News and Events - "Technical Papers Library"

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.


All News and Events

Practical Method for Load and Resistance Factor Design of Deep Foundations at the Strength and Service Limit States

-


All News and Events

Surface Drainage is More Than Just Stormwater Management

-


All News and Events

The Marketing Metaphor

-


All News and Events

Improving Construction Practices with Special Inspections

We are all familiar with Murphy’s Law: anything that can go wrong will go wrong. When it comes to construction projects, the corollary to Murphy’s Law might go something like this: if more than one thing can go wrong, the thing that does go wrong causes the most damage and is costliest to fix.

A Special Inspection program provides valuable quality assurance/quality control that benefits all parties related to the proper fabrication, installation, and placement of specific structural components and other construction materials (e.g. EIFS, fireproofing, and soils and foundations) that require special knowledge, expertise, and attention. Ancillary benefits include improved communication between design professionals and contractors, testing companies and the jurisdictional building official, while providing a safe structure for the public.

The purpose of Special Inspections, structural observation, special testing, and quality assurance requirements set forth in Chapter 17 of the 2006 International Building Code (IBC) is to reduce damage and losses to structures by improving the quality of construction practices and to protect public safety. The keys to successful Special Inspections are clear communication, good record keeping, a drive to keep the project moving forward, and most of all, qualified people.

The national recognition of Special Inspections continues to increase as more jurisdictions are enforcing the requirements of Chapter 17. As a result, many architects and engineers, and even building officials and code inspectors, are being exposed to Special Inspections for the first time. This unfamiliarity with the concept and requirements of Special Inspections often leads to many questions, such as ‘Where did this come from?’, ‘What exactly is this all about?’ and ‘Where do I get started?’

Background
In the early 1980s, U.S. House Subcommittee hearings examined causes and common problems associated with structural failures. The subcommittee concluded that the two most critical factors to structural failures were a lack of organization and communication between parties on construction projects, and insufficient inspection by the design professional of record during construction.

As a result, the subcommittee made two basic recommendations. These included 1) that codes and professional organizations ensure that provisions are in place to make the design professional of record oversight mandatory during construction of public facilities; and 2) that state and local code agencies require the design professional of record, or a designated representative, be on-site at the appropriate times.

Because the design professional of record is not always available, more specific Special Inspector programs were defined and initiated on a regional basis. The International Conference of Building Officials’ (ICBO) Uniform Building Code, Building Officials Code Administrators International (BOCA) National Building Code, and the Southern Building Code Congress International (SBCCI) Southern Building Code all had provisions for special inspection. After the merger of the three model codes into the International Building Code (IBC), IBC Chapter 17 provided a broader scope of special inspection with more clarification.

What are Special Inspections?
Chapter 17, Section 1702 of 2006 IBC defines Special Inspection as:

“Inspection as herein required of the materials, installation, fabrication, erection or placement of components and connections requiring special expertise to ensure compliance with approved construction documents and referenced standards.”

Section 1704 goes on to outline the type of work requiring special inspection in addition to inspections called for in IBC Section 109 by the building official and structural observations in Section 1709 by the design professional in responsible charge. It should be noted that inspections required by Section 1704 do not relieve the building official or the design professional of record of their inspection and observation responsibilities. Types of work for applicable construction where Special Inspections are required by Section 1704 include:

· Fabrication (Steel, Pre-Cast Concrete, Wood)

· Structural Steel

· Concrete

· Masonry

· Soils

· Pile and Pier Foundations

· Sprayed Fire-Resistive Materials

· EIFS (Exterior Insulation Finishing System)

· Special Cases

· Smoke Control

The design professional of responsible charge must prepare a Statement of Special Inspections for the project that lists the critical parts of the building construction that requires special inspection. The statement shall include the materials, systems, components and work to have Special Inspections, the type and extent of the inspections, and identification of whether the inspections are continuous or periodic. Additionally, the statement shall list any additional seismic or wind resistant-related testing or inspections.

What is Exempt?
Section 1704 of the 2006 IBC indicates that designed building components that do not involve the practice of professional engineering or architecture as defined by state statutes and regulations do not require Special Inspection. Additionally, Special Inspection is not required for work considered by the building official to be of a minor nature or structures with occupancies in Group R-3 and Group U that are accessory to a residential occupancy. Other exemptions, or modifications to the IBC-published exemptions, may be applicable by jurisdiction as code enforcement agencies see fit.

Who is involved in Special Inspections?
The parties involved in Special Inspection include the project owner, local building code official, design professional in responsible charge, one or more Special Inspectors, a testing laboratory and the project contractor. Each party contributes to the success of a project’s Special Inspection program and has very defined roles and responsibilities.

Building Code Official
Before a project begins, the local building code official establishes criteria for the authorization of Special Inspection agencies and inspection personnel by inspection type and the inspection reporting processes and procedures. The building official will consider the requirement for Special Inspection prior to issuing a permit and will review and approve the project Statement of Special Inspection and drawings for construction. During the project, the building code official monitors the required inspection activities and verifies that the required Special Inspection is completed.

Owner
The Owner retains and funds a qualified Special Inspection agency, which may be employed through the project designer acting as the owner’s agent. The code specifically states that the project contractor can not engage the Special Inspection agency. In addition, the Owner works with the design team to revise the general conditions and specifications of the contract documents to reflect changes if contractor-supplied testing conflicts with Special Inspection requirements.

Design Professional in Responsible Charge (DPIRC)
During design, the DPIRC identifies specific components and work types that require Special Inspection and clearly states the requirements in the project documents through the Statement of Special Inspections and the Scope or Schedule of Special Inspections for submittal to the building official. In some jurisdictions, the building official may also request that the independent agency(s) engaged by the Owner to perform Special Inspections be identified in the Statement. During the project, the DPIRC should review identified non-conformance items and/or changes to the design for approval or rejection, and prescribe corrective action for any outstanding non-conformance items prior to covering up those items or moving to the next stage of construction.

Special Inspector
The role of the Special Inspector is to observe and test the work assigned for conformance with the approved and permitted construction documents. The Special Inspector may also review material test reports prepared by others for conformance to the design documents and requirements. The responsibility of reporting the Special Inspection observations lies with the Special Inspector as he is required to provide copies of reports of observations and tests to the building official, owner, DPIRC, and contractor. As part of the reporting requirement, the Special Inspector must inform those same parties of non-conformances and discrepancies.

A seasoned, experienced Special Inspector helps a major project maintain its schedule. Minor deficiencies that can easily be corrected are typically resolved the same day, with a minimum of paperwork. More significant non-conformances can be resolved quickly when the Special Inspector can discuss technical issues directly with the design team. The Special Inspector makes sure that the right people inspect the right things, and that complete and accurate records are maintained and kept up-to-date.

Testing Laboratory
In most locales that have incorporated a Special Inspection program, the Special Inspection agency and the testing laboratory are the same. In addition to testing the work assigned for conformance with approved documents, the testing laboratory submits copies of testing reports to the Special Inspector, owner, design professional, and contractor. Laboratories should also bring discrepancies to the attention of same parties.

Contractor
Before any Special Inspections take place, the project’s contractor should understand and make the Schedule of Special Inspections available at the construction site, as well as schedule a Special Inspection Pre-construction Meeting(s) with the responsible parties of the design team, the project owner, the Special Inspection agency and the local building official. The contractor should also provide adequate notification to the Special Inspector and building official to complete the inspections, access to the approved contract documents at the project site, and safe access for all inspections and tests. Following the completion of a Special Inspection work type, the contractor is responsible for correcting deficiencies in a timely manner and retaining the Special Inspection report copies at the site for review by the building official.

Although Special Inspections are defined in the International Building Code, it should be made clear that the enforcement, processes, procedures, scope of Special Inspections and even exemptions may vary by state, city, or county as jurisdictions develop their own programs. Therefore, it is important to understand how Special Inspections are interpreted and enforced locally. The old television phrase ‘check your local listings’ may very well apply to Special Inspections in your jurisdiction.

A Case Study Special Inspections Program
Over the past 20 plus years, special inspection programs have been developed and implemented in some major cities, including Kansas City and Las Vegas . The programs enforced in these cities have changed through the years and are today very advanced and mature programs. Other jurisdictions and municipalities have only recently published enforceable Special Inspection programs or are in the early stages of enforcement or development. One such program is in Charlotte, and Mecklenburg County, North Carolina.

From the introduction of Chapter 17 in the International Building Code until 2006, the State of North Carolina Building Code Commission included language in the State Building Code that left the requirement and enforcement of Chapter 17 up to the discretion of the local building official. Due to staffing and resource concerns, Special Inspections were basically non-existent in the state until 2002 when it was discovered that several new schools in the Charlotte area were missing steel reinforcement in concrete masonry. The magnitude of the discovered construction deficiencies was very surprising and led to officials of Mecklenburg County Code Enforcement to evaluate the need for Special Inspections and the development of a well-defined program.

Knowing that the development and implementation of a Special Inspections program would take time, the local building official began enforcing Special Inspection requirements as part of the permit application process in January 2003. In the very early stages of the program, Mecklenburg County officials relied on the design professional to state the Special Inspection requirements in the project documents when they were submitted for plan review and approval.

Early in the process, Mecklenburg County officials evaluated existing Special Inspections programs, specifically those from Kansas City, Las Vegas and Richmond, VA. Additionally, Mecklenburg County reached out to the local design engineering, testing and inspection professional community for advice and input to solicit ideas on how a Special Inspections program should be set up, implemented and enforced. One area of particular interest to the County was ensuring that truly qualified and experienced individuals were inspecting the work in the field.

The Mecklenburg County building officials recognized that field observations and inspections of work is a vital part of a successful Special Inspections program, and felt strongly that enforcement of inspector qualifications was essential. They evaluated several different means and methods for the approval of Special Inspectors. Again, the County asked local testing and inspection firms for input. Certifications, training, and experience were researched with the end product being 19 classifications of Special Inspector work types, each with criteria for approval by the County.

Another area of interest to Mecklenburg County was integrating information technology and the Internet into the program. Although Mecklenburg County is one of the southeast’s largest code enforcement departments, the County was very aware of the need for resources to develop, implement and enforce a well-defined Special Inspections program. Resource concerns included storing and maintaining records of submitted project documentation, additional administrative personnel, and researching and approving applications for Special Inspectors. The solution to addressing these concerns was to develop an on-line document submittal database that would be accessible by the code officials and the project team.

The result is Meck-si.com, Mecklenburg County ’s Paperless Special Inspection Management System. Implemented in January 2006, Meck-si.com is an Internet-based system that provides users with the definitions, requirements, procedures, forms, approvals, and submittal procedures for a comprehensive Special Inspections management program.

Edward S. Prince, AIA, CSI, CCCA, Esq. of Mecklenburg County Code Enforcement said that Meck-si.com is the solution to paper-based special inspection management.

“The pros of Meck-si.com are that we have improved inspector efficiency, cost savings, and consistency of our program being administered in the same manner,” Mr. Prince said. “There is also an ease of use in Meck-si.com through electronic searches, rules-based workflow, better quality control and better access.”

The program developed by Mecklenburg County is patented and available for other code enforcement agencies that may not have the resources or man-power to implement such a program.

“Essentially, Meck-si.com is Special Inspections in a box,” added Mr. Prince.

Special Inspections is expected to continue evolving over the next several years as the International Code Council, state, and building code officials learn more about the processes and receive feedback from owners, design professionals, contractors and field inspectors. Special Inspections are here to stay – with better communication and more comprehensive inspections resulting in higher quality construction, perhaps we can reduce or even eliminate Murphy’s Law from building construction projects.


All News and Events

Strategic Direction & Alignment: A Practical Application

There are books and books written on the topic of strategic planning. The topic can often be made overly complex and in many cases esoteric. At its most fundamental level, the goal of corporate strategy is about achieving a sustainable competitive advantage in the marketplace. Certainly, Terracon’s strategic plan focuses on the topic of competitive advantage. However, as a practical matter, it is most useful as a tool to set company direction and align our national network of local offices toward a common purpose.

A little background on Terracon is in order. The firm is 100-percent, broad-based employee-owned and provides services to a broad mix of private and government clients in four areas: geotechnical, environmental, construction materials and facilities. During the last 10 years, Terracon has grown from $71 million in annual revenues, 45 offices in 21 states, and 770 employees to annual revenues of $335 million, 98 offices in 34 states and 3,000 employees. About two-thirds of our nearly 500 percent growth has been internal and one-third by acquisition of regional firms offering similar services as Terracon.

The central focus in developing and implementing our strategic plan is to use it to transform our national office structure into a strength and source of competitive advantage. A highly decentralized office structure such as Terracon’s is often looked at as a potential competitive disadvantage, due to each office acting autonomously. We experience the general problem of “herding cats” that is part of all professional service businesses. Aligning nearly 100 offices and 3,000 employees in a common direction is a challenge but a tremendously powerful weapon in a highly competitive industry.

To accomplish this alignment, we use traditional and nontraditional strategic planning methodology. We begin in a traditional fashion with by appointing a strategic planning committee comprising senior managers of the firm. From there, the process is anything but the traditional, high-level approach. Our process can best be visualized as an hourglass shape. We start with broad input and research from many sources, and then narrow down the ideas to a succinct, practical plan. To implement the plan, we return to a broad approach in our communication and engagement of employees.

The specific process for strategic plan development involves multiple steps. First, the strategic planning committee, based on input from many sources, develops a draft plan. Then, a key step is to engage the firm’s 150 “principals” (the most senior contributors in the firm). Our approach is to conduct a hands-on workshop to obtain their specific comments, critique and suggestions on the draft plan. For us, this is a complex, yet critical and beneficial, step in the process. The committee then uses the principals’ input to develop the final plan. During our last planning cycle in 2006, the input from the principals was invaluable and materially improved the plan.

For the plan form and language, we believe in making it short. Our entire plan is printed on a tabloid-size document and consists of four sections; our mission, values, vision and goals (to achieve the vision). Separate from the plan, we also establish a set of financial and non-financial metrics to measure implementation progress.

To communicate the plan to the firm, we again broaden our approach. First, all principals receive a copy of the final plan and attend a web-based presentation to discuss the plan and ask questions. Then employees at all levels receive a summary of the plan, which is developed as a brochure. Office managers are provided with a tool kit, developed to assist them with presenting the plan to their staff.

During implementation, we avoid too much corporate hype and top-down requirements. Rather, we work hard to integrate the plan and the specific plan goals into all aspects of the company. For example, the plan is used at the corporate level to set the annual priorities and implementation initiatives for each corporate function (human resources, information technology, etc.). The strategic plan is introduced to new employees during orientation. We conduct an annual, multi-workshop leadership development program, and the strategic plan is a prominent focus. Fundamentally, we encourage each and every principal to use the plan in a proactive way to set the annual priorities in their area of responsibility.

Ultimately, our goal is for every employee of the firm to understand the plan and their role in its implementation. We have moved well beyond the strategic plan as a board of directors level planning tool. Today, we feel very good about the alignment and engagement of the principals in the plan and its implementation. For the broader employee base, feedback suggests an understanding that the firm has a clear strategic direction and plan, and that we are working effectively to implement the vision and goals set forth in the plan. Full engagement of all employees, that is connecting the plan to their roles, is a work in progress, as there is no such thing as fully accomplishing this goal. We do see principals and offices as well aligned with our company direction and working together to use the resources of a single, national company and a large geographic footprint as a source of competitive advantage.

David R. Gaboury, P.E., is President and CEO of Terracon, a consulting engineering firm providing multiple related service lines to clients at local, regional and national levels. Mr. Gaboury is a licensed Professional Engineer with more than 25 years of experience in environmental, geo-environmental and water resources engineering. He is a graduate of the University of Massachusetts at Amherst with a bachelor’s degree in Civil Engineering. Mr. Gaboury also received a master’s degree in Civil Engineering from the Massachusetts Institute of Technology and is a graduate of the Harvard Business School , Advanced Management Program. Prior to joining Terracon in 1997, he was with Woodward Clyde for 15 years, serving as the Chief Operating Officer and President of Woodward Clyde Consultants for the latter five years.

Headquartered in the Kansas City metropolitan area, the firm has grown from a small Midwest geotechnical engineering firm to a large, multifaceted national firm with more than 100 offices and 3,000 employees nationwide. Terracon’s 2007 revenues were $335 million, and the firm is the 51st largest engineering company in the as ranked by Engineering News Record. Terracon is 100 percent broad-based employee owned and is named by the National Center for Employee Ownership as the 35th largest employee owned company in the United States.


All News and Events

Maintaining Slab Subgrade

Methods to ensure a proper subgrade prior to concrete floor slab construction

By Ronald S. Lech, PE

During the construction of large slabs on grade, construction teams are faced with weather and construction traffic issues that can deteriorate the exposed subgrade prior to concrete floor slab construction. This is a particular concern where the sub-grade is a low-permeability clay or other fine-grained soil that may be sensitive to disturbance. There are several options available to owners, developers, and design and construction teams to maintain, or improve, the exposed sub-grade and subbase and keep your project on track.
A ticking time bomb

The construction of any large floor slab generally requires that the proposed building area be graded flat. This creates a situation of poor drainage that can lead to deterioration of the soil sub-grade, and even the aggregate base course, if these materials are exposed during wet weather. Likewise, construction traffic on the exposed sub-grade and aggregate base course can cause pumping and rutting of soils that are sensitive to disturbance from repeated rubber-tired traffic. This can happen even after the soil subgrade has been properly prepared and compacted. These problems can show up on any size project but are usually more pronounced on large warehouse-type jobs where the floor slab size requires multiple slab pours that may take weeks to complete. Time is often the enemy for exposed soils—the longer the soil and/or aggregate base course is left exposed, the higher the chance that undercuts or additional conditioning will be required prior to slab placement.
Wet subgrade during tilt-up panel construction. Photos: Terracon Co.

Because the extra undercut or conditioning work may cause delays that could ultimately end up being costly in terms of construction dollars and schedule, it is important to have a plan in place to protect these materials prior to achieving subgrade elevation during the mass earthwork phase. The following are several options to consider that maintain the integrity of the subgrade and keep your project on schedule.

* Chemical stabilization often is used to strengthen or make the upper subgrade soils more resistant to weather and traffic. Depending on the type of soil at your site, this could mean mixing lime, cement, or other additives with the upper 8 to 16 inches of soil below subgrade elevation prior to placement of the aggregate base course. If the process is done properly, it may be possible to achieve a higher modulus of subgrade reaction in the stabilized soil that could reduce the aggregate sub-base and/or slab thickness to offset some of the additional cost. It is important to work with the project geotechnical engineer to understand how the proposed chemical stabilization will affect the subgrade soils. During cold weather, lime can temporarily make the soil more permeable, thus creating even greater risk of subgrade deterioration during wet weather. Cement often sets up quickly and requires the contractor to be prepared to immediately fine grade the stabilized building pad. It should be noted that successful chemical stabilization can create a hard crust making excavations for utilities and foundations more difficult.
* Geosynthetics can be incorporated at the subgrade/subbase interface to provide additional strength and separation of the aggregate subbase and soil. Although both geogrids and woven textiles can be used, this is often a good application for a high-strength woven geosynthetic.
* Drainage can be improved by crowning the subgrade or installing finger drains across the building pad. Due to the large size of many warehouse-type slabs, the option of crowning the subgrade may be unattractive because this can require several inches of additional aggregate at the edges of the building pad to make the subbase level. Consideration also can be given to creating a network of shallow drains to control rainwater and prevent ponding. One source of drainage can be any interior utility trenches that are backfilled with free-draining aggregate and sloped for positive drainage. Additional finger drains can be constructed between planned utilities to provide adequate drainage. Often, it is necessary to have drains at a maximum 50 feet center-to-center spacing to provide sufficient drainage for a large, flat building pad.
* Staged construction can be used by only preparing as much subgrade at a time as the contractor can readily follow behind with slab pours. It also may be advantageous to cut or fill the sub-grade several inches higher than proposed grade in areas that will sit exposed. The high areas can later be cut to grade when slab preparations are imminent. These options minimize the exposure time for the subgrade soils but can create scheduling conflicts if multiple contractors are working on the site.
* Thickened aggregate base course can be considered above the soil sub-grade to resist weather and construction traffic. When using a thicker aggregate subbase, it is important to watch the fines content in the aggregate. Even though some state transportation departments allow up to 15% fines for typical dense-graded aggregate, many aggregates become sensitive to moisture and traffic when the fines content is above 10%. There are instances when a contractor thought he was buying additional weather “insurance” by increasing the subbase thickness with additional dense-graded aggregate—only to find that the high fines content resulted in a subbase that was as much (or more) sensitive to wet weather and construction traffic as the soil he was trying to protect.
* Frozen subgrade can be a concern for projects in northern climates. If the project area is too large to enclose and heat, it can be difficult to keep the subgrade from freezing when temperatures consistently dip below the freezing mark. In cold weather, it may be advantageous for the earthwork contractor to work 24 hours a day to avoid having to strip a layer of frozen soil at the beginning of the next day. Consideration can be given to placing a “sacrificial lift” of material over the prepared subgrade. This sacrificial material is allowed to freeze at the end of each work day and is then stripped to reveal unfrozen material. Concrete curing blankets can be used to protect the subgrade, and some blankets contain heating mechanisms that can thaw frozen subgrade.
Right: Shallow sump pits to remove water from aggregate base course.
Having a plan B

When all else fails, or the construction budget and schedule do not allow for the above listed preemptive strikes to be used, you still have options to repair a wet or disturbed building pad. If the soil subgrade is exposed and the aggregate subbase has not been placed, the typical methods include discing and aerating, undercutting and replacement, or chemical stabilization. If the aggregate base course has been placed, there are a few techniques that have been successfully implemented to save the pad without completely undercutting and starting over. If wet weather is the culprit, it may be possible to excavate a series of shallow sump holes and pump the water out of the aggregate base before it has a chance to soak into the soil subgrade. The sump holes usually are excavated adjacent to any interior column pads and at midpoints between the columns with the sump holes at maximum 20-foot spacings. This can be labor intensive, but if done immediately after a large rain event, it can get enough water out of the pad to save the sub-base.

Other techniques of drying the aggregate, such as windrowing and aerating the stone, can be considered if the aggregate subbase is thick enough but this could result in excessive mixing with the underlying soil subgrade. Sometimes the wet aggregate subbase and the uppermost soil subgrade can be mixed together and chemically stabilized in-place to avoid wasting the wet stone. This can create a firm subgrade but often at the loss of the aggregate subbase’s ability to provide drainage, cushion, and a capillary break. It also becomes very critical that the stabilized material be accurately fine graded to avoid variations in slab thickness.

If there is a light to moderate rain event, it is good practice to dig several shallow test holes with a shovel or hand auger to determine the wetness of the aggregate subbase and soil subgrade. Many times the rainwater has only wetted the stone and the upper fraction of an inch of the soil subgrade. Although this amount of moisture may lead to excessive rutting if the concrete is directly end-dumped with concrete truck traffic on the subbase, it may be possible to use a pump truck and successfully complete the slab pour by keeping traffic off of the pad.

Hopefully these techniques can provide food for thought for your next large floor slab preparation. It is important to discuss your game plan with the project geotechnical engineer, as well as the design and construction teams, to confirm that the planned approach is consistent with the project constraints.


All News and Events

Lower Costs, Fewer Delays

A highway expansion project applies XRF technology to obtain cost-effective remediation.

By John Sallman, PG, CAPM

X-ray fluorescence (XRF) spectrometry is a non-destructive, analytical method used primarily to detect the metal composition in soil/solids samples. Field portable XRF instruments can provide rapid, accurate analysis of heavy metal levels in soil on new construction or redevelopment sites. In response to the growing need for field analysis of metals, many of these XRF units have been adapted for use in the environmental field. They provide data in the field that can be used to identify and characterize contaminated sites and guide remedial work, among other applications.

Soils Remediation Challenge
A general contractor was awarded the construction contract for a highway expansion project where a consulting firm contracted by the highway department identified the presence of metals contaminated soils on the project site. The expansion project included the installation of overpasses at the intersection of two major highways, and the contaminated soils were located in the expansion rights-of-way. The highway department requested that the general contractor retain a different environmental consulting firm to manage the contaminated soils during the planned construction/remediation activities. Additionally, the department requested a plan to minimize the costs of the construction/remediation project, including the use of applicable innovative technology.

Because the expansion project was located about a two-hour drive from the nearest metropolitan area with a highway department-approved laboratory, a traditional approach to sample collection and laboratory analytical procedures for the soils was not practical. Additionally, the remediation and highway expansion construction were being conducted concurrently, and the project schedule did not allow for the time needed to analyze samples at a traditional laboratory. Plus, the project budget did not allow for the additional costs to obtain a rush analysis of the soil samples.

Management Plan

The general contractor contacted an environmental consulting firm and presented the highway department’s request for an overall construction/remediation management plan. The construction plans for the site included excavation of soils along areas of the two highways scheduled for widening and placement of imported soils to build new on-ramps and exit ramps. Additionally, several deep structural piers were being installed in the contaminated soils areas.

Initial evaluation of the existing soil data for the project area indicated that the majority of the soils from the site were acceptable for reuse; however, the areas where metals exceeded the applicable reuse criteria were scattered across the project area, and the limits of the soils exceeding the reuse criteria were poorly defined. As a result, testing of the soils during excavation would be required to determine suitability for reuse based on the metals concentrations.

Immediate cost savings for the project could be realized by reducing the overall volume of soils requiring disposal and reusing acceptable soils on the site to build the on-ramps and exit ramps. A total of approximately 75,000 cubic yards of soil were scheduled for excavation across the project area. If the soils were to be properly characterized and disposed, the cost of the remediation project would have been over $2.3 million. In order to comply with state regulations, sampling of the soils on a 50 cubic yard basis would be required to determine their suitability for reuse on the construction project (i.e., collection 1,500 soil samples across the site).

Selection of Metals Testing Technology

Due to the sampling requirements and project time constraints, several field testing technologies for metals were evaluated. For comparison’s sake, the estimated cost for collection and analysis of traditional laboratory samples was approximately $75,000 for a normal turnaround time (five to seven business days) and $150,000 for 24-hour rush analysis.

Immunoassay/test kits were evaluated first. This method of analysis typically requires purchasing a test kit, which includes the reagents and powders necessary to extract the metals from the soil and provide qualitative concentration results. Since immunoassay does not produce reliable quantitative results, this technology was not selected.

The second technology evaluated was a portable spectrophotometer. The initial cost of a portable spectrophotometer is relatively low but requires purchase of various test kits/reagents for digestion and analysis of soil samples. The total digestion and test time for each individual metal is 45 minutes or more to allow time for proper digestion as various reagents are added. The total time required to perform analyses for the spectrophotometer was not feasible with the scheduled collection of 1,500 samples across the site; therefore, this technology was not selected.

Solution
The last technology evaluated was the portable XRF instrument. XRF technology enables soils testing in the field and within tens of seconds to minutes, depending on the number and types of metals. Additionally, XRF instruments can analyze multiple metals at the same time, allowing for quicker result turnaround times. Software bundled with the XRF instrument can test for any metal, and the state agency approved the technique for evaluation of soils.

To test a sample with an XRF instrument, a small quantity of soil is placed into a disposable plastic container that holds the correct volume of soil required for the XRF analysis. Analysis is conducted by placing the analyzer over the plastic container and testing the soils for the time required depending on the number and types of metals being analyzed (typically a few tens of seconds).

The initial cost of an XRF instrument is fairly high (approximately $35,000 to $45,000), and rental rates for an XRF instrument range from about $500-$600 per day. However, due to the quick turnaround times for the analyses, and the reproducibility of the quantitative results provided by the XRF, this technology was selected.

An additional concern with using an XRF instrument is the use of a radioactive x-ray source in the instrument. Using a radioactive source requires specific licensing, maintenance and transportation requirements. Research indicated that XRF instruments utilizing x-ray tubes (similar to cathode ray tubes utilized in televisions) did not have the licensing and transportation restrictions and could be purchased. In order to meet the project objectives, the environmental consultant purchased an XRF instrument equipped with an x-ray tube and the associated soil testing software, and negotiated a lower rental rate of $350 per day for use of the instrument.

The Expansion Project

The initial remediation/construction phase of the project was scheduled to be completed in 90 days. The first phase of the project consisted of a total of 64 working days. As previously mentioned, the project specifications called for soils excavation along the areas where the highways were being widened and emplacement of soils to construct on-ramps and exit ramps. Additionally, the project included the installation of several deep structural piers to support overpasses being constructed for the project.

As the construction began, the excavated soils were stockpiled for analysis using the XRF instrument. During the project, 1,500 samples were collected and analyzed utilizing the XRF instrument (an average of approximately 24 samples per working day). Based on the XRF results, the soils were segregated for reuse on the on-ramp/exit ramp construction or for future waste disposal. Due to the immediate receipt of results using the XRF instrument, no project delays were encountered as a result of waiting on laboratory analytical results. The project was completed within the 90 day schedule. The soils stockpiled for disposal were properly characterized for waste disposal using conventional laboratory methods in order to meet the disposal facility’s requirements.

Project Results

The objectives of the highway department were to reduce overall direct project costs and avoid delays due to traditional remediation projects. Because the XRF instrument was utilized based on a nominal daily rental rate, the cost difference between traditional analysis of the 1,500 samples on a normal turnaround time basis and use of the XRF resulted in a cost savings of over $50,000. Additionally, the project was completed on schedule, resulting in cost savings from avoiding project delays and payment for rental of idle construction equipment. For the approximately 10,000 cubic yards of soil requiring disposal, costs were approximately $300,000, resulting in a savings of approximately $2 million when compared to disposing all of the excavated soils from the site.


All News and Events

Developing a Health & Safety Program


All News and Events

Concrete Answers for the Cold Weather Quandary

-


All News and Events

Items to Consider in SPCC and FRP Plans

-