Woodridge Village Pre-Cristobal Detention Pond Update
Perry Home’s new contractors have excavated the vast majority of virtually all three detention ponds on the north section of Woodridge Village. That means they have almost completed 77% of the detention pond capacity for the whole site in two months. The previous contractors completed only 23% in approximately twenty months.
That represents approximately a 30x increase in productivity.
Overview of Woodridge Village Detention Pond Capacity
The pie chart below shows how that capacity breaks down. And the map shows where it is.
Contractors Scurry as Cristobal Churns in Gulf
Tropical Storm Cristobal could be a game changer next week if it hits Houston. It’s track is far from certain at this point, but the National Hurricane Center still puts Houston within the cone of uncertainty.
Cristobal has the potential to create massive erosion and set the work schedule back. The aerial photos below taken on 6/2/2020 show the current “pre-storm” status of construction for the three northern detention ponds. The two southern detention ponds were completed earlier this year.
N1 Nearing Completion of Excavation
N1 Starts at the northern boundary of the site and runs halfway down the western edge to Mace Street.
Still Widening and Deepening N2 Pond
N3 All Excavated
N3 cuts down the eastern side of Woodridge Village and joins Taylor Gully right above S2.
The pile of dirt in the picture above could be shoved into the connecting channel in the event that Cristobal should strike Houston. That would then help retain water in N3 until after the storm.
All the runoff from the approximately 200-acre northern portion of the site converges here and tries to make its way through a 3-foot culvert at the end of the concrete channel.
Uncertain Still Surrounds Corner of Chaos
Some Elm Grove and North Kingwood Forest residents have called the complex flow patterns in the photo above “The Corner of Chaos.”
Overflow from the concrete lined channel is supposed to go into the kite-shaped S2 pond, and then through the twin culverts into Taylor Gully. However, a hydrology consultant for the plaintiffs in flooding lawsuits contends that floodwaters went the other way. They escaped out of the inflow channel, he says. He further claims that LJA Engineering failed to model the performance of that connecting channel.
If the design of the flow at this “Corner of Chaos” is flawed, there’s little contractors can do to fix that at this point without some major re-engineering.
In that regard, we should also remember that LJA designed these ponds before Atlas 14, so they will only hold approximately 60% of a 100-year rainfall as defined by Atlas 14 standards adopted in Harris County.
How Contractors are Temporarily Funneling Water into Ponds
Because storm drains are not yet installed, contractors are relying on temporary channels to intercept runoff and direct it to detention ponds.
Next Steps in Completing Detention Ponds
A modest amount of excavation remains to complete the full detention pond capacity.
But the capacity already in place should reduce flood risk compared to last year by more than 3X for storms equivalent to May 7 and September 19, 2019.
As some crews focus on completing excavation, others are putting the finishing touches on ponds. Those include concrete pilot channels, backslope interceptor swales, drain pipes, and culverts to control the rate of outflow.
Racing Against Hurricane Season
At this point, contractors are racing against time and the hurricane season. Cristobal underscores the risk of having waited for months to begin the three northern detention ponds in April. Had they begun them immediately after J. Carey Gray’s letter to Mayor Turn in October, they could easily have finished by now.
Posted by Bob Rehak on 6/4/2020 with thanks to Jeff Miller
1010 Days after Hurricane Harvey and 258 since Imelda
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