Need to Reduce Impervious Cover to Prevent Flooding, Protect Water Quality

One of the most thought-provoking articles I have read lately is “The Need to Reduce Impervious Cover to Prevent Flooding and Protect Water Quality.” This brief, well-written article brings many flood-related issues into sharp focus. The Rhode Island Department of Environmental Management produced it. And the National Park Service helped fund it. Even though many of the recommendations would not fly politically in Texas, one might. The report is worth reading just to understand the factors that contribute watershed degradation and their relationship to each other.

Central Role of Impervious Cover In Variety of Issues

One main premise: As impervious cover rises above 10% there is almost always a measurable loss in water quality.

  • Between 10% and 25% impervious cover, these impacts increase, and pollution and flooding become evident.
  • 25%-plus impervious cover creates water quality impacts so severe that it may not be possible to restore water quality to pre-existing conditions.

The report claims that by keeping overall impervious cover below 10%, towns can ensure that land will be able to absorb and filter runoff from developed areas. This, they say, will also prevent excessive flooding, ecosystem impairment and contamination of water supplies.

A second major premise: Because water spends less time on site, infiltration declines dramatically. This can reduce groundwater in urban and suburban areas because there is not enough rainfall soaking into the ground.

The increased runoff that occurs during this process reduces groundwater recharge AND dramatically increases erosion.

Relationship Between Cover, Runoff, Other Measures

According to the EPA, under natural forested conditions, only about 10% of precipitation runs off the surface of a site. Another 50% soaks into the ground. And trees and other vegetation take up a surprising 40% and send it back into the atmosphere through the process of evapotranspiration. This protects the watershed and water quality.

But higher rates of runoff can impact and degrade them. With increasing development, both the rates of infiltration and evapotranspiration decrease as runoff increases. On average, runoff increases more than 5X between natural and fully developed conditions. But extremes can be much higher. See below.

Increases in Runoff Rates

Total runoff for a one-acre parking lot is about 16 times that produced by an undeveloped one-acre meadow.

The Need to Reduce Impervious Cover to Prevent Flooding and Protect Water Quality

Higher rates of runoff create several types of impacts:

  • Hydrological
  • Biological
  • Chemical
  • Physical
  • Health
Hydrological Impacts

The report sums up the hydrological impacts by saying, “Because the water is spending less time on site, infiltration declines dramatically. This is a particular concern in many urban and suburban regions, where groundwater has been reduced because there is not enough rainfall soaking into the ground. The increase in runoff that occurs during this process, combined with the loss of recharge to groundwater, has dramatic impacts on streams.”

Biological Impacts

Biotic integrity is the most sensitive indicator of impervious cover according to the report. “The decline of biological indicators is the first sign of stream degradation, and has been the most commonly studied result of increased impervious cover. As a result of a high percentage of impervious cover, naturally occurring aquatic insects, wetland plants, and amphibians decline and are gradually replaced by species that are adapted to pollution and flooding. … Impacts on overall biotic measurements were seen within a range of 3.6% to 15% impervious cover; the threshold for fish population health ranged from 3.6% to 12%, and macroinvertebrate health declined between a range of 8% to 15%.”

Chemical Impacts

“Impervious surfaces such as roads, driveways and parking lots collect a variety of chemical pollutants and hydrocarbons and discharge them to aquatic systems with every heavy rain.”

“The study found a strong correlation between water quality and percent impervious cover across a range of contaminants, including organic residue, nitrogen, phosphorus, dissolved chloride, and fecal coliform. In each case, as impervious surface increases so does the contaminant of concern.”

Physical Impacts

“Development of impervious cover in a watershed can happen so quickly that stream systems can’t adjust, resulting in erosion of stream banks and alteration of the stream bed, which tends to become straighter, deeper, and more U-shaped.”

“This…sends silt downstream, creating further damage.”

Natural portion of Ben’s Branch downstream from Woodridge Forest. Note heavy erosion and loss of trees. HCFCD spent most of 2019 and part of 2020 cleaning sediment out of the lower reaches of Ben’s Branch and will start another segment in January.
Health Impacts

“There is a strong correlation between increased impervious cover and increased risk to human health. A variety of chronic and acute illnesses are caused by microorganisms that either are swept into water bodies by increased runoff, or flourish because of increased nutrient pollution.”

“People can contract these illnesses through direct contact or through the consumption of tainted seafood.”

Smart-Growth Strategy Reduces Impervious Cover

So what are people to do. We need places to live. As population grows, so must developments.

The next sections of the report deal with strategies to control the growth of impervious cover. Most amount to fighting words in Texas, i.e., regulation and zoning. So here, I will only cover one strategy that the report discussed; it’s market based.

“Generally speaking, as density increases,” says the report, “the amount of impervious cover also increases. However, the overall pattern of development is also important.”

The next part of the report is counter-intuitive. It quotes the EPA, “…the large-lot zoning currently used to accommodate growth requires houses to be far apart, creating unnecessary impervious cover and encouraging more off-site impervious infrastructure, such as roads and parking lots.”

“Moreover, many of the surfaces remaining after large-lot development that are believed to be pervious actually behave like impervious surfaces. Research indicates that the volume of runoff from highly compacted lawns is almost as high as from paved surfaces.”

“The solution is to maintain the overall density [by] encouraging the use of more compact growth techniques that can reduce impervious cover on a per unit basis.”

“…by greatly reducing roads, utilities and other infrastructure costs, this approach can be profitable for developers while reducing house prices for consumers.”

Visually, the strategy looks something like this.

Food for thought as we turn over a new year. As land prices escalate, the market is driving new development in this direction anyway. Land now comprises 40% of the cost of a new home. A homebuilder told me it’s the single largest component of the cost of a new home.

But when I look at Scenario C, it raises a question. What’s the incentive to preserve the open space around the development?

Posted by Bob Rehak on 12/31/2020

1220 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.

Final San Jacinto River Basin Master Drainage Study Released Today, Recommendations Revealed

This afternoon, Harris County Flood Control District (HCFCD), San Jacinto River Authority (SJRA), Montgomery County, and City of Houston released final results of the massive San Jacinto River Master Drainage Plan (SJMDP) study which began in April 2019.

It will take weeks to digest all this information. It consists of:

That’s more than 3,600 pages, EXCLUDING the zipped materials.

Executive Summary Summarized

The executive summary includes a heat map of historically flooded areas, estimated structural damage costs in the next 50 years, and projected population growth during the same period. Not surprisingly, the three fasted growing areas (West Fork, Spring Creek and Cypress Creek) also show the most projected damage.

The summary then proceeds to flood-damage-reduction strategies. They include:

  • Detention Basins
  • Channel Improvements
  • Floodplain Preservation
  • Buyouts
  • Flood Warning Improvements
  • Floodplain Re-mapping
  • Policy updates
  • Formation of a vision group
  • Flood Response Improvements (Evacuation planning, protection of critical facilities such as hospitals, etc.)

The exec summary also lists the top sixteen project priorities, estimates their costs, outlines possible sources of funding, and lays out next steps.

Project Location Map
Project rankings. Note: Rankings do not necessarily coincide with numbers on map above.

“Benching” in reference to the Kingwood Area involves lowering the floodplain near the West Fork to increase flood capacity. This link shows how a similar project in California worked.

The proposed projects will provide tangible benefits, including reduction in the number of at-risk structures for a range of storms as shown in Figure 1.10 below.

With these projects in place, the level of a 100-year flood at I-69 and the West Fork could be reduced by 5.94 feet, Likewise, where Caney Creek meets the East Fork, the 100-year flood would be reduced by 2.82 feet.

Next Steps

That’s good news indeed for everyone who lives in the San Jacinto Watershed. With this information now in hand, we now can quantify the benefits of projects, priorities them, and get on with the hard work of actual mitigation.

More news to follow.

Posted by Bob Rehak on 12/30/2020

1219 Days since Hurricane Harvey

Flash Flood Watch

The National Weather Service has issued a flash flood watch from 6PM tonight through Thursday afternoon. In the north Houston Area, it includes:

  • Houston
  • The Woodlands
  • Coldspring
  • Trinity
  • Shepherd
  • College Station
  • Huntsville
  • Conroe
  • Livingston
  • Madisonville

The watch extends much farther north and west. It includes the Dallas/Fort Worth Area, Oklahoma, Arkansas where NWS predicts up to six inches of rain.

Where heaviest rains will fall.

Jeff Lindner, Harris County Meteorologist reports increasing risk of excessive rainfall along and west of US 59 and west of SH 288. A strong upper level storm system will combine with increasing moisture and a slow/stalling surface frontal boundary over SE TX tonight. The stalling boundary will produce training.

Lindner adds, “Heavy rainfall of 1-2 inches per hour looks possible and this could be maintained for several hours along/near the stalling front. Where the heaviest rains fall will be determine where the front slows and stalls and at this time areas from Wharton and Fort Bend into western Harris and then northward into Montgomery County have the highest chances.”

“Widespread rainfall amounts of 2-4 inches with isolated totals of 5-6 inches will be possible,” says Lindner. “We need to watch for flooding.”

Areas At Highest Risk of Flooding

While grounds west of I-45 are especially dry, Lindner predicts that the entire San Jacinto basin (west, east, and mainstem) and Trinity basins will be affected – especially in the longer term as water works its way downstream.

Northwest and western Harris County will likely see the highest totals. Responses on the creeks in those areas are likely early Thursday.

Lindner believes most watersheds will be able to handle incoming rainfall up to 4.0 inches. Should western Harris County get more, minor flooding would be possible. Especially along the lower end of South Mayde Creek, the upper end of Little Cypress Creek, the upper end of Spring Creek, and the lower end of Keegans Bayou.  

As of noon on Wednesday, the SJRA shows Lake Conroe at 199.41, slightly below its normal level.

The City of Houston began lowering Lake Houston at noon Wednesday as a precautionary measure. Property owners should secure property along the shoreline. Lake levels can be monitored in real time by visiting the Coastal Water Authority website. 

Heavy rainfall will end Thursday afternoon.

PRECAUTIONARY ACTIONS

A Flash Flood Watch means that conditions may develop that lead to Flash Flooding. Flash Flooding is a very dangerous situation. You should monitor forecasts and be prepared to take action should Flash Flood Warnings be issued. See:

Do not enter or cross flowing water or water of unknown depth.

Posted by Bob Rehak on 12/30/2020 based on information from the National Weather Service and HCFCD

1219 Days since Hurricane Harvey

When Developers Claim No Detention Ponds are Necessary…

Harris County residents are spending billions on flood mitigation, even as developers upstream claim they need no detention ponds. So are those developers’ claims valid? Maybe. Maybe not. A ReduceFlooding.com investigation into one found the developer’s engineer consistently mischaracterized soil types in a way that underestimated runoff from the property by 6X to 9X! Soil type is just one of the factors that that determine whether a development needs detention ponds, but it’s a big one.

Understand also that regulations vary widely from county to county and city to city. Some may not allow the type of study that the engineer above performed. But Liberty County does. And so does Montgomery County for developments under 650 acres.

To see whether a new development near you accurately reflects soil types in its drainage analysis , follow these steps.

High-Level Outline

You will need to:

  1. Obtain the developer’s drainage analysis and construction plans.
  2. Look up soils in the development via the USDA’s Web Soil Survey.
  3. Compare the “Curve Numbers” used by engineers in Step 1 to Soil Groups in the development from Step 2.

Curve Numbers represent the rate of rainwater infiltration numerically. But USDA estimates infiltration by grouping soils alphabetically. So comparing them requires translation. Not to worry. Just look them up in the tables below.

Your Goal: To see if the developer accurately depicted the soils in his development.

Engineers can alter inputs to provide the desired outputs. And this is one of the main ways they can do it if they’re going to cheat on the volume of detention ponds necessary. See more below.

Background

Different soils absorb water at different rates. What doesn’t soak in runs off. And under developed conditions, it can run off quickly. That’s why developers build detention ponds. But detention ponds cost time and money. They also reduce the amount of salable land.

So developers and their engineers have a large incentive to avoid building detention ponds…if they can. By misrepresenting soils, unscrupulous engineers can make it look like more rainwater is soaking in, so they have less runoff to handle. Most people don’t have the expertise to challenge engineers and the engineers know it. So here’s one way to check their work before hiring your own consulting engineer.

Step One: Request and Review Plans

To obtain the developer’s plans, file a FOIA (Freedom of Information Act) or TPIA (Texas Public Information Act) request:

  • Find the County Engineer’s email address online.
  • Compose a short email.
  • Put FOIA or TPIA REQUEST in the title.
  • Specify the subdivision.
  • Ask for the Drainage Analysis AND Construction Plans for ALL parts of the development.
  • To speed up the process, request electronic delivery.

By law, the city or county has ten days to comply.

When you get the plans, check the construction docs to see if they have any detention ponds included.

Then look at the drainage analysis. It should contain a discussion about soils.

Also look for numbers on both the Drainage Analysis and Construction Plans preceded by “CN.” CN stands for Curve Number. That’s a numeric representation of the rate of infiltration for soil groups that engineers use in their runoff calculations. Note the curve numbers for future reference.

Step Two: Look Up Developer’s Soil Types Via USDA

USDA has surveyed soils of every county in Texas. They make it easy to see what kinds of soils are present in any development. USDA groups them via rate of infiltration, but assigns LETTERS to groups, not CURVE NUMBERS. (You will translate those in the next step.)

To determine the soils and their groupings:

  1. Go to this link: https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx.
  2. Click on AREA OF INTEREST (AOI) tab. Then NAVIGATE to the development in question.
  3. Over the map, you’ll see the words AOI in two red buttons, one rectangular, the other a polygon. Pick one and click on it. The cursor will then turn into a plus sign.
  4. DRAG the plus sign over the Area of Interest to DEFINE the AOI. A cross-hatched area should appear.
  5. Click on the SOIL MAP tab. A white box will appear on the left showing all soils in the AOI, their acreage, and the percent of the AOI that they comprise. Contours will appear on the map showing soil-type locations.
  6. Click on the SOIL DATA EXPLORER tab.
  7. In the row under it, click the SOIL PROPERTIES AND QUALITIES tab.
  8. From submenu, click on SOIL QUALITIES AND FEATURES.
  9. From the next submenu, click on HYDROLOGIC SOIL GROUP.
  10. Click VIEW DESCRIPTION to learn about differences between soil groups, then…
  11. Click VIEW RATING. Your map should turn into colored groups. Underneath the map, a list of all the soils in the AOI will appear with their Group (A, B, C or D). Group A soils have the highest rate of infiltration; Group D the lowest. Most important, you can see the PERCENT of the AOI that each soil in various groups comprises.
  12. For future reference, click PRINTABLE VERSION in the upper right. This lets you save your findings as a PDF or printout. The file will include: the MAP, a LEGEND, SOIL GROUPS, each group’s PERCENT OF THE AOI, and a SUMMARY of what the different groups mean.
Screen capture for newly developing part of Colony Ridge shows that only 3.2% of the soils should be classified lower than Rating Group D. See comment below about mixed groups after development. This represents undeveloped land.

After you do this once, the second time should take less than five minutes. Next…

Step 3: Compare USDA’s Soil List with Developer’s Curve Numbers

Now you need a way to compare the developer’s Curve Numbers with USDA’s soil groups. TXDoT does the “translation” for you in the two tables below taken from this page.

Table 4-17 shows infiltration rates by soil group in inches per hour. They range from a high of .45 inches to a low of 0.

From TXDoT

Table 4-18 shows Curve Numbers for Development Type and Soil Group. Note how many houses per acre there are from the construction plans. Then look up the corresponding Curve Numbers under each Soil Group.

Table from TXDoT

Create a weighted average of your findings. For soil groups A/D, B/D and C/D, use the curve numbers that correspond to D. That’s because, after development, soil will be compressed, reducing the rate of infiltration. AND note the last line: “Developing urban areas: Newly Graded.” Group D has a curve number of 94, close to the theoretical upper limit for runoff.

Step 4: Evaluate Your Findings

Did the developer use the right curve numbers for USDA soil types? In a 22,000 acre development in Liberty County with almost no detention, I found virtually all Curve Numbers associated with Group A soils (those having the highest rate of infiltration). But the vast majority of soils actually had the lowest rate of infiltration and the highest rate of runoff.

That meant that the development had 6-9X more runoff than the engineer’s runoff models showed.

Comparing TXDot Table 4-18 to Table 4-17

Curve numbers ALL erred in the direction that favored the developer’s profits.

If you find errors like that, demand explanations. Keep the system honest. Let people know you’re checking. Your home could be the next one to flood. In egregious cases, you may want to hire a consulting engineer to verify whether the rest of the analysis is valid and meets local regulations.

Posted by Bob Rehak on 12/29/2020

1218 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.

Widespread Heavy Rains Predicted Later This Week; Minor Flooding Possible

Expect heavy rains Wednesday night into Thursday – New Year’s Eve morning – as two powerful storm systems collide over Texas this week. One front will dip down from Canada, then another from California will ride up over it producing a variety of threats.

Predicted accumulations for the next 7 days. Chances of rain will increase on Wednesday and peak Wednesday night at 90%. Chances of rain will decrease on Thursday, New Year’s Eve, but peak at 70%.

The National Weather Service Storm Prediction Center predicts a marginal risk of severe storms, damaging winds and tornadoes for areas west of I-45. However, the threat from heavy rains will be more widespread. Slow-moving or training showers and thunderstorms will produce 1-2 inches for the entire region and 3-4 inches in isolated locations. One normally conservative forecaster predicts up to 5 inches. North Texas will have it worse.

Impact on Lake Houston Area

In the Houston area, the most rainfall will be east of I-45 and north of I-10 or across the region’s northeast counties.

Jeff Lindner, Harris County Meteorologist

Minor Flooding Possible

Most area streams should be able to handle the heavy rains. However, Lindner, says area watersheds could swell. He blames higher than normal run-off due to low evaporation rates and dead/dormant vegetation. The National Weather Service predicts this may result in minor flooding of low lying, poorly-drained areas.

Holiday travel may be impacted if and where accumulations occur. Take note, especially if you’ve been visiting families in north or central Texas.

How Fronts Will Interact

The strong cold front should be off the coast by Thursday morning. However the Pacific front will lift lots of moisture over the incoming cold air mass. The cooling caused by the rising air (advection) will trigger precipitation. Lindner says areas from northwest of a line between Columbus to Huntsville may see rain mixed with sleet/snow.

Space City Weather predicts potential for heavy storms on Wednesday and Wednesday night with much of the area receiving 2 to 3 inches of rainfall. “We cannot entirely rule out this precipitation turning into a wintry mix north of Houston later on Thursday,” says the popular, normally conservative service. They say they can’t rule out a few isolated areas with 5 inches. They also note that forecast certainty will improve by Tuesday, as higher-resolution models come into play.

NWS predicts cooler and drier conditions Friday through the first weekend of the new year.

Posted by Bob Rehak on 12/28/2020

1217 Days since Hurricane Harvey

Construction of Long-Awaited Edgewater Park to Begin in 2021

Andy Li and Kelly Schafler reported in Community Impact that Harris County Precinct 4 should begin construction on Phase 1 of Edgewater Park by mid-2021. Phase 1 includes a 19-acre park, parking lot, boat launch, fish-cleaning station, restroom, concession building, and detention pond. Cost: $2.3 million. Location: Between Hamblen Road and the San Jacinto West Fork, immediately east of US59. See below.

Looking north at the future site of Edgewater Park from over the San Jacinto West Fork and the new UP Railroad Bridge. US59 on left.
Looking South at Phase 1 of the future Edgewater Park. US59 on right. Hamblen Road in foreground. Humble in background.

Related Projects

Phase 2 will include the cypress ponds north of Hamblen and east of Phase 1. It also includes a potential reroute of Hamblen Road to unsnarl traffic and avoid

The park will provide a second boat launch in the Humble/Kingwood Area that will be open to the public. KSA’s boat launch at River Grove Park is open only to Kingwood residents with K-Stickers.

Two hike and bike trails are also planned as part of improvements. The first trail will connect the Spring Creek Greenway on the south side of the West Fork with the Townsen Park ‘n Ride. The second will connect Edgewater Park with River Grove Park and the Kingwood Trail Network. The Houston Parks Board also hopes to begin work on the second trail in early 2021.

Path of the West Fork Trail being built by the Houston Parks Board.

The old Bevil Jarrell Memorial Bridge will connect trails on both sides of the river.

Reasons for Delays

“Getting approvals for both the right of way and the design to continue the Spring Creek Greenway under the existing railroad bridge took much longer than anticipated,” said Dennis Johnston, Precinct 4 Parks Director.

Back in October 2018, I reported that the County hoped to begin construction of the park in 2019. However, construction of the Union Pacific Railroad Bridge, permitting, and buyouts of the Riverview Townhomes in Forest Cove have all taken much longer than expected.

The Harris County Precinct 4 Parks website already shows the park under construction, but I haven’t seen activity there since the County put up a fence two years ago. Here’s what the plans looked like in 2018 when the County announced the project.

Tentative plans for a new Edgewater Park at Hamblen Road and Loop 494

Posted by Bob Rehak on December 27, 2020

2016 Days since Hurricane Harvey

Webster, Spurlock Add Storm Water Solutions to Lawsuit for Elm Grove Plaintiffs

On December 17, 2020, Jason Webster and Kimberley Spurlock, lawyers for the plaintiffs in the 2019 Elm Grove lawsuits, added a ninth defendant in their eighth amended petition. The defendant is Storm Water Solutions, LLC at 16110 Hollister Street in Houston.

Complete List of Defendants

Defendants now include:

  • Developers:
    • Perry Homes, LLC
    • Figure Four Partners, LTD
    • PSWA, Inc.
    • Concourse Development, LLC
  • Contractors:
    • Rebel Contractors, Inc.
    • Double Oak Construction, Inc.
    • Texasite LLC
  • LJA Engineering, Inc.
  • Storm Water Solutions, LLC

Who Was Responsible for What and When

The eighth amended petition provides an overview of who allegedly did what and when, before Elm Grove flooded on May 7th and September 19th last year when water from Woodridge Village invaded Elm Grove and flooded up to 600 homes.

The developer defendants hired LJA, which had prepared the drainage plans for Woodridge Village, to prepare bid documents, plans and specifications, all of which required a stormwater pollution prevention plan (SWPPP) for all potential contractors. The developer defendants and LJA, through the municipal utility district, hired Rebel, Double Oak, and Texasite. Rebel and Double Oak then obtained the necessary permits for the SWPPP.

Bombshell Allegations

Here’s where it gets interesting. Sometime after that, the developers hired Storm Water Solutions to implement the SWPPP. However, they allegedly told Rebel and Double Oak that they did not have to comply with the specifications in the SWPPP.

The southern part of Woodridge Village on May 9 from a drone. Elm Grove is on left. Note lack of any perimeter sediment controls. Screen capture from Jim Zura video.

One day after the May 7th flood, the developers hired Concourse to inspect the detention ponds on the development. Plaintiffs allege that Concourse did not advise the developer defendants to makes any changes. The plaintiffs also contend that ALL defendants failed to comply with the SWPPP. The TCEQ cited both Rebel and Double Oak for violations of their permits after the May 7th flood for failure to install sediment controls.

The suit alleges that the developer defendants failed to supervise and ensure Storm Water Solutions complied with the SWPPP.

Twin culverts at the county line were severely constricted by sediment after the May 7th flood. Note lack of sediment controls such as gabions (wire baskets filled with rock).

Specific Allegations against Storm Water Solutions in Lawsuit

Storm Water Solutions website claims the company provides “complete storm water regulatory compliance to land developers, commercial and residential builders, general contractors, and utility districts.”

But in Count 10, Paragraph 76, the suit charges Storm Water Solutions with Negligence, Negligence Per Se and Gross Negligence for both the May and September floods. Specifically, the alleged negligence includes failing to:

  1. Create an adequate storm water pollution prevention plan;
  2. Implement a storm water pollution prevention plan;
  3. Comply or follow the Storm Water Pollution Prevention Plan;
  4. Install reinforced filter fabric fences around the Development;
  5. Install adequate reinforced filter fabric fences around the Development;
  6. Comply with Texas Pollutant Discharge Elimination System Construction General Permit No. TXR150000;
  7. Supervise the Contractor Defendants’ compliance with the Storm Water Pollution Prevention Plan;
  8. Enforce the provisions of the Storm Water Pollution Prevention Plan;
  9. Enforce and/or implement the best management practices under the Storm Water Pollution Prevention Plan for the Development;
  10. Implement the proper control measures on the Development;
  11. Ensure a sedimentation basin was constructed at the Development;
  12. Inspect the Development for failure to comply with the Storm Water Pollution Prevention Plan;
  13. Modify the best management practices after the May 7, 2019 occurrence;
  14. Comply with the plans and specifications for the Development;
  15. Pay proper attention;
  16. Provide notice or warning; and,
  17. Coordinate activities and/or conduct.

It also alleges they allowed:

  1. Storm water runoff into Plaintiffs’ properties;
  2. Discharge of storm water from the Development.

Stormwater Pollution Prevention Plan Requirements, Objectives

The EPA provides this easy to follow document about what a SWPPP should include. SWPPP requirements include a site map, description of pollutant sources, controls to reduce pollutants, and maintenance and inspection procedures. Plans should also describe who:

  • Is on the stormwater pollution prevention team?
  • Will install structural stormwater controls?
  • Will supervise and implement good housekeeping programs, such as site cleanup and disposal of trash and debris, hazardous material management and disposal, vehicle and equipment maintenance, and so on?
  • Will conduct routine inspections of the site to ensure all BMPs are being implemented and maintained?
  • Will maintain the BMPs?
  • Is responsible for documenting changes to the SWPPP?
  • Is responsible for communicating changes in the SWPPP to people working on the site?
State of the S2 detention pond on May 9, 2019.

Plan objectives typically include:

  • Site stabilization ASAP
  • Protecting slopes and channels
  • Promoting infiltration of stormwater
  • Controlling the perimeter of the site
  • Protecting receiving waters adjacent to the site (Taylor Gully)
  • Following pollution prevention measures.
  • Minimizing the area and duration of exposed soils.
The southern part of Woodridge Village on May 9 from the ground.

For the complete text of the Eighth Amended Petition, click here.

Posted by Bob Rehak on 12/25/2020 with thanks to Jim Zura

1214 Days after Hurricane Harvey and 461 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.

Colony Ridge Drainage Reports Misrepresent Soil Types, Underestimate Runoff; Many Reports Missing

Drainage reports for the controversial Colony Ridge development in Liberty County misrepresent soil types in a way that underestimate runoff by as much as 6X to 9X. As a consequence, the massive development’s ditches and detention ponds are undersized. That contributes to downstream flooding. 

In addition, virtually all of the drainage reports supplied by the county in response to my FOIA (Freedom of Information Act) request were marked “preliminary” and many were missing. The Assistant County Attorney did not explain why. She said only that she had supplied all documents “responsive to” my request that the county had.

Let’s review soil types first.

USDA Findings Contradict LandPlan Engineering’s

U.S. Department of Agriculture (USDA) classifies soil into four groups (A, B, C, D) that represent rates of rainwater infiltration. Group A has the highest rate of infiltration and D has the lowest. Think gravelly sand vs. clays.

When USDA analyzed soils in the Colony Ridge area, it found less than 2% in Group A. However, virtually all  of LandPlan Engineering, PA reports used model inputs associated with soils in Group A. Hmmmm. Quite a contradiction. LandPlan is the engineering company for Colony Ridge that produced the drainage studies.

USDA says almost no Colony Ridge soils have the lowest rate of infiltration and LandPlan says almost all do.

Comparison of USDA Soil Survey and Landplan Engineering documents

Colony Ridge also has small percentages of soils in intermediate categories:

  • B = 2.3%
  • C = 1.2%

Finally, USDA shows some mixed soil types within Colony Ridge. For instance B/D or C/D. But a flood expert and professional engineer, who spoke on condition of anonymity, said that with mixed soil types, LandPlan should have classified them as Group D. “For all of the areas with B/D and C/D, you should assume that they are D because the soil is disturbed and probably compacted in some way.” So almost 95% of the soils should should be represented with a rate of infiltration equivalent to Group D.

Compacted soil on residential Colony Ridge lot. Note ponding water and damp soil at right. Note also the erosion under back fence next to ditch. Insufficient capacity of ditch contributed to erosion.

Soil Classification Consistently Off in One Direction

Liberty County supplied 39 drainage and construction documents in response to ReduceFlooding.com’s FOIA request. The soil classifications, as shown by the Curve Numbers in the reports all erred in one direction – the direction that favored the developer’s profits.

Almost 95% of the soils should be classified in the least porous group. But virtually all of the “curve numbers” reported by LandPlan Engineering are associated with the most porous group.

By classifying the soils as more porous than they actually are, the engineers could claim there was less runoff and therefore reduce the size of ditches. Likewise, they could reduce or eliminate detention ponds.

What Curve Numbers Mean

Curve Numbers (abbreviated as CN in drainage reports and construction docs) numerically represent the rate of rainwater infiltration. They correlate primarily to soil groups, but also land use and surface conditions. For instance, after soil is paved with concrete, the curve number goes up (indicating less infiltration).

Theoretically, CNs can range from 0 (100% rainfall infiltration) to 100 (totally impervious). In practice, however, the lowest CN is 30 and the maximum is 98, according to the USDA Natural Resources Conservation Service.

What Should Colony Ridge’s Real Curve Numbers Be?

TxDoT’s Online Hydraulic Design Manual shows curve numbers for residential developments (see Curve Number Loss Model section).

For 1/2 acre lots with average impervious cover of 25% (typical of Colony Ridge), USDA estimates the following Curve Numbers: 

  • Group A = 54
  • Group B = 70
  • Group C = 80
  • Group D = 85

LandPlan Engineering used Curve Numbers mostly associated with Group A. They should have used values mostly associated with Group D. See example below from the Drainage Report for Colony Ridge’s Bella Vista Subdivision Section 1.

Excerpt from Bella Vista Drainage Report. Note Curve Number for pre-existing conditions associated with Group A soils, i.e., those having the highest rate of infiltration.

USDA’s soil report for Bella Vista Section 1 shows that the soils are Group C (69%) and Group D (31%). According to USDA and the flood expert/engineer above, the Curve Number used to calculate detention requirements for the “developed condition” should have been closer to 85. But the Curve Number on which the detention is based is 56 (see below) – a number associated with Group A soils. Note: this is a subset of the larger report for Colony Ridge discussed above.

Bella Vista Section 1 shows post-development Curve Number of only 56, associated with the highest rate of infiltration.

Importance of Accurate Curve Numbers

While Group A can absorb .3 to .45 inches of rainfall per hour, Group D absorbs only 0.00 to 0.05 inches per hour. Had LandPlan used the correct values, they would have had to accommodate 6X to 9X more rainfall.

Texdot

That would have required building larger ditches and detention ponds. But by using the Group A numbers, they could claim:

  • Floodwaters were soaking in.
  • Their roadside ditches could hold runoff. 
  • No, fewer, or smaller detention ponds were necessary.
Loss rate for each soil group represents the amount of rainfall infiltration per hour. Infiltration for Group A is at least 6-9X higher than Group D. Source: TXDoThttp://onlinemanuals.txdot.gov/txdotmanuals/hyd/hydrograph_method.htm

This suggests that LandPlan altered model inputs to achieve the desired output. The flood expert above called LandPlan’s Curve Numbers, “just plain wrong.” “Soils like that just don’t exist in this area,” he said.

Developer’s Environmental Consultant Confirms USDA’s Accuracy

One of the developer’s own environmental consulting firms confirmed the accuracy of the USDA’s and flood expert’s soil observations. Berg-Oliver developed a wetland assessment for the developer in 2014. “The United States Department of Agriculture (USDA) Web Soil Survey of Liberty County, Texas, was, for the most part, reasonably accurate in identifying the basic soil types on the property…” says the report. However, nobody in Liberty County, according to the documents supplied, questioned or even noticed the conflict between LandPlan, Berg-Oliver and USDA.

The Berg-Oliver report was NOT one of the documents supplied by Liberty County. I found it attached to an affidavit by the former Liberty County Engineer in a lawsuit between the ex-Mayor of Plum Grove and the developer of Colony Ridge.

Role in Downstream Flooding, FM1010 Washout, Erosion

Plum Grove residents report increases in the severity and frequency of flooding since Colony Ridge started clearing land. Water accumulates faster and peaks higher, they say, because of the loss of trees and wetlands. But the extra runoff that engineers have not accounted for in their calculations makes those problems even worse. That’s because Colony Ridge ditches and detention ponds can’t retain the extra runoff.

Mischaracterization of soil types likely also played a role in the washout of FM1010.

During Harvey, Colony Ridge drainage ditches discharged so much water into Rocky Branch that the stream then overtopped and destroyed FM1010. The blowout worsened during Imelda. No one has repaired it yet.

Finally, the “tractive” force (power) of rapidly moving water through undersized ditches accelerated erosion. Downstream, the eroded sediment built up and forms sediment dams that back water up, flooding additional homes in Plum Grove, or near the San Jacinto East Fork and Luce Bayou.

“Preliminary” Plans

My Freedom of Information Act (FOIA) request to Liberty County asked for ALL drainage analyses/surveys and construction plans for Colony Ridge subdivisions. However…

  • Virtually all of the plans that Liberty County supplied were marked “preliminary.” 
  • None was marked final or approved. 
  • Many were missing altogether. 
  • NOT ONE bore the signature, stamp, or comments of the Liberty County engineer or his agent, LJA Engineering. 

The 39 reports/surveys and plans are too large to post here; they comprise 1.5 gigabytes.

Liberty County has yet to clarify why so many of the plans are named “preliminary” or were missing. However, the Assistant County Attorney did verify that she supplied all Colony Ridge documents that pertained to my request.

Missing Documents

Here is a list of NINETEEN missing documents:

Missing Drainage Plans/Analyses (16)
  • Bella Vista – Section 2
  • Camino Real – All Four Sections
  • Grand San Jacinto – All Five Sections
  • Montebello – All Four Sections
  • Sante Fe – Sections 1 and 2
Missing Construction Plans (3)
  • Camino Real – Sections 1 and 2
  • Grand San Jacinto – Section 2

The problems in the 39 documents that Liberty County DID supply make one wonder what’s in the 19 they DID NOT supply.

Fallacy of Government Oversight

Not only are many documents missing, the ones Liberty County does have appear to be based on false assumptions about soil types.

I’m told by reputable engineers and floodplain administrators that this problem is common. Developers can always find engineers willing to sell favorable opinions – much like junkies know how to find doctors willing to write prescriptions for oxycodone.

Most people don’t have the expertise to evaluate reports like LandPlan’s. The hired guns know it and count on it. Cities and counties could hire engineers to thoroughly check these plans, but they don’t … for several reasons:

  • Awareness of this problem is low.
  • There’s no public pressure for counties to hire plan-checking engineers.
  • Developers make huge political contributions.
  • Floods often happen years after buildout of subdivisions.

By the time people flood, it’s too late. The damage has already been done. And the people responsible are often long gone.

Posted by Bob Rehak on 12/26/2020

1215 days since Hurricane Harvey and 464 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.

Preserve What Makes Lake Houston Area Unique

During my life, I’ve explored 49 states. But the state I choose to call home is Texas, and there’s no place I’d rather live in Texas than the Lake Houston Area. That’s in large part due to our proximity to nature and our fierce commitment to preservation.

This country has a lot to love. But if you love being close to nature, jobs, the arts, education, transportation, and medical care, no place I’ve found offers a better balance than the Lake Houston Area.

Our Unique Selling Proposition

You can find everything in that list above in every major metropolitan area in the country…with one exception – nature.

Sure, when you’re in other cities, you can get in your car and drive several hours to enjoy nature. Here, it’s outside your back door and down the block. Along hundreds of miles of greenbelts that wind through your neighborhood and along waterways. In the country’s largest urban nature park – the 5,000-acre Lake Houston Wilderness Park. And in the national forests and wildlife refuges that surround us.

Looking north toward Lake Houston Wilderness Park. It’s six times larger than New York’s Central Park.
Looking south along the East Fork toward Lake Houston in background over Kingwood’s East End Park, home to more than 140 species of birds, many of them threatened or endangered.

The Value of Nature

Nature is more than a place to explore. It’s a natural sedative. It’s restful. It quiets the soul and the mind. It sustains sanity. It’s an evolutionary anchor in a fast-changing society. The womb of the world. A protective refuge from conference reports, tax forms, sales quotas, deadlines, and performance reviews. It’s a place to just breathe, bask, and be.

Property Rights and Profit

To developers and sand miners who shout “property rights” in their quest for profits, I would say, “Go ahead, develop your land as you wish. Just realize what you’re selling. Don’t destroy the uniqueness that makes your property worth more than it otherwise would be if you cut down the forest, filled in the wetlands, and turned natural streams into concrete ditches.

“Hey, Dear. Let’s take the kids for a walk along the ditch. I hear the sand mine’s water turned neon green! It’ll be fun. What do you say? We can bring the dog. He’ll find plenty of dead frogs to eat.”

Yeah, people will commute an extra hour, and pay a premium to live ten feet from noisy neighbors and that!

Colony Ridge development east of Plum Grove, TX. Not long ago, this was all forests and wetlands. It’s less than three miles from Lake Houston Wilderness Park.
Water at Hallett Mine on West Fork. Photographed 12/7/2020.
Looking west up the West Fork of San Jacinto toward 20 square miles of sand mines. Photo taken in September. Water flows toward camera and then left out of frame into Lake Houston,

Plea for Preservation

So, developers and miners, please think carefully before exercising your property rights. Once the forest is gone, it’s gone forever. You will alter the watershed inalterably. Preserve the wetlands that keep surrounding areas from flooding. Preserve the “brand” you’re selling. You’re not just selling sticks and bricks. You’re selling safety.

Preserving nature preserves profit potential for generations to come.

Posted by Bob Rehak on 12/23/2020

1212 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.

“One of the Best Land Developers in Liberty County”

In 2016, one of the owners of the Colony Ridge Development in Liberty County tried to sue the former Mayor of Plum Grove for defamation. The developer alleged that the mayor bad-mouthed his development while making false statements. The judge ultimately dismissed the suit.

But as part of the lawsuit, Louis W. Bergman, III, PE, provided a glowing affidavit, lauding the development. Bergman served as the County Engineer and Flood Plain Administrator at the time. He also issued licenses and permits for Liberty County. In that regard, he reviewed all plat submittals for compliance with Texas statutes and Liberty County’s subdivision rules.

What a Difference Four Years Makes

Below are some quotes from Bergman’s affidavit. I took all the pictures from a helicopter on 12/7/2020 while flying over Colony Ridge. They show how quickly conditions have deteriorated there.

“In my experience, Colony Ridge has been one of the best land developers in Liberty County.”

Louis W. Bergman, III, PE in Paragraph 3

“Colony Ridge … complies with all applicable laws and regulations imposed on a land developer.”

Louis W. Bergman, III, PE in Paragraph 5

“I respect Colony Ridge Development … and their business because they have earned my respect by representing themselves with integrity and working to build quality developments.”

Louis W. Bergman, III, PE in Paragraph 15

“In my opinion, Colony Ridge Development has built some of the best infrastructure for residential neighborhoods in Liberty County and Colony Ridge Development’s lots do not create a health, safety, or welfare threat to Liberty County.”

Louis W. Bergman, III, PE in Paragraph 11

“I have heard [the former mayor of Plum Grove] make statements that Colony Ridge Development has violated environmental laws, such as regulations by the Texas Commission on Environmental Quality, and I disagree with these statements and believe they are false statements.”

Louis W. Bergman, III, PE in Paragraph 12
Merry Christmas from Colony Ridge

The TCEQ might disagree with Bergman on that last point. The TCEQ has an enforcement action against Colony Ridge. TCEQ’s investigation alleges their development practices may jeopardize human health. The TCEQ has also cited the development’s water and sewer supplier for lead in drinking water and sewage spills.

Strategic and Mitigation Plans Back Bergman Up

Liberty County’s own Strategic Plan cites the need to improve drainage infrastructure and building codes. But it doesn’t mention Colony Ridge by name.

Likewise for Liberty County’s Hazard Mitigation Plan. It discusses the need to improve a variety of safety issues such as drainage; street lighting; electrical service; communications infrastructure; high percentages of mobil and self-built homes; emergency access; and flooding … in every city in the county … all without mentioning Colony Ridge by name.

So maybe Bergman was right after all. Maybe this IS the best that Liberty County has to offer.

But I suspect the judge who dismissed the lawsuit, might take exception.

Posted by Bob Rehak on 12/21/2020

1211 Days since Hurricane Harvey and 459 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.