2014 – HADLEY FALLS HYDROELECTRIC POWER PLANT DIVE INSPECTION
The following scope of work at the Hadley Falls Hydroelectric Project was performed to aid in the development of design details for the new intake fish exclusion rack project. The proposed scope involved the inspection of Western and Eastern Abutments, bottom Condition Assessment along Alignment of Trash Racks; and the submerged rock-filled Timber Crib Dam.
- Record the height/width of fishway exit flume opening relative to the waterline.
- Confirm the layout and dimensions of the exit flume opening.
- Confirm the layout and dimensions as far back into the exit flume as the stop log slots.
- Determine the condition and levelness of the floor of the exit flume upstream of the stop log slots.
- Determine the straightness and plumbness of the exit flume walls upstream of the stop log slots.
- Provide a description of the condition of the existing structure.
- Provide detailed measurements of the location of steel elements, concrete and the transition to masonry (if present).
- Note any other locations of change of material.
- Investigate the bottom condition (solid rock/debris/silt) in-front of the fishway opening and extending out to the proposed Caisson by probing the bottom with a steel rod.
- Investigate the bottom condition (solid rock/debris/silt). Probe the bottom with a steel rod to estimate the depth to a “hard bottom” at a minimum of 8 locations.
- Inspect the vertical structures from the existing station’s trash racks to the far side of the first pier.
- Provide a description of the condition of the existing structure – of particular interest wass the transition from concrete to masonry at the bascule gate and the condition of the masonry walls.
- Measure the typical joint spacing of the masonry block.
- Every 10 feet along the length of the trash rack alignment the divers investigated the bottom condition (solid rock/debris/silt) and probed the bottom with a steel rod to estimate the depth to a “hard bottom”. The location of the probing shall be recorded with enough accuracy to relate the position of the probing back to the bathymetry data.
- Perform a dive inspection that records the construction of the timber crib dam and describe the material on the upstream side of the dam (solid rock/debris/silt), particularly with regards to any material collection towards the top of the dam.
The diver team was equipped with a 3-dimensional sonar, dive video camera and two-way communication. The recording of the dive inspection shall included descriptive commentary by the diver and the two way communication. The dive team accommodated a client representative from who reviewed the video in real time, and asked questions regarding the existing conditions. Throughout the inspection, the dive crew was responsible for note taking for use in the preparation of a dive inspection report. The dive crew shall record the headpond elevation at the time of the inspection. Within two weeks of the dive inspection, two (2) copies of the written dive inspection report and DVD were submitted to client.