Crooks’ Hollow Dam Removal Project

Crooks’ Hollow Dam Removal Project

Trails at the Crooks’ Hollow Conservation Area are now open to the public. Trails were closed in December 2012 to facilitate the decommissioning of the Crooks’ Hollow Dam. The construction phase of the project, including decommissioning of the dam and channel restoration is now complete. Other phases of the project are still underway, including restoration of ecological areas.

The area is now safe for the public to use, provided visitors stay on marked trails. HCA is asking trail users to keep to marked trails so that sensitive areas are allowed to regenerate.

New features to the area include a walkway across the Spencer Creek to connect trails on both sides, access to a new viewing area at the former dam site, riffles and pools within the creek to enhance fish habitat, a small waterfall fed by groundwater migration through the Escarpment face, and wetland creation.

History of the dam
Crooks’ Hollow Dam is located on Spencer Creek, near the community of Greensville. The dam is situated downstream from a series of historic dams that were built in the late 18th century to provide water power to a number of grist mills, sawmills and paper mills. The Crooks’ Hollow Dam was constructed in 1913 for the purpose of supplying water to the community of Dundas, a function that ceased when a municipal water supply was established for Dundas. Between 1959 and 2001, the Dundas Valley Golf and Curling Club used the reservoir as a source of water for irrigation. The reservoir and surrounding lands are currently used for recreation including hiking, fishing and limited boating. In 2000, the ownership of the Crooks’ Hollow Dam along with 9.9 hectares of land was transferred to the HCA.

The decision to remove the Dam
Over the years, several dam condition assessments have identified concerns relating to the integrity and stability of the dam. These studies, along with a Dam Stability and Assessment Study conducted in 2005, further confirmed the need to restore, modify or remove the dam to ensure its safety during major storm events. Responding to the need for action, in 2005, HCA initiated a Class Environmental Assessment (Class EA) to review the options for the dam. The review identified a number of alternatives and involved consultation with stakeholders, the neighbouring community and the public. The Class EA concluded that the dam should be removed as this will address safety concerns regarding the dam’s deteriorated condition, eliminate long-term operating and maintenance costs and enhance local and downstream environmental conditions with no net long-term negative impacts to the environment. In May 2009, the Class EA was approved by the Minister of the Environment (MOE) with conditions that a Sediment Management Plan be developed to show how sediment will be managed during and after the dam removal. MOE has reviewed the Sediment Management Plan prepared by HCA and indicated in October 2010 that it is satisfactory, acknowledging that further details would be provided during detailed design.

What were the benefits of removing the dam?

Removal of the dam provided several benefits to the Crooks’ Hollow ecosystem and the larger Spencer Creek watershed.

  • Improved water quality in Crooks’ Hollow, as well as downstream in Spencer Creek, Cootes Paradise, and Hamilton Harbour.  The ponded water increased water temperatures in the creek and promoted algae blooms.
  • It re-establishes natural sediment transport to downstream reaches of Spencer Creek to help natural channel formation and prevent channel and bank erosion.
  • Fish habitat also benefited, as the historical cool water river fishery was restored from the warm water lake ecosystem.
  • Improved fish habitat will discourage the proliferation of non-native, invasive fish species such as carp and goldfish in Crooks’ Hollow and downstream in Cootes Paradise.
  • Finally, the removal of the dam allowed for the re-establishment of natural, riparian habitats in Crooks’ Hollow, improved species and habitat diversity within the re-established river corridor, and aided in the conservation and recovery of rare and at-risk flora and fauna that have been historically documented in this ecosystem.