LBMC presentation added to Phase 2 Documents Page:




L-31N as-built report added to Phase 2 Documents Page:




Monitoring Reports added to Documents Page:




Wall Construction Completed:




Wall Construction Continues:  Geo-Solutions has completed another move of the slurry mix plant and is roughly a half a mile from completion of the seepage barrier.  They have begun the restoration of the levee and berm at the south end of the site.  A couple pictures of the restored area, before grassing, have been put on the photos page.  The construction required removing about 3 feet from the toe of the levee which is being replaced using the current levee construction guidelines from the Corps, which are much more rigorous than the approach used when the levee was first built.  AMEC engineers have supervised the placement and compaction of the material used to rebuild the levee toe.  Density testing has been done throughout the process and all restored areas have exceeded the specifications set by the Corps.




One mile of slurry wall completed:  Geo-Solutions has completed the first mile of the slurry wall.  An updated lab testing summary is included in the “Documents” tab of the website.  The laboratory has now completed seventeen 28-day permeability tests of the cured cement-bentonite slurry and fifty-nine 28-day Unconfined Compressive Strength tests.  All of the tests have exceeded the project specifications (28-day testing) of a permeability of 9 x 10-6 cm/sec and strength of 10 psi.  As expected, the samples are gaining strength from 14 to 28 days, and the permeability is also improving with time.  Short videos of the trenching operation and slurry wall construction have been added to the “Photos” tab.




Trenching is Complete:  H.L. Chapman has completed construction of the 2-mile long, 35 foot deep trench.  Daily depth soundings throughout the project have confirmed the full designed depth for the entire length.  Approximately 4,800 feet of slurry wall have been completed. Geo-Solutions has also completed the first 1000 feet of levee and berm reconstruction at the south end of the project where construction began.  See the Photos page for the latest.




Second Eight Inch Core.  A second 8-inch diameter steel pipe was placed in the slurry wall and allowed to set for two days before extraction.  Photos of the core are available on the photos page.  A five foot section was cut from the bottom of the pipe and split to expose the slurry, showing a well mixed, and set, slurry with embedded gravel within the slurry matrix to the full depth of the trench.


The trenching contractor, H.L. Chapman is nearing completion of the two-mile trench and expected to begin de-mobilization by the end of April.




Recent Status and Core Photos.   Through April 5th, the contractors have completed nearly 7000 feet of trench and 2900 feet of slurry wall.  An updated lab testing summary is included in the “Documents” tab of the website.  The laboratory has now completed twelve 14-day and six 28-day permeability tests of the cured cement-bentonite slurry and thirty-seven 28-day Unconfined Compressive Strength tests.  All of the tests have exceeded the project specifications (28-day testing) of a permeability of 9 x 10-6 cm/sec and strength of 10 psi.  As expected, the samples are gaining strength from 14 to 28 days, and the permeability is also improving with time. 


To provide additional assurances that the cement-bentonite slurry is being emplaced through the entire 35-foot depth, Geo-Solutions pushed an 8” steel pipe through the wall.  The pipe was removed after two days (so the slurry could harden) and the pipe was cut into two foot sections and split and examined in the testing lab.  Photos of the split core are included in the “Photos” tab and show that the cement-bentonite slurry is present to 35 feet.   Rocks were observed in the core, but all were entrained in hardened cement-bentonite material and as demonstrated by the laboratory tests are not affecting the cured material from meeting project strength and permeability specifications.




 Interim Testing Report.  A report summarizing all the field testing that has been done to date has been posted on the documents page of this web site.  In-situ testing of cement bentonite slurry walls is a challenge so several approaches have been tried.  Based on Cone Penetrometer testing and SPT sampling results, it is clear that the slurry placement to the full depth of the trench has been achieved.  Samples of the slurry collected every 50 feet at depths of 15 and 30 feet have been tested in the lab and all results to date meet the project specifications for compressive strength and permeability.  Informal field permeability tests have been performed utilizing the holes created by the SPT samples.  The results show acceptable permeability of the barrier.  For more details refer to the report.




Testing the Barrier.    A Cone Penetrometer Testing Truck was brought to the job site to collect data from a cone penetrometer that was pushed vertically through the completed section of the barrier.  As can be seen in the photos the site is still very disturbed and it was difficult to insure the instrument was placed directly over the wall.  Nevertheless, 6 full depth penetrations were made.  The data from the instruments is being processed and will be posted on this web site once it is available.




Initial Slurry Placement and Testing:  As of Monday evening the trenching contractor had excavated approximately 700 feet to full 35-foot depth.  Geo-Solutions has placed about 150 feet of slurry wall.  The wall construction is in the intense testing phase to make sure full depth and appropriate curing of the cement-bentonite mixture is being achieved.  All results to date are positive but additional testing is underway to confirm the effectiveness of the approach being used by the contractor.




The Trench.  In the past 2 days the contractor has backfilled the short trench section at the north end of the project, turned the trencher around, which was quite a challenge for a 90 foot long machine on a 40 foot wide berm between the canal and levee, and walked the machine down to the south end of the project.  The trencher has now begun constructing the trench from south to north, which will continue until the entire 2 mile section is complete.   


The Slurry Wall.   The mixing plant for the cement/bentonite slurry has been assembled on the east side of the canal  and is ready for operation.  The double-walled slurry pipe has been floated across the canal to the southern end of the project.  Placement of the slurry is expected to begin later this week.




The trenching machine began work today at the north end of the project.  Since this is the only spot with enough room to turn the machine around the decision was made to face the machine to the south, trench for 100-150 feet, backfill the trench and then turn the machine around and walk it to the south end of the project.  This allowed the trench to be completed as close as possible to the Tamiami Trail right of way.  It will also allow the machine to be pointed in the right direction for removal from the site when it completes the trench back at the north end.  See photos for a view of today’s work.




Geo-Solutions has begun placement of the barrier between the work area and the L-31N canal.  They start with a trench to receive a silt fence fabric close to the top of bank.  They then place interlocking , water filled plastic barriers on top of another strip of silt fence that is then wrapped around the barriers.  This provides a secure barrier to prevent silt or debris from entering the canal and makes the most space available for placement of the slurry in a tight work space.  (see Photos)




The construction contractors have arrived at the site and are preparing the site and their equipment for the project.  H.L. Chapman Pipeline Construction Co. will be responsible for the trenching, and Geo-Solutions Inc. will construct the slurry wall and be responsible for all other construction site activities.  AMEC (formerly BCI Engineers and Scientists) is in charge of project engineering and inspection. 


Trenching, expected to begin during the week of February 6th, will start at the south end of the project and proceed north to the end point just south of Tamiami Trail.




All the construction and design contracts have been signed and official notices to proceed have been issued to the contractors. We expect the trenching and seepage wall contractors to be onsite at the beginning of February.

Five new monitoring wells (3 up-gradient of the proposed barrier on top of the levee and 1 up-gradient/down-gradient pair located one mile south of the southern end of the barrier) have been drilled and water level transducers have been installed in all of the wells. The other down-gradient wells will be installed after construction of the wall.

Two new Acoustic Velocity Meters (AVM’s) in the L-31N Canal at the north and south ends of the proposed barrier were installed at the end of December and are now operating. These will provide continuous flow measurements to document the effect of the barrier on flow in the canal.