Staff Report: Pre-Award - Irwin Dam Improvement Project

Staff Report: Pre-Award - Irwin Dam Improvement Project

Date:

June 18, 2018

Department:

Engineering

Subject:

Pre Award Irwin Dam Improvement Project

Background

The City of Langford has applied for a Structural Flood Hazard Mitigation grant to improve the stability of the Irwin Dam. Staff anticipate receiving confirmation of the success of this grant some time in mid-July.

The purpose of this report is to seek Council approval to award the Irwin Dam Improvement project subject to successfully obtaining the Structural Flood Hazard Mitigation grant.

Commentary

The City inherited the Irwin Dam at the time of incorporation. The dam was an existing earth structure and had an existing water licence attributed to it for the storage of water. Staff inspect this dam monthly as well as having an annual geotechnical engineering inspection completed on the dam. In November 2017 the Dam Safety Officer from the Province also inspected the dam.

At about this same time as the Fall 2017 inspections, the Province, through the Community Emergency Preparedness Fund (CEPF) released opportunities to apply for funding to enhance the resiliency of local governments and their residents in responding to emergencies. Funding is provided by the Province of BC and is administered by the Union of BC Municipalities (UBCM).

The funding streams included:

• Emergency operations centres and training
• Emergency social services
• Evacuation route planning
• Flood risk assessment, flood mapping and flood mitigation planning
• Structural flood mitigation

The City applied for a structural flood mitigation grant to improve the stability of the upper dam in the event of an earthquake. The City applied for the maximum amount allowed for projects which was $750,000 funded 100% by the grant.

While the grant is being considered staff continued to investigate ways to improve the structural stability of the dam with the aid of Geotechnical Engineers at Ryzuk Geotechnical. The City has submitted an Alteration Notice under Section 12 of the BC Water Sustainability Act Dam Safety Regulations to the Ministry of Forests, Lands and Natural Resources to:

• Install 72 tangent piles in 2 tangent lines
• Backfill the piles with concrete
• Remove tailings from the auger holes
• Rip rap the faces of the dam
• Install a proper vehicular access bridge over the dam for enhanced maintenance and servicing

The installation of the tangent piles is estimated to be a 7 week project. Given that the grant will not be known until the middle of July and there is a potential fish work window that ends in mid September staff are seeking approval from Council to retain a local contractor that specializes in this work.

CDI (Construction Drilling Inc) is a local specialist drilling contractor based out of Duncan, BC, who do work throughout western Canada on large building and infrastructure projects. The geotechnical team at Ryzuk Geotechnical has worked with CDI on numerous occasions on southern Vancouver Island, including construction of temporary shoring systems and deep foundation elements such as piles and caissons. They have notably been involved in the recent construction of local bridge foundations and promenade retaining wall.

The potential expedited timeline for this project is unique, as it proposes construction beginning in August, while funding may not be secured until mid July, and requires design, pricing, and contract preparations to be made ready to go if/when funding comes through. In discussions with CDI, they have agreed to provide pricing and hold availability to engage on this project in August with two weeks notice if such proceeds. They have also identified a preferred construction methodology using their available equipment which is less costly than other contemplated alternatives.

Staff feel that based on this available information and the uniqueness of the location and timing of our dam (on Vancouver Island) that CDI is qualified to do the work at the dams and expect that they are the only locally available contractor to mobilize on the project this summer given that construction would need to start within 2 weeks notice of funding in mid July.

Staff anticipate that CDI would retain a local contractor to do the rip rapping and bridge installation.

Financial Implications

The proposed Irwin Dam Improvement project is subject to funding from the Structural Flood Hazard Mitigation grant program. The application that the City has made to the grant program includes engineering design and on site supervision as well as the installation of the tangent piles, rip rap and bridge.

Legal Implications

None noted.

Options

That Council:

1. Direct staff to award the Irwin Dam Improvement project pile and rip rap construction to Construction Drilling Inc. subject to confirmation that the project will be funded by the Structural Flood Hazard Mitigation grant program; OR
2. Not proceed with the Irwin Dam Improvement project if a grant is received.

Respectfully submitted,

Submitted by:
Michelle Mahovlich, P.Eng, P.Geo, Director of Engineering

Concurrence:
George Henshall, AScT, Deputy Director of Engineering and Public Works

Concurrence:
Chris Aubrey, Fire Chief

Concurrence:
Cory Manton, Manager of Parks and Recreation

Concurrence:
Michael Dillabaugh, CPA, CA, Director of Finance

Concurrence:
Braden Hutchins, Director of Corporate Services

Concurrence:
Darren Kiedyk, Chief Administrative Officer

:mm