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Geotechnical Subsurface Investigations

In my years of being involved in the civil engineering realm, several entities, both private and public, have undervalued the information revealed and achieved from a geotechnical or subsurface investigation program.

It has been my experience that the most challenging aspects of any construction project is getting structural foundation elements out of the ground or providing a stable subgrade for various types of roadway pavements, as just a few examples.

A geotechnical investigation looks at the site subsurface for various things such as:

  • Depth to rock, rock type
  • Soil types and depths, their consistency (cohesive soil: clays) and/or relative density (cohesionless soils: sands)
  • Water features and depths, depth to water table, seasonal estimations of water table fluctuations, capillary rise

Industry accepted techniques have been established such as Standard Penetration Tests which can be correlated to soil properties such as cohesion, angles of internal friction, and rock strengths. These values are consistently used for design of foundation systems, retaining wall systems, and slope stability analyses. Additionally, further testing of obtained samples of soil or rock can be catered to mimic in-situ conditions at the site to provide better analysis of the soil-structure interaction.

The most basic subsurface investigation can provide information for designers when performed by experienced geotechnical firms. Because of their experience local to areas where they perform their work, significant history and background of the soil and rock types has been obtained through the years.

The types of information and recommendations which can be presented are as follows:

  1. Allowable bearing pressures – used to design foundation sizes utilizing an allowable load transfer to the soil or rock at the bearing elevation.
  2. Feasibility of reusing cut material as fill and to what standard it should be compacted in a controlled fill scenario.
  3. Moisture conditions to be considered before, during, and after construction which can be useful in deciding long-term maintenance needs.
  4. Evaluation of an existing soil surface for stability characteristics prior to placement of fill material. This is especially important in deep fill scenarios.
  5. Anticipated depths at which rock will be encountered – which we know can be a costly endeavor if unforeseen.

Finally, it should also be noted that borings only provide information relative to where they are drilled. Significant changes in strata borings are always a distinct possibility as the nature of soil and rock in some areas can change drastically. However, information gained coupled with a geotechnical engineer’s experience can often mitigate these concerns substantially, or at least disclose the potential scenarios.

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Importance of Roadway Operations and Maintenance

In our world today we have an incredible amount of freedom to move about wherever and whenever we want. We just hop in the car, spend some time on the road and voila. We go to work, visit friends and family, or just go out for ice cream.

But sometimes we find ourselves asking, “Why is this lane closed? I’m in a hurry,” and assume there must have been an accident to cause this inconvenience. “It must be a bad one, traffic is terrible. I hope no one was injured.” Then when you find out there is no accident but a crew diligently working on the road you think, “What? Why are they doing this now? Couldn’t it wait till a time when I’m not trying to get through?” Unfortunately, if we waited until a time that was convenient for everyone there would never be time for maintenance, and maintenance needs to be done.

Our roadway infrastructure ranges from brand new to 100+ years in age. Even roads that are brand new still need maintenance. There are numerous reports that talk about the condition of the nation’s infrastructure and how bad it is. The majority of the nation’s interstates were built 50 and 60 years ago with some structures approaching the end of their designed lifespan. To make things more challenging for DOTs they have to make decisions with tighter budgets.

Road maintenance (Asset Management) is similar to home maintenance in the fact that there are variables that guide your decisions. Let’s use the roof on your home as an example of different aspects of maintenance to consider.

Condition: knowing the condition of the roof is a critical part of the decision making process. If the majority of the roof is in good shape but you are missing a few shingles you may just want to repair the shingles. Maybe the wind is steady against the front of your house but not the back. You might need to replace the front half every 5 years and the whole thing every 10. When enough shingles have blown off, they are deteriorated, or they are reaching the end of their lifecycle, then it may need to be replaced. If you installed 20 year shingles and it’s been 19 years you might want to consider replacement.

Budget: replacing a roof is an expensive endeavor and you want to make sure you have the money to cover the cost or the roofer might not show up. Knowing the condition helps tremendously with budgeting. Environmental factors: you don’t want to expose the roof to rain or snow. That’s what it’s supposed to keep out, right? You might skip scheduling it in April (April showers) and wait till July or August to make repairs.

Material requirements: the ideal temperature for asphalt shingle installation is between 70 and 80 degrees. Any colder than 70 and they may not seal correctly.

Resources: you’ll inevitably need some resources to help. Probably a ladder or some type of lift, extra manpower, a truck to get your materials to the house, etc.

Safety: if you install your own shingles you’ll want to make sure your ladder is safe, that you always use a three point stance when climbing up and down, and that you have a harness among other things. Or you can hire a professional and let them worry about it. So like the homeowner, budgets, asset conditions, environmental factors (weather/seasonal), material requirements, resources, and safety all have an effect on the decision making process of Transportation Asset Management.

The Asset Manager has to also consider items the homeowner does not: the scale (number of assets and locations) and contending with traffic. Asset locations: the homeowner’s asset is in one location, where the maintenance manager has tens of thousands of assets of different types scattered over hundreds of miles. In this situation, the asset location becomes important to help direct work and eliminate wasted efforts.

But wait a minute! That’s great you are considering all these different factors, but why are you in my way? The homeowner doesn’t have to contend with Traffic. With scheduled work, some maintenance work can be completed at night when traffic volumes are low. But even low traffic volumes have increased risk factors such as an increase in the number of drunk and tired drivers. Some work is just better accomplished during the day. You have more light to see and temperatures are usually more conducive for the workers and materials used.

Either way, the maintenance worker has to keep one eye on traffic and one eye on the job. They work just feet away from 2 ton hunks of steel traveling at 70 miles per hour. Traffic engineers do everything they can to keep workers safe. They design special boxes to go on big trucks that absorb the blow of a misdirected vehicle called crash attenuators; and they require workers to install signs, cones, barrels, messages signs that give the traveling public as much advanced warning as possible. The public can also call 511 for traffic information, check the 511 app, or use third party apps such as Google Maps and Waze all to see how traffic is flowing.

We refer to juggling all these different variables as Transportation Asset Management. This is all done to keep the infrastructure in the best shape possible for as long as possible, to keep the workers and traveling public safe, and make sure travelers can get from point A to point B with as little interruption as possible while staying within budgets. So the next time you run across a work zone hopefully you’ll have a better appreciation for the amount of work and planning that has gone into that work.

https://www.youtube.com/watch?v=Wpzvaqypav8

http://www.cbsnews.com/news/falling-apart-america-neglected-infrastructure/

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Why Land Surveyors Are On Your Property

“Hey, you there!” “Can I ask what you are doing on my property?!”

Every Land Surveyor at some point in his or her career has heard this very question.

Trespassing as defined by Meriam Webster’s Dictionary is “an unlawful act committed on the person, property, or rights of another, one of these unlawful acts is the wrongful entry on real property prior to or without acquiring permission either verbal or written”. As to the Law of Trespassing in Virginia, it is said to “exist for the sole purpose of protecting rights of owners (or people with lawful control) of property both real and personal”.

For now the Commonwealth of Virginia doesn’t have provisions in the state code that allows land surveyors to enter upon lands that adjoin the property that is the subject of the survey. We simply have to rely upon the willingness on the community to understand and allow us to trespass without the fear of criminal charges. But it doesn’t stop at just criminal charges; upon entering a piece of adjoining land to look for monuments that would allow us to re-establish a missing common corner, we also have to consider civil charges for any possible damage that may occur to the property while we are on it. Trampled landscape, a divot cut in the sod of a well-manicured lawn to expose a property corner, a snipped limb from a tree to improve line of site or an accidentally cut signal line for an underground dog fence. The list is endless and each item of this endless list could be a possible civil charge that could result in serious monetary fines.

Even with verbal or written permission to enter upon land we are not exempt from the possibilities of civil charges for action taken upon these lands that are perceived as damaging.

The biggest misconceptions about preparing a survey is that we only have to survey our client’s land. This isn’t the case. In addition to documenting our client’s boundary lines, title lines, and possession lines we also have to document how these lines interact with the boundary lines, title lines, and possession lines of the adjoining properties. After all that’s what a survey is, a detailed document that reflects how each piece of property interacts with each other and the physical improvements placed upon those lands. And in order to truly paint that accurate picture, well we might need to take a few more than one or two steps over the preverbal line. The vast majority of the time we i.e. land surveyors make every effort to talk with adjoining property owners. It’s this initial contact that would hopefully provide them with the information they seek regarding the reason why we are there in the first place. If this is the case then voila we now have permission to enter upon lands that are not the direct subject of our project. But every once in a while you come upon the situation were the owners are not home, out of town, or simply just not interested in hearing what you have to say. Such is the rights of property ownership and great consideration needs to be taken in regards to those rights.

From my experiences over the past decade and a half as a surveyor I have come to the conclusion that if you have permission to be on the property or you are holding to that old saying “forgiveness later instead of permission now” then treat it as if you do not, really consider what actions you take upon that property. If you cut a divot in someone’s manicured lawn make it as small and neat as possible; if you have to cross a fence either look for a gate or gently cross at a post. Because in the end it’s an all new ball game when that “sweat little ole lady” you just talked to (who just came home from a losing day at bingo) finds out you trimmed her prize winning rose bush back a little too far.

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3 Roadway Drainage Maintenance Tips

Rain, and more specifically drainage maintenance, is key to well managed roadways. After the structures and pavement, drainage is the third most important asset making up a roadway system.

Drainage consists of everything from main storm drain trunk lines to ditches and all the way down to pavement under-drains. Preventive and proactive maintenance is critical to keep your roadway functioning for the long term. We will address some broad maintenance issues and strategies in this issue of Pillar Talk.

The storm drain system is designed to quickly drain the pavement surface and channel the water away from the roadway into the BMP (Best Management Practiceusually some type of basin or pond) and ultimately to a nearby creek or river. Basic maintenance is simple: keep large debris from clogging the inlets to preclude flooding events, and prevent or clean the small debris to prevent reducing the system capacity over time. Some strategies to maintain your drainage system include:

1. Debris Removal: While removing debris regularly may be called an “aesthetics” issue, in actuality this task is very important for drainage maintenance. More often than not, a broken Styrofoam cooler, old life vest, or even a large cardboard box will wash down the curb or barrier wall and cover the inlet grate/throat or even make its way down into the inlet and clog the drain lateral. This is easily remedied with routine debris removal operations. Be especially vigilant if your roadway is a tourist route leading to recreational water-sports areas.

2. Sweeping: Routine mechanical or vacuum sweeping will prevent accumulations of sand and sediment in the pipes. Theoretically, storm drains
are designed to be “self-cleaning,” however this only means the sediment makes its way into your BMP or nearby creek, necessitating costly cleanup at some later date. However, if the system has small debris wedged in the pipe or poor joints due to settlement or poor construction, the sediment will deposit in the pipe and cause a flooding condition. Routine sweeping will prevent these issues.

3. Drain Flushing/Vacuuming: If debris removal and sweeping are not performed, the only way to remove debris and compacted sediments is by manual drain cleaning or Vac-Truck flushing. This is an expensive way to remedy a flooded roadway. Typically this work is done on a reactive basis, once the roadway has flooded. Traffic control will likely consist of a shoulder or lane closure installed in an emergency situation at night, in a rainstorm, with traffic trying to pass at high speed with hydroplaning occurring.

As part of your Operations and Maintenance Team, we can provide a preventive maintenance plan to maintain your drainage assets in line with your contract Performance Requirements.