Tag Archive for: Subdivision Rules and Regulations

What Went Wrong, Part II: Lack of Erosion and Sediment Control Worsen Elm Grove Flooding

On May 7th and September 19th, sediment-laden runoff from Perry Homes’ Woodridge Village development in Montgomery County flooded the streets and homes of Elm Grove Village and North Kingwood Forest. On September 26, the City of Houston wrote a cease and desist letter to Perry Homes, its subsidiaries and contractors. The letter alleged that runoff damaged the City’s sewer system and residents’ homes. It demanded that Perry Homes’ proxies stop sending sediment into the City.

After Imelda, Abel Versa had to grab his car to avoid slipping in ankle-deep sediment on Village Springs. The sediment came from Woodridge Village right behind him.

Sediment Control Measures Not Followed in Subdivision Rules and Regs

If Perry Homes and its contractors had followed all the construction regulations affecting drainage, the flooding of Elm Grove would not have happened and the letter would not have been necessary. So what went wrong? I previously reviewed the sediment control measures in the Montgomery County Subdivision Rules and Regulations. Perry Homes received seven strikes. Among the worst apparent violations:

  • They clearcut 268 acres when the rules say no more than 10.
  • They are supposed to plant temporary vegetation but haven’t.
  • They were supposed to make provisions for increased runoff during construction, but didn’t.

In fact, they have substantially completed only 23% of the permanent detention ponds for the whole subdivision despite clearcutting all 268 acres.

The southern section of Woodridge Village has been cleared, filled and graded since last summer. Grass could have reduced the runoff during Imelda. Photo taken on 11/4/2019.
The northern section has also been mostly cleared for months, though workers are still removing piles of dead trees. This shows the area where they filled wetlands. Because no detention exist for the northern section, runoff from 188 acres is supposed to funnel through a 3′ pipe. That’s not working well in heavy rains. You can see how much loose sediment is exposed to floodwaters.

More Regulations in Drainage Criteria Manual Not Followed

Perry Homes also overlooked many provisions in the Montgomery County Drainage Criteria Manual. Twenty-two of the 175 pages also discuss erosion and sediment control (see Section 6 starting on page 85). Among the more serious omissions:

Channel Slopes Severely Eroding

Section 6.2.1 on Grass Establishment states that: “A good grass cover must be established on all areas within the right-of-way (except the channel bottom) disturbed by channel improvements or by any type of construction. An adequate grass stand on the banks helps stabilize the channel and minimize erosion caused by overbank flow and high velocities in the channel. Establishing a good grass cover requires preparing the seedbed, seeding properly. keeping the seed in place, fertilizing, and watering regularly.

The LJA Engineering report never mentions erosion or sediment control by those words. However, it does mention grass-lined and concrete-lined channels and spillways. Only one problem. The channels are not grass lined and most of the areas designated for concrete lining have yet to be lined.

The banks of detention ponds should be lined with grass. They are not. As a result, sediment is slumping to the bottom of the ponds where it is carried downstream by floodwaters.
This closeup shows how severe the erosion is.

Channel Turns Not Protected

Section 6.2.3 on Minimum Erosion Protection Requirements for Bends specifies that bends in drainage ditches must be protected from erosion by grass, rip-rap, or concrete. The material depends on the radius of the curve, the type of soil, average water velocity and maximum water velocity.

Despite funneling 188 acres of sheet flow into Taylor Gulley, which narrows down into a 3-foot pipe, Perry Homes has done little to increase the channel capacity or detention for that area. Worse, the channel design which may have been adequate for forested wetlands, can no longer handle high volume overland sheet flow.

The most obvious needs are on the eastern side of the development. There, Taylor Gully makes a 120-degree turn, then two quick 90 degree turns and two 45-degree turns, all within two hundred yards. Getting dizzy? The floodwater turns 390 degrees in this area!

At each turn the banks take a beating. The full force of the floodwater slams against the far bank and erodes it.

Photo taken on 11/4/2019 along eastern boundary of the southern section of Woodridge Village. That’s North Kingwood Forest on the right and Elm Grove on the bottom. Little wonder that this was the area hardest hit by flooding in May and September.
Where the channel on the right narrows down into the black 3-foot pipe, contractors built an overflow channel into the detention pond on the left but still have not lined it with concrete. Note the severe erosion. Also note the erosion and sediment coming into the pond on the left just below the flow-constricting device in Taylor Gully. Clearly, there isn’t enough channel capacity to handle the volume of water. Photo taken on 11/4/2019, looking north.

Straight Drop Spillway Not Installed

Section 6.2.5.3 states that a straight-drop spillway should be installed in drainage channels to adjust channel gradients which are too steep for design conditions. 

LJA specifies one between where detention pond N3 will be and the 120-degree turn shown above. However, neither the detention pond, nor the spillway have yet been installed. So water from the north comes barreling down the ditch on the right unchecked. The high velocity increases erosion. Here’s what it looked like after May 7th.

Same area shown above but from ground level and looking south toward Elm Grove. Rain did a lot of the excavating for Perry Homes. But unfortunately, the sediment wound up in flood victims’ homes and the City storm drains.

Yesterday I posted about how Perry Homes was supposed to cut only 30 acres of trees on the northern section but cut 188. Still to come in this “What Went Wrong” Series:

  • More Things Perry Homes Didn’t Do in the Montgomery County Drainage Manual
  • Contradictions in Perry Homes’ Plans
  • The Dirt on Perry Homes’ Soil Test
  • The Floodplain that Wasn’t

Posted by Bob Rehak on 11/20/2019 with help from Jeff Miller

813 Days since Hurricane Harvey and 62 since 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.

Perry Homes Apparently Violating Montgomery County Development Regulations, Too

On September 26th, the City of Houston fired off a Cease-and-Desist Letter to Perry Homes regarding its Woodridge Village development just north of Elm Grove. The letter warned Perry and its subsidiaries to stop sending sediment into Houston storm drains. Now it appears the Perry gang is violating Montgomery County regulations, too. Let me call your attention to page 28 of the Montgomery County Subdivision Rules and Regulations. The sediment section reads (and I quote verbatim):

“IV. SEDIMENT CONTROL AND SEDIMENTATION PONDS. The subdivider shall provide effective sediment control measures in the planning and construction of subdivisions. Practical combinations of the following technical principles should be applied: 

  1. No more than ten acres of land in road right-of-way shall be exposed at any one time during development, without prior approval of the County Engineer. 
  2. When land is exposed during development, the exposure shall be kept to the shortest practical period of time. 
  3. Temporary vegetation and/or mulching shall be used to protect critical area exposed during development. 
  4. Sediment basins and traps shall be installed and maintained in properly designated places to remove sediment from runoff waters on land undergoing development. 
  5. Provisions shall be made to accommodate the increased runoff caused by changed soil and surface conditions during and after development. 
  6. The permanent final vegetation and structures shall be installed as soon as practical in the development. 
  7. The development plat shall be fitted to the topography and soils so as to create the least erosion potential.”

Let’s compare these principles with Perry’s practices.

Strike One

Shall provide effective sediment control measures in construction?

Photo taken shortly after May 7th flood on southern section of Woodridge Village.

Strike Two

No more than 10 acres of land shall be exposed at any one time?

How about 268 acres?

Strike Three

Land exposed for shortest practical period of time?

Drone footage of Woodridge Village southern section from May 9.
Shot of same area (from different angle) six months later.

Strike Four

Temporary vegetation?

Photo taken 11/4/2019, months after land was clearcut AND after two major floods.

Strike Five

Provisions to accommodate increased runoff?

Block after block of Elm Grove residents dragged their lives to the curb after being inundated by increased runoff from May 7th and Imelda.

Strike 6

Final structures installed as soon as practical? Let’s look at detention ponds…that aren’t there…despite months of ideal construction weather.

The N1 Detention pond should have been installed in the foreground months ago.
The N2 Detention Area (green triangle excavated by MoCo in 2006) was supposed to be expanded, but was not.
The N3 detention pond was to stretch from Taylor Gully in the bottom of the frame, almost to the tree line at the top. But nothing has been done.

Strike 7

Plat fitted to soils to create the least erosion possible?

Wetlands abounded on this property.
But Perry contractors filled in natural wetlands and streams.

Seven Strikes and You’re Out?

Not if you’re Perry Homes. Because when I first complained to the TCEQ about sediment flowing from the site in May, the TCEQ referred the investigation to Montgomery County. Then Montgomery County referred it to LJA Engineering. Perry Homes, of course, hired LJA to do the engineering on this site. So LJA was investigating itself and its client. Surprise, surprise, everyone called the problem fixed after installing some silt fencing in May. But it wasn’t fixed. Five months later, even more people flooded during Imelda than on May 7.

With the exception of some work on detention pond S2 last summer, Perry has not bothered to:

  • Expand detention capacity
  • Plant vegetation
  • Install sediment basins
  • Reduce runoff
  • Compensate for the wetlands and streams they filled in

Perry has done nothing in SEVEN months that reduced flood risk to Elm Grove. The work they did last summer didn’t prevent flooding in September. And they haven’t done anything since.

Yet Kathy Perry Britton, Perry Homes CEO, talks about the value of character, integrity and decisive action. The value of practicing good corporate responsibility. And Perry Homes’ commitment to excellence and distinguished reputation.

News flash, Ms. Britton. Going 0-7 doesn’t show a commitment to excellence. And suing flood victims certainly won’t establish a distinguished reputation. Although it may put you in the Hall of Shame with Montgomery County Commissioners who refuse to enforce their own regulations.

Posted by Bob Rehak on 11/12/2019, with thanks to Jeff Miller

805 Days since Hurricane Harvey and 54 since Imelda

The thoughts expressed in this post represent 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.