Hyperion 1&5 Outfall Inspections

Overview
Ballard was awarded a multi-year contract to supply diving services, Remotely Operated Underwater Vehicle (ROV) services, and vessel services for the Hyperion Wastewater Treatment Plant. The purpose of this project execution was to ensure the proper maintenance was performed on the necessary infrastructure, within and around the wastewater treatment plant.

Scope of Work
The structures consist of a one-mile, five-mile, and seven-mile outfall. The work is comprised of:

  1. Port Identification and Location 
  2. Plugging and/or Puffing Ports
  3. Status of Four Special Effluent Ports
  4. North and South Diffuser End Structure Areas
  5. WYE Structure
  6. Main Barrel
  7. North and South Transition Structures
  8. Offshore Bell Joint Repairs
  9. Epoxy Bumper Joint Separation
  10. Main Barrel Re-ballast Stone Levels
  11. Inshore Bell Joint Repairs

Ballard concludes each service with a draft report for the owner’s review. Once approved, the video of the inspections and associated findings are presented to the engineering team.

Innovative Solutions
During Ballard’s work window, planning around weather to perform all in-water activities was crucial. Ballard’s Safety Manager worked with the Project Manager to establish an “External Variables and Weather Metrics” table that would assist the field personnel in determining if operations were safe enough to conduct. Variables considered were vessel traffic, fog, sea state, currents, tides, wind, and visibility (underwater and topside). Limited visibility also posed a challenge for the project. To mitigate this, Ballard mounted two imaging sonars on the ROV. One was in the “profiling” view to map areas of scouring and spalling in the section view, and one in the “sector” view which is a forward-looking sonar used to navigate around the structure and determine ROV location. An underwater position system was also used to monitor the position of the ROV related to the structure.

Results
The execution of this contract took place in 2010 and every year since this date, there has been work performed on the various sites. The proper inspection and tracking of the condition of these outfalls have ensured that the Hyperion Wastewater Treatment Plant will continue to serve the City of Los Angeles for future decades.

Client: City of Los Angeles
Location: Play Del Ray, CA
Diver Depth: 220ft

Services

• Biological survey
• Cathodic survey
• Light work ROV
• Limited access ROV
• High resolution multi-beam imaging
• Offshore services
• Sonar
• Surface supplied air diving
• Underwater inspection

Strontia Springs Dam ERDS Rehibilitation

Overview
The Strontia Springs Dam Reservoir’s Emergency Reservoir Drawdown System (ERDS) rapidly releases water in an emergency scenario through a fifty-foot-long tunnel that runs through the base of the dam. The thrust nut on the ERDS control gate was damaged and required replacement, 250 feet below the reservoir’s surface. Denver Water selected Ballard as its Construction Management at Risk (CMAR) partner to perform the necessary repairs.

Scope of Work
Ballard determined that the implementation of an effective dredging plan and careful execution of a massive bulkhead installation was pivotal to the success of the project. Ballard employed a marine barge spread which housed an on-board crane and supported diver-assisted dredging and mixed gas diving operations. Dredging material from in front of the existing trash rack was necessary to gain access to the upstream face of the ERDS. Ballard engineered and fabricated an in-water cofferdam to reduce the volume of material that required removal. Sediment was removed using a hydraulic pump and disposed of in a topside decanting system.

Innovative Solutions
Ballard removed the trash rack, as well as four seventeen-ton fixed wheel gates and their support chains. Ballard worked with Denver Water to design, fabricate and install temporary covers to minimize the opening left by the removal of the four fixed wheel gates. After removing the trash rack, divers guided the 44,000-pound bulkhead into place. Cold weather and high altitude posed operational challenges when lowering and positioning the bulkhead in front of the ERDS. Working 250 feet beneath the surface placed limitations on working time and visibility. To correct the effects of high altitude, Ballard used mixed gas diving techniques to maximize time in the water. Once the bulkhead was fully installed, Ballard coordinated with Denver Water to open the downstream gates which created sufficient differential pressure to seal the bulkhead.

Results
In collaboration with Denver Water, Ballard removed the damaged control and maintenance gates, and oversaw the in-place machining of the gate sills and frames. Ballard installed new discs, stems, and thrust nuts for the maintenance and control gates, and reconnected both cylinders to the existing hydraulic power unit. Ballard then removed the temporary bulkhead, reinstalled the trash rack, and removed the in-water cofferdam.

Client: Denver Water
Location: Littleton, CO
Diver Depth: 200ft