Thursday night at the Kingwood Town Hall Meeting, the City discussed a meeting between Perry Homes and city officials including the City Attorney. The subject: How to avoid flooding Elm Grove and North Kingwood Forest again. City officials said they demanded multiple concessions from “Perry Homes.” Two days later, and only hours before the Town Hall meeting, Perry Homes (according to City officials) sent the City a letter outlining what it could do. Mayor Sylvester Turner read portions of the letter to the overflow crowd. It met with mixed reaction. Some people were grateful; others skeptical; still others angry.
Much to his credit, Council Member Dave Martin posted the letter on his FaceBook page. I have reposted it here for your convenience, along with my reactions and those of several other residents.
I was not in the meeting between “Perry” and the City so I cannot comment on the tone of the meeting or how the City presented its “demands.” However, several things struck me about this letter right from the opening paragraph. First of all, it’s not from Perry. That’s why I put Perry in quotes above.
- The developers expressed how saddened they were by Elm Grove flooding. Yet they are suing the victims. This raises a sincerity issue from the git-go.
- They say, “Your idea of sharing our collective intellectual capital was a good one, and we appreciate having the City’s input.” Sounds pretty collaborative to me. That’s normally good, but it certainly does not fit with how the City characterized meeting.
- The law firm representing Perry’s subsidiaries, PSWA and Figure Four Partners, sent the letters, not Perry.
- Even though the engineering plans for the site call for DETENTION ponds, the lawyer now refers to them as RETENTION ponds. The difference between the two is storage capacity. The latter is like renting a storage shed that’s 80% full…and still paying full price. The City attorney needs to question this.
- The letter only says that they discussed accelerating the schedule, not that they have accelerated it.
- The letter lays out timing to construct each detention pond. But it doesn’t say whether they will perform work concurrently or sequentially. If concurrently, the work would take 9+ months. If sequentially, it could take 26 months. They talk about beginning “each project as quickly as the plans can be approved.” This suggests a one-at-a-time approach that could potentially add up to 780 days…assuming there are only “minimal delays” for bidding, approvals, weather, etc.
- They promised to spend 45 days completing the two southern ponds. Those ponds are already substantially complete.
- The letter promises to build a berm 2 feet above the 100-year flood elevation between Woodridge Village and Elm Grove. An even higher berm failed during Imelda. Floodwaters overtopped it. Perhaps that’s because Montgomery County bases flood maps on data from the 1980s.
- They talk about delaying development of homes and streets (impervious cover) until they complete detention ponds. Delaying impervious cover seems like a genuine concession; developers like to build in sections so profit from one can help bankroll the next.
- The lawyers claim their clients have not yet completed plans and specifications. However, LJA Engineering seemed to have a pretty comprehensive set.
- The letter provides no guarantees and no penalties for non-compliance or missing target dates.
- Because Perry has never revealed a construction timetable, we can’t tell whether this schedule beats their original one.
All in all, the timetable in this letter, seemed to take a lot of time for work that they could have completed by now.
Jeff Miller’s Opinions
Jeff Miller is an Elm Grove resident who nearly flooded on May 7th and during Imelda. Most of his neighbors did flood. For months, he has monitored the progress of Woodridge Village construction on a daily basis. He alerted the community when excavation on the site came to a virtual standstill during ideal construction weather.
Miller recently had an “aha” experience when driving by a 5-acre commercial construction site in Kingwood. It had more heavy equipment operating on it than Perry’s 268-acre site did at its peak last summer, he said.
Miller is a retired process engineer. Based on observation of that and other sites, Miller estimated excavation of three more detention ponds would take only about a month if Perry pulled out the stops. Other engineers and construction experts share this opinion.
Josh and Jon Alberson’s Opinions
Both of these brothers have engineering degrees from Georgia Tech. Josh is a chemical engineer and Jon a civil engineer. Jon works on giant construction projects for one of the largest companies in America. The Alberson brothers estimate only 10 days more than Miller. They shared their calculations. The calculations assume a two-step process. Excavate and stack the dirt. Then spread and grade it at a later time.
Basically, they calculated the volume of dirt that needs to be removed. Then they divided that volume by the per-load capacity of heavy equipment. Next, they estimated the time to move one load and return for the next. Using this technique, they could ultimately determine the total time it would take to excavate the three remaining ponds. They consulted with Caterpillar on the capacity of different types of equipment and their recommendations. Follow along to check their math.
Final Capacity of Detention Ponds
N1 + N2 + N3 = 209.9 acre feet = 338,638 cubic yards. (That’s compacted soil before excavation, i.e., bank cubic yards.)
Scraper Capacity per Load
- Assume typical scraper tractor with 400+ hhp, pulling twin 20 cubic yard (medium size) scrapers. Then assume a worst case 0.75 load factor for uncompacted soil after excavation (loose cubic yards).
- Yards per Load = 20 cubic yards per scraper * 2 scrapers per tractor * 0.75 = 32 cubic yards per Load
- 338,638 cubic yards / 32 cubic yards per load = 10,582 loads
Loads per Tractor per Day
- Assume tractor cycle time for scraping, moving to pile, and returning to pond is 15 minutes. This would be a conservative transit time.
- Then assume the tractor operates 20 hours per day.
- Lunch – 1 hour per shift = 2 hours per day
- Maintenance = 1 hour per day
- Breaks = 2 x 15 minute breaks per shift = 1 hr per day
- Loads per Day = 20 hours per day * 4 loads per hour = 80 loads per day
Number of Days with 1 Scraper Tractor
- 10,582 loads / 80 loads per day = 132 days
Number of Days with 4 Scraper Tractors
- 10,582 loads / (80 loads per day * 4) = 33 days
Assume 20% lost time due to non-productive time, weather, etc.
- 33 days * 1.2 = 40 days
Said Jon, “Most projects can move 8000 cubic yards per day.”
The two agreed on roughly the same time frame but argued over the optimum combinations of day and shift lengths, pieces of equipment, etc.
That’s just the time to dig the ponds. It assumes they stack the dirt somewhere nearby, then grade and compact it at a later date. Let’s assume that takes another month. But the ponds are excavated!
Now, we’re talking roughly TWO months instead of 9 to 26 months. And beating one or two hurricane seasons.
Note: The LJA Engineering report, upon which these calculations are based, shows at least three different storage capacities for the ponds on the northern section under “ultimate conditions”:
- Exhibit 2 shows a total of 209.4 acre feet.
- Table 3 shows a total of 154.2 acre feet.
- Table 7 and the Conclusion show a total of 163 acre feet.
For the analysis above, the Albersons used the highest volume because it represented the most difficult case. Contractors could excavate the smaller totals, if accurate, in even less time. If 154.2 is accurate, excavation would take only 30 days.
Nancy and Abel Vera’s Opinions
Regardless of how Perry Homes staffs this job, it’s going to take some sweat. That’s the one thing that was not in evidence yesterday or today. Despite the assurances of J. Cary Gray, Attorney at Law, multiple residents reported seeing NO activity on the construction site.
As of Saturday afternoon, Nancy Vera still has seen no activity on the construction site. See the video below taken the day after the Town Hall.
Vera’s husband Abel, manages giant construction projects around the world for one of the world’s largest engineering companies. He agrees that the construction could move much faster.
“If they had the proper equipment and man power, they could move fairly quickly. But they have never done that! They took more than six months to put in this one pond by our house [S2]. And they didn’t even really get going till after the May 7th storm.”Abel Vera, Resident just south of S2 Detention Pond
A Faster Way?
This video shows the scraper equipment that Alberson and Caterpillar recommended to move large volumes of dirt quickly. The video runs 13 minutes but you will get the idea after a minute or two. These guys collect dirt while rolling.
Contrast that with what I saw earlier this summer. I watched as a backhoe filled up one dump truck after another. It took several minutes to fill up each truck with multiple scoops. Then each truck took the dirt to its ultimate destination more than a half mile away rather than piling it up near the pond and returning for more dirt. It was a long, slow, dusty procedure with lots of dead time between loads.
A Good Deal?
So, does the letter from Counsellor Gray represent a good deal for the residents of Elm Grove. I think not. If Perry Homes really cared about the safety and peace of mind of Elm Grove residents, they could move much faster. The letter commits them to nothing except delaying homes and streets until all detention is in. That’s something. But with most of the surface being hard-packed clay, the threat of rapid runoff remains until they finish all those detention ponds. And someone really needs to proofread that LJA report. It’s scary to think that this whole development could be based on erroneous calculations. I’m surprised Montgomery County approved it.
Posted by Bob Rehak on 10/19/2019 with help from Josh and Jon Alberson, Abel and Nancy Vera, and Jeff Miller
781 Days since Hurricane Harvey and 30 since Imelda
The thoughts in this post represent my opinions on matters of public policy and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.