Tag Archive for: FM1314

Mavera Wetlands Bite the Dust

Mavera, a 1700-acre new development in southern Montgomery County at FM1314 and US242 has finished clearing a large section of land northwest of the intersection and started pouring concrete. Signs welcome visitors to model homes. The area, once laced with wetlands now has a massive linear detention pond and uses FM1314 for outflow control.

Looking east just north of US242 on right from over FM1314. Note wet areas in foreground. They correspond to wetlands in map below.
Large green area immediately east of 1314 (diagonal) and north of US242 (bottom) correspond to wet areas in photo above. From US Fish and Wildlife Service National Wetlands Inventory Map

Areas west of FM1314 to Crystal Creek are also being cleared, but their current state of development is not quite as advanced.

Looking west from over FM1314 at area being cleared. This area has not changed much since January when I last posted about the development.

Likewise, an area east of FM1314 has expanded north, almost to Gulf Coast Road. Neither is its drainage fully developed.

Looking NE at current limit of development. Gulf Coast Road runs diagonally from left to right just beyond tree line.

Long, Linear Detention

The development relies on a wide linear detention basin – more than a mile long! And that’s only the part east of FM1314!

Looking east toward upstream end of detention basin.

Two smaller basins also exist. One is currently by a small park and recreation center.

Looking WSW. Note small retention pond and rec center in upper right.

In the photo above, also note the small swales that outline lots. Will some drainage go overland? Or is underground drainage just not connected to the detention basin yet?

Same spot. Lower elevation. Looking west from eastern portion of Mavera. I’m not seeing any drainpipes from storm sewers entering pond yet.
Note three new model homes near center of frame.

The Mavera website by Centex homes says the swimming pool at the rec center will open late this summer. Pulte will also build homes in Mavera.

Name Changes and a “Beat the Peak” Drainage Analysis

I previously posted about Mavera in January. Compare the pictures taken then.

The development seems to have undergone a series of name changes. The land was originally known as the Denbury Tract. Later, construction plans and a drainage analysis refer to it as Madera. But now, the builders are marketing it as Mavera.

Screen capture of cover sheet from drainage plan showing first two names of development.

The drainage plans for Mavera (aka Madera/Denbury tract) rely on a hydrologic timing assessment (see last line in screen capture above).

Harris County has tried to discourage neighboring counties from using such analyses. They encourage developers to get stormwater to streams and rivers faster rather than slower. The theory is that if you can beat the peak of a flood then you aren’t adding to it. But if everybody tries to “beat the peak,” eventually you shift the peak and flood downstream neighbors. For a full discussion of drainage issues, see my previous post.

The drainage analysis claims the development will have no downstream impact, but engineers didn’t study those areas. Nor did they study how new development upstream may have already shifted the peak of a flood.

Impact on FM1314?

Long linear detention schemes typically accelerate the flow of water. This one will rely on one culvert under FM1314 to hold back more than a mile of water collected from hundreds of acres. That will put a lot of pressure on FM1314 in a heavy storm.

Looking NW over FM1314. East is to the right. Water will flow west toward Crystal Creek out of frame to the left.

The roadway will act as a dam to detain water collected from almost all of the area shown in the photo below.

Looking east. Virtually all of the cleared area will drain through one culvert under FM1314. FM1314 runs left to right through the bottom of the frame. US242 is on right. Notice how channel is being widened, making culvert off-center. Did someone initially miscalculate or did plans change?

Let’s hope all that water doesn’t blow out the road like Colony Ridge drainage blew out FM1010 in Liberty County.

For Potential Home Buyers

FEMA mapped most of this area in a ten-year flood zone. For the sake of potential home buyers, let’s also hope the engineers got the drainage calculations right.

Potential homebuyers may also be interested in reading about the risks of building homes over wetlands.

Posted by Bob Rehak on 7/16/2022

1782 Days since Hurricane Harvey

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.

The MoCo/LJA Way: Build First; Work Out Drainage Details Later

LJA Engineers submitted a master drainage plan for the 2,200 acre Artavia development that Montgomery County approved. It has no detention ponds. And the drainage channels currently do not connect to the San Jacinto river. Even though LJA said they would connect to the river, the plans do not specify how, when or where. As you will see below.

Dead-end drainage. Currently, the Artavia drainage channel stops just short of the Liberty Materials Moorehead mine in the background. The San Jacinto River lies beyond the mine. This and all other aerial photos below were all taken March 6, 2020.

A Sand Mine Is Not the San Jacinto

The plans DO show the channel terminating in a sand mine between Artavia and the river. A spokesman for the sand mine said the developer is still trying to work out environmental and easement issues.

Aerial photos show the main channel stops about a 100+ yards short of LMI’s shipment facility. Meanwhile, during heavy rains, the dead-end drainage overflows onto surrounding properties. A spokesman for the mine claimed that the overflow flooded the mine last year and caused the dikes to break. He alleged that was the proximate cause for 56 million gallons of white sediment-laden water entering the West Fork.

Exhibit 2 of Artavia Drainage Impact Analysis from 9/20/2018 shows the project outfall in the middle of the LMI sandpit that borders Moorehead Road and the San Jacinto West Fork in Montgomery County.

The project manager for LJA did not return calls to explain their position on the dead-end drainage. And when asked for an explanation, the new Montgomery County Engineer (not the one who signed these plans) only referred me back to LJA.

Below are the drainage plans for Artavia, obtained by a Freedom of Information Act request to Montgomery County.

Several things have jumped out at me so far. LJA has not yet returned phone calls, so to me they remain…

Unaddressed Issues

Elevation Change Accelerates Flow

Elevation drops suddenly as you get near the river – 12 feet. That accelerates water flow and threatens the sand mine. As you can see above and below, the channel is like a firehose aimed at the mine. That mine has enough problems of its own. In the past, dike breaches have affected Lake Houston water quality; we don’t need more of that. The mine blames the breaches on water overflowing from the Artavia ditch.

Note how the water in this short section of Artavia’s drainage ditch does not even pond at one end and reaches halfway up the banks at the other. That shows the slope. The SJR West Fork is between the two sections of the mine in background.
Flow Rates Understated

LJA calculations appear to understate the volume and velocity of flow. They use a Manning’s coefficient of .035, a value associated with pasture/farmland or channels filled with stones and cobbles. The coefficient recommended for smooth channels is 0.022. The difference creates a 63% increase in velocity and a 60% increase in volume of flow. See for yourself. With no real way yet for the water to get to the river or under FM1314, that will cause water to pile up much faster.

Not too many cobbles and boulders in this channel. All sand and silt which is already blocking culverts.

LJA also uses pre-Atlas rainfall statistics in their calculations of 10-, 25- and 100-year peak flows. The new Montgomery County standard is 16.1 inches in 24 hours compared to the 12.17 that LJA used for the 24 hour, 100-year flood.

Did LJA use “good engineering practices” and model Atlas 14 to ensure that it actually contained the 100-yr, 24-hr storm? There’s an ethical issue here. Did they put public safety first? We don’t know because they didn’t say so in any of their documents.

No Mention of Wetlands

LJA never mentions wetlands in their analysis. However, the National Wetlands Inventory shows wetlands on Artavia property and other property Artavia drains through.

Wetlands on Artavia Property or property Artavia drainage would likely have to go through.
Threat to Pipeline

A pipeline crosses the Liberty Materials mine. High velocity flow through the mine could undermine and threaten that pipeline like it did at another Liberty mine and at the Triple PG mine on the East Fork.

Green line shows path of pipeline across across Liberty Materials Mine. White line shows current path of drainage ditch.
No Outlet

There’s no explanation for how Artavia will get water through the pit at the end of their ditch. They can not store Artavia’s runoff in the pit. Their pit is already filled to the brim with highly silty, turbid water. Another unauthorized discharge could affect water quality in Lake Houston...again!

Level of water in the pit that Artavia’s ditch would have to drain through. Pit is already overflowing. West Fork is in background. TCEQ measured suspended solids in pit’s water at 25X higher than river.
Threat to Mine

A representative for the mine owner says the mine owner doesn’t want more water in the pit. They can’t afford the cost from environmental or business perspectives. With the COVID-19 threat, construction activity is way down. So margins are slim. And they can’t afford to have water fill their deep pit where they dry mine.

“No Adverse Impact”

LJA claims the project will have no adverse impact on downstream properties. But it already has. Properties along Greenbaugh and in Oak Tree have flooded since Artavia started clearing land and filling in wetlands.

Oak Tree detention pond (behind camera) used to overflow into wetlands. Then Artavia started clearing and filling. Now water backs up into the 40+ homes in the small subdivision.

The Liberty Materials mine also alleges it was flooded by Artavia’s overflow, resulting in the discharge of 56 million gallons of silty water into the West Fork.

The day the West Fork turned white. TCEQ blamed LMI. LMI blamed Artavia.
Who Pays to Get Water Under FM1314?

LJA can only convey 68 cfs under FM1314. Meanwhile, TxDoT has not yet finished the design for a bridge. They hope to start bidding the job by the Fall of this year. Residents, not the developer, will pay for the improvement through the local municipal utility district.

Artavia ditch on north side of FM1314
Where water exits on the downstream side of FM1314
Channel downstream/south of FM1314.

LJA claims “The culvert crossings were designed to have capacity to convey 100-year storm events.” But they certainly aren’t doing that now.

Diverting Water From East to West Fork

The developer appears to be diverting water from the East Fork watershed to the West Fork watershed. See Section 1.4 and Exhibit One.

It would be harder to “beat the peak” to the East Fork. It’s 12 times farther away; water would take much longer to get there. So the diversion appears to be an attempt to avoid building detention ponds. But the diversion adds to flood volume in heavily populated West Fork areas where far more homes flooded during Hurricane Harvey.

Will LJA Figure It Out In Time?

For the sake of adjacent residents and businesses, let’s hope they figure these loose ends out before the next flood.

We heard of many of the same problems and promises on the Perry Homes Woodridge Village project north of Kingwood that LJA also engineered. Hundreds of homes flooded there twice last year.

Posted by Bob Rehak on 3/20/2020

934 Days after Hurricane Harvey

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.