WA_NP_OLYM_2019(1)_Hydraulic_Report.pdf

Memorandum

Western Federal Lands Highway Division 610 E. Fifth Street

Vancouver, WA 98661-3801

SOUTH BEACH CULVERT

HYDRAULICS REPORT

To: Kirk Loftsgaarden, WFLHD Project Manager From: Matthew Dillin, P.E., WFLHD Hydraulics Engineer Date: April 4, 2019 Project: South Beach Culvert – WA NPS OLYM 2019(1)

Background

The National Park Service is replacing a failed culvert at their Kalaloch South Beach Campground within the Olympic National Park, Jefferson County Washington (Fig. 1). The National Park will maintain the new structure. Western Federal Lands Highway Division (WFLHD) is designing the replacement structure. Recommendations for the proposed culvert design are presented.

Design Criteria

The proposed culvert has been designed per Federal Lands Highway: Project Development and Design Manual, Federal Highway Administration, July 2018 (PDDM). The following requirements have been incorporated into the culvert design:

Design Flood: For the South Beach Campground a High Standard roadway classification was utilized; therefore, the proposed culvert was designed to convey runoff from the 50-year flood (125 cfs).

Check Flood: The 100-year recurrence flood was utilized as the check flood (141 cfs). Used to evaluate the potential for adverse impacts to private property or insurable structures upstream of the crossing.

Stability: Culvert embankments were designed to be stable through the design flood.

HW/D Ratio: For culverts larger than 48” the ratio is limited to 1.2 maximum for the design flood.

Slope: For stream crossings culvert slopes are individually designed to carry the design discharge without exceeding the allowable headwater criteria. The pipe slope will generally conform to the average streambed flow line.

Cover: Where applicable, conform with FLH Standard Drawings for minimum and maximum cover on pipes. For pipe materials and sizes not listed in FLH Standard Drawings, contractor to supply pipe that meets or exceeds anticipated design loads.

Memo to: Kirk Loftsgaarden, WFLHD Project Manager April 4, 2019

Recommended Repair

The proposed replacement culvert shall conform with the following recommendations:

Install new culvert on existing stream alignment.

Install a 146-foot long, corrugated aluminum culvert or smooth plastic pipe with a 5-foot diameter (Sheet E.1).

Place culvert invert at elevation 26.0’ feet upstream and at elevation 20.0’ feet downstream (project datum).

Install culvert at a 4.1 percent grade.

Install Class 4 riprap (FHWA FP-14), minimum 3 feet thick, at the inlet and outlet for controlling road embankment erosion near the culvert (Sheets E.2).

Install Class 1-C nonwoven geotextile (FHWA FP-14) under the riprap.

Shape new channel immediately upstream and immediately downstream for aligning the culvert channel with the natural channel.

Seed and plant any disturbed areas with local native vegetation.

The project partners expressed a desire to utilize a plastic pipe for the replacement pipe. Due to the height of the downstream debris, the recommended culvert will have a slightly higher outlet invert in comparison to the existing culvert.

Site Conditions

The project site is located within the Kalaloch South Beach Campground. The Campground contains 50-sites and is located just off of Highway 101, north of Queets, WA within Jefferson County. The campground is bound on the west by the Pacific Ocean, on the east by roughly 200-feet of forested land and then Highway 101, on the south by Ashenbrenner Picnic Area, and on the north by undeveloped forest land. At approximately the mid-point of the campground, an existing culvert carries flow from an unnamed stream under the campground, outfalling onto the beach. The existing pipe is separating at joints under the campground, allowing material to be piped through the culvert and creating sink holes on the surface areas within the campground.

The Park has had to fix the sink holes twice in the past year to keep camp and RV sites open.

The channel was observed to have a gravel and cobble bed with a bankfull width of roughly 5-feet and a bankfull depth of roughly 18” to 24”. The existing culvert showed signed of abrasion damage on the upstream end and streambed sediment within the pipe. The upstream channel contained some loose wood debris acting a grade controls. Roughly 200-feet upstream, the Highway 101 crossing was perched several feet and was undercut. The channel downstream of the campground had a fairly large plunge pool at the culvert outlet. Roughly 50-feet downstream of the existing culvert, a large sediment and drift wood pile plugged the existing channel. Photos of the site are available in the report attachments.

Stream Impacts

The proposed culvert is expected to improve stream flow conveyance, sediment transport, and woody debris transport; however, the improved transport levels will still be less than the adjacent natural stream system. Given the existing channel grade controls upstream and downstream of the crossing, significant degradation and aggradation are not expected upstream, inside, and downstream of the proposed culvert.

A moderate amount of turbidity and sediment is expected to be released when the flow barriers are removed and stream flow is introduced into the newly constructed culvert. The amount of turbidity and sediment will be reduced by removing the flow barriers gradually introducing the stream flow over an extended two to three-hour time.

Construction

Construction of the project is anticipated to take place in the fall of 2019. Dewatering and/or temporary flow diversions will likely be required for isolating the work area and diverting the stream flow. To limit erosion, the diversion will require the use of plastic-lined channels or pipes for temporally conveying stream flow through the construction area. Contractor will be required to protect the outfalls from erosion. Temporary stream diversions in place must have minimum flow capacity equal to half the 2-year discharge (27 cfs). Before installing the flow diversion, remove fish from the work area to the level and methods specified in the environmental permits.

Vehicular traffic will not be maintained through the work site. Full construction area dewatering is expected up to the groundwater level for excavation and installing the culvert, pipe bedding material, backfill, and riprap. Water pumped from work area must be discharged at an upland area near the site. Access for culvert installation work can be accomplished within the existing road embankment footprint. Temporary access route adjacent to the road embankment is needed for installing flow barriers, removing the channel debris, and completing culvert inlet, interior, and outlet work. Constructing the proposed culvert and in-stream work may require heavy track-mounted equipment operating on the stream bed, possibly in water up to 2 feet deep.

The State of Washington and the U.S. Fish and Wildlife Service will restrict the release of turbidity from the work areas into the stream. The agencies require turbidity control and monitoring, and should be contacted for specific requirements and allowable discharge limits.

Operation and Maintenance

Woody debris will tend to accumulate more frequently at the culvert inlet and inside the culvert barrel. The Park should increase the frequency of culvert inspection and woody debris removal.

Stream degradation is not expected to negatively impact culvert structure or performance. Stream aggradation could reduce the culvert hydraulic capacity. Remove sediment from the upstream channel, inside the culvert when there is less than 5-feet of clearance between the stream bottom and culvert crown at the inlet. Riprap placed at the culvert inlet and outlet should be inspected annually and after each extreme flood event. Replace or reposition dislodged stone.

Floodplain and Flood-rise Impacts

Flood limits and elevations have not been mapped by the National Flood Insurance Program for the site. The proposed culverts will improve hydraulic conveyance and is not expected to negatively impact flooding at the site.

Hydrology

The USGS StreamStats (version 4) web-based application was used for delineating the watershed and calculating drainage area (0.54 sq. miles), and mean annual precipitation (109 inches). Peak discharges were estimated with StreamStats using USGS regression equations from Magnitude and Frequency of Floods in Washington (USGS WRIR 97-4277). Watershed is entirely within Region 4 for the USGS regression equations. The watershed is mostly forested (Fig. 2). Fires and logging have occurred within the watershed and can occur in the future. No flow diversions or lakes occur. The drainage area is steep in the upper basin and flatten out prior to reaching the project site. Area with slopes greater than 30 percent is 3 percent and the mean basin slope is 12 percent. Elevations range from 30 to 600 feet (NAD83/WGS84). A summary of peak discharges and their corresponding water depths at the culvert inlet are presented in Table 1.

Dominant flooding is from rainfall. Larger floods typically occur in November, December, January, and February. Lowest flows occur in May, June, July, August, and September.

Culvert Hydraulics

Water surface profiles and culvert capacities were estimated using the FHWA Culvert Hydraulics Analysis Program, HY-8, version 7.5 (results attached). Floods larger than the 2-year were analyzed assuming culvert slope of 4.1 percent and Manning’s Roughness coefficient of

0.024 for the culvert. Headwater depths are shown on Table 1.

Attachments: Table 1 – Peak Discharges and Water Depths Figures 1, 2, 3, and 4 Photographs 1 to 9 Drawings E.1, E.2 Peak Discharge Estimates HY-8 Calculations

Drainage

Site Area (mi²) 2 5 10 25 50 100 500

Culvert Peak Q (cfs) 0.54 55 77 93 111 125 141 174

Water Elev. at Inlet (ft) 29.2 29.8 30.3 30.8 31.2 31.8 33.2

Water Depth at Inlet (ft) 3.2 3.8 4.3 4.8 5.2 5.8 7.2

HW/D Ratio 0.6 0.8 0.9 1.0 1.0 1.2 1.4

Notes:

1. USGS - USGS Regression Equations, “Magnitude and Frequency of Floods in Washington”, WRIR 97-4277, 1998.

NA = Not analyzed.

Table 1. Peak Discharges (ft3/sec) and Water Depths at Inlets

Recurrence Intervals (years)

Image date: 7/14/2017

Project Culvert Location

Project Area Location

USGS Topographic Maps on Google Earth

N

Queets FIGURE 1

WA NPS OLYM 2019(1)

SOUTH BEACH CULVERT

SITE LOCATION

Project Culvert

500 feet0

PACIFIC

OCEAN

SOUTH

BEACH

CAMPGROUND

Kalaloch

Project Culvert Location

Map printed from Google Earth, Image date 8/19/2016.

N

DA = 0.54 sq. mi.

FIGURE 2

WA NPS OLYM 2019(1)

SOUTH BEACH CULVERT

DRAINAGE AREA

0 5000 feet

FIGURE 3

WA NPS OLYM 2019(1)

CULVERT RATING CURVE

FIGURE 4

WA NPS OLYM 2019(1)

2-YEAR FLOW VELOCITY

Photos

PHOTO 1

PHOTO 2

PHOTO 3

3/22/2019

WA NPS OLYM 2019

Existing culvert has asphalt coating and some streambed material inside of pipe.

Existing culvert inlet partially burried with sediment. Showing signs of abrasion damage at front end.

Inside Culvert Inlet.

Culvert Inlet.

Existing culvert inlet partially burried with sediment.

Culvert Inlet.

PHOTO 4

PHOTO 5

PHOTO 6

3/22/2019

Existing culvert crossing Hwy 101.

An existing crossing under Hwy 101, roughly 200-feet upstream of project.

Large outfall pool and undercut outlet.

When this upstream structure is replaced there will likely be adjustments to the stream that impact the function of the project culvert.

Camground area above culvert crossing.

WA NPS OLYM 2019

Sink holes in campground area above culvert crossing due to culvert separating at the joints.

Upstream Channel.

The channel has a gravel and cobble bed. Left bank is steep with slight undercut overhang. Right bank has a small adjacent floodplain. Bankfull height appears to be roughly 18" to 24" above channel invert. Bankfull width is roughly 5-feet. Some fairly unstable woody debris grade controls were found further upstream.

PHOTO 7

PHOTO 8

PHOTO 9

3/22/2019

Culvert Outfall.

Picture of channel flowing into ocean.

Large plunge pool and steep banks.

Looking at the channel downstream of the debri. Stream goes subsurface through debri and cobble, resurfacing on beach.

From beach looking back at outfall.

Picture shows the amount of debri that forms roughly 50-feet downstream of the outfall. Exisitng culvert can be seen in the background.

WA NPS OLYM 2019

0+00 0+50 1+00 1+50 2+00

Existing Ground

Length=146-feet

Dia.=60-inch

Proposed plastic pipe riprap end treatment method B, class 4

Placed riprap riprap end treatment method B, class 4

Placed riprap class 4, see detail this sheet

Riprap outfall protection elev. 20.0'

DS invert elev. 26.0'

US invert class 4, see detail this sheet

Riprap outfall protection riprap end treatment method B, class 4

Placed riprap riprap end treatment method B, class 4

Placed riprap

Ordinary High Water

Ordinary High Water

Protect to a bank elev. of 19.0' invert elev. of 16.0' elev. 20.0'

E:769659.8314

N:226979.5939 elev. 16.0'

E:769654.4072

N:226982.4250 elev. 16.0'

E:769643.2497

N:226979.8860 elev. 16.0'

E:769646.4420

N:226990.8290 elev. 19.0'

E:769643.5664

N:226971.1484 elev. 19.0'

E:769649.3575

N:227000.8232 elev. 20.0'

E:769663.4274

N:226991.9211 elev. 16.0'

E:769656.7526

N:226990.4649

E:769661.8018

N:226986.3483

E:769801.8415

N:226945.4693

N

Scale in feet

5 0 10 20

10'

2' b o tt o m c h a n n e l

10'

Slope 4.1%

Flow Flow

N.T.S.

OUTFALL PROTECTION PROFILE DETAIL

1.5

N.T.S.

OUTFALL PROTECTION PLAN DETAIL

NOTES:

and loads associated with proposed application.

Pipe material must be able to withstand burial depths 2.

from either polyproylene or high-density polyethylene.

Pipe must have a smooth inteior and be constructed 1.

STATE PROJECT

NUMBER

SHEET

WA NPS OLYM 2019(1) E.1

:3

A

M

A p r il

H

Y D

P P

S h e e t] c p w

-w o rk \d

\W

A

N P

S

O L

Y M

(1

H

Y D

.d g n https://streamstats.usgs.gov/ss/

USGS STREAMSTATS

WA NPS OLYM 2019(1)

PEAK DISCHARGE ESTIMATES

HY-8 Culvert Analysis Report

Table 1 - Summary of Culvert Flows at Crossing: 5' Dia. Outfall

Table 2 - Culvert Summary Table: S.Beach 5' Dia

* Full Flow Headwater elevation is below inlet invert.

Straight Culvert

Inlet Elevation (invert): 26.00 ft, Outlet Elevation (invert): 20.00 ft

Culvert Length: 146.12 ft, Culvert Slope: 0.0411

Culvert Data Summary - S.Beach 5' Dia

Barrel Shape: Circular

Barrel Diameter: 5.00 ft

Barrel Material: Corrugated Steel

Embedment: 0.00 in

Barrel Manning's n: 0.0240

Culvert Type: Straight

Inlet Configuration: Mitered to Conform to Slope

Inlet Depression: None

Discharge Names

Total Discharge

(cfs) Culvert

Discharge (cfs)

Headwater Elevation

(ft) Inlet

Control Depth (ft)

Outlet Control

Depth (ft) Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity

(ft/s) Tailwater Velocity

(ft/s) 2 year 55.00 55.00 29.17 3.174 0.0* 1-S2n 1.446 2.076 1.446 0.383 11.279 13.576 5 year 77.00 77.00 29.81 3.812 0.0* 1-S2n 1.724 2.482 1.724 0.468 12.382 15.366 10 year 93.00 93.00 30.26 4.255 0.0* 1-S2n 1.909 2.737 1.909 0.524 13.035 16.463 25 year 111.00 111.00 30.78 4.777 0.0* 1-S2n 2.104 3.002 2.175 0.582 13.091 17.543 50 year 125.00 125.00 31.22 5.220 0.0* 5-S2n 2.250 3.195 2.335 0.624 13.443 18.307 100 year 141.00 141.00 31.78 5.779 0.211 5-S2n 2.413 3.399 2.413 0.671 14.537 19.107 200 year 152.00 152.00 32.20 6.203 0.799 5-S2n 2.523 3.530 2.615 0.701 14.158 19.618 500 year 174.00 174.00 33.15 7.150 0.0* 5-S2n 2.740 3.775 2.827 0.759 14.726 20.575

Headwater Elevation (ft) Discharge Names Total Discharge

(cfs) S.Beach 5' Dia Discharge (cfs)

Roadway Discharge (cfs) Iterations

29.17 2 year 55.00 55.00 0.00 1

29.81 5 year 77.00 77.00 0.00 1

30.26 10 year 93.00 93.00 0.00 1

30.78 25 year 111.00 111.00 0.00 1

31.22 50 year 125.00 125.00 0.00 1

31.78 100 year 141.00 141.00 0.00 1

32.20 200 year 152.00 152.00 0.00 1

33.15 500 year 174.00 174.00 0.00 1

40.00 Overtopping 288.92 288.92 0.00 Overtopping

Table 3 - Downstream Channel Rating Curve (Crossing: 5' Dia. Outfall)

Tailwater Channel Data - 5' Dia. Outfall

Tailwater Channel Option: Trapezoidal Channel

Bottom Width: 10.00 ft

Side Slope (H:V): 1.50 (_:1)

Channel Slope: 0.6700

Channel Manning's n: 0.0450

Channel Invert Elevation: 20.00 ft

Roadway Data for Crossing: 5' Dia. Outfall

Roadway Profile Shape: Constant Roadway Elevation

Crest Length: 100.00 ft

Crest Elevation: 40.00 ft

Roadway Surface: Gravel

Roadway Top Width: 100.00 ft

Flow (cfs) Water Surface Elev (ft) Depth (ft) Velocity (ft/s) Shear (psf) Froude Number

55.00 20.38 0.38 13.58 16.02 3.97

77.00 20.47 0.47 15.37 19.58 4.09

93.00 20.52 0.52 16.46 21.90 4.15

111.00 20.58 0.58 17.54 24.33 4.21

125.00 20.62 0.62 18.31 26.10 4.25

141.00 20.67 0.67 19.11 28.03 4.30

152.00 20.70 0.70 19.62 29.31 4.32

174.00 20.76 0.76 20.57 31.74 4.37