 Reach 2

Near‐Term* Long‐Term* Near‐Term* Long‐Term*

‐ Channel Widening ‐ Localized Lateral

Erosion ‐ Aggradation ‐ Stable Bed Material

Gradation

‐ Channel Narrowing (Floodplain Creation)

‐ Incision ‐ Armor Development

‐ Localized Lateral Erosion

‐ Incision or Aggradation ‐ Stable Bed Material

Gradation

‐ Uncertain because of Excavation

‐ Inset Floodplain Creation Likely

*Near‐Term and Long‐Term are not specifically defined. They are dependent upon the watershed recovery rate from

Velocity of Water at 4.1’ high is 16.97 ft/s.

This is greater than 13ft/s. An additional vertical 0.70’ still needs to be gained.

100‐yr flow over structure is considered a barrier.

Fish projectile path for 4.1 ‘leap

Assume no hydraulic jump.

Figure 31: Whitewater Creek response to sedimentation due to debris flows by reaches (as defined by the USACE)

The drop structure at MP 1.2 is the beginning of Reach 2. Per USACE (2017), it is uncertain if aggradation or degradation will occur in the short term time frame as well as the long term time frame. If the area below the drop structure at MP

1.2 experiences aggradation, the calculations for the fish barrier are no longer valid. It may be possible for a fish to pass the structure if the channel thalweg elevation is raised due to aggradation.

Images provided by NMDOT show the…