Crystal Gardens Sediment Removal Project

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The City of Avondale Crystal Gardens Water Treatment Facility is a part of a larger facility that includes recharge basins, and recovery wells, known as the Wetlands of Avondale. The Crystal Gardens Water Treatment Facility (treatment facility) portion of the Wetlands of Avondale consists of a series of treatment cells designed to treat the City's Salt River Project (SRP) water allocations to meet aquifer water quality standards. The Treatment Facility is surrounded by the Crystal Gardens residential development but is open to the public. The original Treatment Facility was designed to be an amenity to the community as well as an indirect source of drinking water. Construction of the facility was completed 25 years ago in 1996. While the treatment facility is meeting the permitted water quality goals, it is showing signs of needing maintenance in order to continue to provide water treatment and the wetlands amenity of the facility.

The design flow capacity of the entire system is 4.5 million gallons per day (mgd) or 5,000 acre-feet per year (AFY). The facility is designed to be capable of reducing nitrates (NO3) from concentrations as high as 20 milligrams per liter (mg/L) to below the maximum contaminant level (MCL) of 10 mg/L. The system has a maximum storage capacity of 20,000 AFY. At this higher flow rate, the facility can still meet the needs of transferring water while providing nitrate reduction benefits.

The city has hired Carollo Engineering to evaluate the Gardens lakes who provided a comprehensive evaluation report in June 2022. Part of the recommended improvements was to dredge approximately 60,000 CY of raw sediment and bio solids which was estimated to be 12,000 CY of drained/ dry sediment and bio solids material from cells 1A, 10A, 8B, and 14B. The project is scheduled to start the first week of February for a duration of project expands over approximately 32 months to be completed.

The contractor, Dredge Diver, LLC has provided the following description of work:

"We use Portable Hydraulic Dredging, guided by technical divers. This technique can be multipurpose, resulting in control of both the sediment and the biomatter needing to be removed. Diver-guided dredging aims at (1) targeted removal of the sediment and biomass, (2) eliminating accumulated unpleasant substances creating odor, (3) protecting the pond liner from mechanical damage, and (4) remaining as inconspicuous to the community as possible. Our hydraulic dredge either floats on the water via pontoon or on a trailer on land and pumps the material through a pipeline to the shore nearby or an offsite location, sometimes several hundred feet away. This dredge acts like an underwater vacuum cleaner that can remove sediment very precisely. We use scuba divers to guide the suction in the specific areas where silt is to be removed. The sludge is then dewatered for a period and hauled away when it is sufficiently dry to load and transport. With a hydraulic dredge, the discharge line, geotextile tubes, and water return line are the only obstructions in the environment. The lines are usually on the ground or underwater. Other than this, the dredge, a pontoon boat equipped with the pumps, motor, and hoses is the only machine to be seen. It is a very unobtrusive method that does not require severely disturbing the shoreline or draining the entire body of water. Hydraulic dredging provides the cleanest and least obtrusive method for sediment removal without damaging pond liners, clay bottoms, or the lake edge."

Dredge Diver has provided some additional photos from another job that you can see on the right.

Stay tuned for more information coming on this environmentally positive project!

The City of Avondale Crystal Gardens Water Treatment Facility is a part of a larger facility that includes recharge basins, and recovery wells, known as the Wetlands of Avondale. The Crystal Gardens Water Treatment Facility (treatment facility) portion of the Wetlands of Avondale consists of a series of treatment cells designed to treat the City's Salt River Project (SRP) water allocations to meet aquifer water quality standards. The Treatment Facility is surrounded by the Crystal Gardens residential development but is open to the public. The original Treatment Facility was designed to be an amenity to the community as well as an indirect source of drinking water. Construction of the facility was completed 25 years ago in 1996. While the treatment facility is meeting the permitted water quality goals, it is showing signs of needing maintenance in order to continue to provide water treatment and the wetlands amenity of the facility.

The design flow capacity of the entire system is 4.5 million gallons per day (mgd) or 5,000 acre-feet per year (AFY). The facility is designed to be capable of reducing nitrates (NO3) from concentrations as high as 20 milligrams per liter (mg/L) to below the maximum contaminant level (MCL) of 10 mg/L. The system has a maximum storage capacity of 20,000 AFY. At this higher flow rate, the facility can still meet the needs of transferring water while providing nitrate reduction benefits.

The city has hired Carollo Engineering to evaluate the Gardens lakes who provided a comprehensive evaluation report in June 2022. Part of the recommended improvements was to dredge approximately 60,000 CY of raw sediment and bio solids which was estimated to be 12,000 CY of drained/ dry sediment and bio solids material from cells 1A, 10A, 8B, and 14B. The project is scheduled to start the first week of February for a duration of project expands over approximately 32 months to be completed.

The contractor, Dredge Diver, LLC has provided the following description of work:

"We use Portable Hydraulic Dredging, guided by technical divers. This technique can be multipurpose, resulting in control of both the sediment and the biomatter needing to be removed. Diver-guided dredging aims at (1) targeted removal of the sediment and biomass, (2) eliminating accumulated unpleasant substances creating odor, (3) protecting the pond liner from mechanical damage, and (4) remaining as inconspicuous to the community as possible. Our hydraulic dredge either floats on the water via pontoon or on a trailer on land and pumps the material through a pipeline to the shore nearby or an offsite location, sometimes several hundred feet away. This dredge acts like an underwater vacuum cleaner that can remove sediment very precisely. We use scuba divers to guide the suction in the specific areas where silt is to be removed. The sludge is then dewatered for a period and hauled away when it is sufficiently dry to load and transport. With a hydraulic dredge, the discharge line, geotextile tubes, and water return line are the only obstructions in the environment. The lines are usually on the ground or underwater. Other than this, the dredge, a pontoon boat equipped with the pumps, motor, and hoses is the only machine to be seen. It is a very unobtrusive method that does not require severely disturbing the shoreline or draining the entire body of water. Hydraulic dredging provides the cleanest and least obtrusive method for sediment removal without damaging pond liners, clay bottoms, or the lake edge."

Dredge Diver has provided some additional photos from another job that you can see on the right.

Stay tuned for more information coming on this environmentally positive project!

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Page last updated: 02 May 2024, 02:00 AM