Solidification and Stabilization 
 



Solidification and Stabilization


What type of work will be involved in this contract ?

The Sydney Tar Ponds consists of two tidal estuaries, known as the North and South Ponds. All the 550,000 cubic metres of sediments in the two ponds, including Polychlorinated biphenyl (PCB) material, will undergo Solidification and Stabilization treatment as a means of creating a structurally enhanced, low permeable concrete mass that immobilizes contaminants.
This involves mixing cement into contaminated material using excavators and other equipment, this process works to protect the environment and our health by immobilizing hazardous contaminants within the treated material. The cement reacts chemically with water in the material being treated, creating changes in its physical and chemical properties that stabilize these hazardous constituents and prevent their escape into the environment.
Soil, sediment and sludge impacted with a variety of organic and inorganic contaminants have been treated successfully using this versatile technology In order to carry out the Solidification and Stabilization treatment, surface water controls will be used to redirect surface water flows and outfalls away from the area when Solidification and Stabilization is taking place. Surface water controls will be in the form of temporary pumping stations, and in the construction of permanent channels through the Tar Ponds. The new channels will be permanent, and they will be used to bring water from Coke Ovens Brook and Wash Brook from their current entry points in the South Tar Pond to Sydney Harbour.

What is the cost of this work?

The estimated cost of the contract is $52 million dollars. The funding for this contract is a result of the Government of Canada and the Province of Nova Scotia's Memorandum of Agreement (MOA) of May 12, 2004, committing the two parties to jointly participate in the remediation of the Sydney Tar Ponds and Coke Ovens sites. It is a $400-million agreement that specifies that the cleanup be completed by 2014.

How was this contractor selected?

Agency received six bids. There were three tiers to the bid evaluation, A. Technical B. Cost C. Local Benefits.
Four of the six bids passed the technical evaluation - the first tier. The second tier was the six per cent clause, which means that bids within six per cent of the lowest compliant bid are considered. After the six per cent clause was implemented, only one bid remained compliant. The third tier is the Local Economic Benefits package, which is still valid, but no longer evaluated when there is a single, compliant bid.

What is Solidification and Stabilization?

Sediments in the tar ponds will be solidified and contaminants stabilized. Solidification and stabilization involves mixing cement and other stabilizing ingredients into the contaminated material and works to protect the environment and our health by immobilizing hazardous contaminants. The material will then be capped adding another layer of protection.

How long will the process take?

This process will take 5 years to complete work.

When will work begin?

The work will begin October 2009.

Who was the contract awarded to?

The contract was awarded to Nordly's Environmental, a Cape Breton company owned by J&T van Zutphen Construction Inc. of Southwest Mabou, and ECC of Marlborough, Massachusetts, US.
Has this procedure been done anywhere else in Canada, the world? If so, where?

S&S with cement is a common method for the safe treatment, management and reuse of contaminated waste. Developed in the 1950s, the technology is widely used today to treat industrial hazardous waste and contaminated material at brownfield sites.

How is quality tested on the SS process, who is responsible and what is the reporting process?

There will be a significant amount of time between the mixing of the cell and the confirmation/verification of the testing results. The process will take about 4-5 months, longer if discrepancies are identified. Once the testing results are confirmed, they will be released publicly. An overview of the process once the cell (approximately 250m3 of sludge) is mixed is outlined below. The S/S material is tested at 28 and 56 days for unconfined compressive strength. Leachate and permeability testing are tested 28 and 56 days. The actual leachate and permeability testing can take up to 2 weeks to be completed. Results are then complied monthly by the contractor into a Quality Control (QC) report. The QC report is then reviewed by our design engineer AECOM. This review can take up to 3 weeks. Once this review by is completed and no issues are identified, our Independent Quality Assurance Consultant (Stantec) reviews the report. This review can take up to 4 weeks. Once this review is completed and no discrepancies are identified, the report is determined to be complete and can be released. If during either AECOM or the Stantec review, errors and/or discrepancies are identified, the contractor has to address the errors/discrepancies and resubmit the report. At this time the review clock for AECOM and Stantec starts again.

Where in the 100 per cent design report can I locate more information on how the channels are being constructed?

Please see below:

Q: What material will be used to make the channel? A: Appendix B (Drawing TP6 DWG C-571) shows an x-section of the channel that includes specific details on channel construction.

Q: How wide and deep will the channels be? A: Appendix B (Drawing TP6 DWG C-571) shows that both channels will be about 20m wide at the bottom with a 2:1 slope on either side. The Coke Ovens Brook channel design has been changed to allow for future use, reducing the channel to about 5-7m wide along the bottom.

Q; Will the bottom of the channel go down to the till, or will SS treated material remain under the channel? A:
Appendix B (Drawing TP6 DWG C-571) In places it will reach the till, and in other areas treated material will remain under the channel. This allows for proper water flow and fish passage through the channel.

Q: Will the sediments in the ponds be treated first, or will the channel be constructed before the material is SSed? A: This is not part of the 100 per cent design. The contractor could select which method worked best. In most cases, the contractor SSed the material, then excavated the treated material.

Q: Will water from the sides of the Tar Ponds be prevented from coming in contact with the treated SSed material? A: No.

Q:Will water from under the Tar Ponds be prevented from coming in contact with the treated SSed material? A: No.

Q: Where can I find a diagram showing how water between the new protective cap and the SSed material will be collected and discharged? A: TP7 100 per cent design report, p. 15, section 2.4.4 Drainage Layer.

 

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