Large, lightweight and expensive styrofoam blocks, just like those used to stabilize the ground for the Port Mann Bridge replacement, will be used on the final phase of the Ewen Avenue streetscape improvement project.
Geofoam, or expanded polystyrene (EPS), will replace deep peat and contaminated soft ground underneath the 800 metres of asphalt that will be laid down between Hampton Street and Boundary Road in Queensborough.
“It’s a specialized lightweight material we have to use for the phase three portion. The product itself is very light compared to what we used for phase two, for example pumice. For road projects it provides a good alternative for the environment where the soft soils are present and there are concerns with settlement once you put the asphalt down,” said Amir Aminpour, engineering projects manager for the city. “The material itself is expensive.”
It’s one of the reasons the cost of the final phase of project has jumped from $7.5 million to $12.8 million. The city ran into some challenges during the previous phases (Furness Street to Derwent Way and Derwent to Hampton), so it did some extensive geotechnical testing for the final phase.
Aminpour said the analysis showed chloride, sodium and metal concentrations in the soil exceed provincial standards for industrial land use, including building roads. The contamination is natural, he added, for shoreline areas like those in New Westminster. On top of that, there are significant environmental challenges because of the presence of deep peat and soft ground conditions.
Because the peat removal will be so deep the best option for fill to replace it is the Geofoam, said Aminpour.
It’s hard to pinpoint the exact source of the contamination, said Aminpour. “Generally by looking at it, these are from organic sediments in the floodplain deposits.” He added, unless the contamination is from a long time ago, the contamination is not man made.
“What happened about 100 years ago it’s hard to say, the history of New Westminster itself, but no not to my knowledge. It’s just the ground conditions in New Westminster.”
Mayor Jonathan Cote said the project has been funded by development costs charges (DCC) and there’s enough to cover the increase in the budget, “but with the consequences being there will be less money in our DCC reserve related to transportation.”
In addition to the new asphalt, the project includes full-ditch enclosures, a multi-use pathway, a new sidewalk, 36 new street lights, 105 new trees, 900 metres of sewer main and a reconfiguration of the intersection at Ewen and Boundary.
A request for proposals was put out by the city Aug. 25 with a close date of Sept. 30. The second phase, which involved 1,800 metres of paving, is in the final completion stages and had an approximate cost of $18 million. The first phase, which was 550 metres, was $3 million.
