Project Details

The sinking of the HDPE intake line was the final phase of Dean’s involvement on Enwave Energy’s Deep Lake Water Cooling Expansion project. The Enwave system cools buildings in downtown Toronto’s core using cold lake water. This decreases the use of air-conditioning and its resultant electricity requirements. Construction of the intake took place in Hamilton Harbour. The line itself consisted of fusing 165, 16m lengths of 1600mm OD HDPE pipe, attachment of 600 concrete anchor blocks (each having a mass of up to 8t), 600 ductile iron rings and a steel/poly composite intake cone. The HDPE sections of the intake were fused, assembled and pressure tested to 655 kPa in four 650m lengths creating a total length of 2600m. Custom designed strongbacks were attached to span the flange joints between the sections to prevent the HDPE from buckling during deployment. The intake hood, its support structures and floatation assembly (for installation purposes only) was installed last.

The entire length was then towed 50km to the installation location. The pipe was aligned to its design location, the temporary pumping spool was submerged and connected to the previously installed, submerged stainless steel piping which protruded from an offshore steel sheet pile cell. The entire attachment and deployment operation had to be completed without stoppage. Once the temporary pumping spool was connected the pipe was pulled taut by a 40t bollard pull tug connected to a flat scow equipped with a 100t winch which was required for the controlled intakelowering operation and a tensionometer which ensured that the required pull on the pipe was maintained during the operation. This barge also monitored the pipe’s internal air pressure, verifying that the pressure was in compliance with the predetermined deployment pressures dictated for every point of the sinking operation.

Pumping operations then commenced. This included recording the total volume of water pumped into the intake and comparing that to the design volume and correlated against which anchor block was leaving the lake surface at what time. Realtime position monitoring of the pipe during the sinking operation was performed, along with constant radio communications to the main tug regarding keeping the pipe on station. An ROV monitored the anchor blocks as they contacted the lake bottom. The intake was installed successfully at a depth of 70m. With the intake structure at lake bottom, the temporary pumping spool was removed by divers and replaced with the permanent section of pipe. The trench in which the intake was placed, until it reached a depth of 12m was then backfilled.