A recent stormwater Design Optimization for a large industrial site in Caledon delivered significant infrastructure cost savings – without compromising performance, approvals, or stormwater management objectives. The result shows how disciplined engineering review can create measurable value on large-format industrial developments.

An example of this design was used within the Tullamore Industrial Subdivision, Block 4, Building D, where Crozier undertook a Design Optimization review to determine whether the original storm drainage approach could be improved while maintaining performance.

Challenging the Conventional Approach

The initial concept followed a conventional single-outlet storm sewer approach. That strategy is often effective on smaller sites because it minimizes municipal connections and can limit water quality controls to one location. On a large-format industrial site, however, the same assumptions can create unnecessary cost as drainage areas, pipe lengths, depths, and pipe sizes increase.

The project team challenged the default approach and asked whether the system could achieve the same technical outcomes more efficiently. The conclusion was clear: for a site of this scale, the single-outlet solution was no longer the most effective option.

A Smarter, More Efficient Solution

Crozier advanced a revised two-outlet storm sewer configuration, splitting the system into smaller, looped drainage networks.

This optimization reduced pipe lengths, diameters, and installation depths. This optimized design reduced the demand for separate stormwater storage infrastructure and enabled more efficient pipe sizing and material selection. Importantly, it preserved the intent of the original servicing strategy while improving constructability and reducing cost.

This case study also reflects a broader market shift. While speed dominated much of the past decade’s activity, many industrial clients are now placing renewed emphasis on capital efficiency, optimized building footprints, and reduced infrastructure costs.

Measurable Savings, Lasting Value

Design Optimization creates the space to respond to that shift. By pausing the design cycle, revisiting assumptions, and evaluating alternatives, project teams can reduce cost while maintaining technical integrity, approval confidence, and long-term performance.

This disciplined review resulted in a more efficient and cost-effective stormwater solution.

This outcome highlights the importance of combining sound engineering judgment with commercial perspective to achieve stronger project outcomes. Crozier helps clients look beyond standard approaches to find smarter ways to design and deliver complex industrial developments. By challenging assumptions and aligning technical decisions with project objectives, we help reduce cost, manage risk, and create lasting value.

Written by:

Jim Firth, P.Eng.
Vice President, Crozier

About Choice Caledon Business Park 
Developed by Rice Commercial Group, the Business Park was created as an industrial subdivision consisting of warehousing, distribution centres, and industrial uses. The area is projected to be completed in 2026.

With a booming population and growing immigration, Toronto has become one of the world’s most vertical cities. It now seems almost humorous to recall that the development of The Pantages on downtown Yonge Street in 2003 was seen as somewhat ‘controversial’ because of its 45-storey, 139.9 metre height. Today, 70, 80 and 90-storey proposals are commonplace as Toronto is entering the world of the “supertalls.”

But this reach-for-the-sky approach has a resulting impact underground. Imagine the number of kitchen and bathroom sinks, bathtubs and toilets in a tower with 1,000 units. Imagine the flow rates at common mealtimes or in the evenings. The stress on the city’s sewer system is real, and developers need to take it into account when designing their projects.

For that expertise, many turn to . A sewer capacity assessment is an integral part of a zoning bylaw amendment or site plan application.  It looks at the capacity of the sewer shed for a particular piece of land. Often such an assessment impacts the size of the development being planned.

Crozier is a leading consulting engineering firm in the land development and building industry. They provide services in civil, water resources, transportation, structural, mechanical, and electrical engineering, complemented by hydrogeology, landscape architecture, and building science. In Toronto specifically, Crozier is known for being trusted advisors with expertise in mixed-use residential, industrial and commercial development projects with such clients as ,��,��, and .

Brimley + Progress Towers designed by A & Architects Inc. for Atria Development

The sewer capacity assessment is a component of Crozier’s site services engineering in the Land Development division of its business. Although not directly listed on the City’s Planning Application Checklist, any development application that proposes a change in land use or a net increase in discharge to the municipal sewers compared to existing conditions, is expected to include a sewer capacity assessment.

“We encourage our clients to commission this assessment during their due diligence on a development parcel,” said Ashish Shukla, a Professional Engineer and Associate who heads Crozier’s Toronto office, one of four it has in Ontario. “An assessment is only ‘complete’ when acceptable by the city, meaning all its criteria have been met. However, an initial assessment determining current capacity in the sewer shed can be prepared even before a proposed development concept is finalized, as this assessment can play a key role in scaling the planned development.”

Shukla continues to say such an assessment plays an important role in the entire development application process. “The assessment could be required to accompany a servicing report during a zoning bylaw amendment if the proposed discharge is greater than existing discharge, which is generally always the case when adding density to a site. Submitting an application without this analysis may lead to a returned application deemed incomplete by Engineering and Construction Services (ECS),” he said.

Crozier’s first step in the assessment includes confirming the status of the sewer shed, and whether a base model of the site exists in the City’s InfoWorks hydraulic model.  If so, its assessment is carried out using the same model. If a base model does not exist, the City accepts a static pipe-by-pipe analysis.

Six Points Plaza designed by IBI Group for Liberty Development

“When completing the assessment using InfoWorks, the base model is updated to include a scenario with all other active developments within the sewer shed to confirm the impact of the proposed development. This scenario includes the population and groundwater contribution from the proposed development,” said Shukla. “The model is then run for dry and wet weather flow conditions to determine the capacity within the system. This scenario will ultimately determine whether the City’s criteria for capacity can be simply met, municipal infrastructure upgrades are required, or the proposed development needs to be scaled back to meet the capacity in the system.”

Getting approval on the sewer capacity assessment as part of the site plan application or zoning bylaw amendment ultimately relies on collaborating with approval authorities and developers to find a solution that satisfies all stakeholders’ needs.  One thing is certain, even if the term sewer capacity assessment is not part of the common lexicon – it impacts everything.

“Every single development application in the City of Toronto is impacted one way or another by this assessment,” said Shukla. “We’ve seen several proposed development concepts altered in both directions, either scaled up or down, based upon the results of this assessment.”

While Shukla believes Toronto has found ways to keep up with infrastructure challenges in the past, in the face of burgeoning population growth forecasts, it will take a collaborative effort going forward.

“I don’t believe the City can do this all by themselves,” he said. “It is going to take active collaboration and cooperation between City staff and developers to aid infrastructure improvements as a result of development.”

In 1991, the Government of Ontario released additional guidelines regarding water quality treatment of stormwater. These guidelines further evolved in 1994 and 2003 to promote a treatment-train approach, incorporating small-scale, low impact development (LID) techniques for stormwater management (SWM). However, despite the efforts of some local agencies who have adopted their own updated SWM guidelines, there have been no official updates to the Provincial guidelines for nearly 20 years.

With changing weather and climate conditions, development pressures, and new and innovative approaches, what will these updated guidelines need to consider for the future of stormwater management?

Greening stormwater infrastructure

Traditionally, stormwater was managed using grey infrastructure approaches like stormwater management ponds, dry detention basins, and oil-grit separators. However, innovative approaches to SWM known as low-impact development—or LID—have been gaining a foothold. LID practices, which include rain gardens and bioretention systems, manage stormwater by mimicking the natural processes under pre-development conditions that infiltrate and treat runoff.

In Ontario, initiatives like the Sustainable Technologies Evaluation Program (STEP) are leading the charge to incorporate LID practices across the land development industry. This partnership between several Ontario conservation authorities works with partners to assess and research new SWM techniques. In the future, engineers should expect to use tools like STEP’s Low Impact Development Life Cycle Costing Tool more often to evaluate the feasibility of incorporating green infrastructure into their designs.

In the next 20 years, it may not be a question of whether a development has green infrastructure at all, and instead what types of green infrastructure it incorporates. However, traditional stormwater management solutions will certainly not disappear. Grey SWM infrastructure will still serve an important role in capturing and detaining large volumes of runoff, particularly in the dense urban landscapes that characterize many parts of the GTA. The next generation of guidelines will likely expand further on how to integrate conventional and LID approaches for stormwater management to provide social, environmental, and economic benefits to communities.

A holistic approach

It’s no secret that the best solutions for any problem result from a multi-disciplinary approach. Stormwater management problems are no different. Engineers have traditionally applied basic hydrologic and hydraulic principles to solve SWM challenges. However, the key to optimizing these systems lies in a strong understanding of hydrologic and hydraulic interactions and relationships with local ecology, geomorphology, and hydrogeology. We can expect future innovations in SWM to be advanced by drawing on the expertise of multi-disciplinary teams of practitioners and researchers.

For example, engineers might leverage the expertise from disciplines such as geochemistry and hydrogeology to identify techniques to optimize SWM pond designs. They may also pursue further collaboration with landscape architects and ecologists to design and enhance the natural features of grey and green stormwater infrastructure.

Unveiling a typical future SWM pond design may reveal targeted vegetation plantings that better manage erosion, reduce suspended solids, and selectively uptake problematic pollutants like chlorides. The future of SWM pond designs rely on these field studies now to identify opportunities for future infrastructure. For green infrastructure like bioretention systems, experts in biology and geochemistry might be involved from day one working on how to bind, trap, or uptake nutrients using optimized soil and vegetation characteristics.

An increase in green infrastructure will also drive the need for engineering firms to attract and train team members that are scientifically literate and capable of designing, operating, and maintaining these solutions. This may include hiring staff that come from non-traditional engineering backgrounds, or in some cases, have no engineering background whatsoever. Developing the skillset needed as a civil engineer in the future may involve taking additional courses or gaining certifications that round out traditional engineering expertise with proficiencies in ecology, soil chemistry, or geomorphology.

Fast-tracking innovation

Implementing any type of stormwater management infrastructure comes at a cost. That’s why fast-tracking research towards innovative approaches will be critical to lower the traditionally high up-front cost of LID techniques. Currently in Ontario, financial incentives for developers to incorporate green SWM infrastructure are few and
far between.

Across the province, colleges and universities have been developing and refining innovations in SWM technologies. Engineering firms are in a unique position to bring these innovations into practice as key players in both design and communication with developers about their needs. For instance, firms can incorporate research and monitoring for LID practices at their project sites to learn about how these systems perform under varying development conditions.

For engineering firms without dedicated research facilities and staff, partnering with schools and other organizations can help offset the costs of engaging in research. These partnerships can also cultivate important research skills for in-house staff through opportunities for experiential learning and involvement in field and lab activities. Executing successful research programs will require more than just engineers—they will need experienced technical staff who are comfortable in the field, lab, and on stage presenting at conferences.

We can also expect climate change to be a major driver of innovation in SWM. Future-proofing SWM designs and retrofits for future climate conditions will be critical. While it is uncertain about how these changes will affect rainfall timing and intensity, engaging in research and development now can identify ways to cope with projected scenarios.

For example, enhanced water quality treatment through targeted vegetation plantings may be required to handle increased volumes of runoff into SWM ponds during the winter. Changing rainfall patterns may also affect the storm events that grey and green infrastructure are designed to control. This, in turn, will drive the need for innovative ways to develop resiliency in new and retrofitted systems.

The stormwater management solutions of the future will be holistic systems that integrate both grey and green infrastructure to protect communities and the natural environment. These systems will be designed by engineers who go beyond traditional design techniques to create solutions that consider their sustainability, cost, and long-term resiliency in a changing world. Through research and development, as well as collaborating with and learning from other fields, engineers will be able to leverage what they’ve learned over the past 20 years to shape the direction of stormwater management for the next 20.

This article was written by Nick Mocan, the president of Crozier Consulting Engineers, for the .