In a technology-driven society, we are challenged to adapt and prepare for the changing technologies of tomorrow. As a Visualization Studio Manager, helping clients see the big picture and visualize completed projects drives curiosity and reveals the potential impacts of our work. Creating visualizations plays a crucial role in helping communities and clients evolve. In the past few years, visualization capabilities have changed rapidly, allowing renderings to be completed in minutes. To stay on top of this cutting-edge technology, we must understand the software and carve out new markets from existing industries.
New developments in ray tracing
Up until last month, real-time and ray tracing couldn’t be used in the same sentence without a bank of 10 GPUs and 2500 watts of power. Ray tracing makes renderings dynamic and realistic and thanks to powerful GPUs, shortens the amount of time spent on each frame. This recent advance in technology allows clients and the public to see reflections, higher quality shadows and experience the creation for themselves. Today, we’re utilizing these technologies to create stunning visualizations for our clients. Once the projects have been modeled, iterations are produced in minutes, instead of days or weeks.
For some, classic visualization techniques and development are still the only way to produce the highest quality imagery when secondary shadows, complex caustics, and very high resolutions are required. In real-time, there is an abundance of data creating the visualizations of skyscrapers or roadways. In some cases, classic visualization allows an audience to see specific renderings that assist beyond the scope of just engineering. Ray tracing, augmented reality (AR), and virtual reality (VR) allow us to visualize how things work from transportation and infrastructure to medical devices and demonstrative evidence.
Applying AR and VR
Immersive technologies, both AR and VR, allow clients to become part of their projects months or years in advance. Specifics such as material schedules, lighting, and species-specific landscaping create a three-dimensional rendered experience for people to become immersed in before it becomes a reality. From using VR to drive through a road design or using AR to see a properly placed medical device from any angle, visualizations reveal findings in a way anyone can understand. These technologies provide an unparalleled tool to investigate or market the feasibility and accuracy of a product or service.
Creating a livable city space for residents to enjoy is no easy feat.
Civil engineers who dedicate their careers to supporting a specific city or municipality are known as municipal engineers. You may only know of one main city engineer in your community. However, there is likely a team of municipal engineers working behind the scenes to ensure all city operations are running smoothly.
Here are five things that municipal engineers do to support your community.
1. Design
One of the most noticeable
things that municipal engineers do is design the public infrastructure in a
community. Local streets are designed to get you around town. Public utilities
are designed to provide drinking water and indoor restrooms to homes and
businesses. Trails are designed for recreational enjoyment. Storm sewer systems
are designed to properly manage storm water runoff and prevent flooding. All the
above and more are designed by municipal engineers.
2. Review
Developers and
residents rely on municipal engineers to review developments within their city.
Large-scale developments, usually done by a developer for a residential,
commercial or industrial area, take thorough reviewing by municipal engineers
to ensure the development is compliant with city rules and regulations and adds
value to the community. Similarly, residents with plans to modify their land seek
approval from municipal engineers to ensure their design and modifications meet
community standards and avoid potential issues for neighbors or future
residents.
3. Plan
Municipal engineers are
always looking to the future. They develop Capital Improvement Plans (CIPs) to
identify the most crucial needs of the city and plan for future projects. These
plans typically project 5-10 years into the future. Additionally, municipal
engineers work with city planners and regulatory agencies to establish
comprehensive plans for the community. Most comprehensive city plans typically
project 10-20 years into the future.
4. Budget
Managing a city’s
infrastructure budget is an essential part of being a municipal engineer. Cities
often operate on a limited budget so they must think carefully about where to
allocate their spending. Likewise, municipal engineers assist cities with applying
for state, regional, and federal funding.
5. Collaborate
Municipal engineers collaborate with invested stakeholders to improve their communities. Through public engagement and speaking with residents, city officials, regional and state agencies, they gather input and analyze the best course of action to create a viable city that works for everyone.
John Gerlach, Director of Pipeline Field Operations, WSB
Learn how inspections and monitoring can keep your utilities running smoothly and safely.
Whether filled with natural gas to fuel and heat homes and
businesses or transporting liquid fuels from one location to another, most
communities have miles of pipes embedded underground with other critical
infrastructure. There’s a misconception that these lines are primarily located
in remote areas. In reality, pipeline infrastructure can be found beneath our
roadways and sidewalks or near homes, businesses, landmarks, parks and other
natural resources. Pipeline infrastructure can range from large, high-pressure
steel lines that serve cities and powerplants, to small plastic lines, used to
transport gas from the street to your home or place or business. These complex
networks require expertise to ensure the safety of people and the environment,
as well as reliable access to the fuels we need to enjoy hot showers, drive to
work and keep the lights on.
With increasing federal regulatory standards, now is the
time to become more focused on pipeline integrity and safety. WSB offers
inspections that help utilities and cities understand the condition of their
infrastructure, reduce costly and inefficient repairs, improve safety and
maintain the long-term integrity of these important pipelines.
Why hire a third-party inspector?
Pipeline inspectors can add value and security to any
project near utility lines. Most commonly, inspectors are hired to oversee the
contractors working on infrastructure projects such as roadway improvements or
utility replacements. When these projects interfere with the natural gas
system, pipeline inspectors who can recognize and mitigate potential risks are
invaluable.
Third-party experts can also be utilized to verify the
results of other inspections, like performing audits that identify pipeline
locations before a project is started. A second opinion can identify costly
errors before the damage is done. In our experience, an audit of locate work
finds mistakes roughly 30% of the time.
A new regulatory environment
Investigations into high-profile pipeline releases over the
past decade have prompted new regulatory recommendations and standards. Pipeline
releases can have devasting consequences to people and the environment
including fatalities, injuries, forced evacuation and damage to properties and
natural resources. In many cases, regulators – like the Pipeline and Hazardous
Materials Safety Administration and the National Transportation Safety Board –
require independent, third-party inspections of pipelines and pipeline
projects.
Technology advantage
New technologies have made evaluating pipeline integrity
more efficient. Rather than digging up pipelines under a densely populated area
to check for deterioration, a device can be sent through the line that shows anomalies
like corrosion and damage from past construction. Most pipes should be replaced
every 15 to 20 years. Since pipeline replacement projects are typically planned
in coordination with other infrastructure improvements, this type of check can
help communities identify which projects should be prioritized first.
WSB also offers real-time reporting on pipeline status
through an ArcGIS platform. This technology can detect an increase in pressure
or corrosion on the line and send notifications to technicians in the field.
At first glance, hiring an outside expert to ensure compliance and verify accuracy can appear costly. In the end, pipeline inspectors can make your project run smoothly, reduce issues in the field and reduce the risk of releases, accidents and other safety hazards. Reach out to WSB’s utility and pipeline experts today to learn more.
John Gerlach is a Director of Pipeline Field Operations with more than 30 years of experience. His expertise extends to pipeline design, construction inspection and safety and risk management.
It’s a mouthful. And it happens every day in every wastewater system, but it happens without many of us knowing about it. The sources vary, the flows vary, and the solutions vary, but the motivation to mitigate I/I is the same. The addition of excessive clear water (I/I) into local and regional wastewater systems can have many effects including basement backups, wastewater overflows, the excessive use of remaining pipe capacity reserved for future growth, and added treatment costs.
Inflow and Infiltration – or I/I – are terms that describe clear water that enters wastewater collection systems through defects and consumes treatment and conveyance capacity. Typical sources of I/I are broken service laterals, connected sump pumps or downspouts, aged or defective sewer mains, and deteriorated maintenance holes.
Even though many communities were developing and implementing programs to eliminate combined sewer connections decades beforehand, the story of I/I in the Twin Cities effectively begins in July 1987. Yes, the superstorm of ’87. It had big impacts 30 years ago: sewer overflows to rivers and lakes, flooded basements, comingled water in our streets, and a lingering series of videos on the internet highlighting top-notch 1980s meteorology reporting. In some areas, reported rainfall exceeded 10 inches in one day, as part of the 16 inches experienced over much of the metro region that week. It was even the second wettest summer on record (2016 was the wettest).
The storm and its effects spawned a series of studies to understand the impacts of I/I on wastewater systems throughout the region. A 1990 study by MCES concluded that roughly one-fifth of wastewater treated in the region was from I/I. It was clear (pun intended) that the wastewater systems needed some rehabilitation, and that source removal would have a significant impact on reducing base and peak flows from I/I. In response, communities and MCES ramped-up efforts on I/I mitigation and combined sewer disconnection. After years of investment, peak flows and combined sewer overflow (CSO) volumes had been reduced, but not eliminated.
In 2004, the first MCES I/I Task Force – representing communities served by the regional wastewater system – recommended a long-term systematic approach to reducing peak flow, now known as the Ongoing I/I Program, which is administered by MCES. The superstorm is still having effects today as communities throughout the region work to repair their systems before an event of that magnitude happens again. During much of the last decade, the efforts to mitigate I/I have focused on repairing sewer mains and maintenance holes through lining or replacement projects. There has also been significant effort into mitigating surficial inflow sources such as vented MH covers, rain leaders, and roof drains.
There is evidence of success from all this effort.
At the regional level, there is a diverging trend, with rainfall totals increasing and wastewater flows decreasing, even as the population has increased. Also, by comparing major rainfall events in 2005 and 2014, regional precipitation increasing by 62% in the weeks leading up to the 2014 event, but the peak wastewater flow at the Metro Plant in Saint Paul decreased by 12% for peak hour and 6% for the peak day. However, almost half of communities in the region discharged excessive I/I during the 2014 event.
So, what’s next? When the Ongoing I/I Program began in the early 2000s, the estimated cost to mitigate excessive I/I into the regional system was largely based on removal of sources at the far upstream ends of the systems – namely from private infrastructure such as service laterals and sump pumps. Many communities have worked to eliminate sump pump connections, and some have instituted programs to inspect and repair service laterals. And it has worked. In a 2016 flow study, communities that included private infrastructure as part of their I/I mitigation strategy were able to achieve up to four-times greater reductions in peak flows than those that focused on public sources.
Being the proverbial low-hanging fruit, it’s understandable that many communities have focused on the easily-accessible public infrastructure. And that’s why the MCES I/I Task Force identified some specific strategies to address the technical and financial challenges of private property I/I mitigation. The main outcomes will be increased public outreach (you’re reading some now), technical support, and continued support for funding of public and private I/I mitigation. Why the focus on private infrastructure? In the words of the latest task force:
“Private sewer service laterals represent a significant portion of the overall collection system but are often not part of public system inspection, replacement, or I/I mitigation programs. These service laterals tend to represent an unquantified and unresolved share of the I/I problem. Another reason is because previous studies indicate that up to 80% of I/I is from sources on private property.”
MCES is in process of completing the recommendations of the task force, with most planned for launch in 2018. Communities can expect to see an updated public outreach toolbox intended to share simplified communication materials in a variety of formats. They can also expect more details on an I/I mitigation demonstration project that would provide additional opportunity for measurement of the impact on wastewater base and peak flows. The recommendations are located in the 2016 I/I Task Force Report. A common theme of the recommendations is using regional resources to support communities with effective decision-making and implementation of their respective I/I mitigation strategies.
Anyone interested in more information on the program or the demonstration projects is encouraged to visit the program website at www.metrocouncil.org/iandi or email the team at [email protected].
And if you have more to add to the regional story about I/I mitigation or the superstorm, we’d be happy to have it! Photos and videos, reports, anything you have. There’s a wealth of information throughout the region, and it would be great to capture that. Marcus Bush, PE is a Principal Engineer for the regional wastewater treatment provider, Metropolitan Council Environmental Services. He administers the Ongoing I/I Program that provides resources and incentives to communities for mitigating excessive flows due to I/I. Prior to his role with MCES, he worked in municipal and environmental engineering, land development, industrial brewing, and the bicycle industry.
Marcus Bush, PE is a Principal Engineer for the regional wastewater treatment provider, Metropolitan Council Environmental Services. He administers the Ongoing I/I Program that provides resources and incentives to communities for mitigating excessive flows due to I/I. Prior to his role with MCES, he worked in municipal and environmental engineering, land development, industrial brewing, and the bicycle industry.
Robert’s Rules of Order were first published in 1876 and were named for Colonel Henry Martyn Robert, a military engineer in the United States Army. Robert developed the rules after being asked to conduct a meeting at his church. Due to his inexperience in this role and no shared understanding among the attendees as to how a meeting should be conducted, the outcome was unproductive and disappointing. Robert recognized the need for a uniform understanding of parliamentary procedures and went about developing a reference document.
Robert’s Rules of Order provide a basis for the conduct of public meetings and a framework for the decision-making process. This guide to parliamentary procedures helps ensure that the rights of all participants in the process are recognized and considered. Having a set of rules to follow for decisions can be particularly useful in very contentious situations where there may be very differing and heated opinions.
How to apply Robert’s Rules of Order
The chair or other designated leader of the meeting should have a familiarity with Robert’s Rules of Order as well as any other rules specific to the organization. Even if an organization adopts Robert’s Rules of Order for the proceedings, other rules of the organization may still take precedent. While the specific rules are very detailed and extensive, in most cases conducting business first involves someone putting forth a motion for the assembly to take some sort of action. Most motions require a second, meaning another member agrees that the motion should be considered; this is to prevent a single member from consuming the assembly’s time with matters of importance only to them. Once seconded, the issue is debated and can be amended before a vote is taken.
During debate, assembly members should focus their comments and discussion on the question at hand, address their comments to the presiding officer (chair, mayor, etc.), and leave out remarks related to the personalities or motives of others. On occasion at City Council meetings, the City Attorney may be consulted to provide guidance regarding specific steps that must be taken, as they generally have the most in-depth understanding of statutes and other local rules.
Andrew Plowman, Transportation Project Manager, WSB
Roundabouts have been used throughout Europe and Australia for decades but have only gained popularity in the United States in the past 20 years. There are currently more than 3,500 roundabouts in the United States. Minnesota has also joined the roundabout craze, with more than 140 roundabouts built as of 2014, and upward of 20 additional roundabouts built each year.
Some jurisdictions, such as the New York State Department of Transportation and the City of Bend, Oregon, have implemented a “roundabouts first” policy. These policies require that a roundabout be analyzed and, if feasible, should be the preferred option.
To understand why roundabouts have become so popular, it is important to understand what a roundabout is and why roundabouts perform so well compared to other intersection alternatives.
What is a roundabout? A roundabout is a type of intersection that includes a circular central island and lane(s) traveling around the central island in a counterclockwise direction. A roundabout is different from traffic circles and rotaries.
There are four main differences between rotaries/traffic circles and modern roundabouts:
Right of way
In a roundabout, vehicles already within the circle have the right of way.
In a rotary or traffic circle, entering vehicles have the right of way.
Size
Roundabouts are comparatively smaller (typically 80-180 feet in diameter).
Rotaries and traffic circles can be as big as 300-400 feet in diameter.
Changing lanes
Changing lanes within a roundabout is not allowed. Lane integrity must be maintained through to exit.
Changing lanes is allowed in rotaries and traffic circles (though sometimes this is difficult, as shown in the famous scene from National Lampoon’s European Vacation).
Deflection upon entry
Deflection is crucial to appropriate roundabout design, as it promotes lower speeds and encourages yielding.
In a rotary or traffic circle, entering traffic aims to the right of the central island, which does not promote lower speeds or yielding.
How to drive a roundabout Roundabouts can have a variety of configurations, depending on the capacity requirements on each approach. Driving a single-lane roundabout is easier than driving a multi-lane roundabout, but the basic concept is the same. The primary concept to understand for a single-lane roundabout is this: yield to pedestrians at crosswalks and to vehicles to your left within the circulating lane.
Multi-lane roundabouts add one more step to the direction listed above: choose the appropriate lane. For example, choose the left lane if you are going left or through, and choose the right lane if you are going right or through. (Yellow line: left or through; Blue line: right or through)
Benefits of roundabouts Compared to standard intersections, roundabouts offer significant benefits.
Safety: This is one of the primary reasons roundabouts have become so popular. Research shows that roundabouts reduce fatal and injury accidents by as much as 76%, due to slower speeds and the existence of fewer conflict points.
Capacity and reduced delay: Due to the continuous flow of traffic, roundabouts can handle larger volumes than signalized intersections in the same amount of time. It is a common misconception that intersections are more efficient.
Better fuel efficiency and air quality: There is less idling by vehicles in a roundabout than in an intersection where vehicles must wait through red lights. This equates to a reduction in fuel consumption and vehicle emissions.
Landscaping opportunities: The central island of a roundabout is a great place to provide landscaping and can serve as a gateway to a community or district.
Safety for pedestrians: This is another common misconception about roundabouts. It is often thought that because a pedestrian crossing at a roundabout is uncontrolled, that it is not as safe as a signalized crossing. The figures below illustrate why the roundabout crossing is safer than crossings in standard intersections.
Roundabouts are being implemented in communities throughout Minnesota and continue to score well on many federal grant programs. We continue to stress the importance of educating drivers about how to properly navigate a roundabout, through ongoing communication with the public across multiple platforms.
When people think of slope failure or geohazards, they think of landslides and mudslides in mountainous regions like California. Those of us living in the Midwest don’t typically worry about property damage or disruptions in public services due to slope failure. Unfortunately, slope failure impacts a wide range of landscapes, even those considered relatively level. In fact, in the Twin Cities there have been increasing numbers of slope failures that significantly impacted infrastructure and property. The most recognizable example is probably the 2014 slope failure along the West River Parkway in Minneapolis. This slope failed after more than 11 inches of rain fell in two days, impacting a popular recreational trail as well as a major health care facility. Repairs were completed in 2016, and cost $5.639 million [i].
Slope failure is a geohazard that impacts many types of infrastructure, from individual homes to municipal storm sewer networks to oil and gas pipelines. In fact, the Pipeline and Hazardous Materials Safety Administration requires that natural gas and hazardous liquids pipelines develop risk assessment programs for slope failures in their systems. Likewise, many municipalities are beginning to incorporate these types of risk assessment programs into their own planning activities.
So what causes slope failures? Like all geohazards, the causes are myriad and complex. Establishing a framework of how the physical processes behind slope instability function is crucial in determining risk.
Simply put, slope stability is based on the interaction of two forces: driving forces and resisting forces. Slope failures occur when driving forces overcome resisting forces. The driving force is typically gravity, and the resisting force is the slope material’s shear strength.
When assessing a slope’s stability look for indications that physical processes are decreasing shear strength. These can include:
Weathered geology: Weak, weathered bedrock, jointed rock, or bedrock that dips parallel to the slope can decrease stability.
Vegetation removal: Droughts, wildfires and humans can remove vegetation from the slope, decreasing stability.
Freeze/thaw cycles: Water in rock joints or in soils can decrease slope stability.
Stream action: Rivers can erode the bottom of the slope, called the toe, decreasing stability. This can occur over time through normal stream action or catastrophically during flood events.
Human modifications: Humans modify stability through actions such as excavation of the slope or its toe, loading of the slope or crest, surface or groundwater manipulation, irrigation, and mining.
Slope angle: Steeper slopes tend to have greater risks for instability.
Soil type: Soils have variable amounts of shear strength, dependent on factors such as soil texture, pore water, and particle cohesion.
Water sources: Water works in many ways to reduce shear strength. For example, pore water pressure in soils decreases shear strength, and saturated soils are more likely to lead to slope failure. Perched water tables, groundwater seeps, and excessive precipitation are some examples of water sources that may lead to slope failure in certain conditions.
Many things can impact the stability of a slope. Just like with stream crossings, all geomorphic factors affecting slope stability should be considered when determining the risk of slope failure.
After the geomorphic factors for each slope crossing have been adequately assessed, these indicators can be fed into our geomorphic framework of slope stability to determine how likely slope failure is at a particular location.
An example of a risk matrix developed for slope stability is below. This matrix is determining the likelihood that a slope failure will occur and multiplying that by a known consequence to derive a risk factor (from the formula above). For this type of risk matrix to work, robust rational and consequence definitions should be developed to support the risk estimation. In this example, geomorphic analyses have resulted in a specific set of justifications for the likelihood of slope instability. These categories are then assigned risk factors. Very Low stability slopes, as defined by the rational in the matrix, have an Almost Certain (5) risk factor.
Detailed definitions have also been determined for the Failure at Road consequence, and those definitions are assigned risk factors. A slope failure at a road is considered Critical (5) if the road is a critical evacuation route, major transportation corridor, or restricts access to emergency facilities. Almost Certain (5) slope failures at Critical (5) roads have a Risk Factor of 25 and require mitigation.
While this example matrix only lists one consequence category (Failure at Road), a risk matrix can be designed to include as many consequences as necessary to capture the complete risk profile. Additionally, the application of five risk factors is merely an example. Risk matrices can be designed with as many or as few risk factor categories as necessary.
The outcome of this analysis is a set of risk factors that pipeline operators, city planners, engineers, or transportation officials can use to prioritize capital spending in a non-biased way, proactively estimate capital budget, manage interim risks, and more accurately estimate maintenance budgets.
Boating, fishing, swimming, and enjoying a day near a lake, river, or stream is part of Minnesota’s culture. Unfortunately, nearly 40 percent of Minnesota’s lakes and streams are included on the Minnesota Pollution Control Agency’s (MPCA) Impaired Waters List. (See the list at https://bit.ly/2BwTk3r.)
Meeting surface water quality standards requires monitoring pollutants that can affect the physical, chemical, or biological makeup of surface water. Phosphorus is one of the main pollutants in the state’s bodies of water. Phosphorus is a pollutant that comes from both external and internal loading sources. Today, Minnesota law limits the use of fertilizers containing phosphorus, but prior to these limits, phosphorus was widely used in several commonly used chemicals settling in our lakes, rivers and streams. Meeting water quality standards requires a reduction of phosphorus in the water column. A water column is the vertical section of water from the surface to the bottom of a body of water.
External sources include stormwater runoff, atmospheric deposition, and directed pipe runoff. Internal sources include sediment suspension, aquatic vegetation, and an overabundance of rough fish. Both internal and external loading sources contribute to surface water quality degradation.
Managing water quality is not only important to the community and the people who live and work there, but it also drives ecological integrity. Because of this, water quality is regulated by federal, state, and local governments.
Where to start With the appropriate funding and expertise, it is possible to solve water quality challenges and get bodies of water removed from the MPCA Impaired Waters List. Fortunately, numerous funding resources are available through grants, partnerships, and coalitions.
Since water is continuous across landscapes, developing partnerships is often the most cost-effective way to approach managing water quality. It lessens financial burdens and helps many communities achieve long-term success. It also creates opportunities for communities to create long-term plans to improve and protect water quality.
To begin to make improvements, it’s important to understand a community’s water quality issues. Start putting the pieces of the puzzle together by quantifying the scale and source of the pollutant before selecting an approach. The MPCA’s website offers information on a body of water’s total maximum daily load (TMDL) at https://bit.ly/2BbsrVH.
The TMDL is the maximum amount of pollutant a body of water can receive without exceeding water quality standards, and allocates pollutant loads from internal and external sources. In other words, the TMDL identifies all sources of a pollutant and determines how much each source must reduce its contribution.
TMDL implementation actions Once the TMDL is identified for each body of water, a plan of action can begin to be shaped. Several methods can be implemented to begin to improve water quality.
Public education and outreach. Fertilizers have a major impact on water quality and ecosystems, creating a chain reaction. Excess phosphorus found in fertilizers creates algae blooms. As algae decomposes, oxygen is removed from the water. A lack of oxygen in an aquatic ecosystem effects the native species in a body of water. Educating the public of the harmful effects caused by fertilizer runoff can help limit the amount of phosphorus or other nutrients that flow into bodies of water.
Structural best management practices (BMPs). The MPCA defines a BMP as a stationary and permanent structure that is designed, constructed, and operated to prevent or reduce the discharge of pollutants in stormwater. BMPs can be used for on-site or regional treatment and help a community take a more strategic approach to managing its water quality.
Carp management. Internal loading of phosphorus can be caused by an overabundance of the invasive common carp. High levels of phosphorus cause algae blooms, reduced clarity, loss of aquatic plant and fish habitats, and a threat to human health. Managing and mitigating carp populations improves long-term overall water quality and ecological integrity.
Vegetation management. Invasive aquatic vegetation displaces native vegetation and can release phosphorus into the water column. Vegetation management can help solve this problem. Strategically placed native vegetation can help protect soil from erosion and reduce surface water runoff. Stormwater is then held in place and slowly released, rather than flowing directly into the body of water. Native aquatic vegetation can also help reduce phosphorus-laden sediments through wind and wave action.
There isn’t a silver bullet that can solve a community’s water quality challenges at once, but these are several proven options that can lead to improved water quality and ecological integrity.
Pavement mixes used to build streets, highways and parking lots are not the same. There are several different mix requirements that are applied to each based on the use of the surface. Parking lots carry a low amount of daily traffic, but experience wear and tear due to static loading or from serving as a rest area. Rest areas and truck stops have a high number of creep speed Equivalent Single Axle Loads (ESALs). ESAL is a concept developed from data collected at the American Association of State Highway Officials. It is a road test that measures the damage relationship and the effects of axles carrying different loads.
When determining pavement mix, a parking lot’s classification must be established. Parking lots are divided into two classifications: passenger vehicle parking and commercial vehicle parking. In some cases, parking lots serve as both passenger vehicle parking and commercial vehicle parking. These parking lots require special considerations.
The Minnesota Department of Transportation (MnDOT) has developed mix designations that are included in their Standard Specifications for Construction Book. All project documents submitted must be in accordance with the book. Mixture designations are coded and outlined for their specifications using SPWEA430C.
SP | Design Type
Superpave, which is a gyratory compactor design used for all asphalt mixtures. This is the latest design used to replace the Marshall mix design method.
WE | Lift course
WE indicates wear and shoulder wear, which is the top 4 inches of asphalt on MnDOT projects, or top 3 inches on local projects.
NW indicates non-wear course, which lies below the top 4 inches of asphalt on MnDOT projects or top 3 inches on local projects.
A | Maximum Aggregate Size
2360 Gyratory
Maximum Aggregate Size
A
-1/2”
B
-3/4”
C
-1”
D
-3/8”
4 | Traffic Level
The traffic level is based on the ESAL or the annual average daily traffic (AADT). Higher traffic levels require a higher-level percent of crushed aggregates. This will reduce the effects of rutting on pavement caused by traffic loading when soft mixes are used.
Traffic Level
Million ESAL
AADT
2
< 1
< 2,300
3
< 3
< 6,000
4
< 10
5
> 10
30 | Air Void Requirement
40 for 4.0 percent air void. This is usually used on a surface with high traffic levels. The traffic helps compact the asphalt mixture.
30 for 3.0 percent air void. This is usually used on surfaces or roadways with low traffic level.
C | Performance Grade (PG) Binder Type
2360 Designation
Binder Grade
A
PG 52S-34
B
PG 58S-28
C
PG 58H-34
E
PG 58H-28
F
PG 58V-34
H
PG 58V-28
I
PG 58E-34
L
PG 64S-22
M
PG 49S-34
The first numbers of the binder type are the average seven-day maximum pavement temperature (oC) and the second number is the expected minimum pavement temperature (oC). The letters dictate the traffic level. “S” grade is for standard traffic, “H” grade is for heavy traffic, “V” grade is for very heavy traffic, and “E” grade is for extremely heavy traffic.
Example – Binder Type A:
A PG 52S-34 is intended for use where the average seven-day maximum pavement temperature is 52 degrees Celsius and the expected minimum temperature is -34 degrees Celsius, under standard traffic conditions.
Parking lot mix types:
Below are some recommendations on mix types that will help enhance the overall performance of the parking lots.
Classification
New Construction or Reconstruction
Mill and Overlay
Passenger Vehicle Parking Only
SPWEA430C
SPWEA430B
Commercial Vehicle Parking
SPWEA530F / SPWEA530I
SPWEA530H
Aggregate Size
Aggregate size A is recommended due to the smaller size aggregate yielding a smooth finishing surface.
Traffic Level
Traffic level 4 will help limit the depression in the parking stalls for passenger vehicle parking only.
Traffic level 5 includes an increased percentage of crushed aggregate that helps mitigate creep speed ESAL from trucks.
Air Void Requirement
A 3.0 percent air void will provide a tight finishing surface and an aesthetically pleasing look.
PG Binder Type
The binder type used in a mill and overlay is generally lower than what is used in new construction or reconstruction. Cracks on existing underlying pavement reflect through the new overlay over time. This method is not as cost-effective as a higher binder grade. This does not mean that a higher binder grade in any mill and overlay project should not be used. A high binder grading helps slow down thermal cracking. It is at the discretion of the designer to decide if it is cost-effective to delay the reflective cracking.
On commercial vehicle parking surfaces, asphalt binder grade F is a sufficient option, but in extreme conditions a higher binder grade I (PG 58E-34) should be used to reduce rutting and shoving.
Surface areas where trailer landing gears are down should be designed with concrete pavement to support concentrated loads.
The recommendations above are guidelines. Additional investigation is necessary and should include coring or boring to further evaluate the subsurface conditions prior to a design work.
The materials that are used to build roads and buildings are a vital part of every project. You can’t build a car without all the right parts or make a cake without all the specified ingredients. The final product of a project, whether it be a highway, bridge, or apartment building, is only as good as the quality of materials incorporated. Construction materials specifications become incredibly important when design plans are being developed. When a developer, city, county or the department of transportation sets their project specifications, they do so with longevity and the project’s life expectancy in mind.
Why do we test?
We begin testing at the beginning of a project, and in some cases before, to establish a foundation for success. Both vertical and horizontal construction require material testing and inspections. In both types of development, confirming materials are aligned with the original design helps prevent potential legal claims, safety issues and catastrophic events. It’s why we test materials both in the field and in a lab. Our lab allows us to test construction materials and assure that the materials have been processed, tested, and reported following applicable standards and specifications. Both field and laboratory testing are critical to ensuring the safety and viability of the materials.
What does the future of materials testing look like?
Like many other areas of construction, technology is changing the construction materials industry and they’re not as far off as some may think. A recent blog discusses new materials on the horizon that could revolutionize the industry. Sustainable material substitutes are being introduced like recycled and pollution-absorbing bricks, translucent wood, and light generating cement. These new materials are results of aggressive and intense research and development. Although not widely used today, these changes will make material testing even more important as we begin to see the next evolution of building materials used in our everyday infrastructure.
Up until last month, real-time and ray tracing couldn’t be used in the same sentence without a bank of 10 GPUs and 2500 watts of power. Ray tracing makes renderings dynamic and realistic and thanks to powerful GPUs, shortens the amount of time spent on each frame. This recent advance in technology allows clients and the public to see reflections, higher quality shadows and experience the creation for themselves. Today, we’re utilizing these technologies to create stunning visualizations for our clients. Once the projects have been modeled, iterations are produced in minutes, instead of days or weeks.
