YOSE15(2)_FinalHydMemo.pdf

Subject: Yosemite Glacier Point Road Hydraulic

Recommendations

Date: September 10, 2020

Project Number: CA FTNP YOSE 15(2)

From: Brian Campbell, P.E.

Hydraulics Engineer

FHWA Central Federal Lands

Lakewood, CO

To: Nathan Allen, P.E.

Project Manager

FHWA Central Federal Lands

Lakewood, CO

Summary

The following report summarizes hydraulic recommendations for CA FTNP YOSE 15(2) Yosemite Glacier

Point Road. The project includes hydraulic investigation and recommendations for the existing 76 culvert crossings within the project limits.

Table 1: Summary of Recommendations

Culvert ID Condition Existing Culvert

Diameter (in)

Notes Proposed Culvert

Diameter (in)

115_1 Good/Fair 24 Cut outlet back to fill slope.

Add FES to protect pipe from rock impact.

120_1 Good/Fair 24 Convert to DI. Clean Ditch and

Regrade. Cut outlet back to fill slope. Add FES to protect pipe from rock impact.

125_1 Good/Fair 24 Replace, crushed ends. Convert to DI. Clean Ditch and

Regrade. Cut outlet back to fill slope. Add FES to protect pipe from rock impact.

140_1 Poor 18 Corroded. Replace. Add FES to tie to slope.

140_2 Poor 18 Corroded. Replace. Add FES to tie to slope.

150_1 Poor 36 Corroded. Undersized.

Replace. Add FES to tie to slope. Accommodate organism.

155_1 Good/Fair 18 Extend outlet 10'. Add FES to tie to slope

165_1 Good/Fair 18 Extend outlet 10'. Add FES to tie to slope

165_2 Good/Fair 18 Clean inlet

175_1 Good/Fair 24 Clean inlet

Culvert ID Condition Existing Culvert

Diameter (in)

Notes Proposed Culvert

Diameter (in)

Memorandum

175_2 Good/Fair 24 Leave as is

190_1 Good/Fair 18 Leave as is

195_1 Good/Fair 24 leave as is

205_1 Good/Fair 18 clean inlet and outlet

215_1 Fair 18 Buried. Clean culvert. Vac

Truck Needed

220_1 Good/Fair 18 Grade outlet, Outlet at tree

230_1 Good/Fair 18 Clean outlet

245_1 Poor 18 Corroded. Undersized.

Replace. Add FES to tie to slope.

(1)42

245_2 Good/Fair 24 Extend 10' outlet

290_1 Good/Fair 18 Extend 10' outlet away from fill, clean inlet

305_1 Good/Fair (2) 36 Overtopped Road. Undersized.

Clean Debris upstream.

(2) 54

315_1 Good/Fair 18 Leave as is

325_1 Good/Fair 18 Leave as is

330_1 Good/Fair 18 Leave as is

340_1 Good/Fair 18 Leave as is

345_1 Good/Fair 18 Leave as is

355_1 Poor 18 Corroded. Undersized.

Replace. Add FES to tie to slope.

(2) 28x20 arch

360_1 Poor 18 Corroded. Undersized.

Replace. Add FES to tie to slope.

380_1 Good/Fair 18 Leave as is

385_1 Good/Fair 18 Leave as is

390_1 Good/Fair 18 Leave as is

395_1 Good/Fair 18 Convert to DI

400_1 Good/Fair 18 Leave as is

405_1 Good/Fair 18 Leave as is

410_1 Fair 24 Leave as is

415_1 Good/Fair 18 Leave as is

420_1 Good/Fair 18 Convert to DI

430_1 Good/Fair 24 Leave as is

430_2 Good/Fair 24 Leave as is

440_1 Good/Fair 18 Leave as is

440_2 Good/Fair 18 Convert to DI

445_1 Good/Fair 24 Leave as is

455_1 Good/Fair 18 Leave as is

460_1 Good/Fair 18 Convert to DI

465_1 Good/Fair 24 Leave as is

470_1 Poor 24 Storage upstream but overtops. (2) 35x24 arch

475_1 Good/Fair 18 Leave as is

485_1 Good/Fair 18 Leave as is

Culvert ID Condition Existing Culvert

Diameter (in)

Notes Proposed Culvert

Diameter (in)

490_1 Poor 24 Corroded. Undersized. (2) 42 x 29 arch

Replace.

495_1 Poor 18 Remove, grade ditch to bypass

500_1 Good/Fair 18 Leave as is

505_1 Fair 18 Corroded. Undersized.

Replace.

28x20 arch

510_1 Fair 18 Clean pipe

520_1 Fair 24 Corroded. Undersized.

Replace. Add FES to tie to slope.

525_1 Good/Fair 18 Leave as is

535_1 Good/Fair 24 Leave as is

540_1 Good/Fair 18 Clean inlet/outlet

545_1 Good/Fair 36 Undersized, add 24 to be relief 24

555_1 Good/Fair 18 Leave as is

560_1 Poor 12 Remove, grade ditch to bypass

565_1 Good/Fair 18 Convert to DI

570_1 Good/Fair 18 Leave as is

580_1 Poor 12 Flowfill pipe or remove, grade ditch to bypass

585_1 Poor 12 Remove, grade ditch to bypass

585_2 Poor 18 Corroded. Replace. Add FES to tie to slope. Add underdrain in this area.

595_1 Poor 24 Corroded. Undersized.

Replace. Add FES to tie to slope. Inlet works special DI

600_1 Fair 18 Undersized. Replace. Add FES to tie to slope. Armor roadside ditch

610_1 Poor 18 Adjust outlet away from tree, replace DI

615_1 Fair 18 Undersized. Replace. Add FES to tie to slope.

(2) 28x20 arch

620_1 Fair 12 Corroded. Undersized.

Replace. Add FES to tie to slope.

625_1 Fair 24 Undersized. Replace. 36

630_1 Good/Fair 18 Overtopped Road. Undersized. 42 x 29 arch

630_2 Good/Fair 24 Leave as is

635_1 Good/Fair 18 Clean inlet/outlet

650_1 Poor 18 Corroded. Undersized.

Replace. Add FES to tie to slope.

(2) 24

655_1 Poor 18 Corroded. Undersized.

Replace. Add FES to tie to slope.

Parking Lot DI

Poor 18 Replace existing DI with 4.75’ x 5’ Grate.

Tie to existing

Project Details:

The project is located immediately south of Yosemite Valley on Glacier Point Road, ~N 37°39’54.20”, W

119°39’51.87”. This project scope includes rehabilitating the pavement of approximately 10.6 miles of Glacier

Point Road from Milepost (MP) 5.1 to the Glacier Point Parking Area. Sentinel Dome Trailhead, Washburn

Point, and Glacier Point Parking areas will also be rehabilitated. Pavement preservation actions will be done on the adjacent section of Glacier Point Road from MP 0.0 – MP 5.1.

Culvert inspections were conducted in July 2018. Seventy-six culverts were reviewed within the project limits.

Most of the existing drainage infrastructure consists of 18-inch corrugated metal pipes (CMPs).

Fifty-one of the culverts (≈70%) were determined to be in good to good/fair condition. Many of these were 18-inch diameter pipes. Although the design standard for cross culverts is 24-inch diameter minimum, many of the existing 18-inch diameter culverts were free from clogging material due to steeper pipe slopes. Observations in the field and conversations with Park staff suggest these were performing satisfactory with few needing minor adjustments. Additionally, many of the pipes in the corridor have historic/special inlets and headwalls. Costs to replace or reset these headwalls are significantly greater than a standard headwall configuration. The recommendation to leave these pipes as is or to conduct minor adjustments is, in part, due to the satisfactory performance of the existing condition and the high cost to reset or replace these headwalls.

Figure 1: Project Location Map

Figure 2: Example of Special Inlet

Figure 3: Example of Corroded Invert

Design Methodology:

Roadway Classification

The posted speed for the corridor is 35 mph. The ADT is ≈ 1070. The road is not designated as a critical access road. The Roadway Classification meets Low-Standard Road.

Design Standards

The roadway is classified as a Low-Standard Road.

Per section 7.3.1.3 in the PDDM, Low Standard: Design cross culverts using the following standards:

- Culverts will convey runoff from the 25-year flood

- Culverts for temporary detours will convey runoff from the 2-year flood, unless seasonal construction justifies a lower standard

- Roadway culverts and embankments at culvert locations will be stable for the 25-year flood

Design Criteria

The following bullets outline the applicable design criteria per section 7.3.1.4 in the PDDM:

- Headwater to Depth Ratio o 48” equivalent and smaller culverts: limit ratio to 1.5 o Larger than 48” equivalent culverts: Limit ratio to 1.2

Hydrology:

The Watershed Modeling System (WMS vs 10.1) was used to delineate drainage areas from the tributaries and calculate the time of concentration for the runoff contribution. The Rational Method, as outlined in FHWA’s

HDS 2, Highway Hydrology 2002 was used for all the drainage basins with areas under 200 acres. The areas were classified as “rural unimproved areas” with a runoff coefficient of 0.35. Intensities from NOAA Atlas 14 were used for the calculated time of concentration. A minimum time of concentration of 10 minutes was used per HDS 2, rural areas.

The culvert ID given includes the approximate station followed by the order of culvert within the station. For example, 265_2 is the 2nd culvert between station 2+65 and 2+66.

The drainage area for basin 305_1 was larger than the criteria for the Rational Method, 2.4 mi². For this drainage, regional regression equations as outlined in USGS, 2012 were used.

Figure 4: Basin Delineations

NORTH

Table 2: Summary of Rational Method Analysis

Culvert

ID

Total Area

(acres) C

TC

(minutes) i (25 yr) Q25

115_1 10.75 0.35 10 3.05 11.48

120_1 8.9 0.35 10 3.05 9.50

125_1 4.62 0.35 10 3.05 4.93

140_1 22.84 0.35 10 3.05 24.38

150_1 99.66 0.35 20.61 2.06 71.85

155_1 9.91 0.35 10 3.05 10.58

165_1 4.28 0.35 10 3.05 4.57

165_2 15.78 0.35 10 3.05 16.85

175_1 10.33 0.35 10 3.05 11.03

175_2 22.08 0.35 10 3.05 23.57

190_1 3.86 0.35 10 3.05 4.12

195_1 4.87 0.35 10 3.05 5.20

205_1 6.21 0.35 10 3.05 6.63

215_1 5.12 0.35 10 3.05 5.47

220_1 8.31 0.35 10 3.05 8.87

230_1 4.7 0.35 10 3.05 5.02

245_1 90.34 0.35 19.46 2.12 67.03

245_2 7.98 0.35 10 3.05 8.52

290_1 3.53 0.35 10 3.05 3.77

315_1 4.95 0.35 10 3.05 5.28

325_1 7.64 0.35 10 3.05 8.16

330_1 9.4 0.35 10 3.05 10.03

340_1 11.75 0.35 10 3.05 12.54

345_1 17.88 0.35 10 3.05 19.09

355_1 32.16 0.35 10 3.05 34.33

360_1 38.03 0.35 10 3.05 40.60

380_1 4.28 0.35 10 3.05 4.57

385_1 5.88 0.35 10 3.05 6.28

390_1 7.22 0.35 10 3.05 7.71

395_1 6.38 0.35 10 3.05 6.81

400_1 4.03 0.35 10 3.05 4.30

405_1 6.3 0.35 10 3.05 6.73

410_1 16.96 0.35 10 3.05 18.10

415_1 11.59 0.35 10 3.05 12.37

420_1 13.27 0.35 10 3.05 14.17

430_1 20.74 0.35 10 3.05 22.14

430_2 11.92 0.35 10 3.05 12.72

440_1 17.55 0.35 10 3.05 18.73

440_2 8.65 0.35 10 3.05 9.23

445_1 22.67 0.35 10 3.05 24.20

455_1 5.37 0.35 10 3.05 5.73

460_1 6.38 0.35 10 3.05 6.81

Culvert

ID

Total Area

(acres) C

TC

(minutes) i (25 yr) Q25

465_1 138.45 0.35 21.60 2 1.00

470_1 1.68 0.35 10 3.05 90.91*

475_1 18.39 0.35 10 3.05 19.63

485_1 5.63 0.35 10 3.05 6.01

490_1 156.33 0.35 15.18 2.44 133.51*

495_1 1.26 0.35 10 3.05 1.35

500_1 10.75 0.35 10 3.05 11.48

505_1 26.53 0.35 10 3.05 28.32*

510_1 18.55 0.35 10 3.05 19.80

520_1 59.61 0.35 23.74 1.9 39.64

525_1 7.47 0.35 10 3.05 7.97

535_1 9.4 0.35 10 3.05 10.03

540_1 3.95 0.35 10 3.05 4.22

545_1 194.7 0.35 25.66 1.81 123.34

555_1 3.78 0.35 10 3.05 4.04

560_1 4.62 0.35 10 3.05 4.93

565_1 7.64 0.35 10 3.05 8.16

570_1 1.68 0.35 10 3.05 1.79

580_1 6.3 0.35 10 3.05 6.73

585_1 7.81 0.35 10 3.05 8.34

585_2 19.74 0.35 16.57 2.32 16.03

595_1 56.17 0.35 15 2.46 48.36

600_1 57.6 0.35 18.20 2.21 44.55

610_1 1.09 0.35 10 3.05 1.16

615_1 65.07 0.35 21.43 2.01 45.78

620_1 7.14 0.35 10 3.05 7.62

625_1 76.07 0.35 27.60 1.74 46.33

630_1 5.37 0.35 10 3.05 46.87

630_2 75.24 0.35 26.52 1.78 5.73

635_1 8.14 0.35 10 3.05 8.69

650_1 35.51 0.35 11.06 2.89 35.92

655_1 37.36 0.35 14.13 2.54 33.21

*See discussion below.

Table 3: Modified hydrology to reflect upstream storage

Culvert ID Modified Q25 (cfs)

470_1 68.18

490_1 100.13

505_1 21.24

Table 4: 2012 Regional Regression Equations for Sierra Nevada Region

2-year

5-year

10-year

25-year

50-year

100-year

Table 5: Summary of Regional Regression Analysis

Basin ID Area

(mi²)

Elevation Precipitation Q-25

305_1 2.4 7222 42.4 265

Hydrology Discussion

Culvert ID 470_1, 490_1, and 505_1 have large areas of storage upstream. The stage-discharge relationship can be influenced by storage within a watershed. This relationship can significantly reduce the peak rate of discharge. Sufficient topographic data is not available to accurately model the storage capacity upstream of these sites. Aerial imagery and photographs taken from the field were used to estimate an approximate 25% reduction in peak discharge due to attenuation upstream of these sites. The modified 25-year runoff value is shown in Table 3. The reduction still resulted in the recommendation to replace these pipes as discussed in the

Hydraulics section.

Hydraulic Analysis

For culvert sizes 18-inch and 24-inch in good condition and no reported problems from Park staff, capacity was checked assuming a HW/D ratio of 1.5 (design standard) and inlet control due to the steep terrain (conservative assumption). The calculated hydrology was then compared to the capacity chart to verify the capacity of the existing pipe was sufficient. Appendix B has a summary of this analysis.

The remaining culverts in fair or poor condition were modeled on an individual basis. A summary of this analysis is in Table 6 followed by a discussion for select sites.

Table 6: Replacement Recommendations

Hydraulic Discussion

Variance in Design Criteria, */**

In 3 cases, the HW/D ratio of 1.5 was exceeded. The FHWA HW/D criterial for culverts 48 inches and smaller is 1.5. Some risk considered when evaluating increasing the structure size to meet the 1.5 criteria includes: area available upstream, buoyancy potential, piping potential through the upstream face, sediment aggradation, magnitude of variance, and cost to increase structure size. For the 3 cases, buoyancy is not a concern because

Culvert

ID

Problem Height Available to Meet Cover

Criteria (ft)

Proposed Diameter

(in)

HW/D Design Q/

Capacity at HW/D

140_1 Corroded. Undersized.

Replace.

2.7 24 1.07 13/13

140_2 Corroded. Undersized.

Replace.

2.98 24 1 13/13

150_1 Corroded. Undersized.

Replace. Include measures to accommodate organism passage.

3.9 60 0.99 72/72

245_1 Corroded. Undersized.

Replace.

5 42 1.26 67/67

305_1 Overtopped Road.

Undersized. Clean Debris upstream.

8.48 (2) 54 1.35 265/265

355_1 Corroded. Undersized.

Replace.

1.6 (2) 28 x 20 arch 1.36 34/34

360_1 Corroded. Undersized.

Replace.

3.75 36 1.04 41/41

470_1 Storage upstream but overtops.

2.32 (2) 35 x 24 arch 1.66* 68/66**

490_1 Corroded. Undersized.

Replace.

2.7 (2) 42 x 29 arch 1.53* 100/90**

505_1 Corroded. Undersized.

Replace.

1.7 28 x 20 1.21 21/15**

520_1 Corroded. Undersized.

Replace.

4.3 36 1.08 40/40

545_1 Undersized, add 24 to be relief

8.2 add 24 4.6 123/123

595_1 Corroded. Undersized.

Replace. Inlet works special.

7.5 36 0.44 40/40

600_1 Undersized. Replace. Armor roadside ditch

8.92 36 1.23 48/48

615_1 Undersized. Replace. 1.74 (2) 28 x 20 arch 1.67* 46/46

625_1 Undersized. Replace. 2.93 36 1.15 47/47

630_1 Overtopped Road.

Undersized.

2.29 42 x 29 arch 1.36 46/46

650_1 Corroded. Undersized.

Replace.

2.06 (2) 24 1.27 36/36

655_1 Corroded. Undersized.

Replace.

2.7 30 1.43 33/33

Parking

Lot DI

Clogs. Flows into Parking

Area

2 Replace existing DI with 4.75’ x 5’ Grate.

5.85 Tie to existing

*/** See discussion below the pipes are encased in stone headwalls. Piping potential will be minimized with the headwalls at the inlet.

Sediment aggradation is not a concern as the existing condition for these cases do not show aggradation. The magnitude of the variance is small, 0.17 at the greatest. The cost to increase the structure size will be realized in pipe material costs, excavation, larger headwall and cutoff wall, and is considered large.

In 3 cases, the design Q was not met. The magnitude of the variance is small, 10 cfs at the greatest. The cost to increase the structure size will be realized in pipe material costs, excavation, larger headwall and cutoff wall, and is considered large.

The improvements for the 4 cases where design criteria are not met are still a significant betterment to the existing condition.

Because of the above reasons, the costs to increase the structure size to meet a 1.5 HW/D ratio and the design Q is considered greater than the benefit to increase the conduit sizes.

150_1

The culvert assessment identified the existing pipe as “poor” condition. Follow up analysis shows that it is also undersized for the 25-year design event of 75 cfs. Initially, the pipe was proposed to be resized to a 42” CMP.

This was the maximum height that could fit with the cover requirements and meet the design event.

Figure 5: Culvert 150_1. Note the image on the left. Transvers cracking is occuring directly on the culvert alignment suggesting settlement in the fill.

However, at the 70% site review Park staff voiced concerns that this feature needs to accommodate organism passage during low flow events. From Park staff:

“The federally endangered Sierra Nevada yellow-legged frog (Rana sierrae) occupies and breeds in both the north and south portions of Summit Meadow which Glacier Point Road bisects and is only connected by the deteriorating CMP. The yellow-legged frog is believed to use the culvert for passage between meadow portions, and has been heard calling near (and possibly inside) the culvert by U.S. Geological Survey (USGS) research crews studying the frog at this location.”

In light of the Park request to consider organism passage, multiple options will be evaluated to select the appropriate structure. The bottom of the pipe would be embedded 1.5’ below the thalweg and material placed within the pipe to simulate a natural bottom.

The following selections will meet the intent:

- 5’ CMP, buried 18” with material to simulate a natural bottom.

- Pipe arch buried 18” with material to simulate a natural bottom.

o Span = 77” (6.4’) o Rise = 52” (4.3’)

- Arch Plate buried 18” with material to simulate a natural bottom.

o Span = 76” (6.3’) o Rise = 57.1” (4.75’)

The pipe cover for each option, once embedded, meets the criteria.

Constructability

The benefit of the Arch Plate is the bottom and the sides of the pipe are not connected. The bottom is placed and material placed over the bottom section. After the invert is at elevation, the pipe arch is bolted to the bottom plate. This makes it easier to configure the “natural” stream bed simulation with heavy equipment. This would likely require a longer closure than the pipe arch hand method.

The 5’ CMP and the pipe arch are similar in construction. For constructability, it is sometimes a challenge to bury the invert by 1.5’ given the minimum clearance inside the pipe. Special equipment may be needed with handwork. However, the length is relatively short, 35’. The pipe arch gives a wider channel bed.

There is also the option to oversize a closed conduit so a piece of equipment can get inside. An example would be to embed the bottom of a 7’ CMP 3’ below the invert. This could be done with a bobcat and handwork. The pipe is oversized, but the construction process is easier.

The preferred alternative is to install a 5’ round corrugated metal pipe with 18” of natural streambed material.

305_1

The site consists of double 36-inch CMP. During the 30 percent site visit, Park representatives stated that this culvert has been inundated and evidence of a recent overtopping could be seen.

The proposed solution will replace the existing system with (2) 54-inch CMP with a headwall, wingwall, and cutoff wall at both the inlet and outlet.

Additionally, upstream of the culvert are significant tree/log deposits. This debris could have contributed to the overtopping incident. It is recommended to remove all fallen material approximately within 100 feet of the inlet, see Figure 5.

Figure 6: Remove debris deposition within 100 feet of culvert inlet, Image Google Earth.

595_1

At ≈ 598+40 there is an existing single 24-inch cross culvert. The culvert is undersized and has minimal headwater available. Upstream of the inlet is a hydraulically steep channel. This channel is unstable. During rainfall events, material is mobilized and minor debris flows can occur. This results in pipe clogging. When the pipe is clogged, runoff will either run down the roadside ditch or overtop the roadway in the area, see image attached.

If left in the existing condition, clogging is expected to occur on a frequent basis. Roadway overtopping is expected to continue.

To minimize the overtopping events, the proposed solution will replace the existing pipe with a drop inlet and 36-inch cross culvert. The inlet will be slightly depressed in an effort to increase the headwater above the invert. The grate will act as a debris rack and keep the larger material from entering the pipe. The intent is to capture larger material before it can clog the pipe. However, the inlet will need to be kept clear of material to maintain function.

To minimize the amount of material transported and debris flows in the upstream drainage, a rock buttress is proposed. The buttress will help stabilize the steep channel section and minimize material from mobilizing and clogging the inlet.

Figure 7: The inundated culvert can be seen on the left. The inlet and material mobilized can be seen on the right.

Wet Area at Approximate Station 500+00-520+00, Approximate Station 585+00-588+00

Two specific areas within the project limits show signs of groundwater encroachment. Park maintenance has identified a history of surface challenges, likely from groundwater encroachment, from station 500+00 to

520+00. The area is adjacent to a large meadow that has been known to pond water. A geotechnical solution is being explored that will likely include a free draining base material. See geotechnical report for additional information.

Similarly, from station 585+00 to 588+00, the groundwater table appears to be higher in this area. Figure 5 is an image from the 30% field visit showing water daylighting through cracks in the roadway. A geotechnical solution is being explored that will likely include underdrains to remove water. See geotechnical report for additional information on this site.

Figure 8: The image on the left is from ≈ station 500+00 to 520+00. The image on the right is from ≈ station 585+00 to 588+00.

Glacier Point Parking Lot Drop Inlet Near the entrance of the Glacier Point Parking area, there is an existing drop inlet that connects to the Glacier Point

Parking area storm drain system. The inlet drains an approximate 37-acre basin. An image from the As-Built plans is in the figure below.

It appears the inlet was installed in an area depressed below the parking lot surface making it the low point at the time. Over time this inlet has been subject to clogging and caused deposition of material in the immediate area.

Today, the inlet does not function. During runoff events and spring and early summer snow melt, water flows over the sidewalk and through the parking lot.

If left in the existing condition, runoff is expected to overtop the sidewalk on a frequent basis. In addition, the clogged inlet has resulted in standing water which has created a wet area with woodland vegetation.

To minimize the runoff from flowing through the parking lot, it is proposed to restore the grade to the original intended elevation and replace the drop inlet with a larger structure that will be easier to maintain. The area can be seeded after it has been restored to maintain the woodland vegetation. This solution will minimize runoff from going into the parking area. However, this solution will need maintenance to keep material clear of the intake racks to maintain the drainage function.

Outlet Protection

Riprap is the most common, economical, and available material used for erosion and scour protection for culverts 48 inches in diameter and smaller. Riprap aprons, per Central Federal Lands detail C251-50, are recommended for outlet protection for each identified site.

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 (2012) “Hydraulic Design of Highway Culverts” Hydraulic Design

Series No. 5. US Dept. of Transportation, Federal Highway Administration.

Federal Highway Administration (2002) “Highway Hydrology” Hydraulic Design Series No. 2. US Dept. of

Transportation, Federal Highway Administration.

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.

Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles, 2012, Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific

Investigations Report 2012–5113, 38 p., 1 pl., available online only at http://pubs.usgs.gov/sir/2012/5113/.

Appendix A: Summary of Field Notes with Details Culvert ID Q 25 (cfs) Culvert Type Culvert Diameter Condition Proposed Inlet Proposed Outlet Clean

Inlet

Clean Outlet Replace Adjust new size Notes

115_1 11.48 cmp 24 Good/Fair FES Y Cut outlet back to fill slope. Add FES to protect pipe from rock impact.

120_1 9.50 cmp 24 Good/Fair DI FES Y Convert to DI. Clean Ditch and Regrade. Cut outlet back to fill slope.

Add FES to protect pipe from rock impact.

125_1 4.93 cmp 24 Good/Fair DI FES Y Replace, crushed ends. Convert to DI. Clean Ditch and Regrade. Cut outlet back to fill slope. Add FES to protect pipe from rock impact.

140_1 12.19 cmp 18 Poor Existing Stone Headwall FES Y 24 Corroded. Replace. Add FES to tie to slope.

140_2 12.19 cmp 18 Poor Existing Stone Headwall FES Y 24 Corroded. Replace. Add FES to tie to slope.

150_1 71.85 cmp 36 Poor Existing Stone Headwall FES Y 60 Corroded. Undersized. Replace. Add FES to tie to slope.

155_1 10.58 cmp 18 Good/Fair FES Y Extend outlet 10'. Add FES to tie to slope

165_1 4.57 cmp 18 Good/Fair FES Y Extend outlet 10'. Add FES to tie to slope

165_2 16.85 cmp 18 Good/Fair Y Clean inlet

175_1 11.03 cmp 24 Good/Fair Y Clean inlet

175_2 23.57 cmp 24 Good/Fair Leave as is

190_1 4.12 cmp 18 Good/Fair Leave as is

195_1 5.20 cmp 24 Good/Fair leave as is

205_1 6.63 cmp 18 Good/Fair Y Y clean inlet and outlet

215_1 5.47 cmp 18 ? Y Y Buried. Clean culvert. Vac Truck Needed

220_1 8.87 cmp 18 Good/Fair Y Outlet at tree

230_1 5.02 cmp 18 Good/Fair Y Clean outlet

245_1 67.03 cmp 18 Poor Existing Stone Headwall FES Y (1)42 Corroded. Undersized. Replace. Add FES to tie to slope.

245_2 8.52 cmp 24 Good/Fair FES Y Extend 10' outlet

290_1 3.77 cmp 18 Good/Fair FES Y Y Extend 10' outlet away from fill, clean inlet

305_1 265.43 cmp (2) 36 Good/Fair Headwall Headwall Y (2) 54 Overtopped Road. Undersized. Clean Debris upstream.

315_1 5.28 cmp 18 Good/Fair Leave as is

325_1 8.16 cmp 18 Good/Fair Leave as is

330_1 10.03 cmp 18 Good/Fair Leave as is

340_1 12.54 cmp 18 Good/Fair Leave as is

345_1 19.09 cmp 18 Good/Fair Leave as is

355_1 34.33 cmp 18 Poor Existing Stone Headwall FES Y (2) 28x20 arch Corroded. Undersized. Replace. Add FES to tie to slope.

360_1 40.60 cmp 18 Poor Existing Stone Headwall FES Y 36 Corroded. Undersized. Replace. Add FES to tie to slope.

380_1 4.57 cmp 18 Good/Fair Leave as is

385_1 6.28 cmp 18 Good/Fair Leave as is

390_1 7.71 cmp 18 Good/Fair Leave as is

395_1 6.81 cmp 18 Good/Fair DI Y Y Convert to DI

400_1 4.30 cmp 18 Good/Fair Leave as is

405_1 6.73 cmp 18 Good/Fair Leave as is

410_1 18.10 cmp 24 Fair Leave as is

415_1 12.37 cmp 18 Good/Fair Leave as is

420_1 14.17 cmp 18 Good/Fair DI Y Convert to DI

430_1 22.14 cmp 24 Good/Fair Leave as is

430_2 12.72 cmp 24 Good/Fair Leave as is

440_1 18.73 cmp 18 Good/Fair Leave as is

440_2 9.23 cmp 18 Good/Fair DI Y Y Convert to DI

Culvert ID Q 25 (cfs) Culvert Type Culvert Diameter Condition Proposed Inlet Proposed Outlet Clean Clean Outlet Replace Adjust new size Notes

Inlet

445_1 24.20 cmp 24 Good/Fair Leave as is

455_1 5.73 cmp 18 Good/Fair Leave as is

460_1 6.81 cmp 18 Good/Fair DI Y Y Convert to DI

465_1 1.00 cmp 24 Good/Fair Leave as is

470_1 90.91 cmp 24 Poor Existing Stone Headwall FES Y (2) 35x24 arch Storage upstream but overtops.

475_1 19.63 cmp 18 Good/Fair Leave as is

485_1 6.01 cmp 18 Good/Fair Leave as is

490_1 133.51 cmp 24 Poor Existing Stone Headwall Existing Stone Headwall Y (2) 42 x 29 Corroded. Undersized. Replace.

495_1 1.35 cmp 18 Poor Y Remove, grade ditch to pass flow to next pipe. If this isn’t possible, slip with 12"

500_1 11.48 cmp 18 Good/Fair Leave as is

505_1 28.32 cmp 18 Fair Existing Stone Headwall Existing Stone Headwall Y 28x20 Corroded. Undersized. Replace.

510_1 19.80 cmp 18 Fair Y Y Clean pipe

520_1 39.64 cmp 24 Fair Existing Stone Headwall FES Y 36 Corroded. Undersized. Replace. Add FES to tie to slope.

525_1 7.97 cmp 18 Good/Fair Leave as is

535_1 10.03 cmp 24 Good/Fair Leave as is

540_1 4.22 cmp 18 Good/Fair Y Y Clean inlet/outlet

545_1 123.34 cmp 36 Good/Fair FES FES Y Y 24 Undersized, add 24 to be relief

555_1 4.04 cmp 18 Good/Fair Leave as is

560_1 4.93 cmp 12 Poor Existing Stone Headwall FES Y review abandon Possible ditch pave

565_1 8.16 cmp 18 Good/Fair DI Y Convert to DI

570_1 1.79 cmp 18 Good/Fair Leave as is

580_1 6.73 cmp 12 Poor Remove Remove Y Flowfill pipe or remove, grade ditch to bypass

585_1 8.34 cmp 12 Poor Remove Remove Y Remove, grade ditch to bypass

585_2 16.03 cmp 18 Poor Existing Stone Headwall FES Y 24 Corroded. Replace. Add FES to tie to slope. Add underdrain in this area.

595_1 48.36 cmp 24 Poor Existing Stone Headwall, DI FES Y Y 36 Corroded. Undersized. Replace. Add FES to tie to slope. Inlet works special DI

600_1 48.36 cmp 18 Fair Existing Stone Headwall FES Y 36 Undersized. Replace. Add FES to tie to slope. Armor roadside ditch

610_1 1.16 cmp 18 Poor DI FES Y 24 Adjust outlet away from tree, replace DI

615_1 45.78 cmp 18 Fair Existing Stone Headwall FES Y (2) 28x20 arch Undersized. Replace. Add FES to tie to slope.

620_1 7.62 cmp 12 Fair Existing Stone Headwall FES Y 24 Corroded. Undersized. Replace. Add FES to tie to slope.

625_1 46.33 cmp 24 Fair Existing Stone Headwall Existing Stone Headwall Y 36 Undersized. Replace.

630_1 46.87 cmp 18 Good/Fair Y 42 x 29 Overtopped Road. Undersized.

630_2 5.73 cmp 24 Good/Fair Leave as is

635_1 8.69 cmp 18 Good/Fair Y Y Y Clean inlet/outlet

650_1 35.92 cmp 18 Poor Existing Stone Headwall FES Y (2) 24 Corroded. Undersized. Replace. Add FES to tie to slope.

655_1 33.21 cmp 18 Poor Existing Stone Headwall FES Y 30 Corroded. Undersized. Replace. Add FES to tie to slope.

Appendix B: Capacity Analysis of 18 inch and 24 inch in Good Condition

For culvert sizes 18-inch and 24-inch in good condition and no reported problems from Park staff, capacity was checked assuming a HW/D ratio of 1.5 (design standard) and inlet control due to the steep terrain (conservative assumption). The calculated hydrology was then compared to the capacity chart (Table 7) to verify the capacity of the existing pipe.

Table 7: Capacity Table. HW/D =1.5, Inlet Control

Diameter (in) 1 Pipe

24 18.51

18 14.77

Table 8: Capacity Analysis

ID

Q 25

(cfs)

Culvert

Diameter

Condition Capacity Difference

115_1 11.48 24 Good/Fair 18.51 7.03

120_1 9.50 24 Good/Fair 18.51 9.01

125_1 4.93 24 Good/Fair 18.51 13.58

155_1 10.58 18 Good/Fair 14.77 4.19

165_1 4.57 18 Good/Fair 14.77 10.20

165_2 16.85 18 Good/Fair 14.77 -2.08*

175_1 11.03 24 Good/Fair 18.51 7.48

175_2 23.57 24 Good/Fair 18.51 -5.06*

190_1 4.12 18 Good/Fair 14.77 10.65

195_1 5.20 24 Good/Fair 18.51 13.31

205_1 6.63 18 Good/Fair 14.77 8.14

215_1 5.47 18 Fair 14.77 9.30

220_1 8.87 18 Good/Fair 14.77 5.90

230_1 5.02 18 Good/Fair 14.77 9.75

245_2 8.52 24 Good/Fair 18.51 9.99

290_1 3.77 18 Good/Fair 14.77 11.00

315_1 5.28 18 Good/Fair 14.77 9.49

325_1 8.16 18 Good/Fair 14.77 6.61

330_1 10.03 18 Good/Fair 14.77 4.74

340_1 12.54 18 Good/Fair 14.77 2.23

345_1 19.09 18 Good/Fair 14.77 -4.32*

380_1 4.57 18 Good/Fair 14.77 10.20

385_1 6.28 18 Good/Fair 14.77 8.49

390_1 7.71 18 Good/Fair 14.77 7.06

395_1 6.81 18 Good/Fair 14.77 7.96

400_1 4.30 18 Good/Fair 14.77 10.47

405_1 6.73 18 Good/Fair 14.77 8.04

410_1 18.10 24 Good/Fair 18.51 0.41

415_1 12.37 18 Good/Fair 14.77 2.40

420_1 14.17 18 Good/Fair 14.77 0.60

430_1 22.14 24 Good/Fair 18.51 -3.63*

430_2 12.72 24 Good/Fair 18.51 5.79

ID

Q 25

(cfs)

Culvert

Diameter

Condition Capacity Difference

440_1 18.73 18 Good/Fair 14.77 -3.96*

440_2 9.23 18 Good/Fair 14.77 5.54

445_1 24.20 24 Good/Fair 18.51 -5.69*

455_1 5.73 18 Good/Fair 14.77 9.04

460_1 6.81 18 Good/Fair 14.77 7.96

465_1 1.00 24 Good/Fair 18.51 17.51

475_1 19.63 18 Good/Fair 14.77 -4.86*

485_1 6.01 18 Good/Fair 14.77 8.76

500_1 11.48 18 Good/Fair 14.77 3.29

510_1 19.80 18 Fair 14.77 -5.03*

525_1 7.97 18 Good/Fair 14.77 6.80

535_1 10.03 24 Good/Fair 18.51 8.48

540_1 4.22 18 Good/Fair 14.77 10.55

555_1 4.04 18 Good/Fair 14.77 10.73

565_1 8.16 18 Good/Fair 14.77 6.61

570_1 1.79 18 Good/Fair 14.77 12.98

630_1 5.73 18 Good/Fair 14.77 9.04

635_1 8.69 18 Good/Fair 14.77 6.08

*See discussion below

In 7 cases, the design Q was not met. The magnitude of the variance is small, 5.69 cfs at the greatest. The cost to increase the structure size will be realized in pipe material costs, excavation, larger headwall and cutoff wall, and is considered large.

Because of the above reasons, the costs to increase the structure size to meet the design Q is considered greater than the benefit to increase the conduit sizes.