Abstracts

Milton Quarry. This system is a unique application of recharge well technology to achieve
hydrogeologic mitigation of quarry dewatering effects in a sensitive ecological environment.
Dufferin Aggregates owns and operates one of the largest aggregate quarries in Canada, near
Milton, in southwestern Ontario. At the Milton Quarry, aggregate resources are extracted
from the caprock of the Niagara Escarpment (dolostone of the Amabel/Gasport Formation)
and processed to produce a range of high‐quality crushed stone products. The same dolostone
formation comprises a shallow unconfined aquifer that supports nearby water supply
wells, cold water fisheries, and wetlands, including vernal pools used for breeding by the
Jefferson Salamander Complex which is protected under the Endangered Species Act.
In 2007 an Extension of the Quarry was approved by the Province of Ontario including the
requirement to implement the GRWS to maintain groundwater levels surrounding the Extension
Quarry to prevent negative impacts that might otherwise occur as a result of quarry
dewatering effects.
GHD conceived and designed the GRWS to protect water resources and associated ecological
features in the area of the Milton Quarry from the quarry dewatering influence. This was
a new approach to environmental mitigation for the aggregate industry; in fact, no comparable
example could be found anywhere in the world. The GRWS was critical to the success of
the approval of the Extension Quarry.
The GRWS has been fully constructed and has been operational since 2007. The GRWS
forms part of an overall water management system comprised of a reservoir, dedicated pumping
stations, buried watermains, build-out to over 100 recharge wells, 3 diffuse discharges
to wetlands, and an Adaptive Management Plan (AMP) that provides the mitigation and
monitoring framework. The AMP involves extensive monitoring including on-line data reporting
for access by oversight agencies.
The GRWS has proven to be effective in mitigating the quarry dewatering effects on nearby
water resources and maintaining pre-determined seasonally-varying target groundwater
levels. Ecological monitoring has demonstrated that there have been no detrimental effects
to the nearby water resources and associated ecological features from the ongoing expansion
of the quarry.
The combination of the technical approach and the Adaptive Management Plan makes Dufferin’s
Milton Quarry a showpiece of environmental protection for the aggregate industry.
116 IAH-CNC 2015 WATERLOO CONFERENCE