From Stormwater Management to Integrated RAINwater Management in the Township of Langley
The Routley, Yorkson and Northeast Gordon neighbourhood communities in the Township of Langley illustrate how a ‘water-centric’ approach is changing the way that land is developed in Langley. The plans for these neighbourhoods demonstrate not only integration of surface and groundwater (i.e. to protect water supply), but also integration of engineering and parks to enhance liveability.
When the Township of Langley hosted the second event in Showcasing Green Infrastructure Innovation in Metro Vancouver: The 2007 Series, this provided a timely opportunity for other Metro Vancouver municipalities to learn about the Langley approach to integration.
Each neighbourhood features a different green innovation. Brad Badelt, Water Resources Engineer and leader of the Langley Showcasing Team, described the multi-purpose greenway and shallow infiltration systems on individual residential properties that were first implemented in Routley; the ‘third-pipe system’ for roof drainage that connects to a sand filtration treatment system and deep-well injection for aquifer recharge in Yorkson; and most recently, truly ‘green streets’ in North East Gordon Estates.
Yolanda Leung, a landscape architect in the Parks Department, built on the harmony and integration theme when she described how rainwater management works in parks.
The Showcasing Innovation Series is structured as presentations in the morning and a tour of project sites in the afternoon. The Langley tour featured both the urban and agricultural dimensions of Langley. This provided event participants with a complete experience. Please click on this link to Langley Showcasing Innovation Tour Map to find where these stops of interest are located.
According to Brad Badelt, “We did not want people to leave with the impression that Langley is an intensively developed urban environment. So we included two stops in the agricultural lowlands.”
The first two stops were in the Langley Meadows and Routley neighbourhoods.
“We started with the detention pond in Meadows Edge Park at the downstream end, and then we visited the multi-purpose greenway in the upper part of the catchment,” Brad Badelt reported. “Key features of the drainage system are on-lot infiltration soakaway chambers, top soil depth of 300 mm, and greenway swales with gravel beds,” he explained.
“Routley was the first step towards achieving a water balance approach,” added Brad Badelt, “In 2005, we implemented a monitoring program to asses drainage system performance. To date, the monitoring has shown that the Routley rainwater runoff volume is on average half that from Langley Meadows, an older development that does not have on-site infiltration. In short, the design is meeting expectations.”
According to Jim Dumont, the engineer of record for each successive innovation in the Routley, Yorkson and Northeast Gordon Estates neighbourhoods, “We were tight for space in the Routley area because the rainwater management elements were added after the land use decisions were made. The Meadows Edge pond serves both the original and new upstream neighbourhoods, and is a tight fit. The multi-purpose greenway is located on a gas pipeline right-of-way, and is complete with pathway and stream channel features. It was a major accomplishment to reach an agreement for multi-purpose use.”
“The greenway is part of a comprehensive greenway network that will continue down the hillside in the direction of the Civic Centre,” added Yolanda Leung. This can be seen in the photo below which is a southeasterly view from 196th Street looking down to the lowlands.
The next stop on the tour was the Yorkson uplands. “The Yorkson Lowlands is already prone to flooding problems,” explained Brad Badelt, “Because uplands development must not exacerbate the lowlands situation, we needed a strategy for volume management that would be effective.”
According to Jim Dumont, “We faced three challenges: first, clayey soils extend to a depth of about 30 metres; secondly, the infiltration rate is less than 1mm per hour; and thirdly, the development form is compact lot which leaves little space to do much on individual properties.”
“Our goal was to maintain the pre-development volume of rainwater runoff,” continued Brad Badelt, “We considered shallow infiltration, but quickly determined that even with a 15 square metre soakaway, we could not meet the volume target.”
“The solution was a single deep well,” added Jim Dumont, “Runoff from roofs and perimeter drains is collected from each property and conveyed via a third pipe system to a central sand filter. Once the development is fully built out, the well will be activated so that the treated water can be injected into the aquifer.”
“One of the keys to the third pipe system is maintaining strict control over the type of roofing material that is used,” noted Brad Badelt.
“A focus of the Yorkson neighbourhood is the greenway feature that is integrated with the storage pond that is part of the rainwater management system,” explained Yolanda Leung, “We have two types of greenways. Those that are located along creeks, and those that are not.”
Northeast Gordon Estates:
The tour included a drive-by of the area under development, followed by a stop downstream in the agricultural lowlands where Northeast Gordon Estates outlets.
According to Brad Badelt, “The situation with respect to Northeast Gordon Estates is much the same as Yorkson: poor infiltration; significant fisheries value in some roadside ditches; and downstream erosion issues.”
“The plan is to distribute infiltration across the neighbourhood,” explained Jim Dumont, “The top soil depth requirement has been increased to 450mm, thereby providing a soil moisture storage reservoir of 65mm. Also, the streets will actually be green streets because vegetated swales will be underlain by a permeable substrate.”
Posted November 2007