US Army Corps of Engineers

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Yakima Flood Control Project – Left BankYakima, Washington

Dennis Fischer, P.E.

Levee Safety Program Manager

Seattle District

May 2012

US Army Corps of Engineers

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Levee Overview Seattle District (NWS) Yakima Flood Control Project – Left Bank The Yakima Flood Control Project – Left Bank consists of 4 sections The levee incorporates approximately 700 linear feet of the northern Pacific

Railway Moxee Branch railway embankment. Segment ID 5505000021 Left bank of the Yakima River 18,900 feet in length The Yakima River Flood Control Project was authorized by the Flood

Control Act, approved June 28, 1938 (Public Law No. 761) Operated and maintained by Yakima County Construction was begun in July 1947 and completed in March 1948 Population at Risk: 1,807 (day), 1,286 (night)

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Yakima Flood Control Project –

Left BankYakima County, WA

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Yakima Flood Control Project –

Left BankYakima County, WA

Infrastructure Name Amount

Electric Substation

Roza 1

Schools

West Side Christian Primary School

Riverside Christian High School

Pacific Northwest University of Health Sciences

2 (3)

Sewage Treatment Facilities

Terrace Heights Sewage District 1

YAK

IMA

RIV

ER

Ties into high ground at the upstream end and a highway embankment a the downstream end. Incorporates 700 ft of railroad embankment from Station 286+00 to Station 293+00.

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Summary of Hydraulics

Yakima Flood Control Project – Left Bank was designed to protect against a 65,000 cfs flood. This was determined to be a 160-year flow.

Analysis performed in 1974 determined that the levee was capable of protecting against a 55,000 cfs flow. This was determined to be a 100-year flow.

Overtopped: No Failure: No

2 Year Event

30 Year Return

Record Flood (2009) 48,200 cfs

75% of height

Percent Loaded 25% 50% 75% 100%

Times Loaded (events) 4 2 1 0

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Performance History Yakima Flood Control Project – Left Bank has never overtopped. Yakima Flood Control Project – Left Bank has never breached. Flood conditions during the three months following construction resulted in

considerable berm erosion and loss of levee. This required emergency repairs on several levee sections in the form of additional riprap placement and other protective work. These repairs were completed June 23, 1948.

The southern section of the levee was raised and widened in 1949 to compensate for sediment deposits and channel changes that occurred in 1948.

December 1977, about 670 feet of the levee was damaged near river mile (RM) 112.6. The riverward slope and toe protection were undercut. Rock was replaced along the toe of the levee in 1978.

Flood damage occurred in December 1980 near RM 115 and the Moxee‐Hubbard irrigation ditch. The silty‐gravel streambank was eroded and threatened to undermine the Moxee‐Hubbard irrigation ditch, control gate and service road. A 500‐foot section of the levee required additional riprap bank protection in 1981.

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Performance History The top of the levee along the Roza Wasteway was raised in 1993. The levee segment between the former location of the Highway 24 Bridge

and the new location (referred to as the KOA levee) was raised to meet Federal Emergency Management Act (FEMA) standards in 1995. The segment became part of the federal levee.

In late 1995 and early 1996 two flood events occurred that damaged the levee from RM 111.5 to 113.3. Rock was placed along this section of the levee to restore it to the original level of protection.

Emergency repairs were made to the NC Machinery in 2011 to prevent an erosive failure.

A levee setback of the southern end was completed in February 2012 in association with erosive damage the occurred during 2009.

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Geomorphology / Foundation Geology

The soils are identified primarily as layers of loamy sand, sand and gravel with cobbles, and small boulders to 10 inches with some soils with clay.

Test pits were not dug deeper than 8 feet. Pits were dug in July 1946 and November 2011.

Depth (feet) USCS Description

0-2 SM Sandy loam, some clay

2-4 SP Coarse sand with gravel

4-8 SP, GP Coarse sand with gravel and gravel with sand, contains cobbles and some boulders

Composite Geologic Log (All Test Holes)

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Geomorphology

Location of seepage on right bank. Mitigation work has been performed at this site.

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Typical SectionsLevee Embankment

Elev. 1020 ft 12 ft

2.0

1.0

3.0

1.0

Riverside Landside

Toe Elevation 1013

Representative Crest Height: 7 FtCrest Width: 12 -14 FtFoundation Geology: Loamy sand, sand and gravel with cobblesLevee Materials /Zoning: Compacted Fill/HomogeneousRiverside Erosion Protection: Riprap and Sod

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Typical Section

Typical Levee Geometry Crown Width 12 -14 Feet Landward Levee Height 6-9 Feet Riverward Slope 3H:1V Landward Slope 2H:1V

1954 As-built

1940 As-built

1940 As-built

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Repair Sections

1996 Erosion Repair

1997 Erosion Repair

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Repair Sections

Repairs following 2009 flood

2012 Sportsman Park levee setback

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Review of Assessment Ratings

Inspection Ratings are taken from the 2010 Periodic Inspection report performed by HDR. Ratings are often too conservative.

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EMBANKMENT SEEPAGE SUPPORTING PHOTOS

Station 45+00: Large trees with locally dense shrubs along toe of landward slope.

Station 2+00: 180 LF of large cottonwoods (8-in - 36-in DBH) on landward slope, toe, and within 15 ft of toe.

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EMBANKMENT SEEPAGE SUPPORTING PHOTOS

Station 266+00: Area of uneven grade. Appears to be due to poor grade control during construction.

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Culverts

Yakima Levee culverts were installed in 1949 and 1953.

Yakima Levee Culverts were video inspected in May of 2010.

The video inspections revealed heavy sediment, debris, corrosion, small perforations and root penetrations.

The CMP culverts are 60+ years with signs of deterioration.

Therefore, an unacceptable rating was assigned. FG7A – Root Penetrating Wall. [Right Bank]

FG27 – Corrosion & Minor Deformation. [Left Bank]

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Assessment Ratings Embankment Seepage

Performance Mode ICW Rating

LST Rating

Comment

Embankment and Foundation Seepage and Piping

Unwanted Vegetation Growth (1) U U Several large trees are present in the landward slope of the levee. Trees in the landward slope can cause an increase in seepage through the levee. Additionally, thick brush prevents inspection of the levee slopes and toe.

Encroachments (3) U A HDR identified several encroachments in the levee area including power poles, gates, and debris off the levee toe; however, the encroachments identified are not expected to significantly increase the likelihood of failure due to foundation seepage and piping.

Settlement (7) U A Areas of unevenness in the levee crown were identified during inspection. These areas appear to be due to poor grading and construction and are not expected to be indications of settlement due to seepage.

Cracking (9) A A No evidence of cracking was identified during inspection.

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Assessment Ratings Embankment Seepage (Continued)

Performance Mode ICW Rating

LST Rating

Comment

Embankment and Foundation Seepage and Piping

Animal Control (10) M A The burrows identified during the inspection were small and infrequent and do not appear to penetrate through the levee. Significant increases in seepage are not expected due to the animal burrows identified during inspection.

Culverts/Discharge Pipes (11) U U Interior culvert photos from the 2010 video inspections were received from Yakima County and reviewed. Upon review of the inspection pictures, a few of the culverts displayed heavy sediment, debris, corrosion, small perforations and root penetrations. Video inspection was only performed on a portion of the culverts in this levee system. The conditions observed during the inspection are expected to reflect the condition of the remaining culverts. The interior condition combined with the age of the pipes prompted the inspection team to contradict the findings of the supplemental culvert assessment tab and assign an unacceptable rating for culverts.

Underseepage Relief Wells/Toe/Drainage Systems (14)

N/A N/A No relief wells or toe drains exist on this levee.

Seepage (15) A M No evidence of seepage was indentified during inspection. Minor seepage has been observed during past flood events. Seepage sites have been repaired and no further seepage has been observed at these locations; however, seepage could occur under full loading of the levee system. The rating team does not expect seepage that initiates a piping failure mode. Head will dissipate uniformly through the embankment and foundation, not allowing for conditions in which critical exit gradients will be exceeded. The seepage is expected to be controlled and ultimately not a major failure mode concern. Although the levee incorporates approximately 700 L.F. of railroad embankment, the railroad and levee embankment materials are similar and should perform similarly. The railroad sections are not expected to perform less satisfactorily than the levee embankments. Also, smaller head loading will be experienced by the shorter setback railroad sections. Seepage analysis for this levee system is not retained in the records of the Seattle District.

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EMBANKMENT STABILITY SUPPORTING PHOTOS

Station 32+00:Eight large trees, 12 to 18-in DBH, on landward slope near toe.

Station 298+00: Multiple depressions along crown of levee near riverward slope. Typically 6-in to 8-in deep, 12-in wide, length varies.

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Performance Mode ICW Rating LST Rating Comment

Embankment Stability

Unwanted Vegetation Growth (1) U M Large trees are present at levee toe on both sides of the levee and some in the lower portions of the levee landward toe Overturned trees can uproot parts of the levee embankment and reduce levee stability. The levee is wide in areas with trees embedded in the levee slope. The effect of vegetation toppling, creating progressive slope stability failures, and progressing to breach is not likely. Therefore, a minimally acceptable rating was assigned.

Encroachments (3) U A The inspection team identified several encroachments in the levee area including power poles, gates, and debris off the levee toe. These encroachments are not expected to affect slope stability.

Slope Stability (5) M A Sections of levee with over-steepened slopes were identified during inspection, but they appear stable. No slope stability failures have been observed in association with this levee and none are expected during full loading. Slope stability calculations have not been retained in Seattle District records.

Settlement (7) U A Areas of unevenness in the levee crown were identified during inspection. These areas are likely due to poor grading and construction and are not expected to be indications of settlement due to bank instability.

Assessment Ratings Embankment Stability

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Performance Mode ICW Rating LST Rating Comment

Embankment Stability

Depressions/Rutting (8) U M Depressions between 6-in. to 8-in. deep were identified on the levee crown. The depressions identified are not expected to indicate severe slope instability but may cause ponding of water which can decrease slope stability.

Cracking (9) A A No evidence of cracking was identified during inspection.

Underseepage Relief Wells/Toe/Drainage Systems (14)

N/A N/A No wells or toe drains exist on this levee.

Assessment Ratings Embankment Stability

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EMBANKMENT EROSION SUPPORTING PHOTOS

Station 85+00: 150 LF of erosion from levee fill prism; 2-3-ft high escarpment of soil eroded from levee prism; erosion less severe for at least 100-150 ft upstream and downstream with minor spots. 2H:1V slope intersects above vertical face of riprap. Recently repaired.

Station 85+00: Approximately 50 - 60 LF erosion of bank beyond toe of levee prism, near vertical bank. Recently repaired.

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EMBANKMENT EROSION SUPPORTING PHOTOS

Station 276+00: Good sod cover on levee slope. Crown is gravel-surfaced.

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Assessment Ratings Embankment Erosion

Performance Mode ICW Rating LST Rating Comment

Embankment Erosion

Sod Cover (2) A A Greater than 75 percent of levee sod cover is in good condition.

Erosion / Bank Caving (6) M U Erosion has occurred in several places along the levee. Eroded sections have been repaired and additional protection has been added; however, due to the extent of past erosive damage, additional erosion is likely during full loading and the levee has been rated a “U” for erosion. Although the levee incorporates approximately 700 L.F. of railroad embankment, the railroad is setback from the mainstem of the Yakima River and not as susceptible to damaging scour and erosion. Therefore, the railroad section is not the critically analyzed section.

Riprap Revetments & Bank Protection (12) U M Some toe material has been removed or displaced. Most of the riprap is in good condition.

Revetments other than Riprap N/A N/A Revetments other than riprap are not incorporated in the levee.

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CLOSURE STRUCTURES

Sandbag Closure

3 ft high, 125 ft long, operated by the Bureau of Reclamation

Storage and Condition AThe sandbags are stored in the field shop and are secure. The bags are in acceptable condition. Sand is readily available from several sources for use in the closure.

Available Supply AThe supply of bags exceeds the number required for this closure. The supply of sand is also sufficient. The space available for assembling the closure is larger than needed.

Operating Plan and Experience (Primary Factor) MThe personnel in charge are familiar with the procedures and effort involved. There is no written set of operational plans for when to set up the closure.

Miscellaneous Issues ANo miscellaneous issues affecting ability to set closure structure.

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CLOSURE STRUCTURES

Culvert Gate Closure

Moxee Co. irrigation canal culvert at the upstream end of the Bureau of Reclamation protection dike for Wasteway No. 2. Consists of a 48”x72” reinforced concrete culvert w/ two 36”x48” hand‐operated screw lift gates. Installed by Bureau of Reclamation. The closure does not appear to be in use and is a state of disrepair.

Operating Plan and Experience MThere is documentation establishing who is responsible for this closure but not for when it should be set during flood events. Those responsible for this closure understand how to set the closure.

Operating Environment and Access MThe closure has been set within the last 5 years but not recently. It has been set at various times of the year and can be shut off with emergency actions if necessary.

Condition and Recent Maintenance History (primary factor) MThe closure is in fair condition but is maintained and inspected by the Bureau.

Miscellaneous Issues MA lack of communication between the levee sponsor and the Bureau could lead to this closure not being set at the proper time. Additional documentation establishing the timing for setting the closure is needed.

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Consequence Data Summary Weighted Fatality Rate: 0.45 Threatened Population with Breach prior to Overtopping: Day- 421

Night- 299 Threatened Population with Overtopping: Day- 176 Night- 125 Estimated Loss of Life with Overtopping: 1 Estimated Loss of Life Breach Prior to Overtopping: 2 Number of structures Inundated: 665 Economic Damages: $46,220,000

Infrastructure Name Amount

Electric Substation

Roza 1

Schools

West Side Christian Primary School

Riverside Christian High School

Pacific Northwest University of Health Sciences

2 (3)

Sewage Treatment Facilities

Terrace Heights Sewage District 1

One of the electrical substations, "North Park," included in the protected area has been removed. Only the "Roza" substation is still in use. One additional school, Pacific Northwest University of Health Sciences, is also located in this protected area. The primary school and high school enroll approximately 550 students. This school appears to have not been included in the census data. Due to the number of students in this school, the young age of the students, and the difficulty of evacuating the school, a population day index factor of 1.4 was used.

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Emergency Preparedness Evacuation Planning = Minimally Acceptable.

► Yakima County created an emergency action plan in 2007 that established authorities and procedures for evacuation planning and execution. No evacuation map has been created.

Community Awareness = Minimally Acceptable. ► Flood fighting teams are familiar with the equipment needed for flood fighting but

no specific community awareness efforts have been made to raise awareness of the hazards surrounding the levees.

Flood Warning Effectiveness = Acceptable.► The Yakima County emergency action plan includes authorities and procedures

for flood warnings. The plans involve use of several media for flood warning.

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Assessment Rating SummaryPrimary Factors

Embankment & Foundation Seepage - M

Embankment Stability - A

Erosion - U

Culvert Gate Closure - M

Sand Bag Closure - M

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Major Contributors to Overall Risk Rating

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Major Contributors to Risk Prior to Capacity Exceedance

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Segment Ratings Compared to All Segments

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Performance Index vs Life Loss

Overtopping

Prior to Overtopping

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Risk Whisker

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Performance Index vs Property Loss

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Recommended LSAC Rating Prior to Capacity Excedance LSAC = xx Capacity Excedance LSAC = xx

Recommended LSAC = xx

Add Reasons for adjusting LSAC rating