B.08_ADV_2020 BON Spillway ROV Rock Inspection Report.pdf

2020 BON Spillway Apron ROV Inspection Report (Advertisement Copy)

Inspection date: 12/02/2020;

Inspection conducted for: NWP Small Projects Team;

ROV Inspection by: NWP Office of Dive/ ROV Operations and Safety;

Inspection location: Bonneville Dam, Cascade Locks, OR;

Desired inspection targets: Verification of rock debris in spillbays;

ROV and Sonar description:

The BON spillway and apron structures were inspected using a Deep Ocean Engineering Phantom XTL remotely operated vehicle (ROV). Visual inspection was conducted using the installed high-resolution camera and documenting on HDD. Sonar imaging was conducted utilizing a BlueView 2D multi-beam sonar as well as a Tritech SeaPrince Sector/ Polar Scanning sonar.

Figure 2 VideoRay ROV and sonar

Figure 1 Deep Ocean Engineering Phantom XTL ROV

Figure 2 BON Spillway. Red boxes indicate approximate area of inspection coverage.

Project description and inspection findings:

The Bonneville spillbay ROV inspection was conducted to verify recent bathymetric hydro-survey data.

The plan was to inspect all spillbays, apron and baffle block structures to determine rock pile locations, size and pile extent. The weather experienced on 2 December presented challenges that prevented the inspection of the entire structure. Winds on the day of the inspection were forecasted 25-35 mph with gusts of +40 mph from the east. The inspection proceeded as planned as the downstream location was somewhat protected from the east wind. Once on location, due to the gusting winds, we were only able to capture sonar imagery of Bays 1-6 and Bays 16-18. The vessel was unable to stay on-station in the area between Bays 7 and 15.

The following items were found during the ROV inspection:

-Bay 1 is clear of rocks;

-Bay 2 has a small rock pile approximately 4’ x 6’ consisting of small 2-4” diameter round river rock.

There is also a boat propeller and outboard motor lower unit laying in the pile;

-Bay 3 through 6 was found to be clear of rocks;

-Bays 7 through 15 were not imaged due to the +40 mph wind gusts affecting this area;

-Bay 16 was difficult to image due to the wind but appears to be clear of rock;

-Bay 17 has the largest pile of rock in it. The pile is approximately 1-3 ft. high at it’s highest point but this is difficult to accurately determine as the pile slopes uphill along the base of the ogee. It is primarily comprised of 6-8” or smaller round river rock. Only a few rocks were noted to be in the +10” range. The pile is approx. 20’ long by 15’ wide;

-Bay 18- most of the bottom is clear of rock. There is a pile of small rock and gravel near the base of the ogee, but it is small in diameter and the rock size is very small as well. Some of the areas on the ogee were also found to be filled in with woody debris;

Video imagery below highlight areas of interest found during the inspection.

Figure 3 Small rock pile found in Bay 2 along with a boat propeller and outboard lower unit.

Figure 4 Bay 2 Rock pile with outboard motor lower unit.

Figure 5 Bay 2 Small rock pile and propeller.

Figure 6 Bay 17 rock pile.

Figure 7 Another image of rock in Bay 17.

Figure 8 Image of Bay 17 rock pile showing relative rock sizes.

Figure 9 Bay 17 rock showing relative sizes.

Figure 10 Bay 17 with rock.

Figure 11 Additional images of rock n Bay 17.

Sonar imagery below highlight areas of interest found during this inspection. Yellow arrows in sonar imagery indicate direction of water flow for image reference.

Figure 12 White circle indicates small diameter pile of rock and debris in Bay 2.

Figure 13 Imagery showing Bay 17 rock pile. Solid line at the upper portion of the image is the Bay 17/18 dividing wall.