Geoform ER DPT Injection
- toddwhanna
- Apr 29
- 3 min read
The Legacy Remediation team recently completed two successful Direct Push Slurry Injection events at a project site in Alameda County. The groundwater remediation strategy involved the injection of GEOFORM® Extended Release (ER) slurry, followed by bioaugmentation with the SDC-9 microbial culture.
All reagent mixing, pumping, and monitoring was carried out using one of our full-size, self-contained Injection Trailer Platforms.
The trailer was hydraulically powered by one of our Support Trucks, which also transports all necessary tooling and injection support equipment.
GEOFORM ER is used to treat groundwater contaminated with chlorinated solvents. It provides a long-term source of sulfate, iron, electron donors, pH buffers, and nutrients to promote multiple mechanisms of dehalogenation, including enhanced anaerobic bioremediation, abiotic degradation, and the formation of reactive minerals.
Our mix water source came from a nearby fire hydrant.
Legacy coordinated with the local water agency to have a construction meter installed.
The GEOFORM ER slurry was mixed in alternating batches in our dual mix tanks, and was pumped with a double-action Piston Pump.
The GEOFORM ER dry product was provided by Evonik in 50 pound bags.
Due to limited secure storage space at the project site, the material was shipped to our Northern California regional office in Benicia. From there, we managed inventory and coordinated daily deliveries of the reagent to the site to support ongoing injection activities.
The GEOFORM ER was mixed into a 30% by weight slurry to maintain solid suspension, resulting in a thick, stable mixture, as shown in the image.
Despite the high viscosity of the slurry, we successfully maintained injection pressures at the manifold between 200 and 400 psi.
The target treatment interval was between 9 and 25 feet bgs.
We used our Geoprobe 420M Dolly Rig for the Limited Access points, and the points locate around the above grade SVE piping.
We used a full size Geoprobe 7822DT Track Rig for the other injection points.
Track mounted Geoprobe's are the best for Direct Push Injection, due to their ability to easily move between multiple Injection Points.
In each 2-foot long treatment interval, we also bioaugmented with a SDC-9 Microbial Culture. To facilitate this, we prepared anaerobic flush water using Newman Zone OS, it is an oxygen scavenger.
Newman Zone OS is specially formulated to quickly remove dissolved oxygen from water and create the reducing conditions.
We simply measured out the proper amount of Newman Zone OS and mixed it with water in a bucket, then poured it into a tank.
Within minutes the DO and ORP were within spec:
DO less than 1 mg/L
ORP less than -75 mV
This was injection sequence for each of the 2-foot long treatment intervals:
22 gallons of GEOFORM Slurry
5 gallons Anaerobic Water
0.4 liters SDC-9 Microbial Culture
5 gallons Anaerobic Water
22 gallons GEOFORM Slurry
If you have experience with slurry injection projects, you know that surfacing or daylighting of the slurry mixture can occur, and often does at some point.
After hand-augering the first 5 feet bgs and with injections starting at 9 feet, we had only 4 feet of native soil available to create an effective seal. Surfacing was successfully managed using our standard mitigation methods.
Upon completion, each injection point was grouted, bottom-up, using a Tremie with a portland cement/bentonite (≤ 6%) slurry.
3 gal water
50 lb Portland Cement Powder
≤ 3 lb Bentonite Powder
As with most of our projects, they are industrial areas and are not very scenic. The best view we had at this site was the sun shining through the transmission towers, chain link fence, and barbed wire over our portable toilet :-).
Like many slurry injection projects, this one presented typical challenges, but it was completed safely and on schedule. If you have any questions about this project or would like to discuss how we can support your current or upcoming projects, please don't hesitate to please contact us.
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