Gallanough Park and Surrounding Area Stormwater Management Improvements

The City of Vaughan is planning stormwater management improvements to Gallanough Park and surrounding area. Stormwater management facilities are designed and built to collect rainfall and surface water runoff.

View Project File Report - Gallanough Park SWM - Nov. 2020

View Public Information Materials - Gallanough Park SWM

The public information materials outline the study area's existing conditions and constraints, studies undertaken, design alternatives evaluated, the preliminary prefered design alternative, mitigation measures and next steps. Citizens were encouraged to provide input and feedback during the public consultation phase.

BACKGROUND AND HISTORY

In 2007, the City identified the need to reconstruct selected roads in the Thornhill community. Prior to initiating the detailed design, a study was undertaken to assess the effectiveness and/or performance of the existing storm drainage system in the area. The Thornhill Storm Drainage Improvements Study (2008 Genivar Ltd. Study) summarizes the investigations and assessment of the existing drainage system deficiencies that pose a flooding risk in the area. Following the study, an engineering design was completed for the reconstruction of the local roads identified in the Thornhill community. Drainage system improvements were incorporated into the scope of the work to address the recurrent flooding problems in the area. The Thornhill Area Road Reconstruction/Stormwater Management Report completed by W.G. Clarke (2009 W.G. Clarke Report), provided the hydrologic and hydraulic stormwater model analyses of the drainage systems that supported the design for the drainage improvements incorporated into the road works. The drainage design work builds on the original plan of recommendations of the Thornhill Storm Drainage Improvements Study completed by Genivar Ltd. The recommended drainage improvements included:

• Replacement of undersized ditch inlets and catchbasins and deficient culverts;
• Improvement of road side ditch conveyance capacity;
• Construction of a new stormwater management facility in Gallanough Park; and
• Construction of new diversion/relief storm sewers along sections of Thornridge Drive, Brooke Street and Arnold Avenue.

In 2010 the City completed road reconstruction and watermain replacement for Thornridge Drive, Charles Street, Raymond Drive, Clarkhaven Street, Calvin Chambers Road, Brooke Street, Elizabeth Street and Old Jane Street. The drainage improvements on these streets included replacing undersized ditch inlets/catchbasins, deficient driveway culverts and improving road side ditch conveyance capacity. A Municipal Class EA process for a stormwater management facility in Gallanough Park was initiated based on the recommendations from both the 2008 Genivar Ltd. Study and 2009 W.G. Clarke report. The objective of the EA process was to develop a plan for short term stormwater storage to assist in alleviating the risk of flooding that exists in the Thornhill area, north of Gallanough Park during high intensity rain events.

The Municipal Class EA was completed November 2010 and a dry pond stormwater management facility was determined to be the preferred solution. In September 2013, the engineering consulting firm, Cole Engineering Group, was retained by a Request for Proposal to complete the detailed design for a dry pond within Gallanough Park.

As part of the design process, a Public Open House was held June 2014 to present the proposed project for the park and stormwater management improvements. The detailed design was approximately 90% complete. Prior to finalizing the detailed design of the dry pond in Gallanough Park, it was determined that a review of the original hydrologic/hydraulic stormwater modelling would be prudent to validate the current course of action and take into account the actual benefits of the completed drainage improvements in the Thornhill community.

In December 2015, the City retained the engineering services of Amec Foster Wheeler to complete a preliminary reassessment of the stormwater modelling, for the purpose of confirming and/or refining the design of the Thornhill area flood mitigation plan. The modelling review was completed in June 2016 and identified an overall improvement to the stormwater drainage and conveyance in the Thornhill community. The updated stormwater model illustrated a lower risk potential for surcharging in the Brooke Street storm sewer. Following the results of the preliminary reassessment, the City’s Environmental Services Department completed a comprehensive review of the hydrologic/hydraulic stormwater modelling and the proposed Gallanough Park SWMF project. It was confirmed that a SWMF is still required and that alternative storage options should be considered. The alternative storage options should take in to consideration; the recent technological advancements/options in stormwater management practices, a grant the City recently received from the Federal Disaster Mitigation Adaptation Fund and the City’s new Stormwater Rate (dedicated funding for storm water works), all of which were not available at the time of Municipal Class EA (in 2010). It was determined, to ensure that the most appropriate investment is made, an analysis of the alternatives identified within the original Gallanough Park SWMF Municipal Class EA should be undertaken and incorporates the reassessed stormwater modelling and staff review/analysis.

Project Details – Gallanough Park and Surrounding Area Stormwater Management Improvements In April 2020, Resilient Consulting was retained by Request for Proposal to provide engineering consulting services for stormwater management improvements in the Gallanough Park and surrounding area. The scope of work includes:

• Complete an Addendum to the Gallanough Park SWMF Municipal Class EA (Revision to Schedule B Projects). The design and construction of the preferred solution for the SWMF in Gallanough Park.
• The design and construction of a storm relief sewer on Arnold Avenue. The previously completed studies considered a relief sewer on Arnold Avenue east of Brooke Street as part of the overall stormwater management solution for the Thornhill area.
• The design and construction of an overland flow path in Gallanough Park. To reduce the occurrence of surface flooding in the Tanjo Court and Springfield Way immediate area, a lowering of the pathway/sidewalk leading in to Gallanough Park (at Springfield Way and Tanjo Court) and convey the overland flow into the park.