Key Woodridge Detention Pond Missing, Only Small Percent of Total Detention Developed Before Elm Grove Flooded

On the plans, LJA Engineers calls it S2 – the second detention pond in the southern portion of the new Woodridge development north of Elm Grove. Even though all drainage on the 268 clearcut acres slopes toward S2, the developer did not start building this crucial pond before the May 7 storm that flooded Elm Grove and North Kingwood Forest. The pond will ultimately hold 49.4 acre feet of water during a storm, but holds something less now because Rebel Contractors has not yet fully excavated it. Further, it appears that less than 10% of the site’s required detention was fully excavated when May storms struck.

Rebel Contractors Starts Expanding S2 After Flood

At the time of the May 7 flood, it appears that Rebel Contractors had not yet begun excavating the largest part of S2. I could see only a ditch connecting S1 with the large box culvert at the entry to Taylor Gully.

Photo taken on May 11, four days after Elm Grove Flood, shows extent of excavation for crucial S2 detention pond. Only this ditch connected S1 pond with Taylor Gully. Photo looks northeast, where giant pond should extend almost to tree line on both sides of image.

In the last seven days, however, Rebel has roughed out the pond. You can see it starting to assume its final shape, though it has not yet reached its final size or depth. See pictures below.

On Friday, May 24, I observed a steady parade of haulers moving earth from the future detention pond, S2. The contractor is using the excavated material to raise the height of streets and home pads elsewhere on the property in a process called “cut and fill.”

According to numerous residents that I have talked to, much of this area once consisted of wetlands. To develop such property, contractors use a process called “cut and fill.” They build up one area, by excavating another.

*S2 pond in early stages of development. Plans show this should ultimately cover more than three acres and be 15 feet deep.* *Photo taken 5/25/19* *looking west from Taylor Gully toward Woodland Hills Drive.*

Plans for Woodridge Village show five detention ponds. Before the May 7 storm, it appears that only S1 was in place though even it was not finished. This raises the question, “Why did the developer focus on clearcutting the northern section before finishing crucial detention ponds on the southern section, where all the water from the north would flow?”

Only S1 Pond Fully Excavated at Time of Storm

Houston City Council Member Dave Martin investigating job site shortly after the May 7 flood on May 9. Shown here: The area that will become detention pond S1. It appeared to be the only semi-functioning detention pond on the entire 268 acres. This photo shows it almost fully excavated but not fully finished. Contractor will eventually slope right side to create more detention capacity and vegetate both sides to reduce erosion.

91% of Detention Capacity Not Completed at Time of Storm

Ultimately, the 268 acre site should hold five detention ponds with a total of 292.3 acre feet of storage. An acre foot would cover one acre to a depth of one foot. The bullet points below summarize the total storage of each pond in the map above.

N1 = 16.9 acre feet (not started)
N2 = 143.3 acre feet (started, but does not appear complete)
N3 = 56.4 acre feet (does not appear to be started)
S1 = 26.3 acre feet (mostly functioning, but not finished)
S2 = 49.4 acre feet (not exacted at time of May 7 storm)
Total = 292.3 acre feet
Not Started or Incomplete on May 7 = 91%

*People in construction often use the term “substantially complete” to mean functional, but not fully finished.*

The developer, Figure Four Partners, LTD, a subsidiary of Perry Homes and PSWA, Inc., issued a statement after the flood claiming that: “… many of the detention ponds are COMPLETE.” (Emphasis added.) Many appears to be 1 out of 5. And not even that one appeared complete. Complete, as their own engineer LJA pointed out, would have entailed sloping the sides and planting vegetation. See photo above; not even S1 was fully complete at the time of the flood.

The Figure Four Partners statement also claimed they had “improved drainage to the area that did not previously exist.” Residents say their contractor filled in existing streams on the property. Yet residents that did NOT flood during Harvey DID FLOOD after the so-called “improvements.”

How Detention Ponds Work

Detention ponds collect runoff during a heavy rain. Then they release it at a slow, controlled rate that drainage ditches like Taylor Gully can handle without flooding people downstream. That’s the theory anyway. They do this by restricting the outflow compared to inflow. However, to function, they have to be BUILT.

How Much Rain Detention Ponds Should Have Held vs How Much Fell

Had all five ponds been complete on May 7, the entire site should have detained 1.1 feet of rain, a little more than 13 inches. However, we received less than 8 inches.

Jeff Lindner, the Harris County meteorologist, issued a statement on May 13 summarizing the storm that flooded Elm Grove and North Kingwood Forest. In it, he said, “A 30-min rate of 2.9 inches was recorded at US 59 and the West Fork of the San Jacinto River and a 1 hour rate of 4.0 inches. A 6-hr rainfall rate of 7.9 inches was recorded at the East Fork of the San Jacinto River and FM 1485. Rainfall rates between the 15-min and 6-hr time periods on Tuesday afternoon and evening averaged between a 2-yr and 50-yr frequency over the extreme northeast portions of Harris into southeast Montgomery Counties.”

Questions Owners and Contractors Need to Answer

In the last four years, we received three so-called 500-year storms. Two happened in the spring.

Knowing that, why did Rebel Contractors wait six months after clearing to begin excavating S2, the detention pond adjacent to areas that flooded?
Why did Rebel grade the rest of the site to funnel water toward Elm Grove before detention was in place?
Did economics factors push Rebel Contractors to clearcut the entire site before constructing detention that could control the runoff?
Why did Rebel Contractors fill in existing drainage features that could have helped reduce flooding before starting work on S2?
Why did Figure Four Partners claim that many of the detention ponds were complete?
If Figure Four improved drainage, why did homes flood that never flooded before?
Silt fences were supposed to be put up before any land was cleared. However, they were not put up until AFTER the flood on May 7. Why?
The plans required an onsite engineer to ensure compliance with permit provisions. Who was that engineer? How could he/she have possibly missed glaring deficiencies?
Stormwater Pollution Prevention Permits were supposed to be posted at all job site entrances. They were not. Why? And why did the contractor put them up the day before LJA Engineers inspected the site for Montgomery County and the TCEQ?

I hope I live long enough to learn the answers! I hope officials care enough to look for the answers! Tens of thousands of Kingwood homes did NOT flood during the May 7th storm; 196 homes next to this development did. They deserve answers.

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

Posted by Bob Rehak on 5/26/2019

635 Days after Hurricane Harvey