drainage impact Archives - Reduce Flooding

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.

*Where water exits on the downstream side 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.