Cost overruns, rains hit watershed dam remake
A $2.58-million Capital Regional District project to replace a 115-year-old dam is facing construction cost overruns, and its completion is being challenged by recent heavy rains.
The dam replacement project is on Lubbe Lake — one of three reservoirs in the Goldstream watershed that serves as a backup water supply for Greater Victoria.
The CRD started lowering the lake level in June and work started in July to remove and replace the 45-metre earthen dam known as Lubbe Lake Dam No. 4.
But staff say that despite pre-design and pre-construction site investigation, once the old dam was removed “unexpected geological conditions” were discovered, including the presence of a large rock knob with channels on either side and undulating and highly fractured bedrock.
Those conditions have necessitated substantial additional grouting and foundation work, pushing the anticipated project cost to $3.16 million — almost 25 per cent over the original budget.
“The record drawings and record information from the original dam, given the original construction date, obviously was limited,” said Ted Robbins, CRD senior manager of water services.
“We had to remove the old dam and then undertake some revised design work, which resulted in some additional concrete being required to form the base of the dam before we started reconstructing the dam with clay,” he said.
“Given the need for that work, the schedule has been pushed and the additional concrete work, it’s going to require a budget increase.”
The original $2.58-million budget includes a project contingency of $230,000, which will be eaten up to finish the project. CRD staff are seeking another $581,000.
Additional unexpected construction costs include: $200,000 for foundation design and construction monitoring; $368,000 for foundation and abutment preparation; $440,000 for engineered concrete foundation; and $170,000 for weather delays, says a report going to the Regional Water Supply Commission on Wednesday.
Replacement of the dam was supposed to start in July, but because of the additional foundation work, that didn’t begin until December.
Meanwhile, it has been a challenge during the recent heavy rains to maintain the lower water levels needed to do the work. Pumps have been working overtime and because there’s no nearby power source, the diesel needed to fuel them has been flowing as fast as the water they’re pumping away.
“Essentially, we’ve had to drain the lakes, Lubbe Lake and the reservoir, to undertake the original dam decommissioning and then the rebuild. So in the wintertime here, we’ve had to maintain a lower level in the lake below the foundation work, which has also been added to some of the costs,” Robbins said.
“With the rains we were having last week, we were running 24-7. As long as we’re not having the heavy precipitation, we don’t need to run the pumps so it’s just on a day-by-day basis,” he said.
According to the report going to the commission, pumping will likely be required until the dam complete or rains subside.
All costs associated with pumping are being allocated to the 2018 and 2019 operating budgets, the report says.
The work was originally to be completed by the end of September 2018. The hope now is that it can be finished by late March.
As part of the backup system for Greater Victoria, the dam work poses no threat to this summer’s drinkingwater supply.
However, the Goldstream system is used to assist the Goldstream River fishery with water releases in the fall. Robbins said it’s too early to say how that could be affected.
“We do rely on it in the event of an emergency. We do also provide some fishery releases for the Goldstream River,” he said. “We are anticipating the Lubbe dam work to be complete hopefully by March of this year and depending how much rain we get between March and the summer, we’ll accumulate some storage there.”
The dam was built between 1895 and 1903. Pre-design, detailed design and contract administration was done by Stantec Consulting Ltd. The contract for replacement was awarded to Stone Pacific Contracting.