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City says environmental benefits of recycled aggregates hard to estimate

There are obvious benefits of recycling the concrete pulled up from city street works each year, but quantifying them is not on the agenda, the Infrastructure Renewal and Public Works committee of Winnipeg’s city council heard this week.

“We all know if we recycle aggregates there’s going to be environmental benefits,” Manager of Engineering Brad Neirinck said April 20 in giving a verbal report on the progress of a working group the City established with the heavy construction industry.

The committee asked the working group to come up with recommendations for the increased use of recycled concrete aggregates (RCA) in city works projects. It was formed as a result of changes to roadbuilding specifications in 2019, which made the use of RCA very difficult, due to the new requirements of physical characteristics and performance standards.

Neirinck said that the task of quantifying the environmental and resource management benefits of recycling concrete aggregate has proven difficult to estimate because the suppliers of RCA within the heavy construction industry do not collect data on greenhouse gas emissions in the production and transportation of virgin aggregates (limestone) or of RCAs. The City had also asked the industry to supply measurement of noise pollution and how much excavated concrete went to the landfill in 2020; the industry does not collect such information.

To get that data would require a special project with financing, and the department prefers instead to work on seeing the best quality of material produced and the cost involved in that, Neirinck said.

The industry said it could not supply how much each supplier held in reserve in their limestone quarries as that is proprietorial information.

Neirinck said the City cannot estimate the limestone reserves in the Capital Region as that is outside of Winnipeg’s authority. It is something the province would have to do, and the last time such an estimate was done provincially was in 1976.

That report said there “appears to be sufficient high-quality sand and gravel within the Region (including the Forest Reserves) to meet demands until 2026 but probably not more than 5 to 10 years beyond that time. The availability of limestone within the R.M.of Rockwood and adjacent areas, should be sufficient to meet the crushed limestone requirements to beyond the year 2026.”

The committee was told that of the five tenders that have been awarded for road reconstruction projects for the 2021 season, three will see RCAs used, and there may be opportunity to see it used in the two others with some change to the bids submissions. However, Neirinck also noted that for rehabilitation of streets, RCA is included as an allowable base material.

Public Works will report in July on the total tonnage of RCA to be used this year on road works. All future reports on the working group’s progress will be made in writing, rather than just verbally.