COLLIERY DAMS TECHNICAL COMMITTEE STATUS UPDATE

COLLIERY DAMS TECHNICAL COMMITTEE, January 10, 2013

Background

Mandate of Technical Committee:

On October 21, 2013 the City of Nanaimo struck the Technical Committee with a mandate to focus on outcomes that only involve remediating the existing dams, using the following phased approach:

  • Phase 1: Review the existing data and direct additional data collection as necessary.
  • Phase 2: Develop option(s) for remediating the existing dams that will satisfy the requirements of the Dam Safety Section of the Ministry of Forests, Lands and Natural Resources.
  • Develop plans for short-term physical alterations to the dams in 2014 to provide the necessary time to carry out the long-term strategy (if required).

Composition of Technical Committee:

The Committee is comprised of representatives of the City; Snuneymuxw First Nation; the Colliery Dams Park Preservation Society; and engineering firm Golder Associates. Committee facilitator Katherine Gordon was appointed on November 26. Both Golder Associates and Gordon were appointed by the Committee after review of a number of candidates.

Katherine Gordon will act as the contact person in relation to any questions about these updates or the work of the Committee.

Role of Technical Committee:

The Committee is tasked with making viable recommendations on rehabilitation options to be reviewed by the City, Snuneymuxw First Nation and the Dam Safety Section. Those recommendations are to be made by February 28 2014 to the Executive Committee, which is comprised of City senior staff and Snuneymuxw advisors directed by the Chief. The Executive Committee oversees the Technical Committee and if necessary provides guidance and advice to the Technical Committee.

Decision-making process:

In due course the Executive Committee will provide commentary and recommendations to the Policy Group (Mayor and Council/Snuneymuxw Chief and Council) for consideration and discussion. As owner of the dams, City Council must make the final decision on which rehabilitation option to pursue and any short-term mitigation options required before permanent remediation takes place.

The parties involved at the table agree that this is a fair, credible process to follow.

Meetings of Technical Committee:

The Technical Committee has met twice, on December 5 and 13, and three meetings are scheduled for January to discuss communications and risk assessment approaches and technical options being developed by Golder Associates for committee consideration. Representatives of the Dam Safety Section attend meetings in order to ensure they are fully informed and are able to contribute to the progress of technical discussions.

Objective of Technical Committee:

The Committee has agreed on the following overarching objective for its work:

Development of an environmentally minimally invasive, cost- and time-effective solution while satisfying required safety standards – i.e. a solution that addresses:

  • The safety of downstream residents and workers;
  • Dam Safety Section requirements;
  • The respective objectives of the City, Snuneymuxw First Nation, the Colliery Dam Park Preservation Society and the community;
  • Environmental concerns, including fisheries habitat and ecology;
  • Cost-effectiveness; and
  • Having a timely permanent solution in place in 2014 if possible, but no later than 2015, with shorter term mitigation in place if required in 2014.

Approach to development of rehabilitation options

Investigation work

The Committee is combining work on Phases 1 and 2 of its assigned tasks. Golder Associates is in the process of reviewing the existing data and collecting additional data as required. The Committee has provided Golder with copies of historical and other relevant documents and reports and City staff are working with Golder to provide whatever support is required in order to conduct any additional physical site investigation of the Lower and Middle Dams.

The physical site investigation involves a limited geophysical examination of the two dams that will take place during the week of January 13. This is a non-invasive way to survey a large area of the dams with hand-held equipment that can be used in areas that are difficult to access with conventional drilling equipment and minimize disturbance to the dams and watercourses.

The objectives include providing information related to the internal dam fill zoning of the two dams, gathering information about the water table, underlying foundations and reinforcement (such as rebar) within the concrete wall, collect information which may help to establish whether a low-level-outlet may exist, and gather any other geophysical information, including seismic velocities, that will help in developing suitable remediation options.

The work will be carried out on land, is non-invasive and is not expected to have adverse

environmental impacts as the radar and seismic signal sources are all very low energy. However, it may be necessary, during one day of seismic surveying, to limit public access in order to minimize vibration noise during the seismic recordings. If this is the case, notices will be posted at entrances to the Colliery Dams Park and on the City of Nanaimo website, as well in local newspapers.

A second phase of site investigation will likely take place in the first half of February and involve investigative drilling in the embankments and concrete core of the dams. The geophysics work may provide information that will influence the scope of the drilling.

Risk assessment

At the same time, Golder has adopted an approach which includes the revised (2013) Canadian Dam Association Dam Safety Guidelines to satisfy Dam Safety Section requirements. This approach applies a risk assessment methodology to the development of satisfactory rehabilitation options. Dam Safety Section staff have indicated that they are willing to work with this new approach. It is an approach that both governments and industry are increasingly moving towards in developing cost-effective strategies to address risk issues.

Over the next few weeks, Golder will be undertaking a risk assessment of the dams and concurrently developing technical remediation options. The preliminary work will be presented to the Committee in late January.

______________________

This document came from Colliery Dams Park Preservation Society on Jan. 10, 2013.  Emphasis has been added in the case of the new Risk Assessment guidelines from the Canadian Dam Association which may have a bearing on the new assessment of risk associated with the dams.

RB

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