I'm not an expert, or pretending to be "in the know", but as it was explained to me the holding pools are too small for the amount of run-off that is directed to them from UniverCity (bad engineering?) and in major or successive rain events that fill the pools the blow-off dumps water straight down Gear Jammer.
Basically, the work they are doing to fix Gear Jammer right now is a waste of time/money (as were the repairs that were done, literally, right before the latest major rain event which were utterly trashed) as any time we have an excessive amount of water for the holding pools to handle the trail is going to be an emergency creek bed?
Tungsten pretty much has it right, with the initial failure and subsequent issue a result of contractor error.
DrewM's information is largely incorrect. The communication on this issue is basically a game of telephone, so the message gets distorted or changed from ear to ear and mouth to mouth.
I am involved with the investigation and remediation of the outfall and GJ, working with the City and the team hired to do the work. I also regularly use the trails (daily), and so have a vested interest in ensuring we find a permanent long-term solution. The City and UniverCity are working well together to expedite this work as we head into the core of winter.
Below is a summary of the stormwater system as well as the chain of events, the work to date, and the work going forward.
The Stormwater System:
There are 4 agencies monitoring the stormwater system, ensuring that the ponds are functioning properly: The City of Burnaby, a civil engineering firm, a water quality consultant, and the Stoney Creek Environmental Committee. They also sit together on a group that meets quarterly to share reports.
The ponds are designed to capture and retain water from development as it passes from the building to the street to the ponds. The ponds then use a weir/damn system to direct water into particular tributaries of Stoney Creek at prescribed flow rates and volumes. If the ponds exceed the weir/damn, they simply drain into the standard storm drain that is in the ring road and goes into the Burnaby municipal storm system.
There are several outfalls throughout Burnaby Mountain that are highly controlled in terms of flow rate and quantity and they are monitored regularly. The monitoring reports are publicly available, as is the design system. They do not overflow or blow off into GJ or any other trails. Data indicates that the stormwater system is working largely as designed.
The Issue and Resolution:
The failures that started occurring last January and are now being mitigated, were the result of a major "blow off" or "overflow" through a culvert connected to the first pond. A contractor working on civil works in the ring road was constructing a new stormwater line/bypass in the ring road. In order to do so, they needed to stop flows into the first upstream pond (the one who's design outfall goes near GJ). This outfall, as noted, is designed for a very prescribed "pre-development" volume of water. However, the contractor "plugged" the pond outlet below this outfall point in order to do their works during a dry period. Once done, the contractor failed to remove the lower plug. A major storm event in January, 2014 occurred and pushed all the upstream stormwater out the culvert, creating the drainage issues and channels we have today. The source of this failure was not immediately identified by the contractor and was found by the reviewing engineer, so a couple of additional blow-offs occurred.
Once the plug was removed and water flows were restored to normal, it was noticed that the excessive flow had essentially expedited the erosion/channelization of water ways that predominantly headed toward upper and middle GJ. So, even with "normal" flows now coming out the outfalls, rather than dispersing through the watershed, much of the water was finding this channel toward GJ.
The contractor hired Jay Hoots, with agreement of the City, to "fix" the trail in October. Jay did the work in 2 or 3 days and returned the trail to good condition. But the contractor failed to address the problem at the source, by remediating the area below the outfall. Immediately following Jay's trail work, an intense 3 day storm continually fed water back toward GJ, causing all of Jay's work to be literally flushed down the drain.
Following this, the City and UniverCity basically stopped trying to get further work from the contractor and are collectively addressing the issue from the outfall through the trail. Since the bulk of the work on the outfall and Upper and Middle GJ was completed just over 1 week ago, one typical storm cycle has passed through. Water flows are measured back to normal. 80% of the trail work is supporting the water flows at this time. A few additional drainage issues are now marked (flagged) and will be dealt with over the next week. This should leave GJ as it was prior to last January.
There will always be wet spots. GJ has a history of wet spots and below-surface ground water. But it will be of the level that can be managed via regular maintenance as with any trail.
Fingers crossed for this final round of remediation.