f.Hells_Canyon_Boat_Launch_Condition_Assessment_Report.pdf

22 May 2015

Doug Argo, PE

Holladay Engineering Co.

32 N. Main

Payette, ID 83661

Subject: Condition Assessment– Boat Launch, Hells Canyon, Oregon

Conducted on 14 April 2015

BergerABAM Job No. A15.0253

Dear Mr. Argo:

This letter report summarizes our condition and structural assessment of the boat launch located on the Snake River in northeastern Oregon. Our report outlines the structure type, its present condition, observed deficiencies, and recommendations for rehabilitation along with the anticipated construction costs that would be associated with rehabilitation.

INTRODUCTION AND AUTHORIZATION

On 27 March 2015, Holladay Engineering Co. authorized BergerABAM to perform a condition and structural assessment of the Hells Canyon boat launch and boat dock facility located on the

Snake River in northeastern Oregon (see Figure 1). The boat launch consists of a concrete ramp and adjacent concrete apron, accessible to the public and used for launching boats into the river.

Because of high river flows and flooding, the concrete ramp and apron have experienced scour, potentially reducing their structural capacity.

The project involved a below‐ and above‐water condition assessment of the boat launch to verify the current condition of the ramp and apron structure and the extents of the scour. The project also involved developing concept alternatives for rehabilitation and estimates of their probable construction costs.

Figure 1 – Aerial View of Site

STRUCTURAL ASSESSMENT ACTIVITIES

On 14 April 2015, BergerABAM divers performed a topside and underwater inspection of the boat launch facility located downriver from the Hells Canyon Dam. The three‐person inspection team was led by Nick Colson, PE, dive supervisor/engineer‐diver, and included Brett Ozolin, PE, assistant dive supervisor/engineer‐diver, and Matt Perry, senior construction specialist‐ diver. The team used surface supplied air to perform the underwater inspection and performed the topside inspection on foot. The inspection was limited to visual observations of the condition of the concrete ramp and apron, and did not include any materials testing. The inspection team worked from shore to access the boat ramp and support diving operations.

The water level elevation during the inspection was approximately 1,465 feet (NGVD29 datum) according to the local station gauge. According to the topographic survey performed on the day of the dive, the water level elevation was approximately 1,468 feet (NAVD88). The end of the boat ramp was submerged below the water surface and the depth of the water at the ramp end varied from approximately 3.2 feet at the northwesterly corner to 4.2 feet at the northeasterly corner of the main ramp concrete section.

The team walked the ramp area to assess the above‐water conditions. A single diver in the water, assisted by a diving tender/standby diver, performed the underwater inspection. A third team member, stationed in the dive support trailer, provided rack operation assistance and took inspection notes during the dive.

The underwater inspection began at the base of the ramp, progressed around the perimeter of the ramp, and terminated at the ramp surface. The team inspected the precast and cast‐in‐place concrete visually to determine the overall condition of the ramp structure. The diver inspected the extent of the scour voids below the ramp visually, and used a ½‐inch diameter by 3‐foot‐ long probe to estimate the void sizes. Because of the freshwater environment, little aquatic growth was present to hinder the inspection.

The condition of the concrete and the extent of scour associated with the above‐water and shallow water portion of the ramp were inspected by walking around the ramp and by wading in the shallow water adjacent to it.

Concurrent to BergerABAM’s field activities, WH Pacific performed topographic and bathymetric survey of the site.

STRUCTURE DESCRIPTION

Original construction drawings for the boat ramp are dated May of 1992. The boat ramp is approximately 75 feet long and is constructed of precast and cast‐in‐place concrete (see Photo

1).

The approximately 36 feet of the ramp nearest the river are precast concrete panels. A raft apron adjoins the ramp. The apron is cast‐in‐place concrete and slopes from the side of the ramp into the river.

Crushed aggregate beneath the area of the ramp was placed before the installation of the concrete. Geotextile fabric was installed to contain the crushed rock and prevent it from washing out when underwater. Two W6x16 beam rails were embedded in the base course and supported and guided the precast panels during construction. A steel stop at the river end of the rails is intended to prevent the panels from sliding into the river (see Photo 2).

Photo 1 – Boat ramp and apron

Photo 2 – Beam at end of precast panels

OBSERVED CONDITIONS

Concrete Condition The concrete appears to be in good condition with minimal cracks and spalls. However, in several locations, the top grooved surface at the tongue and groove joint between precast panels exhibited spalling for up to 3 feet along the edge (see Photo 3). Typically, this spalling was on the land side end of the panels, although one shallower spall was also observed near the middle of the panel joint (see Photo 4). Some concrete spall locations have been filled in with gravel.

Photo 3 – Spall along joint between the western end of precast panels

Photo 4 – Shallow spall along the joint at mid-panel

Three adjacent precast panels below the water surface exhibited an approximate 1‐inch differential elevation at the panel joint (see Photo 5). According to the WH Pacific survey, there is an elevation difference of 1 foot between the top of ramp at the northwest corner and at the northeast corner. A differential elevation and separation of less than 1 inch exists between the end of the apron and the adjacent concrete panel.

Photo 5 – Elevation difference between precast panels approximately 1-inch

Apron Scour The apron measures approximately 45 feet along the eastern edge and approximately 10 feet along the northern edge. Approximately 25 percent of the apron surface was below water during the inspection. Scour voids and base material loss were observed around the perimeter of the apron. Typically, a few‐inch gap separated the bottom of the concrete and the underlying material (see Photo 6). The gap extended up to 2 feet horizontally beneath the concrete along the eastern edge. The largest of the scour voids was along the lower, eastern edge of the apron.

Photo 6 – Gap at apron eastern edge

As the inspection progressed further into the river, larger rocks and larger voids between the rocks beneath the apron were encountered. The largest void was approximately 1 foot high by 3 feet wide by 4 feet deep (depth dimension is horizontal extents beneath the apron). Several other locations had voids up to 2 feet high by 3 feet deep. The rocks around and below the apron were typically 1 to 2 feet in diameter with some larger rocks supporting the edge of the concrete apron. At the northern end of the apron no large voids were observed. The slope beyond the end of the apron is near vertical for approximately 5 feet below the end of the apron.

Ramp Scour At the joint between the northern end of the apron and the eastern edge of the ramp, there is a

2‐foot diameter rock located approximately 2 inches beneath the precast panels. A 2‐inch‐high gap opens to approximately 1.5 feet high for the remainder of the eastern edge of the ramp. The

1.5‐foot‐high gap between the concrete and the river bottom extends under the ramp for 3 feet, to the W6x16 beam.

See Figure 2 and Figure 3 below for the approximate extents of scour at the ramp and apron.

Figure 2 – Boat Launch Scour Extents – Plan View

Figure 3 – Boat Ramp Scour Extents – Section View at Ramp Centerline

The substrate material under and around approximately the end 5 feet of the W6x16 beams has been lost, although the very ends of the beams are supported. The visible portion of the beams are experiencing minor surface corrosion but with little to no section loss (see Photo 7).

Photo 7 – Minor corrosion of beam end, and material loss below precast panel

Along the northern end of the ramp, the void under the concrete decreases from 1.5 feet on the east side to fully supported on the west side near the shore. A gap under the ramp between the two W6x16 beams measures approximately 1 foot high and extends at least 5 feet beneath the ramp. Because the 3‐foot probe could not reach the full extent of this gap, it likely extends further. At the end of the probe, the height of the gap lessened to approximately 2 to 3 inches between the concrete and substrate.

Torn geotextile fabric was observed at several locations around the apron and the ramp and no crushed rock was present at those locations.

The western, shore‐side, edge of the ramp is hard up against rock and showed no loss of material.

STRUCTURE CONDITION ASSESSMENT

Based on our observations of the boat launch structure and surrounding supporting rock material, we rate the condition of the overall structure as fair. A fair rating has been assigned because all primary structural elements are sound; but some minor concrete cracks and spalls are present. Additionally, moderate localized scour exists around and below the ramp which has led to a reduction in load bearing capacity of the ramp.

The scour below and along the eastern edge, near the end of the ramp, appears to have produced an approximate 1‐foot differential settlement of the supporting precast panels and steel beams. In addition, the last few panels of the ramp are not continuously supported by a gravel substrate. The original design of the precast concrete panels requires a full gravel bearing surface below the panels. Because the scour below the ramp has left some panels supported by only the steel rail beams below, the load carrying capacity of the panels has been reduced from its original design. Furthermore, the W6x16 beams were not originally intended as flexural members but are acting as such in the current condition.

RECOMMENDATIONS

We recommend limiting the use of the ramp (as shown in Table 1 and in Figure 4) until the ramp has been rehabilitated. Table 1 below shows limiting axle loads for a 1‐, 2‐ and 3‐axle trailer arrangement for the current condition of the ramp (without a wheel stop) and for a condition where a wheel stop is installed at least 18 inches from the bottom edge of the ramp.

Number of Axles (Min 3'‐0" Axle Spacing)

Total Allowable Load Capacity (lbs)

With Wheel Stop Without Wheel Stop

1 10,800 5,400

2 21,600 10,800

3 32,400 16,200

Table 1 – Boat Ramp Axle Load Limitations (with and without Wheel Stop)

Figure 4 – Boat Ramp Axle Load Limitation Diagrams (With and Without Wheel Stop)

Furthermore, we recommend replacing the scoured rock material below and around the ramp and apron to reduce the risk of further damage and potential failure. The scour has undermined the ends of the ramp and apron and caused some settlement and cross slope between ramp panels and between the ramp and apron. It is not necessary to restore the ramp and apron to its original elevation in order to restore the structural capacity of the ramp.

However, if the cross slope presents a functionality issue for launching boats, then jacking up the beams and ramp to its original elevation may be an option.

While the present condition of the boat ramp concrete does not require immediate repairs, maintaining the concrete regularly and repairing it will help extend the life of the facility.

The sections below outline alternatives for the ramp rehabilitation and their construction costs.

Alternative A: Prior to commencing any in‐water work, install a sediment curtain to contain construction debris. Install empty grout bags into the voids below the ramp and apron. Place grout bags around all voids at the perimeter of the ramp and apron, and extend grout bags beneath the ramp and apron to the maximum extent possible, with a minimum of 1 foot horizontal extension beneath the ramp and apron. Pump grout into the empty grout bags to fill the voids. Grout bags should be filled to the point at which the grout bags are bearing at the underside of the concrete (see Figure 5). Install engineered riprap material around the ramp and apron.

Our opinion of probable construction cost for rehabilitation with Alternative A is $108,700. A breakdown of the costs for Alternative A is included in Appendix A.

Figure 5 – Alternative A – Grout Bags and Riprap Repair

Alternative B: Prior to commencing any in‐water work, install a sediment curtain to contain construction debris. Remove the steel beam stops at the end of the beams and remove precast panels from the bottom of the ramp moving up towards shore. Remove any panels that do not have full rock bearing beneath them and replace the missing base material below the ramp (see

Figure 6).

Install empty grout bags into the voids below the apron. Place grout bags around all voids at the perimeter of the apron, and extend grout bags beneath the apron to the maximum extent possible, with a minimum of 1 foot horizontal extension beneath the apron. Pump grout into the empty grout bags to fill the voids. Grout bags should be filled to the point at which the grout bags are bearing at the underside of the concrete. Install engineered riprap material around the ramp and apron.

Our opinion of the probable construction cost for rehabilitation with Alternative B is $111,100. A breakdown of the costs for Alternative B is included in Appendix A.

APPENDIX A – OPINION OF PROBABLE CONSTRUCTION COSTS

PROJECT: BergerABAM Job No.: PAGE:

A15.0253.00

OPERATION: ESTIMATOR: DATE:

TAD/BDB

ITEM UNIT QUANTITY UNIT

NO. COST

1 Mobilization * LS 1 7,100.00$ 7,100.00$ 2 Sediment Fence for In-water Work LS 1 4,000.00$ 4,000.00$ 3 Grout Bag Installation LS 1 27,800.00$ 27,800.00$ 4 Install Engineered Riprap LS 1 15,000.00$ 15,000.00$ 5 Site Access Premium ** LS 1 4,700.00$ 4,700.00$

6 Permitting and Engineering LS 1 25,000.00$ 25,000.00$

* 15% of total of items 2 through 4 (varies depending on estimate) ** 10% of items 2 through 4 (accounts for remote location of project)

SUB TOTAL

30% Construction Contingency

TOTAL ESTIMATE ROUNDED $108,700

$83,600

$25,100

Hells Canyon Boat Launch Assessment

Estimate of Probable Construction Cost - Boat Ramp - Alternative A 22-May-15

TOTAL

COST

PROJECT: BergerABAM Job No.: PAGE:

A15.0253.00

OPERATION: ESTIMATOR: DATE:

TAD/BDB

ITEM UNIT QUANTITY UNIT

NO. COST

1 Mobilization * LS 1 7,300.00$ 7,300.00$ 2 Sediment Fence for In-water Work LS 1 4,000.00$ 4,000.00$ 3 Remove Panels and Replace Gravel Bedding LS 1 19,200.00$ 19,200.00$ 4 Grout Bag Installation LS 1 10,000.00$ 10,000.00$ 5 Install Engineered Riprap LS 1 15,000.00$ 15,000.00$

6 Site Access Premium ** LS 1 4,900.00$ 4,900.00$

7 Permitting and Engineering LS 1 25,000.00$ 25,000.00$

* 15% of total of items 2 through 5 (varies depending on estimate) ** 10% of items 2 through 5 (accounts for remote location of project)

SUB TOTAL

30% Construction Contingency

TOTAL ESTIMATE ROUNDED $111,100

$85,400

$25,700

Hells Canyon Boat Launch Assessment

Estimate of Probable Construction Cost - Boat Ramp - Alternative B 22-May-15

TOTAL

COST