White PaperSinkhole 101 –

Understanding and Conquering

Sinkhole Repairs with URETEK’s

Deep Injection Process

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The URETEK Deep Injection process is one of the best ways to repair shallow sinkholes that occur close to the surface.

Hi-Tech Concrete Coatings, Inc. is a premier applicator of high-performance coatings and resurfacers for concrete floors. The launch of our URETEK ICR Northeast division expands our services to include soil stabilization, concrete lifting and infrastructure sealing and repair.

The URETEK Deep Injection process provides customers with a minimally disruptive, economical, long-term solution for sinkhole repairs.

Overview:

• Recent weather events that have impacted our region with rain and floods have caused an extreme amount of sinkhole issues.

• When initiating a sinkhole repair, the objective is to prevent further movement of loose material and remove the triggering mechanism that causes the sinkhole.

• Repair methods are varied depending on the economics and location of the sinkhole.

• Many repair options are costly and time-intensive – requiring the use of heavy machinery, a wide range of repair materials, and much manpower.

• The URETEK Deep Injection process offers customers a timesaving, money-saving solution for sinkhole repairs.

Executive Summary

Hi-Tech Concrete Coatings, Inc.

430 Oak Lane, Lititz, PA 17543

Phone: (800) 220-COAT (2628)

Email: info@hitech-coatings.com

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Hi-Tech Concrete Coatings and URETEK ICR Northeast offer a unique, highly effective sinkhole repair solution, that creates soil stabilization where needed. This is made possible through the use of our revolutionary URETEK polymer and the URETEK Deep Injection process.

This white paper will:

• Define what types of sinkholes can occur and what causes them.

• Discuss different sinkhole repair options.

• Discuss the URETEK Deep Injection process that is offered by URETEK ICR Northeast.

• Provide an understanding of how sinkhole repairs are executed using the URETEK Deep Injection process.

• Highlight the benefits that are realized from using the URETEK process.

Introduction

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On their 1967 album, Sgt. Pepper’s Lonely Hearts Club Band, the Beatles featured a song called “Fixing A Hole”. The song holds some interesting lyrics that can apply to the saga of dealing with sinkholes: “I’m fixing a hole where the rain gets in…”

The reality about sinkholes is that without extensive geo-technical testing, they are very unpredictable – a black hole, literally.

The recent weather-related events that have bombarded the entire East Coast, particularly our region, have left a path of damage on homes, commercial buildings, and the ground beneath and around these structures. Shallow sinkholes are one of the many problems that have surfaced and caused headaches for many.

Types of Sinkholes

The following points are the basics related to repairing sinkholes – whether “true” or “false” sinkholes:

Sinkhole-like subsidences (“false” sinkholes) can appear for several reasons – mine subsidences, the decaying of buried organic material (such as tree roots or trash), the collapse of buried relict structures, or the washout of fill around pipes, especially due to a water main break.

“True” sinkholes are caused when surface material collapses into a void space beneath the surface. Under natural conditions, this process occurs very gradually but can be hastened by human activities. The timing, location and extent of a collapse usually have many influencing factors.

Sinkholes: Understanding the Causes and Challenges Behind Traditional Repair Options

Causes

Sinkholes can result from the collapse of the roof of a cave (called cover collapse) but typically it is the piping of unconsolidated material from one location to another that causes most sinkhole events. This means that underground soil particles erode and wash through channels in the subsoil down through the Karst drains (Karst: a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite). Water is generally the primary triggering mechanism for sinkholes.

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The two primary goals of sinkhole repair are:

1. Stabilize the affected area – by stopping loose material from flushing down into the drain (a fissure in the bedrock that returns water to the aquifer).

2. Prevent recurrence of the failure – by removing the triggering mechanism and its source. It is important to understand why the failure occurred so that a durable repair can be made.

Repair methods are varied, and the method used depends largely on economics and the location of the sinkhole. The method and materials needed to fill in a small sinkhole in a backyard or in a rural area can be quite different from those needed to repair a sinkhole in the middle of a street or under an occupied home or business in a highly urbanized area. Repair tools and material vary greatly as well.

During repair, the sinkhole’s triggering mechanism must be addressed in order to minimize additional soil settlement or sinking. As water is generally the primary triggering mechanism, it is necessary to identify and remove to the extent the possible source of the water that may have caused the sinkhole.

It is better to construct the plug (drain stopper) directly at the location of the bedrock drain. This allows the plug to be in direct contact with the bedrock, providing a better seal. Sinkholes in which no bedrock is encountered, and where the soil cover is thick, require careful geologic analysis followed by various costly repair methods, ranging from pressure grouting (also called permeation grouting) in the subsurface, to driven piles having concrete caps and gravel-mat backfilling.

Repair Methods – Inverted Filter Approach, Compaction Grouting, Permeation

Inverted Filter Approach

The inverted filter approach is often used for sinkhole repair, especially when the sinkhole is not located near structures that require advanced, engineered support. Under this method, the sinkhole area is excavated to expose either bedrock or the throat of the sinkhole. A course of rock large enough to bridge the throat of the sinkhole is placed at the bottom of the excavation. Courses of progressively finer rock and gravel are compacted above the base course. A geotextile fabric may be placed above the finest gravel course to prevent excessive loss of the uppermost course, which may consist of sand and/or soil. One benefit of the inverted filter method is to provide filtration treatment of storm water and to permit controlled infiltration and groundwater recharge (the drain is still unplugged but water flow is controlled).

Compaction Grouting

This sinkhole repair technique may consist of excavation to bedrock, placement of low-slump mix (such as cementitious grout) in the excavation, and placement of compacted fill to grade level. This approach should be taken with caution, because grout loss may be excessive if the underlying solution conduits are large (the hollow nature of karst terrain provides conduits through which underground streams flow through).

In 1997, a contractor in central Pennsylvania attempted to grout cavernous rock at a roadway project and found that the cavernous area took an enormous quantity of grout (4-5 truckloads). Within hours, the job site was visited by the Pennsylvania Fish and Boat Commission who was called to investigate an extensive fish kill at a nearby wild trout stream. In this case, the grout flowed readily through bedrock openings into a major, water-filled karst conduit and then to the nearby stream.

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Typically, compaction grouting is the injection of a very stiff, pumpable cementitious grout mixture at very high pressure into specific areas in the soil. The expanding globular mass of grout then compacts the soil around each point of discharge. Compaction grouting is most commonly done in stages, working from the bottom up, since this is the fastest method. It is generally used for pre-construction site improvement, to halt foundation settlements, rectify sinkhole problems, and to lift and level slabs and foundations.

Advanced grouting techniques, such as compaction grouting, may be used for more demanding sinkhole repairs. The grout consistency, pressure of grout delivery, and grout placement strategy are important aspects of these more advanced methods. Consideration should be given to the potential for interference with groundwater circulation and induced flooding due to the sinkhole repair. Sinkhole repairs should include active measures to limit the exposure of the repaired area to storm water, if feasible. This is related more to high volume cementitious grout blocking the subterranean natural path of runoff.

Permeation

Permeation methods are effectively used to fill voids, cracks, fractures, cavities, and to create barriers to the movement of liquids through the ground. Permeation grouting is the direct pressure injection of a fluid grout (chemical or cementitious) into the ground to fill the spaces between particles. Pressure grout methods are used for preventing water flow, stabilizing granular material, encapsulating organic material, and improving the physical properties of soil or rock. Structural chemical grouting, when used in granular soils, permeates the spaces between the soil particles, binds the particles together, and improves the soil’s bearing capacity. This process is not necessarily intended to restrict water but when injection points are laid-out in a well-designed grid pattern, these masses interconnect to form an underground structure or curtain that inhibits fluid migration from moving through the soil. The process is quite flexible, can be designed to cause minimal disruption at the surface and therefore, is advantageous for use in urban areas or areas of limited access.

Repair Methods – Inverted Filter Approach, Compaction Grouting, Permeation (continued)

Challenges

There are many challenges associated with sinkholes and the traditional methods that are used to repair them:

• Heavy machinery is often required to repair sinkholes. This equipment can require a lot of manpower to get it to the site and to operate it.

• A wide variety of materials and mixes are typically needed for a repair, including concrete, soil, grout, synthetic filter fabrics, and various sizes and mixtures of crushed stone.

• Injection holes for the repair materials are large and very invasive.

• High pressure is required to pump the heavy grout to the location of the repair.

• There is no expansion strength in the repair materials used, so over lift occurs to compensate for any shrinkage that may occur.

• More water is introduced when using a cementitious grout – adding more weight (approx 135 lbs per cubic foot) to already distressed soils.

• Repaired sinkholes can reactivate and collapse repeatedly if the drain into the bedrock is not satisfactorily sealed off. A new sinkhole can appear next to one just repaired, utilizing the same bedrock drain. This can lead to additional costly damage or safety hazards.

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The URETEK Deep injection process is one of the best ways to repair a shallow sinkhole. Because severe structural damage can result from shallow sinkholes, immediate and conclusive sinkhole repair is critical.

URETEK Deep Injection is a combination of chemical, compaction and permeation grouting that will not cause environmental damage, stabilizes the soil at perimeter of the throat, can fill and plug the throat, and can cap the soil pipes, filling the voids and micro-fissures within the soil at the injection site. The unique URETEK polymer is the key factor in the repair.

While traditional chemical grouting fills the soil cavities and pores with a waterproof material, it does not have expansion characteristics of the URETEK process. The URETEK Deep Injection process gives long-term stability to the area affected by the shallow sinkhole and is the best solution for shallow sinkholes and sinkholes that occur close to the surface where compaction grouting is not an option. The URETEK Deep Injection process is the safest and most accurate method of filling sinkhole voids and densifying loose soils that exist within 15 feet of the surface.

The use of our revolutionary URETEK polymer in conjunction with the URETEK Deep Injection process, delivers long-term results that are:

• Fast – the unique repair process requires no digging, and projects can often be completed in hours or days. With traditional sinkhole repair methods, additional digging can be required and the time required for project completion can last weeks.

• Effective – The URETEK polymer has been used to successfully complete over 75,000 projects nationwide. The lightweight, expansive polymer material not only realigns concrete liabilities but also addresses the problem at the source – giving the customer a long-lasting solution.

The Solution: URETEK Deep Injection Process

• Economical – The repair process is priced consistently below alternative repair methods, and implementing repairs significantly reduces the chance for further repair costs down the road.

• Minimally Disruptive – Unlike other repair methods, the URETEK process is minimally disruptive to the surrounding elements – which could be home residents, building workers, or vehicle traffic (depending on sinkhole location).

• Durable – The URETEK polymer that is used in the repair process is specially formulated for stability and strength – even in the harshest environments. The URETEK polymer is moisture resistive, and the Deep Injection process is guaranteed against loss of dimensional stability or deterioration.

• Safe – Liability risk is greatly reduced by the repair process, as a result of a safer environment. The process and material are eco-friendly and meet today’s high environmental standards.

The benefits realized by the URETEK Deep Injection process are many:

• Minimally disruptive environment – for residents, workers, or traffic patterns.

• Reduced liability concerns that result from a safer environment.

• Long-term cost savings from the extended durability of the URETEK process.

• Continued high value of property asset.

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The goal of any sinkhole repair is to quickly and effectively achieve a stabilized environment with minimal intrusion on the affected property. A properly executed sinkhole repair requires the expertise of URETEK ICR Northeast. This division of Hi-Tech Concrete Coatings specializes in stabilization applications, with the use of its revolutionary URETEK polymer. The URETEK polymer technology was developed through a partnership with leading chemists at Bayer Material Science. The polymer material is formulated to be lightweight yet have powerful lifting and stabilization features, and maintains impressive compressive strength under the heaviest of loads. The polymer is also proven effective and environmentally safe in over 125,000 projects worldwide over the past 20 years.

The URETEK Deep Injection process is a simple yet highly effective method for stabilizing strata and repairing sinkhole environments:

• Dynamic cone-penetrometer tests and engineering evaluation of structure and soils determine placement and volume of the URETEK polymer.

• The expanding URETEK polymer is placed precisely at the soil strata depth where soil compaction and densification is needed.

• The URETEK polymer is injected using a controlled, low-impact process that is managed by a small, skilled team of URETEK operators.

• Multiple injections at varying depths build columns of vertical support. This “top down” injection method is often used on shallow injection applications as it strengthens the upper layer of soil to help contain the pressures of the lower levels of compaction.

• Once injected, the polymer material expands up to 25 times the material’s liquid volume, and strengthens to 100% within 30 minutes. This rapid expansion is what causes compaction (and is referred to as chemical grouting).

• Through this non-destructive process, soil compaction and densification occurs, and void areas are filled and fully stabilized.

Understanding The URETEK Deep Injection Process

• The end result is that problematic sinkholes are effectively fixed at the source.

Other URETEK Facts:

• The unique URETEK polymer is specially-formulated to uphold stability and strength over time – even in the harshest, saturated soil environments.

• URETEK operators have precise, surgical control of polymer placement during the injection process.

• The URETEK process can also be an effective solution for infrastructure sealing and repairs, including emergency restoration. The versatility of the URETEK polymer makes it ideal for repairs involving manholes, sewer systems, dams and levees.

Many sectors within the industrial, commercial and residential market have benefited from the stabilization solutions offered by Hi-Tech Concrete Coatings and URETEK ICR Northeast:

Engineering – Soil stabilization at industrial plants and parks; concrete lifting at manufacturing facilities in the automotive, steel, food & beverage and pharmaceutical industries.

Property Management – Soil stabilization and concrete lifting at apartment and condominium complexes to repair walkways, driveways and parking lots; infrastructure repair for emergencies such as sinkholes.

Commercial – Lifting and stabilization for sinking office foundations and shopping center plazas; alignment of warehouses to loading docks; densification of eroding soil under a golf fairway; stabilization of sunken concrete at big box stores.

Rails and Ports – Stabilization of soil in dock areas and railway crossings; filling of concrete voids in eroding bulkheads in port cities.

Residential – Stabilization of weak soil underneath patios or pool decks; erosion control at waterfront homes; sealing and stabilization of eroding joints and failing bulkheads in bay and lake houses.

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So if the “rain gets in”, it will likely “stop your mind from wandering” – since that mind will now start seeking solutions for “fixing the hole.” The Deep Injection process offered by URTEK ICR Northeast is the best way to fix that hole! It’s minimally invasive, economical, and long-lasting and utilizes a simple yet effective method that provides a complete solution for achieving success in your sinkhole repairs.

The URETEK Deep Injection process provides many benefits:

• Increased productivity from the minimally disruptive repair process

• Reduced liability concerns

• Long-term cost savings

• Continued high value of property asset

The end result is a properly repaired sinkhole environment with stabilized strata that is durable and will provide maximum efficiency for years to come.

To learn more about the URETEK Deep Injection process and how it can resolve your sinkhole or other soil and concrete challenges, visit our website at www.hitech-coatings.com.

Or contact us at:

Hi-Tech Concrete Coatings, Inc. 430 Oak Lane, Lititz, PA 17543 Phone: (800) 220-COAT (2628) Email: info@hitech-coatings.com

Summary

Hi-Tech Concrete Coatings, Inc.

430 Oak Lane, Lititz, PA 17543

Phone: (800) 220-COAT (2628)

Email: info@hitech-coatings.com