In order to maintain a safe and healthy public facility, it has been identified that a stormwater retrofit design is required for the Exhibition Place in Toronto ON. The implementation of low impact development (LID) practices has been determined as the most effective solution. The design objectives include improving water quality, reducing flood risks, achieving a more natural regional water balance, and addressing climate change impacts. LID features implemented in this design include rain gardens, green roofs, tree boxes, raised planters, bioretention cells, permeable pavement, and a vegetated swale. PCSWMM modelling was performed to evaluate the existing site condition and the proposed design. Distribution of these LID features throughout the site reduced the runoff coefficient by 30%-40% for a 12 hour event for a range of 1 to 100 year return period storms, and from simulating climate change projections. The LID features intercept and treat 47 % of runoff from impermeable surfaces on the site. The capital cost associated with year one of the design is $3,965,134.6. Operation and maintenance costs of the design were determined to be $18,620 for the first two years, and $8,620 per year after year two. Recommendations for improved results include the implementation of permeable pavement, an improved hydrologic analysis, and improved model calibration.