During the first phase of River Grove dredging, the contractor, Kayden, removed vegetation from the area to be dredged adjacent to the boardwalk (see photo below).
River Grove Boat Ramp and Lagoon on 2/13/2020 before dredging operation started. Looking south.
They completed vegation removal last week. They also completed cleaning silt out from under the boardwalk without impacting its stability or support. This week, they’re back with a tiny dredge and a giant mobile dewatering plant.
The Little Dredge That Could
The dredge was selected because it could maneuver in the tight spaces adjacent to the River Grove Boardwalk. It’s 12 feet wide and 51 feet long. The first word that came to mind when I saw it was “cute.” The second thing that came to mind was the child’s story “The Little Engine that Could.” As it sat there chugging away at sand and silt, I thought I could hear the John Deer, 6-cylinder, 13.5 liter diesel engine chanting, “I think I can, I think I can.”
Dewatering Plant Processes Sand for Removal, Returns Water To River
The giant dewatering plant operates much like shakers used in oil field drilling work. Water and sediment are pumped up from the lagoon by the dredge. They enter one side of the dewatering plant. There, they are pumped through centrifuges, then across a series of screens that vibrate. Water falls through the screens into a tank below. Sand accumulates on the screens until they dump it down chutes. From there, a front end loader scoops up the dirt and piles it up until trucks haul it away.
Video of dewatering plant in operation courtesy of Josh Alberson.Front end loader removes dirt from dewatering plant and piles it up for removal from River Grove.
Kayden then pumps the water back into the river.
Water returned to river after sediment removed. Photo courtesy of Josh Alberson.
Dredge Designed for Tight Spaces
River Grove dredging will not move nearly as fast as the dredging that Great Lakes and Callan were doing, but it seems to work well for the location. A major concern is overly aggressive dredging that could undermine the supports for the boardwalk and boat ramp. Another word that comes to mind is “precise.” Think about the difference between a van and an 18 wheeler. The major issue here is fitting in small spaces.
KSA intends to dredge only 50 feet from the boardwalk instead of all the way over to the trees. This shows the area where vegetation was removed earlier. Dredging will take place within this space.
Despite the size of the equipment at River Grove, the operation itself is far more compact than previous dredging operations. This could form a model for the dredging of inlets around the lake, like the one at Walden. However, County Engineer John Blount emphasizes that no decisions have been made in that regard yet.
The Safety Moment
If you take your kids to River Grove to see this operation, make sure you stay behind the yellow tape for your own safety.
Also, until the operation is complete in another month or so, remember that traffic at River Grove will be two-way. Just be aware.
Posted by Bob Rehak on 3/4/2020 with photos and video from Josh Alberson
918 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/03/20200304-RJR_8795.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-03-04 16:56:292020-03-05 09:27:23River Grove Dredging Operation Moves to Next Phase
We step on them. Spit on them. Park on them. Ride on them. But we rarely think about them. If there’s anything we truly take for granted, it’s the lowly storm sewer inlet.
Critical Rate-Limiting Factor in Drainage
I’ve always known they were there. But I never realized how important they were until I posted about street flooding last week, omitted them, and an expert called them to my attention. Unless properly sized or designed, they can limit how quickly streets drain in heavy rains.
Think of storm sewer inlets like fire exits. Better have enough capacity in the right locations when you need it!
How tall is your inlet?
How wide is it?
Does it have a grate or a plate in it?
Or is it just a hole in the concrete between the street and the curb?
What is the slope of the street towards it?
Can it capture all the water that runs toward it?
Or does some get by?
What’s the spacing between inlets?
Have you ever really thought about these things? Who on earth does?!!!
Visual Inventory of Drain Types
Fortunately, engineers DO. And standards constantly evolve as they come up with better designs. Here are a few variations I spotted as I drove around.
Rectangular grate design in North Woodland Hills.Five inches high.Five feet wide.Steel plate design in Bear Branch. Also five feet wide.Also five inches tall.All concrete version in Sugar Land. Five feet wide……but 7.5 inches tall. That’s 50% more surge capacity than a 5-inch high inlet.
Inlet Trivia
In researching this topic, I discovered many fascinating pieces of trivia.
Thirty years ago, Sugar Land decided to enlarge all its storm sewer inlets. Street flooding is very rare there, almost unheard of.
Storm sewer inlet size and design varies by the type of street.
Thoroughfares usually get bigger inlets than feeders.
Feeders usually get bigger inlets than residential streets.
Hills and busy intersections often get special attention.
Double-wide inlet at the bottom of Kingsway Court by Kingwood High School. Below hillwith approximate 10% grade at end of cul de sac. Better not let the water get by this one!.
Many municipalities (including Houston) frown on grates. While they theoretically offer higher capture rates, they also clog easily and require constant maintenance, increasing costs.
The slope of the street (from the highest point of the crown to the lowest point of the gutter) can radically affect the capture rate of water flowing down the gutter. The slope “forces” the water into the inlet.
The geometry of grates can also radically affect capture efficiency (measured as percent of water intercepted). Below is a video by the U.S. Department of Transportation that shows the efficiency of different geometries for grate designs in a table-top experiment. (Attention science teachers: this is a “must see” video that will fascinate students and could even intrigue some enough to pursue careers in engineering.)
Produced by US Department of Transportation
City of Houston and Other Resources
For those who want to learn even more, here is a link to the current City of Houston infrastructure design standards for stormwater runoff. Page 139 shows you how much the capacity of inlet types can vary. Some inlets can handle four times more cubic feet per second than others.
When looking for a new home, storm sewer inlets may be the last thing you think about. But just like plumbing, maybe they should be one of the first.
Posted by Bob Rehak on 3/3/2020
917 Days after Hurricane Harvey and 166 after Imelda
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/03/20200229-RJR_8776.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-03-03 19:22:342020-03-04 09:59:02Storm Sewer Inlets: Often Overlooked in Cases of Street Flooding
Randy Reagan is tough. He grew up in the Conroe oil fields and riding bulls. But nothing prepared him for flooding five times in four years and the series of events that followed.
Reagan raised his family on a 5-acre lot in Bennett Estates. That’s a neighborhood between the San Jacinto West Fork and FM1314, just south of SH242. He made a modest living for himself as an oil-field technician by repairing turbines, first for a local company and then for GE. He harvested all the meat his family ate from his own property and the surrounding forests. Life was good.
Built Home Above 1994 High Water Mark
Bennett Estates rises up from the banks of the San Jacinto West Fork through the 100- and 500-year flood plains to even higher ground. Reagan’s slab is a foot above the high-water mark from the 1994 flood, which at the time involved a massive release from the Lake Conroe dam. So he figured he was safe for anything the future brought. Wrong!
Reagan lives between the sand mines east of the river, just above the mine at the bottom, in the aqua-colored 100-year flood plain. Source: FEMA.
A Happy Life, Until…
While Reagan was never destined for riches, he led a happy life. Until the sand mines came. Then everything changed.
Reagan now lives in a neighborhood five blocks deep – sandwiched between three sand mines comprising almost 1500 acres.
Despite being in the 100-year flood plain, his property has only flooded twice from the San Jacinto – in 1994 and 2017 during Harvey. However, in the last four years, he says, it has also flooded four times from sand mines – twice in 2016, once in 2018 and once in 2019 during Imelda.
As the sand mines have grown, they’ve removed forests and wetlands that used to slow water down during rainfalls.
Now the water rushes through sand pits largely unimpeded. While the mines like to tout how they offer detention capacity in storms, aerial photos show that they offer little. That’s because they are often filled to the brim…even before storms. So, it doesn’t take much to make them overflow in heavy rains.
Water flows down into the mines from higher ground and quickly fills the pits. The pits can then spill over into the river and surrounding neighborhoods.
LMI Pit to the North Sends Water South into Neighborhood
That’s what Reagan contends happened with the LMI pit to the north of him.
During Harvey, a satellite photo in Google Earth shows the water blew out the mine’s perimeter road, sending water gushing into Reagan’s neighborhood.
During other recent events, Reagan has ground-level photos that show silty, sandy-brown water coming from the direction of the mine, not the river.
LMI breach into Reagan neighborhood on 8/30/2017 during Harvey.Five HVL pipelines are now trying to repair damage caused when this mine mined too close to them.The LMI mine to the north of Reagan on Feb. 13, 2020. In heavy rains, there’s little to keep water from the mine from escaping into Reagan’s neighborhood out of frame at the bottom of the photo.Photo taken in moderate drought conditions.
Hanson Pit to South Backs Water Up into Neighborhood
The mine to the south of Reagan affects him in a different way. Twice, says Reagan, the mine has built walls that blocked the flow of ephemeral streams that used to run through his neighborhood.
The mine dug a ditch to the river in 2011 to let the water drain to the river. That worked for about five years. Then the ditch became overgrown and the volume of water coming from the northern mine became too much. Reagan flooded on Tax Day and Memorial Day in 2016, 2018, and Imelda in 2019. Not to mention the 93 inches he got during Harvey in 2017.
Dirt wall erected by Hanson Aggregates between their pond and Reagan’s property. The drainage ditch in the foreground that they dug in 2011 is no longer any match for water flowing south from the LMI mine behind the camera position.
Problems Grow as Sand Mines Grow
“The sand mines have destroyed our lives,” said Reagan. “We’ve lived here all our lives. This all used to be woods for acres and acres and acres. The first problem I had was back in the 90’s when the sand pits were getting bigger.”
“As they started developing more ponds, they started interrupting the natural runoff.”
Randy Reagan
“When we moved here in the late ’90’s, we had our homesite raised four feet. That’s where FEMA drew the line for insurance at the time. We figured if we built higher than the high water mark from 1994, we would never have to worry. Because in 1994, we had Lake Conroe releasing all that water on us.”
“There was another flood in 1998, but it never affected us. We were high and dry here. LMI still had not built the mine to the north of us at that point,” said Reagan.
“Now we’ve got water coming at us up from the river, downhill from one mine and backing up from another mine. Sand from the mines even blocks the street drains that lead to the river,” said Reagan.
“All this used to be woods back here with natural creeks and natural drainage. It’s just all gone now. These sand pits done tore it out,” said Reagan. “They’re like giant lakes with no water control.”
Memorial Day Flood in 2016 invades Reagan’s shop.Memorial Day Flood in 2016 nearly invades Reagan’s home. Note color of water.93″ of floodwater took this home in Harveyone year later.
“In 2016, we got a lot of rain, but the river never got out of its banks much,” he continued. “The people that live next to LMI (on the north) tell me that the LMI walls keep breaking. The water rushes through their property, coming from the sand pit. In 2016, we had milky brown, silty water sweeping through here. It was so swift that it almost took my truck off the road. I got about 20 inches in my garage during Tax Day and Memorial Day storms. But it never got in my home at that point.”
“The Tax Day Flood in 2016 was our wedding anniversary. We tried to celebrate our anniversary while our garage got flooded. That was LMI. And then we got flooded again on Memorial Day. That was LMI,” said Reagan. “In 2016, the river here was NOT out of its banks. We got flooded from the sand pits.”
“Then came Harvey. We might have been fine if all we got was the rainwater. It came close. But then they opened the gates at Lake Conroe. And the sand mine upstream of us broke loose again.
Floods Cause Cascading Series of Problems
“Not only did we lose our house, I lost my job and I lost my health. We really hit bottom.”
“I’ve got breathing problems,” says Reagan. “Everybody in our family has breathing problems.”
“I was still trying to recover from Harvey, the day I lost my job in 2018. I was admitted into the emergency room because of my breathing that same day.”
“In the meantime, we were living in a used camper. And it caught on fire. We didn’t have insurance on it,” said Reagan. “My mother had just died. So we were going through that grieving process. Then the camper burns!”
Never-Ending Noise and Vacant Homes
“It used to be quiet here,” he says. “The sand trucks used to run during the days, but never on weekends and never at night. Now they run 24/7 it seems.”
The sand mines and floods took more than Reagan’s health and home. When long-time residents fled to higher ground, they left behind vacant houses. He worries about a criminal element coming in now.
During Harvey, Reagan says water reached 93 inches in his shop. That’s above the door frame.
Reagan yard during Imelda. Note color of water…again.
“We’re living in my shop now. Everything we have left is in there.”
Posted by Bob Rehak on 3/3/2020
917 Days since Hurricane Harvey and 166 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.
River Grove Dredging Operation Moves to Next Phase
During the first phase of River Grove dredging, the contractor, Kayden, removed vegetation from the area to be dredged adjacent to the boardwalk (see photo below).
They completed vegation removal last week. They also completed cleaning silt out from under the boardwalk without impacting its stability or support. This week, they’re back with a tiny dredge and a giant mobile dewatering plant.
The Little Dredge That Could
The dredge was selected because it could maneuver in the tight spaces adjacent to the River Grove Boardwalk. It’s 12 feet wide and 51 feet long. The first word that came to mind when I saw it was “cute.” The second thing that came to mind was the child’s story “The Little Engine that Could.” As it sat there chugging away at sand and silt, I thought I could hear the John Deer, 6-cylinder, 13.5 liter diesel engine chanting, “I think I can, I think I can.”
Dewatering Plant Processes Sand for Removal, Returns Water To River
The giant dewatering plant operates much like shakers used in oil field drilling work. Water and sediment are pumped up from the lagoon by the dredge. They enter one side of the dewatering plant. There, they are pumped through centrifuges, then across a series of screens that vibrate. Water falls through the screens into a tank below. Sand accumulates on the screens until they dump it down chutes. From there, a front end loader scoops up the dirt and piles it up until trucks haul it away.
Kayden then pumps the water back into the river.
Dredge Designed for Tight Spaces
River Grove dredging will not move nearly as fast as the dredging that Great Lakes and Callan were doing, but it seems to work well for the location. A major concern is overly aggressive dredging that could undermine the supports for the boardwalk and boat ramp. Another word that comes to mind is “precise.” Think about the difference between a van and an 18 wheeler. The major issue here is fitting in small spaces.
How It All Works Together
Here’s a contractor animation that shows how everything works together. And here are the specs of the equipment. It could conceivably be used for dredging other channel inlets around the lake such as the one at Walden.
Despite the size of the equipment at River Grove, the operation itself is far more compact than previous dredging operations. This could form a model for the dredging of inlets around the lake, like the one at Walden. However, County Engineer John Blount emphasizes that no decisions have been made in that regard yet.
The Safety Moment
If you take your kids to River Grove to see this operation, make sure you stay behind the yellow tape for your own safety.
Also, until the operation is complete in another month or so, remember that traffic at River Grove will be two-way. Just be aware.
Posted by Bob Rehak on 3/4/2020 with photos and video from Josh Alberson
918 Days after Hurricane Harvey
Storm Sewer Inlets: Often Overlooked in Cases of Street Flooding
We step on them. Spit on them. Park on them. Ride on them. But we rarely think about them. If there’s anything we truly take for granted, it’s the lowly storm sewer inlet.
Critical Rate-Limiting Factor in Drainage
I’ve always known they were there. But I never realized how important they were until I posted about street flooding last week, omitted them, and an expert called them to my attention. Unless properly sized or designed, they can limit how quickly streets drain in heavy rains.
Think of storm sewer inlets like fire exits. Better have enough capacity in the right locations when you need it!
Have you ever really thought about these things? Who on earth does?!!!
Visual Inventory of Drain Types
Fortunately, engineers DO. And standards constantly evolve as they come up with better designs. Here are a few variations I spotted as I drove around.
Inlet Trivia
In researching this topic, I discovered many fascinating pieces of trivia.
Thirty years ago, Sugar Land decided to enlarge all its storm sewer inlets. Street flooding is very rare there, almost unheard of.
Storm sewer inlet size and design varies by the type of street.
Hills and busy intersections often get special attention.
Many municipalities (including Houston) frown on grates. While they theoretically offer higher capture rates, they also clog easily and require constant maintenance, increasing costs.
The slope of the street (from the highest point of the crown to the lowest point of the gutter) can radically affect the capture rate of water flowing down the gutter. The slope “forces” the water into the inlet.
Inlet spacing is a function of gutter slope! (See page 137 of COH Infrastructure Design Manual).
The geometry of grates can also radically affect capture efficiency (measured as percent of water intercepted). Below is a video by the U.S. Department of Transportation that shows the efficiency of different geometries for grate designs in a table-top experiment. (Attention science teachers: this is a “must see” video that will fascinate students and could even intrigue some enough to pursue careers in engineering.)
City of Houston and Other Resources
For those who want to learn even more, here is a link to the current City of Houston infrastructure design standards for stormwater runoff. Page 139 shows you how much the capacity of inlet types can vary. Some inlets can handle four times more cubic feet per second than others.
For COH construction standards, click here.
For budding engineers, here’s a primer on the design of inlets and storm drains.
Buyer Awareness
When looking for a new home, storm sewer inlets may be the last thing you think about. But just like plumbing, maybe they should be one of the first.
Posted by Bob Rehak on 3/3/2020
917 Days after Hurricane Harvey and 166 after Imelda
“Sand Mines Destroyed Our Lives”
Randy Reagan is tough. He grew up in the Conroe oil fields and riding bulls. But nothing prepared him for flooding five times in four years and the series of events that followed.
Reagan raised his family on a 5-acre lot in Bennett Estates. That’s a neighborhood between the San Jacinto West Fork and FM1314, just south of SH242. He made a modest living for himself as an oil-field technician by repairing turbines, first for a local company and then for GE. He harvested all the meat his family ate from his own property and the surrounding forests. Life was good.
Built Home Above 1994 High Water Mark
Bennett Estates rises up from the banks of the San Jacinto West Fork through the 100- and 500-year flood plains to even higher ground. Reagan’s slab is a foot above the high-water mark from the 1994 flood, which at the time involved a massive release from the Lake Conroe dam. So he figured he was safe for anything the future brought. Wrong!
A Happy Life, Until…
While Reagan was never destined for riches, he led a happy life. Until the sand mines came. Then everything changed.
Reagan now lives in a neighborhood five blocks deep – sandwiched between three sand mines comprising almost 1500 acres.
As the sand mines have grown, they’ve removed forests and wetlands that used to slow water down during rainfalls.
Now the water rushes through sand pits largely unimpeded. While the mines like to tout how they offer detention capacity in storms, aerial photos show that they offer little. That’s because they are often filled to the brim…even before storms. So, it doesn’t take much to make them overflow in heavy rains.
Water flows down into the mines from higher ground and quickly fills the pits. The pits can then spill over into the river and surrounding neighborhoods.
LMI Pit to the North Sends Water South into Neighborhood
That’s what Reagan contends happened with the LMI pit to the north of him.
Hanson Pit to South Backs Water Up into Neighborhood
The mine to the south of Reagan affects him in a different way. Twice, says Reagan, the mine has built walls that blocked the flow of ephemeral streams that used to run through his neighborhood.
The mine dug a ditch to the river in 2011 to let the water drain to the river. That worked for about five years. Then the ditch became overgrown and the volume of water coming from the northern mine became too much. Reagan flooded on Tax Day and Memorial Day in 2016, 2018, and Imelda in 2019. Not to mention the 93 inches he got during Harvey in 2017.
Problems Grow as Sand Mines Grow
“The sand mines have destroyed our lives,” said Reagan. “We’ve lived here all our lives. This all used to be woods for acres and acres and acres. The first problem I had was back in the 90’s when the sand pits were getting bigger.”
“When we moved here in the late ’90’s, we had our homesite raised four feet. That’s where FEMA drew the line for insurance at the time. We figured if we built higher than the high water mark from 1994, we would never have to worry. Because in 1994, we had Lake Conroe releasing all that water on us.”
“There was another flood in 1998, but it never affected us. We were high and dry here. LMI still had not built the mine to the north of us at that point,” said Reagan.
“Now we’ve got water coming at us up from the river, downhill from one mine and backing up from another mine. Sand from the mines even blocks the street drains that lead to the river,” said Reagan.
“All this used to be woods back here with natural creeks and natural drainage. It’s just all gone now. These sand pits done tore it out,” said Reagan. “They’re like giant lakes with no water control.”
“In 2016, we got a lot of rain, but the river never got out of its banks much,” he continued. “The people that live next to LMI (on the north) tell me that the LMI walls keep breaking. The water rushes through their property, coming from the sand pit. In 2016, we had milky brown, silty water sweeping through here. It was so swift that it almost took my truck off the road. I got about 20 inches in my garage during Tax Day and Memorial Day storms. But it never got in my home at that point.”
“The Tax Day Flood in 2016 was our wedding anniversary. We tried to celebrate our anniversary while our garage got flooded. That was LMI. And then we got flooded again on Memorial Day. That was LMI,” said Reagan. “In 2016, the river here was NOT out of its banks. We got flooded from the sand pits.”
“Then came Harvey. We might have been fine if all we got was the rainwater. It came close. But then they opened the gates at Lake Conroe. And the sand mine upstream of us broke loose again.
Floods Cause Cascading Series of Problems
“Not only did we lose our house, I lost my job and I lost my health. We really hit bottom.”
“I’ve got breathing problems,” says Reagan. “Everybody in our family has breathing problems.”
“I was still trying to recover from Harvey, the day I lost my job in 2018. I was admitted into the emergency room because of my breathing that same day.”
“In the meantime, we were living in a used camper. And it caught on fire. We didn’t have insurance on it,” said Reagan. “My mother had just died. So we were going through that grieving process. Then the camper burns!”
Never-Ending Noise and Vacant Homes
“It used to be quiet here,” he says. “The sand trucks used to run during the days, but never on weekends and never at night. Now they run 24/7 it seems.”
The sand mines and floods took more than Reagan’s health and home. When long-time residents fled to higher ground, they left behind vacant houses. He worries about a criminal element coming in now.
“We’re living in my shop now. Everything we have left is in there.”
Posted by Bob Rehak on 3/3/2020
917 Days since Hurricane Harvey and 166 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.