Before Perry Homes bought the ill-fated land now known as Woodridge Village, it hired a company called Terracon to sample soils and submit a geotechnical analysis. Their objective: to see whether the land was suitable for residential development. Perry also hired LJA Engineering to analyze drainage. However, it appears that LJA did not consider Terracon’s findings when it modeled runoff (see Section 1.4 of LJA’s report).
LJA also assumed that “sandy loam” covered the entire site when the National Resources Conservation Service soil database shows sandy loam covers only 60 percent. The Terracon report, however, never even mentions “sandy loam.”
Different Findings Could Have Skewed Runoff Analysis
Both the different characterizations of soils and their extent could have skewed the results of LJA’s runoff analysis.
LJA said the soil was “fine sandy loam,” everywhere, period. Terracon bored holes to 20 feet at four locations and found mostly clay-based soils. Terracon did, however, find “sandy silt” with “clay pockets” in the first foot of ONE of their borings.
According to the USDA’s Natural Resources Conservation Service (NRCS), clay, sand and loam absorb rainfall at vastly different rates that can approach or even exceed 10X.
The NRCS site above does show “sandy loam” on 60% of Perry Homes’ property. However, the NRCS sampling technique usually involves a shovel. They appear to classify primarily surface soils (not surprising for the Department of AGRICULTURE).
That’s why NRCS clearly states that the infiltration rates above only apply to the first two inches of rain during an event. After that, the water may percolate down to another, less permeable layer of soil, such as the clay that Terracon found. At that point, fully saturated ground could force additional rainfall hitting the surface to pond or, if the land slopes, run off. That’s exactly what happened on May 7th and September 19th this year when Elm Grove flooded from Woodridge Village runoff.
But Terracon’s preliminary investigation sampled only four widely spaced spots at the perimeter of the property. None coincided with the locations of planned detention ponds, known wetlands, or streets. Only one even came close to a future home site. And the Montgomery County Engineer’s office has no record of Terracon performing additional work on the Woodridge site.
Also note that while NRCS shows sandy loam on 60% of the site, LJA assumes uniform distribution everywhere. That could also have skewed LJA’s computer modeling. NRCS showed that another 33% of the site (see below) contained soil consistent with wetlands. Wetlands don’t typically absorb water, often because of clay underlying them.
Wetland-Type Soils on ONE THIRD of Property “Overlooked”
A top geologist retired from one of the world’s largest oil companies sampled the soil at one of Terracon’s borehole sites shortly after the May 7th storm and confirmed Terracon’s findings as to surface soil type – mostly clay.
He also says, “The presence of clay close to the surface can cause water to pond and lead to the formation of wetlands wherever you find depressions in the land.” And in fact, the USGS National Wetlands Inventory shows extensive wetlands on the northern portion of the site.
It’s not clear where LJA found its soil information; they don’t specify. But if it was from NRCS, they should have been alarmed by the presence of hydric topsoils on ONE THIRD of the property. Hydric soils are one of the defining ingredients of wetlands. Compare with map below, taken from the NRCS site. SosA and SouA are soil types typical of wetlands.
Building homes over wetlands is dangerous because shifting soil can crack foundations. Wetlands also typically serve as collection points for water.
But LJA never mentions wetlands and the Terracon borehole sampling sites came nowhere near the wetlands on the property. Terracon spaced them widely around the perimeter as you can see from the site map with the red lines above.
Groundwater Levels Not Mentioned In LJA Drainage Analysis
LJA, had it read the Terracon report, might have also been concerned by the discovery of ground water at 15 feet, more than a half mile from Taylor Gully. At Taylor Gulley, contractors hit ground water at about 10 feet when excavating the S2 detention pond. But the pond was supposed to hold 15 feet of runoff. That means ground water reduced its capacity by a third. Even worse, a pond by N3 has had standing water near the ground SURFACE for months!
That means these ponds will never be able to achieve their promised detention capacities with their current dimensions. There just isn’t enough depth. Engineers measure detention capacity from the top of any standing water, not the bottom of the pond.
More Curiosities Re: Testing and Reports
How strange that LJA’s drainage analysis never once mentions the words “water table” or “groundwater”! Especially when detention ponds are a central feature of the report and mentioned 42 times. LJA never mentions “retention” ponds once, although J. Carey Gray, the high-powered litigator representing Perry Homes, called the ponds that in his letter to the City. For the record, detention ponds have no permanent standing water; retention ponds do.
The first thing you notice about the Terracon report: the title says PRELIMINARY. Terracon also put “preliminary” at the top of every page. And repeated it 35 times within the report. Sometimes as many as three times in a single paragraph. Terracon also specifically recommended several followup tests. But if they were done, the Montgomery County Engineers office says it has no record of them.
Five Previous Developers Sold Site Rather than Develop It
At Thanksgiving Dinner yesterday, we had three engineers at the table. I posed the question, “Do you ever reach a point in projects when you say to yourself, “We shouldn’t do this,” as opposed to “How can we do this?”
The general consensus: There’s always a way to engineer a solution…if you don’t consider cost.
I wonder if that’s why five previous developers who owned this site didn’t do anything with it. They included Lennar, Kingwood 575, Reddy Partnership/Kingwood, Woodbridge 268, and Concourse Development.
It could be that they were just holding it and hoping to flip it at a higher price. Land generally appreciates faster than the rate of inflation. But it could also be that they investigated the cost of developing it more closely than Perry Homes did.
Below: the sales histories for the two major pieces of land that comprise Woodridge Village.
Of all the curiosities associated with this development, the sales history ranks near the top. Concourse held the property for less than a week before selling it to Perry Homes’ subsidiary, Figure Four Development LTD.
Perry Homes even commissioned and received Terracon’s Geotechnical report BEFORE Concourse bought the property. But that’s the subject for another post at another time. What was that about?
The important thing to note for now: When you’re selling dirt, it pays to know what kind of dirt you’re selling.
As Perry Homes Drags Out Court Case, It Could Incur More Liability
The once-proud Perry Homes is now buried under a mountain of law suits alleging that their actions flooded hundreds of homes…not once, but twice…in six months.
As Perry Homes drags these lawsuits out, Kathy Perry Britton could expose her father’s company to enough liability to bring it down. Can you imagine how a jury would react if Elm Grove flooded a third time when so many regulations have been flaunted? And when Perry has made no further attempt at mitigation since early August? I can.
Posted by Bob Rehak on 11/29/2019 with help from Jeff Miller
842 Days after Hurricane Harvey and 71 after Imelda
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.