By Peter Kumar
When tasked with finding an efficient and compliant stormwater management system for a large multi-family mixed-use development in North Vancouver’s Lynn Valley area, the developer enlisted the help of a local civil consulting firm. They, in turn, approached BARR Plastics Inc. for a durable solution that would not only protect the development against flooding, but would also work with the site’s unique, tight and hilly profile.
It was also key for the system to meet the District of North Vancouver Hastings Creek Watershed Stormwater Report stringent storage volume requirement of 1,143 m3/Ha.
The consultant and BARR Plastics specified, designed and supervised the installation of three stormwater infiltration systems, which were installed in two phases. During the first phase, a 1,180 m3 two-tank system was installed.
It was built using 5,760 heavy-duty EcoBloc Inspect Flex modules in order to meet a burial depth of 5 m, with in-built inspection channels for easy maintenance. During phase two, a second, 658 m3 system was installed which consisted of 3,210 EcoBloc Inspect Flex modules.
Due to the hilly profile and minimal footprint available on site, the stormwater system needed to be deeper underground, with a 5 m burial depth and provide HS-25 loading. The solution was a three-tank system using Ecobloc Inspect Flex in combination with Vario 800 flex shafts. These were located to provide full access into the tanks for inspection and maintenance. The first tank required a minimum earth covering of just 560 mm, whereas the second and third ones needed a minimum cover of 2,000 mm.
Post-construction, the developer requested the temporary installation of two Liebherr LTM 1095.1 270 Ton and 120 Ton mobile cranes over the buried Ecobloc tanks to be used to dismantle the man hoist. Due to the consultant’s design providing vertical and lateral loading capacity of Ecobloc Inspect Flex, the design factor of the modules met the load requirements. Personnel from the design consulting firm, BARR Plastics and a local geotechnical consulting firm worked together to approve the crane installations.
This system was built with enough capacity to resist the kind of extreme storm only likely to happen once in a 100-year period. There is also an additional 15% contingency buffer for climate change.
Peter Kumar is with BARR Plastics. This article appears in ES&E Magazine’s February 2020 issue.