Below are aerial images from two new developments under construction. They show two detention ponds in two different counties. Can you tell which is in Montgomery County and which is in Harris County? I took both photos on the same day, 2/13/2020.
Look where the grass has established itself:
In A, the land was cleared before the detention pond was completed.
In B, the detention pond was completed before the land was cleared.
And the Answer Is…
If you guessed that Pond A is in Montgomery County, you guessed correctly. Pond A is in Woodridge Village, just north of Sherwood Trails and Elm Grove. It is their S1 detention pond (first southern).
Pond B is in Harris County just north of Bush Intercontinental Airport and Mercer Botanic Gardens.
How You Can Tell
Montgomery County does not require developers to install detention ponds before they clearcut the whole development. So they sometimes come long AFTER clearcutting.
Also, even though Page 44 of Montgomery County’s Drainage Criteria Manual says that “slopes must be revegetated immediately after construction to minimize erosion,” no one apparently enforces the regulation. The sides of Pond A have gone without grass for about a year. See close up below.
All 268 acres of Woodridge Village have been clearcut for the better part of a year. Meanwhile Perry Homes and its engineering firm LJA are just now taking bids on additional detention ponds for the northern section. And the sides of Pond A still have yet to sprout grass.
Harris County Regs Differ
Note in the Pond B photo how the sides of the channel have been stabilized with grass before the developer has even finished clearing the land.
The text states, “The clearing, grubbing and scalping (mass clearing or grading) of excessively large areas of land at one time promotes erosion and sedimentation problems. On the areas where disturbance takes place the site designer should consider staging construction [emphasis added], temporary seeding and/or temporary mulching as a technique to reduce erosion. Staging construction involves stabilizing one part of the site before disturbing another [emphasis added].”
Two Different Approaches
You would think that preventing erosion would be cheaper than cleaning it up. Why do a job once when you can do it twice? Right?
Evidently, Perry Homes prefers it that way. Last Thursday, I spotted men digging out the pilot channel of Pond A and restoring slopes…again. This was at least the third or fourth time. No wonder those Perry Homes are so expensive.
Posted by Bob Rehak on 2/16/2020
901 Days After Hurricane Harvey and 150 after 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/02/Pond-A-or-B-e1581859478892.jpg?fit=894%2C1200&ssl=11200894adminadmin2020-02-16 07:41:032020-02-16 10:57:16Detention Pond Construction: Montgomery vs. Harris County
When looking at all the sediment in the San Jacinto, it’s logical to think, “Why don’t we just let sand miners mine the river?” However, many countries in the world have outlawed the practice of river mining, largely because of the dangers of over-mining. If Texas explores this solution, experience has shown that it should be under strict governmental supervision to prevent excesses which have widened rivers, damaged properties and destroyed the river environment elsewhere.
Sedimentation in the East Fork of the San Jacinto. This dune constricts the conveyance of the river by approximately 50 percent. It would be a likely target for river miners. But where would they mine after such obstructions are removed?
River mining differs from the type of remedial dredging that we are doing now. The objective for river mining is to maximize profit, which often means pushing limits. The motivation for dredging is to maximize profits by staying within the limits outlined by the client (i.e., the U.S. Army Corps of Engineers).
“Evidence of environmental problems associated with river sand and gravel extraction is increasing. So also is the community’s expectation of river systems. Future management decisions must be based on the principle of sustainable development – sustainability not only of the sand and gravel resources but also of other river uses and values.”
The discussion of risks begins with an admonishment. “Management of sand and gravel extraction must ensure that the activity does not conflict with the aims of other component policies.” For instance, they say that, “Wild and scenic rivers, wetlands and designated recreational areas are all places where sand and gravel extraction would have a highly visible and adverse impact. Extraction should not be considered in such areas.” (Sec. 6.1.1, Page 16.)
“Increased rates of river erosion and other channel changes can occur in the shorter term, due to both natural and human-induced changes. These changes include increases in the size, magnitude and frequency of floods…” (Sec. 6.1.3. Page 17.)
“…excavation below existing bed level may be a direct cause of bank collapse.” (Sec. 6.1.4. Page 19.)
“Most of the finer sediments (sand, silt and clay) released from erosion of alluvial banks will be transported downstream, often for considerable distances. Increased siltation in these downstream areas can cause problems to navigation … and adversely impact flooding in the area.” (Sec. 6.1.5. Pages 19-20.) The U.S. Army Corps of Engineers found an increase in flood risk from sedimentation in its value engineering study on the West Fork last spring.
“If extraction is below the riverbed level, groundwater recharge from rivers to floodplain aquifers may be severely reduced. This will impact adversely on bores and wells in the area.” (Sec. 6.1.6. Page 20.)
“Extraction of river sand and gravel often involves direct clearing ofvegetation (that stabilizes soil). … Construction of access tracks and processing sites associated with the extraction process can also involve clearing of vegetation.” (Sec. 6.1.7. Page 20.)
“Suspended solids adversely affect many waterusers and ecosystems. They can significantly increase water treatmentcosts, especially where they act as a substrate for bacteria and so increasethe problems and costs of disinfection in water treatment plants.” (Sec. 6.1.9. Page 20.)
“There will be some rivers, however, where the value to other users will be such that extraction may need to be precluded. Similarly, where past extraction has over-taxed a river system, future extraction may need to be precluded until the river has recovered sufficiently, if it does so at all.” (Sec. 6.1.12. Page 22.)
What to Do
The Australian report then goes on to talk about the need for sand and gravel to support road building and economic growth. (Sec. 6.2).
Section 6.3 talks about alternative sources for sand and gravel.
Section 6.4 talks about governmental costs to monitor sand and gravel extraction.
Section 7 talks about guidelines for safe extraction when mining in rivers and how to crack down on illegal activity (something we desperately need to do here as well). Here they talk about the opportunity to involve community members as extra pairs of eyes and the need to enroll major purchases (such as TxDoT) in the enforcement effort.
Section 8 talks about permitting procedures.
Section 9 talks about performance measures and monitor programs. Here they have some novel measures that we could learn from. I especially like Section 9.3, Community Monitoring. Inputs include:
Data collected by local community groups including extractors;
Reports by local ‘care’ groups and riparian landowners;
Reports by local environmental or recreational interest groups;
Reports by local TCM Committees;
Reports by local government.
Such an inclusive approach helps guarantee that the needs of various interest groups are balanced.
Australian Conclusions: A Cautionary Tale
Section 10, the Conclusion, says on page 36: “There are many natural causes which may increase the rate of riverbed and bank erosion. However, extraction of large amounts of sand and gravel from within the channels has exacerbated the situation in many rivers.Past experience in some areas of the State has shown that crisis point can be reached. In other areas, increasing conflict with other river uses has made extraction of sand and gravel a less viable option.”
If the State of Texas decides to permit river mining, I sincerely hope we can find a workable balance for the San Jacinto that protects everyone’s interests.
Posted by Bob Rehak on 11/5/2018
433 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/03/Harvey-SanJac_323-e1524608786151.jpg?fit=1985%2C940&ssl=19401985adminadmin2018-11-05 21:30:122018-11-05 21:35:47Immediate and Long-Term Risks Associated with River Sand Mining