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High Efficiency In Situ Treatment Technology for Contaminated Groundwater

Final Report Summary - HEISTT (High Efficiency In Situ Treatment Technology for Contaminated Groundwater)

Executive Summary:
The HEISTT project has provided a proof of concept prototype that provides a novel Side Grip Excavator Mounted Vibrator, Ultrasound enhanced piling, geotextile well lining and liquid injection to rapidly install treatment chemicals into the subsurface treatment zone. The improved installation rate, control over well depth and accuracy in chemical injection ensure that in situ treatment can be delivered in a cost and resource efficient manner, lower or removing barriers to its use.

The HEISTT model considers contaminant concentration and location alongside 3D groundwater flow and contaminant transport simulations to deliver an optimised treatment plan in which the minimum number of wells and volume of reagent are placed strategically rather than in the more traditional grid pattern. Because groundwater modeling software are advanced level tools that require a significant amount of knowledge and training, a simpler online calculation tool is developed within the scope of this project to predict injection well numbers and spacing.

The HEISTT method was tested on site first at DAWSON’s own trial area, where only the piling system was tested without any injection materials being used. In Doncaster, the UK and Hoek, the Netherlands, two private property contaminated areas were selected for trials. Both sites were surveyed first and then modelled in order to determine injection well locations and remediation chemical amounts per well. Injection wells were placed as close as possible to the points suggested by the model. Regenesis’ product called ORC for on-site chemical oxidation was injected inside the plume areas and periodic monitoring has been going on since.

HEISTT proved to be a fast piling and injection method for remediation chemical delivery as initially intended. The online calculation tool is likewise a quick method that does not require professional knowledge of groundwater modelling to be used. HEISTT method proved practical and showed commercially promising results overall.

Project Context and Objectives:
HEISTT is a European collaborative project with the intention of creating an innovative system of injecting remedial chemicals in to the subsurface for the purpose of treating contaminated groundwater. The proposed technology aims to develop a rapid and highly efficient method of application providing enhanced efficiencies for the installation of this type of treatment and removing cost based entry barriers for those wishing to implement in-situ oxidisation based remediation.

The idea for the HEISTT concept derived from the rapid installation of multiple band drains, deployed to introduce chemical treatment for the remediation of polluted groundwater plumes. Chemical remediation treatments such as oxidation and reduction are generally well established and successful, nevertheless at individual sites they can be financially uncompetitive, with high installation costs as a result of specialist rig hire, and slow rates of drilling.

Project Results:
Scientific knowledge of ultrasonication in soil is gathered through experimentation of the effects of sonificiation on pile insertion force. It can provide basis for future product development on many sectors that use piling as part of their processes (i.e. construction, remediation, bulk handling, pharmaceuticals, agriculture, geographic modeling and in-situ analysis). Further experimentation is needed in order to achieve better understanding of the effects of sonification on soil. The potential for the system to operate in a much gentler manner than is currently available on the market is clearly demonstrated by the ability of the ultrasound probe to reduce force by around 25%. European Design Rights Application has been made for the probe produced within HEISTT project.

The HEISTT groundwater treatment system is the main S&T result which is a combination of integral S&T results. It offers the force of a Dawson excavator mounted vibrator (EMV), enhanced soil fluidisation from a Sinaptec ultrasound enhanced piling tip, an Afitex geotextile well lining system and reagent injection function which can be used together to provide a single operation remediation solution or as standalone modules depending on site specific requirements.

The EMV grip provides a firm hold for cylindrical piles. This permits the system to index vertically along a leader facilitating continuous piling of longer length stems. The leader also allows the crowd force of the EMV to be deployed without the vibration function.

The combined design of the pile stem and ultrasound tip facilitates the delivery of both power/control for the ultrasound tip and liquid injection. A comprehensive in-line diagnostic and tuning system allows the system to be tuned in-line with the ground resistance being encountered. Site treatment results reported via the HEISTT database will inform pre-set modules which will be available in commercial models supplied with Sinaptec’s NexTgen Ultrasound Power Pack.

Piling rates for the HEISTT system show the full range of combinations possible and demonstrate it’s suitability for use in a wide range of construction applications beyond remediation.

The high performance geotextile from Afitex has a multifunctional role, providing a low friction casing for the drill string during piling/extraction and faciltating targeted application of remediation chemicals. The geotextile is durable and can be inserted in to the well with no further well liner required in many cases. It is particularly suited to the creation of permeable reactive barriers in locations where possibilities for excavation are limited.

To shape the geotextile it is passed through a funnel shaped former which wraps the textile around the pile as it is inserted. A sacrificial anchor is used to couple the geotextile to the drill string during piling.

A decision support tool is designed to help novice level users get an estimation of likely treatment costs on contaminated land. The tool is hosted at web address as a functioning and free in situ remediation design tool. It is unique because it is primarily designed using the physics behind pressure injection of sludge material into pervious media. It calculates the Radius of Influence of injected material underground, and therefore determines the number of injection wells needed in a given contaminated groundwater site.

Further information on science and technology results can be found as case summaries attached to this report.

Potential Impact:
HEISTT system was proposed to represent a change over the existing in situ chemical remediation of contaminated sites. Through the implementation of the Landfill Directive (199/31/EC), disposal of contaminated soil and landfill will be banned across the EU. The HEISTT system was designed to offer an alternative to those SMEs currently involved in off-site remediation of contaminated soil without burdening them with capital expenditure. This meant a simple in situ treatment system which the companies could use to replace their current systems in compliance with the Landfill Directive.
The HEISTT system allows the user to calculate the number of boreholes and the dosage of remediation chemicals required according to site specifics via a user-friendly software. The piling system allows for increased speed for the installation of boreholes, speed and efficiency of chemical deployment is increased, resulting in an increased rate of remediation. The industry is expected to benefit from this system which could allow for a lower cost of compliance with the new legislation.

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