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V O L 1 5 , I S S U E 2 S U M M E R 2 0 1 2A B R A U N I N T E R T E C P U B L I C A T I O N

To retrofit or replace – that is the question. But, is it really just one question? Many considerations come to mind when deciding whether to update an existing concrete structure or replace it. The

influencing factors for making the decision could be based on environmental, structural, or architectural issues, or the fear of what surprises will be uncovered during the retrofit process. Fortunately in the concrete industry, there are many tools available to evaluate the retrofitting of concrete structures. First and foremost, to help achieve optimal outcomes, both destructive and nondestructive testing of structural concrete systems should ideally be coordinated under the supervision of a licensed structural engineer familiar with the current design codes and local practices. Changes in design codes and standards are placing a greater emphasis on the constructability of structures, requiring them to be more efficient with material usage. As a result, understanding the structural system you’re working with is essential in minimizing unnecessary construction costs and using the best available materials for a retrofit project.

There are a significant number of test methods you can use to evaluate existing concrete structures. The American Concrete Institute (ACI) currently has two published documents, ACI 228.2R-98, “Nondestructive Test Methods for Evaluation of Concrete in Structures,” and ACI 437.1R-07, “Load Tests of Concrete Structures: Methods, Magnitude, Protocols and Acceptance Criteria,” that address the available testing options.

Of the nondestructive test methods presented in ACI 228.2R-98, one of the tests Braun Intertec provides is impact-echo testing. Impact-echo testing was invented in the 1980s, and is used to evaluate defects and dimensions of a concrete structure. Defects such as delaminations, voids and “honeycombing” are detected with impact-echo testing through the use of sound waves. Just like sending an echo across the edge of a canyon, as the sound waves travel through the concrete any defects or external surfaces will reflect the sound waves back to the impact echo receiver. Not only used in structural concrete, impact-echo testing has proven extremely valuable in evaluating existing concrete bridge decks for delaminations and cracks, pavements for thickness, and voids in grouted tendon ducts for post-tensioned concrete structures. Impact-echo testing requires a thorough understanding

of both the test method and structure being tested.

Braun Intertec has recently begun providing wireless concrete maturity system evaluations to collect data more safely in the field and in some cases, without leaving the office. The word “maturity” is used in concrete terminology to describe how concrete gains strength over time by measuring its heat signature. This test method was standardized by the American Society of Standards and Materials (ASTM) as ASTM C1074, “Standard Practice for Estimating Concrete Strength by the Maturity Method.”

Taking the Fear Out of Retrofitting Concrete

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By Gregory Bauer, PEgbauer@braunintertec.com

By using the wireless concrete maturity system, data can be collected and evaluated without leaving the office.

The impact echo receiver is used to evaluate defects and dimensions of a concrete structure.

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Recent changes by the Minnesota Pollution Control Agency (MPCA) to its best management practices for off-site use of fill soil give site owners more options

to reuse, rather than landfill, excess fill soil during redevelopment. These added options may result in large cost savings to projects, but owners still need to weigh the pros and cons of reusing fill soil.

This spring, the MPCA’s voluntary brownfields programs expanded its definition of unregulated fill. Until March of this year, excess fill soil from redevelopment sites could only be reused off-site provided that contaminant levels were less than the most conservative cleanup criteria, no indications of contamination were observed in the field, no debris was present, and concentrations of diesel range organics and gasoline range organics (DRO/GRO) were less than 10 parts per million (ppm). The last criteria – DRO/GRO levels less than 10 ppm – often was the toughest to meet, because naturally occurring organics found in soils can affect the analytical result and produce a DRO result above 10 ppm. In response to concerns that fill soil could only be taken off-site for reuse if DRO concentrations were generally not detected, the MPCA re-evaluated the risk associated with soil with DRO impacts, and revised the DRO/GRO threshold for off-site reuse of unregulated fill from 10 ppm to 100 ppm. The expanded definition also raises the field screening level of organic vapor readings from 0 ppm to 10 ppm.

The expanded definition of unregulated fill can result in a significant cost savings during redevelopment by allowing for the off-site use of unregulated fill, rather than disposing of the excess soil in a landfill. The off-site reuse of unregulated fill also provides for a more environmentally sustainable practice, potentially reducing the

distance that soil is hauled off-site and saving limited landfill space. Nevertheless, site owners need to consider the short-term and long-term risks associated with sending unregulated fill off-site for reuse and accepting unregulated fill onto its property. For instance, accepting unregulated fill could limit future site uses. While the MPCA provides guidelines for how much sampling and testing is needed, site owners are ultimately responsible for deciding how much investigation and sampling is needed to be representative of the fill soil. An open dialogue is needed between site owners, contractors and environmental consultants to understand where soil is coming from, what testing has been done, and how it will be reused. Moreover, long-term site use should be considered, as the MPCA only allows for reuse of unrestricted fill on commercial or industrial sites.

For more information, please contact Jen Force at jforce@braunintertec.com or view the MPCA guidance at: http://www.pca.state.mn.us/

MPCA Broadens Rules for Off-site Use of SoilBy Jennifer Force, PGjforce@braunintertec.com

Changes in MPCA guidance now provide greater opportunities to reuse excess fill soil on properties.

Braun Intertec is proud to be named one of the “Top Workplaces” in Minnesota by the Star Tribune. We create a culture that exudes collaboration, service and growth. It shows in our work and our people. After all, it’s all about our employees, and we couldn’t do it without them.

Braun Intertec Turns 55!

From the original days of founder Jack Braun

operating out of his Minneapolis home to

today’s 15-office, 600+employee company,

Braun Intertec is excited to celebrate its 55th

anniversary. A special thanks to all of our

clients, partners, industry associations, and

friends for all of your support and business

over the years.

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I remember getting a call in the early ‘90s from a vinyl composition tile (VCT) flooring manufacturer asking what’s new in concrete formulation that is causing an objectionable odor in new construction locations where its products were placed. At the time, there were no recent changes to concrete or other reports of odor issues other than those connected with this manufacturer. Not to mention, the flooring product had been on the market for years. As a chemist for an independent chemical testing laboratory, Rebel Construction Chemistry, I’ve had extensive exposure to a cross-section of problematic concrete samples and issues, but this inquiry presented a new challenge for me.

The odor problem was reportedly showing up at new concrete construction projects where VCT was installed, but not the sites where the product was placed over old concrete. Initially there were no complaints about the odor, but after a few months, building occupants began noticing and expressing concerns about the smell. These comments were occurring most often in newer construction where concrete was placed without a vapor barrier. I became suspicious about what was causing the odor until the “ah-ha” moment came when I correlated that when it rains outside, the concrete gets wet and activates the reaction, producing an awful odor. In other words, it usually doesn’t show up until after the tenant moves in.

After analyzing a stinky sample of concrete, I identified the odor as an alcohol. The alcohol is a component of the phthalate plasticizer used in the manufacturing of the VCT. This alcohol odor is similar chemically to the more pleasant odor of a new car smell or a vinyl shower curtain. Phthalates are added to the VCT to provide plasticity or increase the fluidity of what would otherwise be a rigid, hard poly vinyl chloride (PVC), as in plastic pipes. The reaction that activates the odor is due to an interaction of the plasticizer in the vinyl and concrete. Using infrared spectroscopy (FTIR), I was able to show that the phthalate plasticizer migrates from the vinyl through the adhesive into the concrete.

Yet the mystery remained. Why was the problem only exhibiting in new concrete and not old concrete? Fresh concrete is moist and has a very high pH due to the release of calcium hydroxide. New concrete generates the calcium hydroxide as a byproduct of the curing of portland cement and is the source of fresh concrete’s high pH. The phthalate plasticizer that migrates to the concrete reacts with the calcium hydroxide and the alcohol component releases, resulting in a stinky concrete mess.

In older concrete, the calcium hydroxide carbonates and converts over time to essentially calcium carbonate, which lowers the pH of the concrete. Therefore, even though the plasticizer migrates into the carbonated concrete, the reaction doesn’t take place and the odor problem doesn’t occur.

One of the initial attempts in remediation was replacing the VCT with new product, but once the phthalates are in the concrete, and as long as there is moisture and a higher pH, the reaction will continue. In most cases, the carpet and adhesive has to be removed and the concrete must be ground off to the depth of the migrated plasticizer to eliminate the odor issue.

The remaining question is why didn’t the manufacturer have this problem in the past? The manufacturer had switched to a different

phthalate product. Initially, it was not much more than asking for a Coke and getting a Pepsi. The new plasticizer was chemically similar and had the same properties as the old plasticizer, but it was created with a different alcohol. The new alcohol stunk, whereas the old one was pleasant. The reaction was always there; it just didn’t stink.

In summary, with input from the field representatives, flooring and coatings manufacturers learned that concrete is not an inert substrate but a potentially reactive host. This odor issue along with the later government solvent content restriction that

led to reformulation of adhesives, initiated the requirement and application of moisture mitigation systems.

The new question is: Why, more than a decade later, are we starting to see this stinky problem again. The short answer is the famous quote by George Santayana, “Those who cannot remember the past are condemned to repeat it.”

After this odor issue was diagnosed, the plasticizer product that generated this odor was replaced. Moreover, there was an increase in the use of moisture barriers in subgrade concrete to minimize moisture vapor in the concrete. There was also a rise in the use of a coating barrier on the concrete to stop plasticizer migration.

The practical solution is to get your expert’s together. Have team meetings prior to construction, use experienced suppliers and manufacturers, know how your materials and products worked in previous applications, and utilize test batches and trial mock-ups.

The Story Underneath Stinky Concrete By Bill Rebel, Rebel Construction Chemistry, LLC

Core sampling showed the concrete did not have a vapor barrier. The water vapor in the soil passed into the concrete. Lab testing later identified plasticizer degradation as the source of the odor.

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The maturity system evaluation determines the heat signature of any concrete measured in the laboratory, and then uses that same heat signature to evaluate the in-situ concrete strength.

There are many other considerations besides structural concerns that may require testing to achieve both an efficient and elegant design. For example, flooring systems have specific testing requirements. Over the last 30 years, significant changes in flooring adhesives have occurred, and now that “reuse” of structures is the preferred, environmentally-friendly option, new considerations apply that weren’t even options 30 years ago.

When you talk to a flooring contractor about replacing an existing flooring system and estimating costs for this replacement, you might hear, “you don’t know what you’ve got until you open it up.” In most cases, this is absolutely true. Unless documentation is available from the original flooring installation, everything from multiple flooring layers, mortar beds, and old adhesives, to an unsound concrete substrate should be expected. The composition of the existing flooring system isn’t the only consideration. Formulations for flooring adhesives have also changed over the years, mostly since the late 1980s, to limit the total volatile organic compounds (VOCs), styrenes, and formaldehyde in the adhesives.

The limits set on these chemicals were put in place to improve the indoor air quality of buildings, but have proven to be less effective in adhering to concrete subfloors.

Many newer adhesive formulations, particularly water-based adhesives, don’t have the performance capabilities that the previous formulations provided. One limitation is the sensitivity of water-based flooring adhesives to moisture and high pH levels. High water vapor transmission in concrete slabs present a challenging situation for fast-track construction projects. Various test procedures are available to evaluate moisture issues; however, the two common test procedures specified by flooring manufacturer warranties are the anhydrous calcium chloride and relative humidity probe tests.

The anhydrous calcium chloride test procedure is detailed in ASTM F1869, “Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.”

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The anhydrous calcium chloride test procedure requires 48 hours of test area stabilization, followed by 60-72 hours of collecting moisture vapor in a Petri dish of anhydrous calcium chloride.

KOSTER Partners with Braun Intertec to Train Flooring ContractorsIn May, Braun Intertec hosted an all-day certification class for KOSTER American Corporation. The class included a lecture and hands-on demonstration coordinated by KOSTER, demonstrating how to apply its vapor reduction system. KOSTER specializes in concrete waterproofing, water vapor and alkalinity mitigation products, and an oil removal system for oil and hydrocarbon contaminated concrete. Its products are distributed from Virginia Beach, Va., to the U.S., Canada, Mexico and Puerto Rico.

KOSTER’s class, “Approved Applicator Training,” permitted each applicator in attendance, by special invitation, to send at least one estimator and one or more field supervisors/mechanics to complete the training. This training is a requirement for applying KOSTER products on projects intended to be covered by a KOSTER warranty.

The all-day training was conducted by Bill Harrill, technical director for KOSTER. As part of the program, Braun Intertec was given the opportunity to present on the concrete core sampling and laboratory analysis portion that KOSTER specifies for concrete core analysis prior to the application of its products. Of the tests specified by KOSTER, Braun Intertec performs concrete core sampling at multiple office locations as well as X-ray diffraction (XRD), ion chromatography (IC), and petrographic examination at our Bloomington, Minn., location. Bill Rebel with Rebel Construction Chemistry, a consultant to the Braun Intertec concrete consulting group, presented on infrared spectroscopy (IR). IR is another laboratory test required by KOSTER.

Thirty-two trainees from 17 premier flooring contracting companies attended the class. Feedback from the trainees indicated they were very impressed with the program and found great value in the information they gained from the class.

Mark Sutherland from Valley Lake Flooring demonstrates the application of a vapor reduction system.

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The anhydrous calcium chloride test procedure requires 48 hours of test area stabilization, followed by 60 to 72 hours of collecting moisture vapor in a Petri dish of anhydrous calcium chloride. The resulting water vapor collected and absorbed in the calcium chloride is used to calculate the rate of transmission in pounds per 1,000 square feet per 24 hours (lbs/sq.ft./24hrs). The typical allowable maximum rate is specified by most flooring manufacturers.

The other common test procedure is ASTM F2170, “Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes.” Relative humidity probes indicate moisture deeper in the slab. In this procedure, a shallow probe is installed in the upper 40 percent of the slab thickness, and temperature and humidity readings are taken after 72 hours of environment stabilization. This procedure is becoming more commonly specified by flooring manufacturers.

Even with all the sophistication and planning that is spent on slab-on-grade construction projects, flooring failures still occur. So what can you do about it after the flooring has failed? Evaluate the service conditions and selection of flooring materials to determine if a moisture mitigation product is recommended. Prior to applying a moisture mitigation product, it requires the existing flooring system to be removed and the concrete surface to be mechanically sandblasted or shot blasted. It is a costly endeavor, not to mention the costs associated with the shutdown and loss of rent or revenue.

Concrete flooring products consultant KOSTER American Corporation requires analytical chemistry and physical testing on the concrete slab prior to applying its products. This laboratory examination and testing checks for the presence of organic compounds and levels of inorganic compounds that may contribute to failure

mechanisms, including adhesive degradation,

delamination and osmotic blistering after a vapor mitigation system is installed. The three tests KOSTER requires include the use of X-ray diffraction, ion chromatography and infrared spectroscopy.

X-ray diffraction determines the mineralogical composition of a concrete sample. In the case of a concrete slab-on-grade, samples are taken for analysis from a concrete core in the upper 3 millimeters to check for the presence of minerals that may contribute to adverse bonding. Ion chromatography determines the type and quantity of inorganic cations (alkalis) in a sample, which at certain levels can promote failures including osmotic blistering through a moisture vapor mitigation system. Infrared spectroscopy identifies the presence of organic compounds that would adversely affect the bonding of the vapor mitigation system to the concrete substrate.

Unfortunately, the vapor mitigation systems available are rarely included in the price of the project, i.e., “what surprises am I going to uncover if I try to retrofit this structure?” When a project timeline is on the “fast track,” consideration for installing a vapor mitigation system should be included in the cost of the project if sufficient time is not available for the slab to dry out or if a vapor retarder is not used. A rule of thumb in the industry is that it takes one month for 1 inch of slab to dry out, but of course, this is dependent on the permeability of the slab and surrounding environmental conditions. Until flooring adhesive technology catches up with our construction schedules, moisture vapor will continue

to pose a challenge for slab construction and is worthy of thoughtful consideration during the design process.

Both new construction and retrofit projects require a knowledgeable design team with access to modern evaluation tools. With their guidance and collaboration, a safe, efficient and long-lasting concrete structure is possible.

Jamie Langdon, Braun Intertec materials specialist, performs X-ray diffraction of a concrete sample to determine the mineralogical composition.

Concrete - Continued from page 4

Relative humidity probes can indicate moisture located deeper within the concrete slabs.

Infrared spectroscopy pattern output. Provided by Rebel Construction Chemistry, LLC.

Chris Clark, Braun Intertec inorganic lab supervisor, uses ion chromatography to check for the presence of organic and inorganic compounds.

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Dear Professor: Can I call you that? If I recall, you graduated with a Bachelor of Science degree in Geology and barely made it out of that program alive. I like your cartoons, but good luck convincing everyone of the idea that engineers (excuse me, geologists) have a sense of humor. Anyway, I wanted to ask for your advice regarding my pursuit of a vacant site here in the Twin Cities. I have a geotechnical report from the late ‘90s that was prepared for a redevelopment plan that withered on the vine, and I also have a more recent (2009) Phase I Environmental Site Assessment (ESA) that evaluated the site’s history fairly accurately from what I’ve been told. I’m just wondering if I can rely on this information or not. It looks pretty good, and I’m not that interested in delaying efforts to procure a site purchase agreement in order to schedule more borings and research. What do you think?

- Here ‘Til Thursday (and it’s your turn to buy dinner)

If you were an NBA diva and were looking to change your name, I would recommend “Blind Faith.” Otherwise, tread with caution. If you are the latest and greatest interested party to approach this project, you should take time to understand the intent and limitations of the information you have. Boring logs may be the only thing you can take from available geotechnical reports, but their locations (are there borings in the area where you plan to build?), depth and sampling schedule may not be appropriate for your plans (20-foot borings are okay for a one- or two-story commercial building on spread footings but not for a taller, heavier building or a building with a below-grade structure). The scope and usefulness of geotechnical laboratory tests performed for past projects may also be scanty and of little use to a more ambitious project, as may be the subgrade preparation, foundation and pavement design recommendations that were provided.

The site may also look the same as it did when the last adventurer tried to broker a marriage, but underground structures could have been removed and backfilled, material borrowed from the site and

replaced with unsuitable backfill, and underground storage tanks may have commenced to leak, etc. Your Phase I ESA may or may not reflect such changes, or the site’s entire history. The American Society of Standards and Materials (ASTM) and the Environmental Protection Act give Phase I ESAs a six-month shelf life. Conversely, if you have documentation indicating that site conditions haven’t changed since the report was issued, you can note that some local agencies such as the MPCA may accept older reports. In the end, a lot depends on what you need the report for (general information, site redevelopment grant application, etc.), and the strength of the information you have.

If you are serious about this site, know that the cost of redevelopment will be in the millions of dollars. Investing a few thousand dollars in an updated Phase I ESA and possibly performing some additional borings in previously unexplored areas will go a long way to help you pursue a redevelopment plan strategically and with less risk. —The Professor

Ask The ProfessorBy Charles Hubbard, PE, PG

chubbard@braunintertec.com

Ah, My Favorite Scorekeeper:

©2012 Braun Intertec Corporation

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Fueled by global demand for steel, particularly in China and India, these are good times for the mines

of northern Minnesota. While many of these mines were faced with shutdowns or reduced production just a few years ago due to the onset of the Great Recession, most are now operating at full capacity, and many are moving forward with facility improvements.

According to the Iron Mining Association, Northeast Minnesota currently has eight operating iron ore mines capable of producing more than 40 million tons of taconite each year. The companies that operate the mines include ArcelorMittal, Cliffs Natural Resources, Magnetation, Steel Dynamics and U.S. Steel. Minnesota’s economy benefits $1.8 billion from the iron mines due to purchases, wages, benefits, taxes and royalties. Iron mining is also responsible for an additional $1.6 billion as a subsequent business impact. The total economic impact results in $3.1 billion. Additionally, the mines employ around 4,200 men and women, and sustain an additional 13,000 employed by vendors.

New iron mining ventures on the Iron Range include Essar Steel Minnesota and Magnetation. The new Essar facility near Nashwauk is currently under construction with mine production slated to begin as early as 2013. The Essar project may also include a future steel plant. Magnetation currently operates two concentrate plants, with a third under construction, and plans to construct two additional plants in the next few years. Magnetation is unique in that the company is “mining” historic tailing basins – a byproduct of previous mining activities. According to Magnetation, it has developed a patented

mineral reclamation process (Magnetation Process™) to extract weakly magnetic particles, which makes it viable to reprocess the tailings to extract iron using the new technology.

In addition to the ferrous mining projects, according to Mining Minnesota, the more than 4 billion tons of crude, non-ferrous ore located in Minnesota is estimated to be the largest deposit of base and precious metals in the U.S. In the ‘50s and ‘60s, “strategic” metals were discovered and explored, including platinum, palladium and nickel, as well as gold, silver, and copper deposits. Back then, these ores didn’t have the proper technology to be processed and treated; therefore, the ore was unable to be sold. Non-ferrous projects currently in the permitting stage include PolyMet’s NorthMet project near Hoyt Lakes and Twin Metals Minnesota’s project near Babbitt, Minn.

With an optimistic outlook for the years to come, Braun Intertec proudly supports the mining industry, and is well suited to provide technical assistance for new and existing mines in Minnesota and the Upper Midwest.

Minnesota Mining is ThrivingBy Jim Bonner, PE jbonner@braunintertec.com

Braun Intertec provides construction observation and testing for embankment construction, such as tailings dams.

Braun Intertec supports the mining industry by providing a variety of services, including:• Geotechnical investigations using Standard Penetration Test

(SPT) borings or Cone Penetrometer Test (CPT) soundings

• Installation and monitoring of geotechnical instrumentation such as piezometers, inclinometers, and settlement plates, to monitor tailings dam performance

• Geotechnical evaluations for new structures or modifications to existing structures

• Seepage and slope stability analyses

• Assistance with environmental permitting

• Stream gauging and monitoring of lakes and mine pits

• Wetland monitoring

• National Pollutant Discharge Elimination System (NPDES) water quality sampling and reporting

• Observation and testing for tailings dam construction

• Vibration monitoring to evaluate effects of blast- and construction-induced vibrations

• Nondestructive examinations (NDE) for structural steel

• Construction materials testing of soil and concrete for structure construction

• Certified analytical laboratory

For more information about our mining-related services, contact Jim Bonner at 218.263.8869 or jbonner@braunintertec.com

11001 Hampshire Ave. SMinneapolis, MN 55438

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Minneapolis 800.279.6100Bismarck 701.255.7180Cedar Rapids 319.365.0961 Dickinson 701.255.7180Duluth 218.624.4967Fargo 800.756.5955Hibbing 800.828.7313La Crosse 800.856.2098Little Falls (Geothermal) 320.632.1081Mankato 800.539.0472Milwaukee 262.513.2995Rochester 800.279.1576Saint Cloud 800.828.7344Saint Paul 800.779.1196

Questions, requests and comments

Charles Hubbard, PE, PGBraun Intertec Corporation1826 Buerkle RoadSaint Paul, MN 55110Phone: 651.487.7060chubbard@braunintertec.com

©2012 Braun Intertec Corporation

This newsletter contains only general information. For specific applications, please consult your engineering or environmental consultants and legal counsel.

Prepare for October 2012 Licensure Exams: MnSPE Offers PE/FE Exam Review Courses Minnesota Society of Professional Engineers (MnSPE) is sponsoring review courses for the PE Civil, PE Mechanical, and Fundamentals of Engineering exams that will take place in October 2012. MnSPE also anticipates offering a PE Electrical Power exam preparation course prior to the October 2012 exam as well. You can participate from anywhere – all courses will be offered via live, interactive webinar, and the mechanical PE course will also be available in a classroom setting in the Twin Cities. All students have on-demand access to previously recorded class webinars and current course webinars within several days of the class. Courses will begin in late August, and meet once or twice a week until just before the exam date.

Courses are taught by a licensed PE or certified Engineer-in-Training (EIT) with experience and expertise in various subject areas. Chuck Hubbard, “The Professor” with Braun Intertec, is one of the course instructors.

Reduced rates are available to MnSPE members and members of other National Society of Professional Engineers (NSPE) state societies. Order course materials through MnSPE and receive a 15 percent discount. Visit MnSPE online for additional details.