News and Events - "DS Article"

Welcome to our newsroom! Here you will find the latest information about our company, projects and people. Browse articles published by our engineers and scientists in national publications and conference proceedings, view our press releases and read through news coverage of Terracon.

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We have an App for that: Bringing Efficiency to Process

Environmental AssessmentSaving time and money on your next environmental site assessment just got a little easier. Terracon’s new Environmental Site Assessment (ESA) Field App allows assessors to be more efficient while conducting the site reconnaissance and completing report writing for Phase I ESAs.

This mobile app, developed by Terracon, is the first of its kind in the environmental industry. It can be used for most of Terracon’s Phase I ESA projects. Technology associated with the app creates opportunities for Phase I Practitioners and other Terracon professionals to streamline assessment processes, efficiently coordinate project deliverables, and communicate issues to clients faster. The mobile app is estimated to save 25,000 to 30,000 total labor hours per year and won the EDR 2017 PRISM Technology Innovation Award.

“We are fortunate to have an incredibly dynamic team who enjoy rising to the challenge of making our processes better each day.” John Sallman, National Director, Terracon Environmental Services.

Prior to the development of the app, each assessor would take a site reconnaissance form, note pad, camera, and/or mobile phone into the field to complete each reconnaissance. Then, back at the office, photos would need to be uploaded to the project file and notes taken would be transcribed into the applicable sections of the Phase I report.

Now with Terracon’s ESA Field app, all the assessor needs is a mobile phone!  Once on-site, our assessor collects necessary data to populate  several sections of the ESA report, including the interview, site observations, adjoining properties, and if applicable, additional services such as limited sampling of building materials. The content of the app is structured based on the ASTM standard requirements. Additionally, the assessor can take representative photos and begin a site diagram, all within the app.

With necessary questions and user friendly answering options, the app allows the assessor to streamline site reconnaissance and be confident the necessary information was collected in the field. Once the required questions in the app are answered, the data can be uploaded to Terracon’s server. The  ESA report draft can be generated, with information entered in the interview, site observation, adjoining properties, and additional services sections of the app transferred to the applicable sections of the report. Photos taken in the app will be uploaded to the project file and the site diagram features will be uploaded to Terracon’s GIS Toolbox.

“It was really fun to be part of the team that was given the time and creative freedom to design this app,” said Emily Blakeway, field scientist in Terracon’s Seattle office. Emily Blakeway was part of the app development team that included several assessors and IT personal from Terracon offices across the country.

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Using Collaboration and Communication to Reduce Geotechnical Project Risk

One of today’s buzzwords is “Risk.” We all have experience with the prime example of risk and risk mitigation: insurance. Simply stated, insurance mitigates financial risk by paying some money to make sure that we never have to pay a lot of money if something goes wrong.

Risk is certainly relevant to the geotechnical profession. It comes into play when characterizing the subsurface soil, rock, and groundwater conditions (which, it turns out, can be quite variable), evaluating foundation design options, and selecting a particular design addressing the pertinent construction and performance problems to the satisfaction of the owner’s risk tolerance. But who “owns” the risk, and how is it exposed and mitigated?

 Preparing you to make informed decisions

Communication is a critical aspect of risk awareness and mitigation. At Terracon, we have developed a collaborative platform to inform our clients of the site conditions, foundation options and risks associated with the options. We want our clients to be well informed. With the right information, you can make the decisions that impact your construction costs and schedules, and adequately address your risk tolerance.

Using our web-based GeoReport platform, we inform you of subsurface condition, and associated compatibility considerations for your planned structure, and suggest various foundation designs and means of construction, noting the risks associated with each. For instance, a larger foundation, which may be more expensive, and slowly constructed, can reduce the obvious risks; however, a well-informed owner can select a foundation choice consistent with his or her risk tolerance, perhaps one that shortens construction time or reduces cost and maximizes value. To accomplish this interaction, vibrant collaboration among the consultant, owner, and other appropriate team members is essential.

The Hidden Risk

Geotechnical risk considerations can include unforeseen construction delays, unexpected subsurface conditions, poor foundation performance (such as excessive movements), and end-user safety.  There is also another risk that is always present, yet rarely discussed: the risk of excessive foundation costs and associated construction time for foundation elements that were not necessary in the first place. Overly conservative designs are the result of insufficient designer/owner collaboration and insufficient risk assessment. Just as it is important to understand risk exposures when buying insurance to avoid being over- or underinsured, collaboration is essential for a more complete understanding of your risk tolerance and can lead to more efficient designs and improved long-term performance.

Learn more about GeoReport

For a quick introduction to GeoReport, how it quickly provides the information we gather, our geotechnical recommendations for design and construction, and how it allows all stakeholders to think through the options together, watch this 80-second video.


We encounter risk in all we do, and that certainly applies to geotechnical aspects of construction. At Terracon, we are building a better way to work with you, our clients, as a team to understand and mitigate risks on your next project.

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Structural Steel and Welding Inspection – A Critical Service for Building Construction

FAA tower with rainbowStructural steel and welding inspection is a critical service for building construction. Poor welding or misalignment of steel components can adversely affect the structural performance or safety of a building. This is important for all buildings, but especially for critical structures such as hospitals and schools that must be able to withstand seismic events.

To protect buildings and their occupants, Terracon’s approach on structural steel projects is to form a close working partnership between our project inspectors and structural engineers.

Communication Yields the Best Results

Communication on these complex projects is key. Pre-fabrication and pre-erection meetings should be mandated to be sure that all team members (general contractor, inspector, fabricator, erector, and structural engineer) understand the requirements. These meetings are a good opportunity for the structural engineer to review the important aspects of the structural steel design, such as critical components like brace frames and moment frames.  Opening communication between inspectors and structural engineers saves time, allowing the inspector to help clarify project requirements, when questions come up during construction.

Welding procedures, applicable to the project, must be submitted and approved by the structural engineer.  Many structural engineers do not have the expertise to review welding procedures, and will utilize other consultants to advise and recommend acceptance.  Terracon has in-house welding experts to perform this welding procedure review.

Details are Critical

It is very important that structural components such as brace frames, moment frames, and other elements are installed in the proper location, within specified tolerances.  For upgrades in existing structures, there can often be existing conditions that interfere with the placement of the new structural steel members.

Inspectors must carefully detail any fit-up issues in the inspection report. The inspector needs to make sure that the contractor accurately describes nonconforming issues in Requests For Information (RFI) forms and submits them to the structural engineer for clarification and/or approved fixes.  Inspectors are required to be certified by the American Welding Society and/or the International Code Counsel and also need to be certified to perform, when required, nondestructive testing, such as ultrasonic or magnetic particle testing on welds.  These certifications require a high level of training and expertise.

A welding inspector must measure the size and length of every structural weld.  Field welds on brace frames are critical.  These welds are often welded out of position or can be undersized if there is a gap between the tube and gusset plate.  The fillet weld size must be increased by the size of the gap.  The alignment tolerances of the brace frame tubes are also critical and are usually detailed on the structural drawings.  There is often an erection bolt through the tube and gusset plate.  If the erector can’t get the erection bolt through the hole, there is likely an alignment issue that requires an RFI.

When welding new structural steel to existing structural steel, the existing steel must be cleaned to bare steel prior to welding.  Welding through coatings such as paint and galvanizing can lead to weld cracking and lack of weld fusion.

Bringing it All Together

When structural steel inspection is a required part of the project, it is important to build a collaborative team.  Structural steel and welding inspectors must have a high level of expertise and good communication skills. At Terracon, our materials professionals add value to your project at any stage. By joining your team early in the design process, we can identify, evaluate and recommend the right materials selection, welding procedures, and nondestructive testing, optimizing them for the project, which can speed construction and reduce costs.

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What’s Under the Hood (Concrete)?

Using ultrasonic echo tomography is a very useful structural diagnostic technique for diagnosing surface and internal concrete defects.

Ultra Sonic Echo Testing

Cracks, spalls, and surface defects such as voids, honeycombing, exposed rebar, etc., are typical symptoms of distress associated with reinforced concrete structures. These symptoms are typically identified as a precursor to a potentially larger issue hiding under the concrete surface. To an owner, this can mean unanticipated costs, potential impacts to building operations, and even safety concerns. The process of finding what has caused the defects will include an evaluation of distress symptoms such as cracks, voids, and surface defects. This effort requires a combination of visual assessment, and field and lab testing to develop a prognosis of the issue. One very useful and powerful tool used for assessment is ultrasonic echo tomography.

Defects in new or existing construction come from improper construction practices, improper design details, accidents, or sometimes natural disasters. These defects can impact the integrity of the structure and lead to sustainability and usability issues.

What is Ultrasonic Echo Tomography?

Ultrasonic echo tomography is a non-destructive test method used for evaluating the condition of hardened concrete by measuring the time of ultrasonic shear-wave transmitting in the hardened concrete. A shear-wave which is transmitted in an isotropic medium will be partly reflected when it reaches another medium with a different acoustic impedance. The amount of energy reflected depends on the significance of difference in the acoustic impedance of the two media. The effectiveness of ultrasonic echo testing in identifying defects inside concrete has been proven in many field applications.

3-D Ultra Sonic Testing

Diagnosis of A Reinforced Concrete Aeration Tank

This project involved a newly constructed cylindrical aeration tank that was designed to hold wastewater. The tank had an inner diameter of 63 feet, and a height of 18 feet. Our client observed concrete construction defects, including map pattern cracking, cold joints, and honeycombing on the exterior face of the reinforced 1-foot thick concrete wall of the tank after the forms were removed. These defects raised serious concerns related to the water-tightness of the concrete structure and its structural integrity.

Ultra Sonic Testing

To identify the probable causes of the observed defects, and determine if subsurface defects existed that were not visible on the surface, Terracon performed Ground Penetrating Radar (GPR) test and ultrasonic echo tomography test on the wall (on both interior and exterior faces) at several locations. The results of GPR test indicated inconsistent and less than specified concrete cover thickness near the exterior face of the wall which had contributed to the map pattern cracking mimicking the pattern of the reinforcing steel cage. Based on the 3-D models obtained from ultrasonic echo tomography test, the defects appeared to be limited to the vicinity of the exterior surface of wall, with no additional subsurface concrete flaws.  This was verified by through-wall coring performed on the concrete wall.

The findings allowed the client to determine that the new tank structure did not require demolition. They could be confident that the extent of observed surface defects were limited in nature. The structural engineer of record proposed a surface sealing repair coating to verify the water tightness of the structure. Significant demolition cost and schedule impacts were avoided.

Ultrasonic echo tomography is just one of the non-destructive techniques that can be utilized in evaluating concrete structures. With each unique project, a combination of a reasonable structural/materials evaluation and use of appropriate advanced non-destructive testing technology can help save time and money for all stakeholders.

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Prevent Damage: Advance Testing of Chert Can Prevent Concrete Integrity Issues

ChertThe integrity of structural concrete is critical in projects large and small. The composition of the concrete varies, and common components of aggregates such as chert can have a great impact. Known for its beauty by rock collectors and gemologists, chert, when contained in aggregates used in concrete can be a source of integrity issues. Testing of aggregates for chert content in advance can help prevent issues in structural concrete down the road.

Ubiquitous and beautiful

The use of aggregates containing chert in concrete mixes is common in the southern United States, where chert occurs as massive beds and in river gravels. Its presence is also common in the Midwest where it tends to occur in river gravels and in glacial sediments, and where it occurs as a relatively small percentage of the total aggregate composition.

Chert is of interest to rock collectors, gemologists, geologists, and knappers (those who produce stone tools like those of Native Americans), and it is used in the production of sharpening stones and abrasive products. But one of the most common uses of chert is as part of the aggregate in concrete products.

Challenges caused by use

The issues relative to the presence of chert in concrete aggregate are two-fold. The physical properties of chert are variable – it can be non-porous and dense, or contain vugs*, macro pores, and micro pores, which render the chert highly absorbent. Absorption of water and subsequent freezing can result in what are commonly called “pop-outs” in the concrete because of the chert particles fracturing and dislodging from the concrete surface as a result of the expansion and contraction that can occur during the freeze-thaw cycle. Typically, these pop-outs are confined to the chert itself, and result in minimal damage to the surrounding concrete, although they can be cosmetically undesirable. In other cases, chert pop-outs can be a significant issue. For example, when they occur on airfield pavements they can lead to significant damage to landing or departing aircraft. Loose chert particles from pop-outs on a runway can cause airplane tire damage and can even be ingested by jet engines.

Of even more significance is the chemical composition of the chert. Because chert is essentially silicon dioxide, certain types of chert (chalcedony, opal, agate) can chemically react with the alkalis (sodium and potassium) present in Portland cement, the key bonding ingredient in structural concrete. The chert and alkali interaction cause a reaction known as alkali-silica reactivity (ASR). ASR can result in the formation of expansive amorphous (non-crystalline) silica gels, and in turn result in severe damage to structural concrete. These issues often happen over time and may not be obvious early in the life of the concrete.

Preventing issues down the road

Fortunately, testing for potential damage due to chert content can be performed before the first batch of concrete is placed on a project. Terracon can perform laboratory testing to pre-qualify the proposed aggregates to assess aggregate chert content and potential reactivity to avert potential issues. Analysis of in-place structural concrete can also be done on specimens from the existing structure that may show signs of deterioration so that issues can be assessed and solutions addressed.

Once initiated in the presence of water, ASR is progressive and irreversible. For this reason, the initial identification of the presence and quantity of chert by a qualified petrographer, such as Terracon can provide, prior to use as concrete aggregate is recommended. If chert is found to be present, more sophisticated mortar bar tests can be used to determine whether the chert is indeed reactive with the alkalis in the Portland Cement and, if so, the rate of mortar bar expansion and potential mitigation measures needed before the mix designs are finalized and concrete is mixed.

What is Chert?

Chert is a sedimentary rock consisting almost entirely of microcrystalline or cryptocrystalline silica (silicon dioxide) with minor impurities. Included in the term “chert” are the varieties of silica known as chalcedony, jasper, flint, agate, opal, onyx, porcelanite, and novaculite (metamorphosed chert).

*Vugs are irregular cavities in rock caused by dissolution of minerals, which may or may not be lined with crystals.


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Critical Roadwork: Design for Crucial Florida Road Project

I-75 corridor in FloridaAt one point, the north/south corridor of Interstate 75 (I-75) in Florida’s Broward and Miami-Dade counties was a road with relatively light traffic allowing motorists to cruise along at highway speeds most of the time. This changed after Hurricane Andrew blew through in 1992. Andrew leveled thousands of homes and businesses, causing a mass migration to the newer, available homes along the I-75 corridor. With this shift, new traffic patterns developed along I-75 and other major roadways, creating significant areas of congestion in some cases.

The Florida Department of Transportation (FDOT) responded to the challenges with plans to alleviate traffic congestion and improve connectivity. The plans included additional lanes and enhancements to existing roadways and reversible, dedicated open-road toll lanes. Early in 2014, construction began on the $485 million road project, which was scheduled in four segments.

Having provided geotechnical and materials testing services for a number of South Florida projects, Terracon served as an instrumental part of the Segment E improvements. As with most area projects, the geotechnical design was complicated by existing marshy terrain and unknown subsurface conditions. Terracon’s subsurface exploration team worked quickly to collect all the necessary data from the field, enabling our geotechnical engineers to collaborate with the project’s lead designer, WSP USA, to understand the conditions.

In order to test and confirm pile depths and capacities, Terracon’s pile-driving analyzer and operating engineers were deployed together during construction to work with the team. This data gathering phase was complicated by the need to keep traffic moving. Key challenges for the maintenance of traffic included reducing traffic shifts, limiting lane closures, and reducing weaving and merging.

As the project progressed into construction, Terracon went on to perform all the contractor quality control (CQC) testing of the materials on behalf of Dragados USA, the design-build contractor. CQC services included laboratory testing of soils and concrete, and other key components including bridge inspection, to ensure contractor compliance with FDOT plans and specifications.

In addition to working closely with WSP USA and DUSA, the Terracon team needed to coordinate with the construction engineering consultant firm (CEI), Target Engineering, and FDOT. Tasks included communication about data, scheduling, testing, and reporting results. A unique challenge for data reporting on this project was moving data entry from the Laboratory Information Management System to the Materials Acceptance Certification system at the midpoint of the project.

Terracon provided reliable data using properly trained, certified, and experienced staff to confirm the integrity of the materials used met the project specifications. The Terracon team included technicians who had completed FDOT’s Construction Training Qualification Program (CTQP).

They observed and tested more than 600,000 cubic yards of excavation and embankment material; 700,000 square yards of base material; more than 35,000 tons of asphalt materials; and more than 50,000 cubic yards of concrete.

With the project nearing completion and soon to be fully open to traffic, South Florida residents and commuters will greatly benefit from these unique, reversible toll lanes. The project provided an opportunity for Terracon to further demonstrate our transportation support capabilities and capacity utilizing multiple team members from three of our nearby offices. As a go-to consultant for critical transportation projects like I-75, Segment E, Terracon is committed to the transportation industry and proud to help our design and construction clients solve challenging issues through creative solutions.

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The Age of the Drone: How Unmanned Aircraft Systems Expand Building Investigation Boundaries

Unmanned Aircraft SystemWhen a window is too high to reach, a building is difficult to access by scaffolding, or a facility is too large to survey—call in the drones! The introduction of small Unmanned Aircraft Systems (sUAS), or drones, has added exciting new options for providing building investigation services with greater accuracy and increased efficiency.

Traditionally, assisting owners, architects, and contractors tackle building enclosure issues, performance deficiencies, and maintenance investigations of their properties has meant setting up staging equipment or acquiring the largest boom lift available and hoping for safe access. This access can be time consuming, expensive, and inadequate for the task at hand. Drones can provide a safer and quicker option for examining the components of a curtain wall, accessing a recessed ledge on an architecturally-challenging building, performing construction monitoring, or inspecting large roofs and structures in substantially less time.

Revolutionary Service Options

Access improvements and increased safety are attractive and easily recognized benefits of sUAS for due diligence services. The lesser known, more exciting, features are what drones are doing to revolutionize services and options for building investigations. Services such as photogrammetric mapping and thermographic imaging are quickly expanding in both application and effectiveness. Photogrammetric mapping is the use of photography for surveying and measuring distances between objects. Industry applications include mapping of architectural features for historic preservation, measuring existing structures’ elevations to be converted into CAD drawings and repair documents, and measuring spoil piles in geological and environmental earth moving projects. Photogrammetry allows a sUAS pilot to preprogram flight patterns over a desired location, and record the photos sequentially. The sequence of photos can later be “stitched” together to generate real-time overhead location maps, footprints of existing facilities, up-to-date elevation drawings for as-built documentation, and design and retrofit documentation.

Unmanned Aircraft System in flightThermography, a process utilized by building enclosure consultants for decades, is simplified through the use of sUAS. The value of a thermographic image allows technicians to identify temperature changes caused by possible moisture within a system, voids, or installation deficiencies not visible to the eye. Thermography equipment is most effective during a small window of time in the early evening dusk; when the sun has yet to set, but is low in the sky. Temperature differences between the roof assembly and the conditioned interior space are greatest during this time frame and allow for optimal imaging from thermographic cameras. Naturally expedient thermographic surveying of the roof area is critical for large facilities, but walking a large roof can be time consuming. Now, a thermographic camera can be mounted to a drone allowing the operator to cover more of the roof area. The GPS coordinates for all photos and drone footage are recorded when the image is captured, which allows for quick and accurate location and documentation.

Piloting the Industry

These new commercial capabilities require new licensing, permitting, safety considerations, and government oversight. The Federal Aviation Administration (FAA), state, and local authorities have several operation regulations of drones, with most states differing from federal requirements, and from one another. Private organizations, hobbyists, and businesses collaborate with the FAA to provide feedback for this dynamic industry, in an attempt to make sUAS effective and safe for the public. A remote pilot in command must be well aware of airspace when communication with air traffic control towers is required, where restricted and prohibited flight areas are designated, and of national airspace rules.

This technology is rapidly accelerating the execution of building enclosure investigations. Terracon’s facilities professionals are using drones to help clients with large scale projects and routine maintenance inspections, making building inspections easier and safer than ever before.

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Complex Demolitions: Do you have the right team to succeed?

Riviera Hotel and Casino demolition

Razing the Riviera

It’s not every day a Las Vegas icon needs to be demolished, but when it does, special expertise is required.

Terracon was selected in the summer of 2015 by the Las Vegas Convention and Visitors Authority to be a team member for a project to demolish all buildings on the 28-acre site of the iconic Riviera Hotel and Casino, located between the existing Convention Center and The Strip. Space was needed to attract larger conventions, and the Riviera site provided both the land for growth and direct access to the popular tourist area.

Working Together

The project team met multiple times over several months to discuss the project and work out responsibilities, schedules, and budgets. Other entities invited for input included the city, county, fire department, utilities (water, electric, and gas), regulatory authorities, and client stakeholders. The group was advised about possible environmental issues, including a Phase I site investigation.

Our team’s initial responsibilities included site exploration and reconnaissance to determine the impact, location, and quantity of asbestos, lead paint, hazardous materials, past leaking underground storage tanks, and associated contaminated soil at the site. After exploration and sampling, Terracon presented the results and provided budget estimates for complete removal of identified environmental concerns from the site. The collected data was then used to perform additional in-depth investigations and write remediation specifications for the removal and disposal of all asbestos and other hazardous materials, along with removal of the underground tanks and associated contaminated soil.

Safety is King in Demolition

After the bidding process and selection of a demolition and remediation contractor, the remediation and demolition began concurrently in April 2016. This meant safety considerations and procedures became even more important on this very busy and complex demolition site. The work was complicated by the intense summer heat (up to 115 degrees), which created a risk of dehydration to those working onsite. During the remediation phase, our team provided oversight and hazardous material removal verification. This work occurred while demolition was ongoing in areas with no environmental concerns and after other buildings were remediated.

Most of the buildings were mechanically demolished as the demolition contractor worked from east to west across the site. In the early summer, one building was imploded while remediation work continued on the older buildings on the west side. By mid-August, the remediation work was completed in the remaining buildings. In the early morning on August 16, the final three buildings were imploded and only rubble was left of the historic property. The remediation phase and the overall project was completed on time, meeting a very ambitious schedule within budget parameters and in a safe manner.

See the demolition work:


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Paving the Way: Preserve and Maintain Your Investment with Pavement Management Programs

Pavement managementYou wouldn’t consider driving your car 20,000 miles without changing the oil, rotating the tires, or having it inspected. Similarly, it is not a good idea to ignore needed maintenance of your pavements. Postponing timely pavement maintenance may buy more time, but that time will be expensive. Escalated costs for more extensive repairs are the likely result. Exposure to sunlight, rain, freeze/thaw cycles, traffic, and time, all have damaging effects on pavement. Pavement deterioration begins immediately after construction and without maintenance, environmental, and structural stresses can accelerate the process.

Life-Cycle Understanding Aids in Management

Pavement quality deterioration follows a typical life cycle. The initial 40 percent reduction in pavement quality occurs over the first three quarters of the pavement’s lifespan. At this point the pavement has reached a critical level of wear. Beyond that point, the pavement quality rapidly declines. The next 40 percent of quality reduction occurs over the next 12 percent of the pavement life. What may cost $1.00 per square foot to maintain pavements prior to the critical point rapidly increases to about $5.00 per square foot for repair if the pavement is left to further deteriorate.

Keeping pavements at certain levels of quality involves timely inspections, application of fundamental engineering decisions, and expenditure of funds. But if critical decisions about how and when to engage preventive maintenance strategies are appropriately made, the life-cycle costs of pavements can be lowered by 400 percent, even when the time value of the money to perform preventive maintenance is considered. Traditional approaches have left these maintenance decisions up to facilities personnel, who may engage a local contractor to select treatments based on reactionary, limited or biased information.

Planning Helps to Establish Engineering Budgets

Pavement management brings applied science and engineering into the process of identifying requirements needed to maintain pavements. An engineered pavement management program should consist of three major components:

  • A regular, scheduled pavement inspection program
  • A database to inventory collected data and consistently rate pavement quality
  • Engineering and economic analyses to evaluate strategies to increase return on investment and provide the engineer’s cost estimate associated with each strategy

This management approach is used to plan annual pavement repair/preservation programs and is an integral part of developing annual maintenance budgets for pavements. The management of pavements generally takes place at two levels, network and project.

This management approach is used to plan annual repair and preservation programs and is an integral part of developing maintenance budgets. The management of pavements generally takes place at two levels—network and project.

Network Level Management
In network level management, a relatively small percentage of the pavement is inspected to obtain a snapshot of the current condition. The data is also used to project the future condition of the pavement. Projections provide the information needed to identify and schedule potential project-level areas requiring maintenance and rehabilitation in current and future years.

The forecasted maintenance requirements can also be compared with the actual costs which can be allocated for pavement maintenance and rehabilitation. Using this comparison, coupled with projected pavement condition, priorities can be established for the entire network.

Project Level Management
At the project level, a detailed condition survey is undertaken to develop actual quantities for maintenance and repair. The results of project level pavement inspection are combined with budget and/or management constraints or both to produce the final maintenance and rehabilitation project list for any particular program year. Final plans and specifications are developed and used in the bidding process.

Terracon’s engineers can help clients with any of these pavement management services for city and county roadways, as well as parking lots and drive lanes associated with commercial developments, educational facilities, hospitals, and airports. In addition to evaluation and engineering services, we can provide construction support to include construction administration management, assist with the bidding process, and construction materials testing and observation. Our teams provide start to finish solutions for your pavement needs.

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Demolition and Clean Up Heat Up: Commissioned demolition of an incinerator

Many communities have obsolete infrastructure that represents an underutilized asset, often posing an environmental or safety hazard to the community. Terracon recently assisted one such community with a former municipal solid waste incinerator removal to allow repurposing of the building. Challenges on this project included the presence of hazardous ash impacting porous and non-porous surfaces, significantly limiting the recycling and reuse options for the non-porous (steel) components of the incinerator. To eliminate the exposure hazards and maximize the recycling potential to help control overall project costs, Terracon developed a cleaning and monitoring plan that allowed a large volume of the steel and other non-porous components to be recycled safely and effectively.

Terracon was contacted by a demolition contractor with whom we had completed previous demolition and cleaning projects at former incinerator sites. Our team developed a cleaning and management plan that was approved by the Minnesota Pollution Control Agency that allowed recycling of large volumes of metal materials. Terracon completed supplemental assessment for asbestos and cleaning validation to document the effectiveness of the cleaning process.

Unique Cleanup and Disposal

Cleaning was completed using high pressure washing, with wash water collected within the incinerator building. Terracon provided visual clearance of cleaned materials prior to off-site shipment for recycling. After cleaning was completed, the wash water and accumulated sediment required management and disposal.

Similar projects had utilized settling and/or bag filtration to remove heavy metal laden particulate from the wash water to below discharge limits of the local publicly owned treatment works (POTW).  Initial settling and bag filtration tests on the water showed that zinc and cadmium concentrations were well above the applicable discharge limits of the POTW. Terracon’s industrial wastewater group was contacted to assess the situation and determine if treatment was feasible, bringing our experience with pre-treatment of heavy metal laden wastewater in industrial settings to bear on this field application.

A round of jar tests was conducted to determine if the metals were dissolved, chelated, or present as a fine particulate. The metals were determined to be dissolved but not chelated. A pH of 10.5 was selected for the initial treatment, which is between the minimum solubility pH point for zinc and cadmium, and would provide for precipitation of metals from the wash water. The pH was then adjusted prior to discharge in accordance with POTW requirements.

Safety Considerations Met

Significant safety considerations were discussed and mitigated due to the handling of strong acids and bases in the temporary system under bad weather conditions. Terracon conducted the on-site treatment in temperatures below zero degrees F. Initially, the pH of the water was adjusted to 10.5 with caustic using an air wand for mixing. The solution was allowed to settle and was pumped into a temporary batch treatment system. Two plastic, 1,000 gallon tanks were used to neutralize the water prior to discharge.

The water met metals and pH limits of the POTW and the treated batches were discharged to the sanitary sewer system. This treatment process was significantly less costly than other management options considered. The project was completed on schedule and on budget. Following the project, the demolition contractor’s supervisor made a point to call the Terracon department manager and thank him for the professional, efficient, and friendly service that had been provided on-site under difficult conditions.

Terracon is a provider of environmental, facilities, geotechnical, and materials testing services. This project is an example of the collaboration of multiple practice areas within the environmental service line to help our clients meet their regulatory, business, and community needs.