N3 Archives - Reduce Flooding

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.

*Percentage of detention pond capacity in acre feet for each of the five Woodridge Village ponds.* *Source: LJA Drainage Addendum.*

*General layout of detention ponds on Perry Homes’ property.*

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.

*Looking north at N1 from Mace Street in Porter to the northern boundary.*

*The area between the culverts will eventually become an extension of Mace Street (top of photo) which will traverse the entire subdivision to Ford Road on the eastern side.*

*While some contractors continue excavating, others work on installing concrete pilot channels. Shown here, the pilot channel near Ivy Ridge in Porter.*

*The northern part of N1 is not yet complete. Contractors still use the Webb Street entrance (upper left as their main access point to the site.* *Note how height of road dwarfs excavator in pit.*

Still Widening and Deepening N2 Pond

The area left of the diagonal road is the expansion of N2. The area near the diagonal embankment is deep enough to conceal trucks and excavators. However, the grassy triangle in the middle left was a previous detention pond constructed my Montgomery County in the early 2000s.

*Contractors are deepening the MoCo pond a small amount to create additional storage capacity.* *The dirt is being used to build up other portions of the site.*

Looking north along the western boundary from the southern part of the grassy triangle. Much work remains to extend the N1 channel south to N2. Jeff Miller reported today that contractors started working on this *this morning.*

*On 6.3.20, contractors were removing dirt from the northward extention of N2 with three dump trucks running in a relay fashion. Photo courtesy of Jeff Miller.*

*Twin culverts installed in Taylor Gully will control outflow rates from N1 and N2*.

N3 All Excavated

N3 cuts down the eastern side of Woodridge Village and joins Taylor Gully right above S2.

*Looking north. Excavation of N3 appears complete although few of the finishing touches have yet been installed.*

*N3 widens out about halfway down the eastern border.*

Then it narrows down again *to help control outflow speed* *as it approaches the junction with Taylor Gully.*

Water from the entire site converges here. Erosion patterns, fence damage and grass matting show this is where the overflow started that contributed to the flooding of Elm Grove (right) and North Kingwood Forest (left) twice last year.

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.

*Small ditches like one on right catch runoff and direct it to ponds for the time being.*

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

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.

After six months of virtual inactivity, Perry Homes’ new Woodridge Village contractors have significantly stepped up work on three detention ponds. All detention ponds are on the northern section of the development. However, recent heavy rains have saturated the soil. The rain also filled two of the three ponds one-third to one-half full. The result: a big muddy mess.

Tuesday, according to Elm Grove resident Jeff Miller, only one excavator was moving. It was trying to let water out of the N1 pond so that work could continue.

Twelve Aerial Photos Taken on Memorial Day

Below are 12 aerial photos of the site taken on Memorial Day, 5/25/2020.

*Looking north along the western boundary of Woodridge at the tail of the N1 Pond.*

*Further north, you can see where work has stopped on the tail of N1 (foreground), the Webb Street Entrance in Porter (left), and the N1 pond itself are at the top.*

The N1 pond has the least development. Most work to date has focused on the tail. That’s presumably so contractors can keep the entrance to the site open. N1 will probably be the last pond they finish. And they will probably complete it only after they develop a second entrance to the site off Ford Road (see below).

Only Work Tuesday Was Trying To Drain N1

Looking south along the western boundary from over N1, you can see where the tail ends. The tiny trench letting water out of the tail slows down water. It will eventually be replaced by the four-foot culverts you see on the left.

That tiny trench is where the excavator was working today.

Site Holds More Water than N2 Detention Pond

Still looking south, but further down the western boundary, we can see the old and new portions of the N2 detention pond. It is not currently holding much water because contractors have already opened up the sides. That allows water to escape into Taylor Gully (top center).

*Note how there’s more water on the site than in N2.*

*Closer shot shows how workers opened up N2 to Taylor Gully (left of top center). They also continue to widen and deepen the pond toward the upper right corner.*

*Rotating about 90 degrees, we can see how saturated the soil is. The northern portion of the site contains an amazing amount of standing water that isn’t yet able to reach the detention ponds.*

The northern portion of the site is roughly 200 acres. Assuming an average of three inches of standing water (one quarter foot), that means the northern portion may contain 50 acre-feet of standing water!

Taylor Gully Did Not Appear to Overflow

*Looking southeast at North Kingwood Forest (left) and Elm Grove Village (right), areas where hundreds of homes flooded twice last year.*

A closer shot shows where water in Taylor Gully, when high, is forced to make multiple turns within a few hundred yards to bypass a 3 foot pipe that connects the channel on either side of the county line. Luckily, water did not reach the overflow spillway from the concrete-lined channel during recent heavy rains, according to Jeff Miller.

N3 Pond Greatly Reduced Flow in Taylor Gully

The pond below (N3) sits directly above the portion of Taylor Gully that flooded Elm Grove and North Kingwood Forest twice last year. The vast majority of this excavation took place earlier this month.

*Rotating to the northeast, you can see the N3 detention pond, now mostly excavated. Miller estimates it’s still one half to one third full.*

Traveling up the eastern side of Woodridge, we can see tremendous erosion along the banks of N3. Those parallel stripes running down the sides of the pond are called rilling, shallow channels cut in the surface of soil by running water.

Simply Excavating Ponds Does Not Mean They Are Complete

Above, you can see that contractors did not yet have backslope interceptor swales in place. Nor did they have the pipes installed to channel intercepted runoff to the detention pond. Accordingly, runoff went over the edges of the pond and washed sediment into it.

The ponds will not be complete until backslope interceptor swales and pipes have been installed and grass planted along the edges of the ponds to prevent future rilling. The ponds also need concrete pilot channels to prevent erosion in the areas of constant use.

New Entrance on East

The new entrance to the subdivision (background below) will be an extension of Mace Street in Porter on the West. It will connect to Ford Road on the East.

*Looking straight east from the top of N3. Note two things: a channel designed to funnel standing water to N3 and the new entrance to the subdivision cut into the woods in the distance.*

Mace enters the western side of the subdivision just to the left of that silver roof in the distance of the shot below.

*Looking directly west across Woodridge Village while hovering over N3 on the eastern border.*

Why You Don’t Build On Wetlands

The last image above shows why you don’t buy homes built over wetlands, even if the Army Corps ruled that the wetlands weren’t jurisdictional. Any homes built here would likely have foundation problems from shifting soils. Of course, by then, the builder would be long gone.

In reviewing the complaints lodged with the Better Business Bureau against Perry Homes, most of them had to do with failure to honor warranties. Digging deeper, you can see many of the underlying complaints had to do with drainage, flooding, mold, and mildew.

There may be a connection between the type of property Perry develops and the problems that customers later develop. If Perry builds on this property, I pity any poor unsuspecting customers who fail to research its history.

No New Statements on Potential County Buyout

To my knowledge, neither Harris County, the City of Houston, nor Perry Homes have issued any public statements about the status of a buyout of this property. Harris County Flood Control District was considering using it to build a regional flood-detention facility. But County Commissioners added new conditions on any buyout in their last meeting.

Twice-flooded residents in Elm Grove and North Kingwood Forest eagerly await new details on the deal. Even if Perry completes work on all the ponds, it will likely not be enough to handle a true hundred-year rainfall event.

Ponds Still Would Not Likely Detain Hundred-Year Rain

Perry rushed to get plans permitted before new Atlas-14 rainfall standards went into effect. They would have required 30% to 40% more detention than the plans that the City and Montgomery County approved.

In the meantime, though, the new detention ponds will greatly reduce the risk of flooding from lesser storms. Also, the National Weather Service has reduced the risk of rain in the next several days. That may give Woodridge Village time to dry out and downstream residents time to catch up on their sleep.

Posted by Bob Rehak on 5/27/2020 with reporting from Jeff Miller

1002 Days after Hurricane Harvey

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Woodridge Village Pre-Cristobal Detention Pond Update