City of Hamilton Bumpout Stormwater Low Impact Development

In response to the City of Hamilton’s increasing challenges with heavy rainstorms, this case study reviews Hamilton’s low impact development (LID) bumpout project, which began in 2018 and involved the design and construction of a rain garden at a pilot bumpout site at the intersection of Bay Street North and Simcoe Street in the City of Hamilton. Partnerships involved in the project, aside from the extensive coordination needed among many internal departments, included Aquafor Beech Ltd., IBI Group, and Rankin Construction. The purpose of the LID project was to control stormwater runoff and improve infiltration on site. Overall, the project aims to improve stormwater management within the road right-of-way; increase pollutant removal through proper drainage and stormwater treatment; reduce pollutant loading to the Hamilton Harbour; improve water conveyance and eliminate standing water at road right of way; improve the overall aesthetic appearance of streets; and, address resident concerns regarding drainage difficulties.

Understanding and Assessing Impacts

This case study addresses the climate impacts risks and vulnerabilities related to extreme precipitation events. In the last decade, the City of Hamilton has experienced many unprecedented heavy rainstorms, such as events in 2009 and 2013, causing devastating damages to both private properties and public infrastructure as a result of flooding. As such, it is critical for the City to implement a diverse set of stormwater management strategies, including Low Impact Development (LID). Currently, the City of Hamilton is working on implementing their North End Traffic Management Plan, the purpose of which is to resolve neighbourhood traffic and transportation problems through the application of traffic improvement measures, including the installation of temporary traffic calming measures. This provided an excellent opportunity for the City to include a rain garden at a new road bumpout site in order to pilot the use and implementation of LID. Ultimately, the City hopes to make LID a standard practice in their suite of stormwater infrastructure solutions through pilot implementation.

Identifying Actions

The LID bumpout project is a part of Hamilton’s North End Traffic Management Plan, which means the LID design was incorporated into the overall traffic design by a third-party consulting firm, IBI Group. Planning for the LID bumpout began prior to the commencement of the CIG project in January 2017. Preliminary assessments were completed in March 2016, while several planning meetings and workshops also took place in 2016, and included stakeholders from the City’s Wastewater Collection Group, Road Operations, Horticulture, and Storm Pond Management. A Public Information Centre was held to educate the general public about the project in October 2016.

In January 2017, Aquafor Beech Ltd. began developing detailed designs for the LID. Over the next several months, the designs were reviewed and edited by various City departments, with a final review completed by IBI Group. In consultation with the Horticulture department, a number of native species were selected to be planted in the rain garden, including blue flag iris, purpose dome aster, and heavy metal switchgrass. Once the design of the LID was finalized, construction tendering took place in July 2017, and Rankin Construction Ltd. was selected as the final successful bidder in August 2017. Approval was secured for the project in August. Development of the communication strategy for the project was lead by the City’s Customer Service & Community Outreach (CS&CO) Section, which included a LID public education mailout, creating a LID information page on the City’s website, installing signage at the LID site, and including information concerning the project in a local Councillor’s newsletter.

It was also discussed that the City needed to develop a LID Governance Model for future projects, as ownership, operations, and maintenance of the LID site are critical for the project to function permanently. The LID Governance Model will help the City with future LID projects to identify ownership, operations and maintenance issues, and is expected to be completed in July 2018.

Implementation

IBI Group undertook soil testing to ensure there is no soil contamination before construction began. Construction of the LID began in November 2017 and was completed in May 2018. This rain garden contains a mix of perennials and grasses designed to tolerate spring flooding, summer drought and winter salt. The plants selected offer year-round beauty and colour while attracting pollinators and benefit local biodiversity. The plants used in this garden include Blue Flag Iris, Heavy Metal Switch Grass and Purple Dome Aster. The rain garden functions by directing stormwater from paved surfaces towards the garden where mulch and native plants absorb the water and nutrients from the runoff. The water is then slowly filtered through layers of sand and other organic materials eventually travelling to a gravel layer below the soils where the water is cleaned once more, and allowed to seep into the ground. Excess stormwater that is not filtered into the ground is then fed into the storm sewer through a flood drain.

Outcomes and Monitoring Progress

Several positive outcomes were achieved as a result of the project. Possibilities for scaling up: This project ultimately assisted the City in developing its ability and capacity to adopt and implement LID solutions on a citywide scale. Standardization: The creation of the Governance Model for future LIDs as a result of this project will create a standardization for operation and maintenance of current and future LID sites within the City of Hamilton. The Governance Model will provide responsible departments with a long-term framework regarding LID O&M, including the frequency of inspections and maintenance, the responsible entity, etc. Increased awareness: The communication and outreach initiatives undertaken as part of the project will help to increase both staff and citizen awareness of LID solutions. This awareness may help increase the number of LID sites installed throughout the city, both on public and private property.

In order to measure public engagement and outreach in relation to the project, the City will be counting the number of outreach events hosted, as well as the number of attendees. Furthermore, the City will track the number of communication materials developed to promote the project, including mail outs, signs, and web page articles. The City will also be measuring the success of the rain garden in offsetting wastewater treatment. This will be based on calculations completed during the design stage and on the treatment cost per unit of wastewater reduced due to infiltration. Lastly, the City will also be measuring the volume of stormwater interception of the rain garden, which will also be theoretically calculated during the design stage of the project.

Next Steps

The City will also be completing its LID Governance Model for the operation and maintenance of the rain garden and future LID projects, which will be completed in March of 2018. Continued operations and maintenance of the rain garden will involve inspection of the LID after each storm event greater than 15mm for the first 6 months, with subsequent inspections occurring each Spring and after rainfalls of 60mm or greater. Routine maintenance of the site will involve trash removal, pruning and weeding, mowing, and watering as needed. Additional outreach events, including tours of the LID sites and field trips with local schools, are expected to commence once construction is complete.

Resources

Link to Full Case Study

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Soak it Up! Brochure

Soak it Up! Brochure