The Highland Creek STS And Maintenance Hole Rehabilitation Project involved trenchless rehabilitation of 2134mm (84”) Diameter Sanitary Sewer, up to 18m (59’) deep with multiple bends located in a densely populated  residential area in Toronto’s east end. The rehabilitation method of choice for this sewer section was GRP Slip Lining. This process was chosen due to the necessity of allowing the main flows through the sewer at the end of each production shift. To fully bypass the daytime flows would have driven the project costs beyond an acceptable level. Accordingly, it was determined that flows through the night could be bypassed allowing crew to install the GRP panels, securing them into position and then allowing flows to return to the main during day time hours. Site works included the installation of 2 large shafts and the rehabilitation of 30 additional manholes and chambers throughout the City. One of the first projects of its kind for the city of Toronto, the GRP panels were designed to accommodate the many irregularities throughout the pipe section which culminated with the annular space grouting and shaft restoration.  Manholes and chambers were rehabilitated utilizing the Warren Environmental product in thicknesses of up to 36mm largely due to the non circular brick profiles.