One month into the 2019 hurricane season, only about 23 percent of the Woodridge Village Detention Ponds have been substantially excavated and have outflow control devices installed. At the time of the May 7th Elm Grove flood, that percentage was only 9 percent. So in a little less than 2 months, Rebel Contractors has more than doubled the percentage completed. However, as we head toward the peak of hurricane season, approximately three quarters of the detention capacity remains unexcavated, dysfunctional, or both.

Contractors also have yet to finish grading, planting, and cementing portions of the ponds that they have excavated.

Only 2 of 5 Detention Ponds Substantially Excavated

The first phase of the 268-acre Woodridge Village shows a total of 4 detention ponds. But Rebel Contractors has excavated only two on the southern end so far: S1 and S2.

Together they provide a total of 49 acre-feet of storage. Pond N1 has not yet been excavated and Pond N2 does not yet have an outflow control device that will retain the water upstream from Elm Grove.

In Phase 1, Pond N2, has no additional excavation. Existing excavation was done by Montgomery County starting in 2006. The county removed approximately 3-4 feet of dirt in a 20 acre area. Ultimately, N2 will be the largest pond in the development with 154.7 acre feet of detention. Note: the figures quoted below differ slightly from those I quoted earlier because LJA Engineers presents conflicting data in its Drainage Impact Analysis for Montgomery County. See pages 7 and 54.

Ultimately, the 5 ponds will have a total of 271 acre feet of storage. An acre foot covers one acre to a depth of one foot. So the five ponds will hold a little more than one foot of rainfall per acre of development.

That means, 12 inches of water should be able to fall on the entire development without flooding any adjoining properties. But with only 23% of detention functional (S2 – green, and S1 – blue), that 12 inches of detention is effectively reduced to 3 inches right now.

How Much is Functional and Where?

The bullet points and pie chart below summarize the total storage and current status of each pond as of July 1, 2019. The figures for acre-feet are taken from the map above representing the ultimate phase of development.

• N1 = 13.2 acre feet (not started)
• N2 = 154.7 acre feet (started by Montgomery County circa 2002, but is not fully excavated, nor is there any outflow control device installed to detain water upstream of Elm Grove)
• N3 = 42 acre feet (does not appear to be started)
• S1 = 18.6 acre feet (mostly functioning, but not fully finished)
• S2 = 42.5 acre feet (mostly functioning, but not fully finished)
• Total detention when complete = 271 acre feet
• Total detention not functional as of July 1, 2019 = 77%

Photos and Video of S2 as of End of June 2019

Jeff Miller shot his video of S2, the pond immediately north of Village Springs in Elm Grove. It shows what progress looked like at the end of June. The pond has been widened by sloping the sides even more since the last update.

N2 Will Contain More than Half of All Detention

N1 – Still No Excavation

N3 – Still No Excavation Visible

Much More to Come Per Hydrologist’s Report

In Phase 1, Figure Four, a subsidiary of PSWA and Perry Homes, will develop 30 acres in the northern section and 58 acres in southern section. Ponds N1, S1 and S2 are to be built during this phase.

The hydrologist notes that a portion of N2 is already in place (although there is nothing there yet to detain the water upstream from Elm Grove). She also notes that:

• N2 will be widened during the Ultimate phase
• A pilot channel within N2 and  the E-W channel immediately downstream will be graded during Phase 1 to provide flow-line continuity with other proposed structures.
• A concrete lined channel on the eastern side of the subdivision will be extended 150′ between the E-W junction and a 36″ plastic pipe.

Much work remains before their tables and charts on water flow can be used.

Remember, per their own report, the larger portion of Woodridge Village is in the north. It comprises two thirds of the development and the ground there slopes 10 times greater than the southern portion. (1 degree vs.  0.1 degrees).

The Woods are Gone, But We’re Not Out of the Woods Yet

As Elm Grove resident Jeff Miller said, “It sure seems to me that once they clear cut the north, that the potential for flooding rose exponentially.”

Let’s see!

• More clear-cut area.
• No functional detention.
• Sloping toward Elm Grove.
• And only one fourth of the total detention installed on the southern section.

I would agree.

As we approach the second anniversary of Harvey in 7 weeks, everybody on the periphery of this development is on edge…no pun intended.

Montgomery County needs development rules that protect neighbors from such development practices.

Posted by Bob Rehak on 7/1/19 with help from Jeff Miller

671 Days since Hurricane Harvey

All thoughts expressed in this post are matters of opinion and safety involving public policy. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.