Monitoring Low Impact Development at the IMAX demonstration site

A number of innovative stormwater management retrofits on both public and private properties have been implemented across the Credit Valley Conservation (CVC) watershed, including the 2018 IMAX corporate office parking lot low impact development (LID) retrofit project. The IMAX corporate office is located in the Sheridan Business Park, which is a highly industrial area in the headwaters of the Sheridan Creek Watershed. In 2012, IMAX retrofitted its parking lot with a variety of innovative LID stormwater management technologies, which collect, adsorb, and filter pollutants from stormwater runoff before it is discharged into Sheridan Creek, Rattray marsh (a provincially significant wetland) and eventually Lake Ontario, the source of drinking water for 8 million people. The LID features used at the site also promote infiltration, retention and the slow release of treated stormwater runoff. The IMAX parking lot retrofit was completed in partnership with CVC, as part of the Province of Ontario’s Showcasing Water Innovation program.

Understanding and Assessing Impacts

Local climate projections were one of the drivers for CVC’s LID monitoring that led to the monitoring of the IMAX project. The primary goals associated with this corporate-focused project included improving the function, efficiency, and aesthetic of the parking lot, allow for future expansion, lower operational costs, limit IMAX’s potential stormwater utility costs, upgrade the existing parking lot and stormwater management infrastructure from asphalt and traditional stormwater conveyance systems to modern LID techniques. It should be noted that building climate change resilience is a secondary goal of this project, not a primary goal. Main climate risks considered in this project include the increasing frequency of extreme storm events and flooding, which increases insurance and maintenance costs accordingly, and water quality degradation. Flooding has the potential to do considerable damage to a business. Flood waters can cause considerable damage to a business, such as causing property damage and disruption to normal operations. The IMAX parking lot is situated in the low point of the property. The surrounding land is elevated approximately 2-3 m higher than the parking surface. Pre-retrofit, groundwater seepage from the surrounding highlands and low permeability of the subsoils caused saturated conditions for days following wet weather events. The constant saturation of the subsoils weakened the supporting structure for the existing asphalt surface causing severe asphalt degradation. Throughout the winter, water would build up in the potholes and turn to ice which put employees at risk for slipping. Salt was extensively applied to eliminate the ice and risk of slipping. A business can also be found liable if flooding or drainage related issues put individuals at risk, such as from slipping on ice. The costs of construction justified and situated against this potential harm.

Map of Site and Watershed

Map showing the location of IMAX within the Sheridan Creek watershed

Map showing the location of IMAX within the Sheridan Creek watershed

Identifying Actions

In 2007-2008 CVC was developing the Sheridan Creek Watershed Study. Through the landowner contact process, IMAX granted CVC permission to access the wetland on the grounds of the corporate head office to better assess the existing conditions within the watershed. IMAX was asked to participate in a series of focus groups designed to refine the Watershed Study by identifying key natural resources and features, environmental issues, and other questions the study should answer.

In July 2007, a representative from IMAX participated in a bus tour for the focus group. The group visited various sites within Sheridan Business Park and received information on the benefits of LID practices that might suit the location. The IMAX parking lot was a stop on the tour. During the visit, the IMAX representative identified concerns such as poor drainage, formation of ice during winter, infrastructure damage, and watershed contamination. Following the tour, IMAX and CVC continued to discuss the possible options for retrofitting the parking lot with LID and developing a working partnership. As part of the Showcasing Water Innovation fund, CVC made cash and in-kind contributions towards the upgrade and construction of the parking lot. CVC covered the monitoring infrastructure costs. Prior to construction, CVC and the IMAX design team contacted the City of Mississauga and Ministry of the Environment representatives to verify any approval requirements for the work to be undertaken as part of the project.
The monitoring program is based around a set of objectives that have been developed with an advisory committee consisting of municipalities, provincial and federal environmental agencies, academia, and engineering professionals.

Implementation

Several pre-design tasks were required in order to fully characterize the site conditions and guide the detailed design development: topographic survey, geotechnical investigation, infiltration testing, groundwater monitoring, and identifying bedrock constraints. Before site design began, the project was intended to incorporate LID features such as permeable pavers, dry swales (bioswales), and proprietary stormwater management units. The intent was to meet client needs such as an expanded parking area, addition of priority and motorcycle parking and a specific aesthetic standard. The implementation of these innovative technologies was driven by design tasks and budget constraints in order to support project partnerships and gather monitoring data. The parking lot surface was a combination of traditional asphalt and permeable pavement. The north part of the parking lot was set to be reconstructed using permeable pavement, whereas the south two thirds used asphalt paving. The proportion of permeable pavers to asphalt was a result of project budget and bedrock constraints. Repaved areas that used traditional asphalt were designed to drain to a series of vegetated bioswales situated within a median that separates the two repaved sections. The bioswales are intended to treat stormwater runoff from the expanded asphalt surfaces. In addition to the bioswales and permeable pavers, the parking lot area incorporates various proprietary stormwater management technologies including Imbrium’s Jellyfish® Filter and Sorbtive® Vault.

The costs involved in a demonstration site are expected to be higher than a typical LID retrofit. In this case, many contributing partners and stakeholders made the project possible. Future LID projects should benefit from the monitoring data collected from the IMAX project. Capital costs: construction costs $776,000; design consultant fees $78,000.

IMAX Parking Lot Retrofit (Bioswale)

Image of a bioswale in the urban IMAX parking lot. Image of vegetated bioswale integrated into the parking lot design.

Outcomes and Monitoring Progress

Construction of the parking lot retrofit at IMAX was completed in October 2013. Performance assessment monitoring partially began in April of 2013 as construction completed and deficiencies were being addressed, and most stations came online by the end of 2013. Performance assessment involves continuously monitoring precipitation, amount and quality of discharge from the six stations, and water temperature. Staff conduct bi-weekly visits to conduct regular equipment downloads. To evaluate the performance of LID systems, researchers monitor climatic (precipitation, temperature etc.) and hydrologic (inflow/run-on, water level/moisture, and outflow) parameters, and collect water samples for water quality analysis. Details regarding methodology for the data collection and monitoring of each of these parameters are included in the case study.

Several challenges were encountered during various phases of the project. These challenges, how they were overcome, and lessons learned are outlined in the case study. An example of a barrier during design is low-bearing capacity soils were found throughout the permeable pavement locations. As a solution to this challenge, the project team used a high-strength woven monofilament geotextile to support the permeable pavement in these areas. A key lesson learned from this challenge is that new innovative technologies can help meet design goals and objectives.

Results from IMAX and other similar performance studies will provide private land owners and municipalities with the knowledge they need to make informed decisions on the role of green infrastructure for stormwater management. This data can help inform the planning and implementation processes required for green infrastructure such as informing the credit application process for the City of Mississauga’s stormwater charge. Studies such as IMAX are also providing the local, long-term performance data needed to conduct the integrated life-cycle analysis required for asset management, including tracking operations and maintenance activity need, frequency and cost.

Next Steps

IMAX is just one of the many projects implemented and monitored by CVC as part of the Infrastructure Performance and Risk Assessment (IPRA) program. IPRA is a multi-year stormwater monitoring program focused on gathering detailed information to evaluate stormwater facility performance in various land use types, climate conditions and development stages. The IPRA program also evaluates the effectiveness of stormwater facilities in flood control, erosion protection, nutrient removal, cold climate performance and the maintenance of pre-development water balance. One of the main objectives of the stormwater monitoring program is to educate and communicate the performance outcomes to our partners and stakeholders about the effectiveness of LID at managing stormwater risks, reducing infrastructure costs and liability, and improving the resilience of our stormwater management systems. CVC communicates monitoring results through reports, presentations, site tours, and other public forums.

To further share its monitoring knowledge and expertise, CVC has partnered with the Sustainable Technologies Evaluation Program (STEP). STEP was established as a multi-agency initiative to provide data, scientific evidence, analytical tools, and the expertise needed to support broader implementation of sustainable technologies and practices with a Canadian context. Through STEP, CVC has co-developed a monitoring training module to complement the existing design, construction, and inspection and maintenance modules focusing on stormwater and LID facilities. The module is offered in a variety of formats include half and full day workshops where participants have the opportunity to learn monitoring techniques, explore case studies and participate in activities including monitoring plan development and hands-on equipment sessions.

CVC will continue LID performance monitoring to inform the monitoring program and objectives, and deliver on its commitments to partners. Moving forward, CVC is looking for partnership opportunities to grow and develop the monitoring program and address its core monitoring objectives. This may require modifying our monitoring methodology to explore new monitoring techniques, such as the soil moisture monitoring.