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.

If you are a member of the media, you may contact our media relations representative at media@terracon.com.


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Helping A Hospital: Diagnosing Indoor Air Quality and Building Operation Issues

Hospital culture demands that nothing is as important as the people in its care and those who serve them. So when a healthcare facility experienced elevated relative humidity levels, condensation on ductwork, and mold growth following general renovations and building additions, the building owner contacted Terracon. Our team began an evaluation of the performance of the heating, ventilating, and air conditioning system (HVAC) to determine if the system was maintaining cooling, dehumidification, relative humidity, and positive indoor air pressure per the original design.

DIAGNOSING THE ISSUES
A diagnostic assessment of the building mechanical HVAC and exterior enclosure systems were conducted to determine the potential causes of elevated humidity levels and related issues. Additionally, spotted ceiling tiles and mold growth on interior walls was found in several care rooms and common areas. Our facilities experts determined that the HVAC system was operating at a negative indoor air pressure and was in need of repairs along with recalibration of the automatic controls. With help from the commissioning agent, mechanical contractor for the project, and owner’s maintenance personnel, the automatic controls of the HVAC were re-calibrated and air balanced to provide a net positive indoor air pressure in the building and to correct and maintain relative humidity levels in the acceptable performance range.

The Terracon team of building specialists also provided extensive diagnostics of the building exterior to determine the pathways of moisture infiltration into the building interiors. Partial destructive investigative work was required to the building façade to observe the condition of the building exterior construction, air barriers, and sealants. The building height and limited access to the façade necessitated the expertise of our building exterior professionals trained to access the exterior façade via rope access. Architectural details for the building renovations and additions were studied to understand the designed versus installed methods of weather proofing and placement of air barriers. Extensive visual observations of the building exterior wall sections were also conducted to locate potential pathways of outside air infiltration and air movement between the outdoor environments and the indoor conditioned areas.

MONITORING MOVEMENT

In a further effort to investigate the potential areas of air movement between the outside environment and inside conditioned areas, and due to the urgency and target height, an infrared camera was mounted to an unmanned aircraft system (UAS) to scan the southern façades and identify variations in building surface temperatures. Scanning revealed isolated areas of the building façade that were possible areas of air movement between the outdoor ambient and indoor areas. To perform even more in-depth diagnostics, one area was selected for testing. A propeller blower door fan was installed with calibrated airflow and differential pressure measurement software to accurately determine air movement through the building façade. By testing a baseline of air leakage at an indoor air pressure of approximately 0.01-inches water gauge, air movement was quantified through the selected test area for comparison to any future repairs and improvements to the façade and air barrier. Safe smoke was introduced into the ceiling plenum of the test area to trace movement of air through the façade and other pathways in the exterior wall. The results from testing indicated that careful, detailed repairs to the façade and air barrier would be needed to reduce air movement from the outside environment to the inside areas, mitigating condensation and biological growth inside the building.

To develop a plan for detailed repairs to the elements of the building façade, Terracon assisted the design and contracting team in selecting fire-rated materials and sealants suitable for use in performing needed repairs that would improve the effectiveness of the air barrier and withstand typical building pressures generated by the HVAC system. Terracon performed a test of a prototype of the detailed repair for the test area and identified further areas in the façade for repairs.

MAINTAINING BUILDING HEALTH

As the detailed repairs were being performed, Terracon provided observations and testing of the installed repairs. Terracon will also observe the ongoing operation of the mechanical HVAC system to verify that the representative,interior areas in the building are maintained at desired positive pressure and an acceptable relative humidity. This hard work has paid off, providing a safer, more comfortable environment for the facility’s occupants.


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Experience Prevails: Uncovering Hidden Obstacles

Located just 10 nautical miles from the Atlantic Ocean in Jacksonville, Fla., Dames Point Marine Terminal is JAXPORT’s newest marine facility. Opened in 2009, it includes a state-of-the art container terminal capable of handling an annual volume of 800,000 to 1 million Twenty-Foot Equivalent Units (TEUs). With an increase in container volume, JAXPORT recognized the need for an effective rail connector and the development of an efficient intermodal transfer facility (ICTF). In 2014, it decided on a design-build delivery for the project. Terracon partnered with TranSystems and D.B. Kenyon to deliver a quality project while optimizing the budget within a tight time frame.

FACING COMPLEX PROJECT COMPONENTS

The new facility was constructed on approximately 45 acres of JAXPORT property and required relocating a mile-long public road that bisected the site. Components included remediation of lead from an old gun range facility, wetland mitigation, clearing and grubbing, unsuitable material removal, excavation and filling, importing base material, rock, asphalt pavement, reinforced concrete, roller compacted concrete, high mast LED lighting, buildings, gates, canopy, and railroad track.

According to Tom Selfridge, senior geotechnical engineer in Terracon’s Jacksonville, Fla., office, the team decided to further investigate a minor mention made in a preliminary report of possible debris buried in the soil at the construction site. Historic aerial photos were quickly reviewed and indicated relatively large areas of disturbed ground. These areas were scanned with a geophysical survey, utilizing ground penetrating radar (GPR) and electromagnetic induction, to look beneath the ground surface for possible voids or debris deposits. Finally, suspect areas were ground-truthed with backhoe-excavated test pits. Results of the testing were significant. More than eight acres of the construction site had debris hidden under ground level, including pieces of charred wood timbers and sheets, and shredded metal intermixed with sand.

“Without a thorough investigation of the site, the debris could’ve been missed and negatively impacted the construction,” said Selfridge. Terracon’s early awareness and resolution of the debris issue protected the project’s budget and schedule. Additional value was added by Terracon’s recommendation to screen the excavated debris deposit which allowed for re-use of its sand component and reduction in the volume and cost of the off-site waste disposal. Terracon’s resourcefulness continued to the construction phase as Chris Martin, Terracon materials specialist also in the Jacksonville office, adopted use of a geophysical tool (Kessler MIT Scan T2) to obtain real-time measurements of layer thicknesses during placement of roller-compacted concrete (RCC) pavements. After an initial test strip was completed to calibrate the contractor’s equipment and methods, the RCC was placed in multiple lifts up to a maximum total thickness of 20 inches. In addition to the value of real-time data, the scanner tool saved approximately $20,000 in testing cost as compared to the conventional rotary coring method, according to Martin.

Testing of the rail components required knowledge and application of requirements set forth by The American Railway Engineering and Maintenance-of-Way Association (AREMA). Field density testing was completed on the sub-ballast material and welding of the steel rail tracks was checked by ultrasonic testing.

In January 2016, the Port took beneficial occupancy of a $25 million state-of-the-art ICTF, delivered via design-build, on time and within budget.


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Determining Stability: Evaluating a Tunnel to Predict Performance Under Catastrophic Loading

Could a tunnel constructed more than 50 years ago still rapidly drain a reservoir if a catastrophe happened? This was the question Terracon helped answer regarding the 185-foot deep reservoir at the Broken Bow Hydroelectric Dam in Broken Bow, Okla.

Following Hurricane Katrina in 2005, the United States Army Corps of Engineers (USACE) mandated that each public reservoir be retrofitted to drain if there was a catastrophic event threatening the stability of the reservoir’s dam. To comply with this requirement, Terracon joined the team led by Mead & Hunt to evaluate the complex geology, subsurface conditions, and the concrete tunnel liner condition to determine the stability of the existing tunnel. To make sure the 18-foot diameter diversion tunnel met stability requirements, the USACE needed a geotechnical study performed. In the study, the USACE requested that no test borings, rock coring, or destructive testing of the tunnel liner be performed.

DISCOVERING HISTORICAL RECORDS

As part of the team, Terracon developed a multi-stage work plan to understand the original tunnel construction and assess its current condition. Boxes of USACE files of the original dam construction documents were reviewed, including 14 soil test boring logs, geological studies of the steeply dipping rock formations, and construction plans and photographs of the 1960s construction.

UNDERSTANDING GEOLOGIC CONDITIONS

After gaining a thorough understanding of the tunnel design and the geotechnical/geologic conditions, it was time to investigate the tunnel with the team. With the safety of the workers a priority, Terracon crafted a 200-plus-page safety plan including an activity hazard analysis for each team member responsible for accessing the wet tunnel and climbing the rock outcrops.

The work plan included a review and geologic mapping of nearby outcrops of the same rock formations cut by the original tunnel excavation and performing sensitivity analyses. Geologic strike and dip measurements were made, as well as joint spacing and the location of faults and discontinuities. The team then interpreted aerial Light Detection and Ranging (LiDAR) images of four major outcrops for joint patterns and bedding characteristics of the native bedrock. Rose Diagrams and Stereonet Pole plots were created to define structural geology properties such as the dominant orientation of bedding planes, folds, and faults. Using the collected data, Terracon provided calculated estimates for the Rock Mass Rating characterization parameters (RMR) and the Rock Quality Designation (RQD) for the rock along the tunnel alignment, as well as Headcut Erodability indices.

DOCUMENTING TUNNEL CONDITIONS

The next stage of work included conducting a detailed visual condition study of the concrete tunnel liner, documenting the location and width of all cracks, mapping areas of seepage, and estimating seepage flow. To approximate the compressive strength of the tunnel’s liner concrete, the team also performed Windsor Probe testing. Terracon performed ground penetrating radar (GPR) data acquisition to determine the concrete liner thickness, assess the presence of voids in the liner, and to detect the presence of delaminations within the concrete.

Terracon concluded that most of the original tunnel liner was in good structural condition and suitable for use as an emergency spillway of the Broken Bow Reservoir under high velocity flow. The conclusion that the 55-year-old liner could perform under catastrophic loading was great news. The report did document local areas where the concrete liner was detached from the bedrock face, as well as many areas where active seepage was occurring. To control seepage and fill voids in the liner created by the original wooden blocking points and rotted timber cribbing, Terracon recommended the tunnel liner be pressure grouted with chemical grout.

Controlled and engineered weep holes would be designed and placed through the concrete tunnel liner to relieve hydrostatic pressures. This fast-paced, detailed study was impacted by record rainfalls during the data-gathering field operation. This project was truly a collaborative and seamless effort with Mead & Hunt and the Tulsa District USACE personnel.


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Brownfields Redevelopment: Revitalizing a Cultural Heritage Center

 

A touchstone to the Hispanic community in Utah, Centro Civico Mexicano (Centro) is a place where generations celebrate the traditions of their heritage. Centro was first established in 1935 by Mexicans who came to Salt Lake City and surrounding communities to work on the railroads and in the mines. Today, the well-loved cultural center is solidifying its commitment to future generations by revitalizing its downtown property; made possible through a combination of brownfields funding tools.

IDENTIFYING HISTORICAL USES

Originally purchased in the 1950s, the Centro property was facing the all-too-familiar challenges of urban neighborhoods—aging facilities in need of repair, pressure from surrounding development as part of downtown gentrification, and options to sell the property and relocate. Knowing the challenges at hand, community leaders decided it was time to reconstruct and design a new facility at the site of Centro’s existing home.

“The best reason for the cleanup and new construction is to build a showpiece representing the history of Hispanics in Utah and to give them something to be proud of, including taking part in an environmental improvement of the District,” said Brandy Farmer, president and CEO, Centro Civico Mexicano.

Serving as a trusted partner, Terracon helped Centro assess the property’s history, identifying past industrial uses on the site and surrounding properties as part of the Phase I Environmental Site Assessment. Terracon discovered the site had been contaminated by Polycyclic Aromatic Hydrocarbons (PAHs) from past coal use, and chromium and petroleum hydrocarbons from other past industrial activities. These needed to be cleaned up to meet the requirements of the new development. Development money was raised to cover the new proposed Centro buildings, but not the environmental costs.

BROWNFIELDS FUNDING SOLUTIONS AID CLEANUP

Terracon provided solutions to address both the environmental issues identified and the unexpected financial challenges associated with the cleanup. By helping Centro prepare successful applications for both an EPA Brownfields Cleanup Grant and a Revolving Loan Fund Cleanup Subgrant from the Wasatch Brownfields Coalition, Centro received $400,000 in funding to aid in the cleanup.

Although a small footprint, this piece of downtown Salt Lake City has a powerful future. The new plan for mixed-use development will include low-income senior housing, offices, classrooms, a multipurpose gymnasium, a rooftop soccer facility, and a black box theater.

“This has been one of my favorite projects. The people working on this are fantastic, and together they are all bringing solutions to the table,” said Craig Eaton, Terracon’s environmental department manager in Salt Lake City. “My thanks go out to everyone at Centro Civico Mexicano, Corroon Development Company, Salt Lake City Corporation, Salt Lake County, Utah’s Voluntary Cleanup Program, EPA Region 8, EPA Office of Brownfields & Land Revitalization, and the generous foundations in the local community.”

Belinda Richard, Terracon’s national Brownfields program manager added, “This project is a wonderful example of how local partners, community members, and regulatory agencies can come together to make a project happen—it takes a village.”


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Earth-Sheltered Buildings Require Special Expertise for Roofing and Waterproofing

When you think of an earth-sheltered building, what image springs to mind? For some, this could be Hobbit homes like those seen in Lord of the Rings movies. In the real world, these buildings can offer a number of advantages and unique challenges for their owners. Benefits include the protection soil can offer from extreme weather and they have very little exterior up- keep. Yet, over time the materials used to originally waterproof the facility can begin to breakdown and can be difficult and costly to repair due to tons of soil overburden installed to protect the very building.

In commercial buildings, waterproofing failure can commonly cause a host of issues. This was the case with an earth-sheltered utility building at a hospital facility in Anderson, S.C. where years of leaks led to rusting reinforcement and spalling concrete from the concrete deck. The South Carolina Department of Mental Health (SCDMH) contracted with Terracon to provide Design and Contract Administration services for the waterproofing of their earth-sheltered utility building that had been built in the 1980s. The facility provides the utilities, laundry, storage, automotive repair, grounds keeping, and facility management office space to support the nearby hospital.

The utility building was built with two of the four elevations and the roof underground. The foundation level of the facility was approximately twenty-four feet below grade and the roof had approximately two feet of soil over the concrete deck. A masonry parapet wall retained the soil from being pushed over the edge to the elevations at the lower grade level.

Previous attempts to fix the leaks along the top of the below ground wall met with little success. With the knowledge of the attempted repairs in mind, Terracon’s team accomplished field work and generated a design that waterproofed the entire wall down to the footing level to alleviate the persistent leaks occurring throughout the below-ground portions of the building.The design also lowered the grade to below the roof level. By doing this, Terracon’s team eliminated having saturated soil resting over horizontal surfaces such as the roof deck and at critical junctures such as at the intersection of the roof and wall.

The design required that the contractor excavate down to the roof deck and the foundation. The existing waterproofing on the roof and walls was made up of a peel-and-stick asphalt membrane over the concrete and a layer of gravel to provide drainage down to the sub-grade drain. The contractor removed all existing waterproofing membranes, and existing drainage piping and exposed the concrete deck, wall, and top of the foundation.

In lieu of reinstalling a “green roof” type assembly, which would look most like the pre-existing system, the Terracon team designed a more typical and economical roof system utilizing asphalt sheets over insulation. Not reintroducing the soil to the top of the roof helped provide easier access to maintenance personnel to identify leaks and perform routine maintenance.

Additionally, due to the age of the structure and presence of rusting reinforcement, there was concerns with re-loading the roof deck with soil. Doing so may have caused excessive deflections or possible failure of the structure.

Leaving the below ground walls exposed was not an option due to the height of the surrounding soil, so a system was designed with redundancies to help prolong the life of the waterproofing. The system utilized a liquid applied membrane over the concrete wall, and a self-healing waterproofing sheet. Drainage is accomplished by a protective drainage board to take the water within the soil to the drain that led to a nearby existing detention pond. The drainage board alleviates hydrostatic pressure from the wall and waterproofing system and also serves to protect the waterproofing from the adjacent soil.

The result is a practical compromise with a building that serves the needs of the South Carolina Department of Mental Health by eliminating leaks, failed leak repair attempts, providing a roof system which is easier and more economical to maintain and simultaneously maintaining some of the advantages of below grade construction at the walls, all for the long term asset performance of this building for the state agency.


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Accreditations Matter: Being the Best Project Partner

For many municipalities, protecting the public and homes and businesses from the threat of flooding is a major priority. Based on geographic location and local topographic and man-made drainage conditions, they may be more susceptible to flooding due to heavy rains, hurricanes, and or downstream floodplain issues. Such was the case for rehabilitation of the floodwater-retarding structure for the Olmitos and Garcia Watershed #7 near the Rio Grande Valley in South Texas.

The Heeter Construction project management team quickly recognized the need for a partner with specific experienced staff and accreditation to provide quality control during construction. Terracon had the experienced staff and facilities, and was also able to draw additional staff from our other offices in the region to fully support the project demands.

Unique project needs met

Terracon met the general overall needs and requirements of the project with our ACI and NICET certified personnel and our AASHTO accredited and U.S. Army Corp of Engineers validated laboratory. In addition, the project involved the use of roller-compacted concrete (RCC), a construction technique that is not new to this type of construction project but one that was new to the region. RCC can be simpler, faster, and more economical than conventional concrete using the same components – cement, water, and coarse and fine aggregates – but using a drier mix stiff enough to be compacted into place by vibratory rollers.

With the wide breadth of Terracon’s experience in other regions of the country on similar projects, our team could bring their knowledge of the roller-compacted concrete process to the project and reduce the learning curve for our other staff and quickly support the project. Terracon was also able to provide quality control services that were new to the region as well. This included conducting a Vebe consistency test for RCC and slurry wall inspections (a construction technique used to build reinforced concrete walls in areas of soft ground near open water or with a high groundwater table).

Going the extra mile

Because Heeter could not proceed with certain phases of construction until test results were completed, submitted and reviewed, our team set up a 24/7 schedule and provided on-site quality control throughout the project’s construction stage. To save both time and money, our team also set up a mobile laboratory on site to avoid the need for transporting samples to our main laboratory 40 miles away, saving our client and the project time and money.

By providing the necessary qualified and experienced staff and accreditation along with our knowledge of the specialized construction methods used, Terracon played a key role in supporting Heeter’s on-time delivery of this important project. The result: a safer, more efficient process to make sure floodwaters can be properly controlled to protect the residents, homes, and businesses in the Olmitos and Garcia Watershed #7 region – and a successful partnership.

“Everyone has been fantastic and exceptional in response to our project needs and requirements” said Tony Rathbun, manager/business development, Heeter Construction. “We are very pleased and consider you folks a ‘project partner’ as we move forward.”


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The Advantages of Non-Destructive Testing (NDT) Techniques for Evaluating the Compressive Strength of In-Place Concrete

The evaluation of compressive strength of in-place concrete is often needed for projects of new constructions, structural additions and remodeling, and structural repairs. Traditional method of testing the compressive strength of concrete cores retrieved from a structure can be time-consuming and possibly damaging to the structure when a large number of structural members are under evaluation.  Alternative methods that reduce the needs of coring and cause no damage or limited superficial local damage to the structure are becoming more popular.

Non-Destructive Testing (NDT) Techniques

Non-destructive testing (NDT) techniques of evaluating in-place concrete strength measure some properties of concrete which can be correlated to the compressive strength of concrete cores. The well-known guidance of performing in-place concrete strength estimation are ACI 228.1R and ACI 228.2R which are issued by American Concrete Institute (ACI) Committee 228. Pullout testing is recommended by ACI 228.2R as the primary method of estimating the compressive strength of in-place concrete based on accuracy compared to other NDT techniques.

Test Methods for Determining Material Properties of Hardened Concrete in Existing Construction (referencing ACI 228.2R-13 Table 4.1.1)

Property Method
Primary Secondary
Compressive strength (ACI

228.1R)

Cores for compression testing

(ASTM C42/C42M and C39/C39M);

pullout testing (post-installed)

(ASTM C900)

Penetration resistance (ASTM C803/ C803M)
Relative compressive

strength

Rebound number (ASTM C805/

C805M); Ultrasonic Pulse Velocity (UPV) (ASTM C597)

In-place pulloff test (ACI 503.1R:

BS 1881-207) with appropriate

calibration.

NDT Techniques Prevents Project Delays

Pullout-TestThe Terracon team recently worked with a client on a project where a sixteen-story steel framing structure is proposed to be built on an existing twelve-year-old one-story reinforced concrete structure. The concrete mixture design information and concrete material testing records for the in-place concrete were not available to the client. To assist the client in determining if the existing reinforced concrete structure had sufficient capacity to carry the load from the proposed steel structure, pullout testing was performed on three footings and twenty-nine plinths which were identified as critical structural members by the structural engineer of record.

Terracon performed both core strength testing and pullout testing on 15 structural concrete members to develop a job-specific strength correlation. Once the strength correlation was established, the in-place concrete strength of additional members was estimated with pullout testing only. Pullout testing at each additional location was completed in about 40 minutes total from sample preparation to strength estimation The results indicated that the concrete compressive strengths were structurally adequate per the acceptance criteria given by ACI 221.1R. The pullout testing procedure allowed for testing of more locations more efficiently than if only testing core samples. A significant delay in project schedule was avoided.

Pullout testing is just one of the several NDT techniques that Terracon uses to evaluate in-place concrete strength, depending on project variables. Terracon is experienced with field and laboratory testing and statistical analysis, which assures NDT options that can be coordinated with the client and reliable and resourceful services are delivered in a cost-efficient and time-saving manner.


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Terracon Leads Efforts for “Legacy” Oilfield Site Reclamation

Thousands of oil and gas wells have been drilled in North Dakota over the past six decades – many long before the environmental regulations of today were in place. Today, some of the sites damaged from early exploration and production activity, referred to as “legacy sites”  remain and need attention.

In many cases, legacy site locations have been known for years but could not be addressed due to lack of funding or jurisdiction. Now, under state law with funding allocated and legislation in place, abandoned legacy site wells and production facilities where no responsible party remains, can be evaluated and action taken to address environmental impacts. The goal of this funding under the North Dakota Abandoned Oil and Gas Well Plugging and Site Reclamation Fund (AWPSRF) is to repair damages from legacy oil exploration and production to restore the land to productive use.

Developing feasible corrective action plans

Terracon was selected by the North Dakota Industrial Commission (NDIC) to provide environmental response services to remediate and reclaim legacy sites damaged by exploration and production activities and unclaimed petroleum hydrocarbon and brine releases associated with former well pads, pits, and seismic boreholes. Terracon’s environmental services include environmental response, site investigation, clean-up, remediation, reclamation, and well plugging, as well as drilling or other geotechnical and materials testing services.

Recently, Terracon was tasked with investigating subsurface impacts of a legacy reserve pit in western North Dakota where obvious surface impacts of stressed and dead vegetation were observed below the historical pit toward a nearby creek. A limited site investigation (LSI) was conducted to determine the extent and magnitude of contamination and to provide corrective action recommendations for remediation and reclamation. Based on the LSI results, initial cost estimates to remove and replace impacted soils, and the site’s priority level based on environmental risk, corrective action was put on hold until additional funding could be made available through the state legislature.

The initial design of the corrective action was revised to limit the amount of soils to be hauled offsite and avoid impacts to the nearby creek. The revised corrective action focused on: source removal of the pit and soils identified to be too contaminated to support vegetation based on electrical conductivity and chloride; mixing “borderline” soils and placing them in the bottom of the excavation; and experimenting with a soluble algae bioremediation product in wetland areas. This redesign reduced the cost to the state by more than $500,000 and resulted in 50,000 tons of soil being removed from the site. Because of the success of previous remediation and reclamation projects under the AWPSRF, the state approved additional funds to address the legacy reserve pit.

Restoring the natural environment

A Corrective Action Plan (CAP) was submitted to and approved by the NDIC. The scope of services in the CAP included the solicitation and selection of an excavation contractor experienced in brine and petroleum hydrocarbon soils remediation and selection of a special waste landfill to dispose of the impacted soil. To accomplish goals of final reclamation desired by the state, landowner, and tenant, environmental consulting oversight was provided during excavation to document site activities, field screen soils for segregation, and directly place backfill for grading. A storm water pollution prevention plan was designed as part of the CAP, and the erosion and sediment controls implemented ultimately proved vital to the project as drought conditions at the beginning of the project gave way to many work days being cancelled due to rain. Drone and GIS services were also provided in conjunction with laboratory analytical results to maintain remediation goals throughout the project to ultimately return the impacted area to productive agricultural use.


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Building an Airport in a Swamp: New Orleans Airport Construction Presents Challenging Site Conditions

The City of New Orleans is known for many things—Mardi Gras, the French Quarter, and Cajun cuisine, to name a few. This unique, diverse city located along a bend of the Mississippi River will celebrate its tri-centennial in 2018. As a tribute to this historic milestone, a new world class airport terminal was planned—the Louis Armstrong New Orleans International Airport.

The airport is one of the critical infrastructure projects that the City of New Orleans initiated after Hurricane Katrina devastated the area in 2005. The $950 million terminal complex will include three concourses encompassing over 1,000,000 square feet of space, 35 gates, a 2,000-space parking garage, and elevated access roads.

Terracon was selected by the global engineering design firm, WSP, to serve on the Quality Assurance (QA) team along with other consultants on behalf of the New Orleans Aviation Board.

Materials Testing Challenges

The new airport site, along with much of the city, is developed on very unstable soils that can be considered swamp land. To build on these subsurface conditions, significant ground improvement is necessary. Deep pile foundations were required to support buildings, as well as wick drains and surcharging to reduce settlement before construction of pavements could begin. Although Terracon’s engineers and technicians typically perform pile capacity and integrity testing on a percentage of piles in a given project, the airport project required testing on more than 7,600 piles.

Ready for the challenge, the Terracon project team quickly developed a strategy to undertake this massive testing requirement. The pile monitoring program developed by the team included almost 1,000 18-inch diameter concrete piles in the elevated roadway, and more than 6,600 14-inch concrete square piles in the main terminal and concourses. Piles ranged from 95 to 110 feet in length.

Value-Added Services

As the project has continued over the past two years, our scope has evolved and grown to include not only QA, but also special inspections, and building enclosure testing services for this massive project.

To support the project’s extensive materials inspection needs, the team provided field engineers to perform pile integrity testing on 100% of the precast piles supporting the buildings, and pile-driving analyzer (PDA) on 2% (150+ piles) of the precast piles driven for the project. We also provided special inspectors for reinforcing steel and concrete, masonry construction, structural steel connections, spray applied and intumescent fireproofing, and technicians for concrete sampling and testing.

As the project progresses, more testing will be required. We are also performing special inspection of masonry construction for the concourses, fireproofing inspection and roofing observation for the terminal and concourses. On the site, utility installation continues with Terracon technicians performing density tests of backfill, as well as cement treatment of pavement subgrade soils.

The Louis Armstrong New Orleans International Airport is currently scheduled to open in early 2019. We are proud that Terracon’s team of engineers, technicians, and partners are making a major contribution to keeping this momentous project on track for a safe, quality, and timely completion.


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Save with Seismic Site Evaluation: Piedmont Atlanta Hospital's Expansion

The science of structural design serves to protect the well-being of facility patrons and surrounding communities. The International Building Code (IBC) requires that structural design must account for the forces imposed by a potential seismic (earthquake) event. The design is governed by three factors:

  1. The Seismic Design Category (the critical or non-critical nature of the structure),
  2. The Site Class (a function of the subsurface conditions to 100 feet), and
  3. The proximity and magnitude of a probable seismic event.

The first factor, Seismic Design Category, is based on the anticipated use of the structure and occupancy, and leaves no room for interpretation. The IBC usually puts a hospital among the most rigorous design categories. Similarly, the third factor, probability of a seismic event, is based upon published information. The real work goes into determining the second factor; Seismic Site Class. When designing a hospital, it is important to get the second factor, Site Class, right.

Site Class is determined by the shear wave velocity of soil and rock within the upper 100 feet at the site. This can be estimated from Standard Penetration Test N-values (STP N-values), the geotechnical engineer’s experience and laboratory test results. But estimation of such a value must exercise conservative assumptions, and the cost of such conservative estimates may be very large for structures such as hospitals. Direct measurement of shear wave velocity can be accomplished, but at greater expense than simple estimations. When is it appropriate to directly measure this critical parameter, and when will estimations from SPT N-values suffice?

Meeting Challenges with Experience

In 2014, Piedmont Healthcare began planning and designing a new inpatient tower and subsurface parking deck at the Piedmont Atlanta Hospital. This top-rated acute-care community hospital, originally built in 1954, needed a major update. The project, totaling more than $600 million, included approximately 900,000 square feet of new construction and 47,000 square feet of renovations. Terracon’s skilled consulting and specialized field services allowed the seismic design for the hospital to be optimized, and resulted in estimated savings of hundreds of thousands of dollars.

This hospital is a IBC Seismic Design Category IV, requiring the highest level of protection during seismic events. Understanding the impact of conservative estimates on this large structure, the Site Class was initially established during the geotechnical exploration using surface measurement techniques of shear wave velocity, a common approach for typical projects. This geophysical testing approach resulted in a Site Class C. This Site Class requires significant foundation and structural elements to address the stability of the structure in the event of an earthquake.

Define the Problem to Create the Solution

The initial structural designs for the Site Class C conditions would require a significant outlay of funds to meet structural code requirements. Thinking proactively, Terracon collaborated with the structural engineer and architect to consider options that would alleviate this costly condition.

We developed an innovative solution to the challenging seismic evaluation and approached the problem from two fronts; reducing the amount of softer materials below the building and refining the shear wave velocity measurements with more rigorous geophysical site characterization.

The bottom floor level was lowered to within 10 feet from the top of rock. In addition, a more comprehensive downhole seismic test was employed to optimize shear wave velocity measurement. This testing approach utilized a single deep borehole drilled into bedrock using a downhole pneumatic hammer. A temporary casing was inserted to protect a sensitive geophone that was lowered to test depths throughout the profile. The geophone measured the first-arrival times of surface-generated shear waves. By comparing shear wave arrival times at different depths, the average shear wave velocity profile, well into bedrock, was calculated.

Staff from three Terracon offices worked together to perform the downhole seismic testing and successfully determined the necessary conditions were present to recommend a more favorable Site Class B.

The Value of Partnership

Following work on the design phase, Terracon’s Materials professionals addressed specific needs of construction materials testing and special inspections. Our partnering approach, knowledge of site conditions, the use of experienced field personnel, and multi-year commitment to working with the design and construction team, all contributed to Piedmont Healthcare’s selection of Terracon for construction materials testing and inspection services.