March 3, 2023
By Matt Indihar, Sr Project Manager, WSB

Did you know that the most effective way to manage pavement maintenance in your system is to plan five to ten years in advance? Many municipalities are forced into reactionary pavement maintenance projects. In these cases, decision makers are forced to spend their budgets repairing roads in the worst condition creating large, costly projects. This prevents resources from being allocated towards cost-effective treatments that focus on keeping pavements in good condition before they fail. To get ahead of reactionary maintenance and plan a roadway budget that maximizes the cost-effectiveness of each dollar spent, there needs to be accurate data on the condition of each pavement segment within a system. This provides the necessary information for a data driven pavement management and capital improvement plan to be implemented. Having a pavement network inspection done on a regular basis can bring clarity to condition trends, identify maintenance issues, and allow decision makers to be confident they are implementing the best possible pavement fix at the appropriate time.

Why is this important?

With all of the environmental factors and traffic loads that pavements are exposed to on a daily basis, deterioration is inevitable. With newer or better pavement, only a few distresses may be present so repair costs are lower. However, as pavements age their deterioration continues at an increasing rate. These damaged pavements are more expensive to maintain and may even require major rehabilitation. Knowing the current age, condition, and maintenance history for a pavement section can help determine the most cost effective fix for it based on where it is in its life cycle. Systematic pavement evaluations are one tool network managers can use to monitor their pavement and make the best use of maintenance and construction budgets.

What are pavement inspections and what do they do?

Pavement inspections provide scientific data about the existing conditions of a network of asphalt or concrete surfaces. The process involves a trained inspector evaluating the pavement and cataloging all distress by size, quantity, and severity. With this data, an overall Pavement Condition Index (PCI) can be calculated. This PCI number is a single value that is used to grade the condition of each pavement segment. From there, a report that contains analysis on the condition of the network and a series of recommended solutions for any deficiencies is generated. Additionally, the report may contain specific maintenance recommendations for each road, budget recommendations, trends in pavement conditions, and ideas on how to stretch a limited pavement budget to maximize the overall system condition.

What is the value of a pavement inspection?

A pavement inspection report is a key tool for decision makers to use when determining capital improvement plans and setting budgets. It provides data and rationale to support funding decisions on projects that can be shared with interested parties. The systematic method of determining roadway conditions ensures the most cost-effective and critical projects are being planned for without guessing or relying on personal opinions. In most cases, the cost of implementing pavement inspections pays for itself by optimizing the time and location of pavement repairs. Additional cost savings can be realized when planning the projects 5-10 years out so that similar projects types can be group into larger more cost effective projects.

WSB has the technology and expertise to develop a pavement management plan for your community. Contact us to learn more about a plan for your community.

February 13, 2023
By Bart Fischer, Sr Public Administrator with Joe Carlson, Project Engineer and Amy Fredregill, Sr Director of Sustainability, WSB

Government entities, at all levels, are working on plans to reduce greenhouse gasses. Many cities have been establishing sustainability and climate plans that aim to decrease their carbon footprints while some states have enacted laws to support more climate-friendly building practices.

When it comes to building resiliency and establishing more sustainable practices, pavement isn’t always top of mind. Bart Fischer, Sr. Public Administrator, sits down with Joe Carlson, Materials Project Engineer and Amy Fredregill, Sr. Director of Sustainability to discuss the advancements in sustainable pavement and how cities can help achieve their resiliency goals

BF: First, what is driving the push for more sustainable pavement options?

AF: There is an increased focus across the nation to reduce greenhouse gases and build resiliency. A lot of this is being driven by evolving customer demand and federal, state and local government. I think we’ll start to see more incentives and expanded programs in the coming years related to this developing area of emphasis. For example, the Governor of New Jersey signed the Low-Carbon Concrete Law earlier this year. The bill allows producers to receive an income tax credit of up to 8% of the concrete cost for providing low-embodied carbon products on state projects. It’s thought to be the first tax-incentive-based legislation of its kind in the nation.

JC: We are also seeing this expansion across Minnesota. Recently the Minnesota Department of Transportation (MnDOT) issued a provision to their specifications that allows an increase in the Recycled Asphalt Pavement (RAP) content that new asphalt mixtures can contain. Prior to this adoption, most mixes were only allowed to contain up to 20% RAP. Increasing the allowable RAP content leads to a significant reduction of carbon dioxide (CO2) emissions while simultaneously bringing down the cost of asphalt for owners.   

BF: Interesting. I didn’t realize that sustainable pavement options existed until recently. What are you seeing or hearing in the pavement industry?

JC: I’ve been hearing a lot of talk about concrete that has CO2 injected into the mix. This allows CO2 to be incorporated and locked into the concrete mixture and prevents it from being discharged into our atmosphere. Injecting the CO2 into the concrete has benefits including an increase in strength. The cost has little impact on the overall price of the concrete mix.   

BF: Stronger concrete and competitive pricing seems like a win for everyone. Anything similar in the market for asphalt?

JC: There is a recycled fiber reinforced asphalt available that is used for mill and overlays that provides performance benefits that dovetail with advancing sustainability goals. The fiber reinforced asphalt contains recycled plastic fibers that prevent what we refer to as reflective cracking. Reflective cracking occurs when there are cracks left in underlying layers of asphalt after milling. These underlying cracks come through (reflect) into the new pavement overlay surface rather quickly. The recycled plastic fibers are said to extend the life of the asphalt and significantly reduce the number of reflective cracks that develop. Extending the lifecycle advances sustainability because it reduces cost, waste, materials use and the overall footprint of a project.

How can cities implement sustainable pavement in their communities?

AF: Sustainable pavement is one area where cities can build resiliency and help reduce their carbon footprint, sometimes as stand-alone efforts, or increasingly as part of climate or sustainability plans adopted by cities we work with across the state. Net-zero goals and climate plans feel overwhelming but starting small has a major impact by testing out new approaches, engaging key stakeholders to get their feedback and build on their expertise, and learn from the experience. Sustainable pavement is one example of a minor change that has lasting impact.

JC:  We don’t need to rely on construction materials to make an impact. Our industry tends to overbuild and overengineer leading to more expensive projects, resulting in a larger carbon footprint. Communities can achieve success by ensuring a strong geotechnical exploration program is performed prior to any type of roadway construction or reconstruction. The results of these explorations provide the community with vital information and options for pavement construction or rehabilitation methods. In addition, a robust pavement management plan results in a more strategic approach to maintaining and repairing roads before pavement rehabilitation options become limited and expensive.  

By Matt Indihar, Sr Project Manager and Matt Henderson, Graduate Engineer, WSB

Pavement management plans are crucial for cities to properly oversee their networks of pavement. These plans help decision makers maximize their limited budgets by implementing the most cost-effective maintenance solutions on every segment of their roads, parking lots, and trails. A good pavement management plan helps decide which roads should receive maintenance, when they should receive it, and what kind of maintenance would be best. Additionally, a pavement management plan must be frequently updated to accurately capture pavement conditions and needs.

It can be complicated deciding how to allocate funds in a network of roads. Fortunately, there are analytical and scientific ways to help cities decide on the best way to use their street maintenance resources. While the process of creating a pavement management plan can seem overwhelming at first, it can be broken down into six steps.

1. Assess Inventory

The first step in creating a pavement management plan is to take inventory of all the roads that are to be included in the plan. This usually results in an updated map of all paved streets. Roads can be broken up into numbered segments so each section of pavement can be identified. Taking inventory can also include gathering maintenance records from recent pavement maintenance.

2. Pavement Inspection

Next, gather raw data from the pavement segments in the inventory. To understand the condition of each segment, the present pavement distresses are noted. Walking the streets and visually documenting distresses is one of the most detailed methods of capturing the data. An inspector can provide notes relating to unique distresses, maintenance, and other factors that cannot be captured by simply driving the road.

3. Condition Assessment

Once the raw data is recorded, the condition of a pavement section can be quantified using a single number such as a Pavement Condition Index (PCI) or Overall Condition Index (OCI) value. These numbers are calculated from the amount, type, and severity of the distresses surveyed. Having a segment represented by a single number makes it easier to compare against other segments. An average value condition index of the entire pavement network can be calculated to set budgets and track trends in the city’s pavement.

4. Condition Forecasting

Most pavements in a specific area exhibit a common pattern as they age. A standard degradation curve or a custom curve based on historical pavement maintenance tracking can be used to predict the condition of a segment in the future. This is important because pavement degradation is not constant. Knowing when a segment is about to enter a period of steep decline in condition is useful when deciding how to allocate maintenance resources and dollars.

5. Scenario Modeling

Using the current condition information and future condition information, a model can be created to analyze the future of a pavement network. Inputs such as budget, priority segments, preferred maintenance techniques, and construction costs are all variables that can be analyzed as models are created. These factors are dependent on discussions with the city to maximize the pavement conditions and align with a preferred strategy.

6. Capital Improvement Planning

The condition analysis allows cities to create a plan that optimizes pavement condition. Results usually include a list of road maintenance and construction projects that should be completed in each of the upcoming years. Furthermore, letting a computer optimize spending removes the guess work and ensures travelers are getting access to the highest quality roads possible. City officials can use the work plan to request work from contractors and notify residents of future projects.

While the six fundamental steps of pavement management are outlined above, every city has something that makes them unique. WSB has the technology and expertise to help tailor a pavement management plan for your community. We would be happy to discuss how we can help meet your pavement needs.

A Q&A with Bart Fischer, Senior Public Administrator and Mike Rief, Sr. Vice President of Construction Services.

With summer fast approaching it’s comforting to know that we’re free of icy road conditions for the next several months.  As I drove over a recent pothole and began noticing the sand and salt being swept off the roads in my community, I wanted to learn more about pavement management and its impact on city budgets and plans. I sat down with Mike Rief, WSB’s Sr. Vice President of Construction Services to better understand the importance of pavement management in our communities.

BF: Why is pavement management so important for communities?

MR: It all comes down to planning and budgeting. The predictability that a pavement management plan brings a community is the biggest benefit. If a pavement management plan exists, minor improvements and maintenance can potentially double the lifespan of a roadway.  Without any maintenance or improvements, a typical road will last about 20 years. Instead, with a pavement management plan, a community could extend that lifespan to about 40 years, maximizing their investment.

BF: That’s interesting. What exactly does a pavement management plan entail?

MR: I’ve found that comparing pavement to caring for a backyard deck has a lot of impact. We start by building a deck – similar to how we start building a road.  We form the foundation, wood for the deck and pavement for the road.

BF: We love our outdoor spaces in Minnesota! This is a great comparison. So, there is a preventative maintenance component after the foundation is formed?

MR: Exactly. Once the foundation is formed, we perform preventative maintenance.  In the case of a deck, we stain and seal it. For pavement, we seal the pavement cracks and perform surface treatments.

BF: What happens if a board rots out? How would you compare that in the pavement scenario?

MR: I like to call this the preservation stage of the pavement management plan. The best comparison to replacing a rotting board would be performing a mill and overlay on the road. A mill and overlay is a type of street maintenance that requires the removal of the top 2” of a street and the addition of a new layer of bituminous pavement in it’s place.

BF: When does it make sense to do a full road reconstruction?

MR: Yes, the reconstruction phase of the process is inevitable, but can be extended through preventative maintenance and preservation. Eventually, we’ve repaired the deck so many times and it makes sense to stop investing more dollars into it.  At some point, reconstruction is necessary, but through pavement management, it’s decades out and has been budgeted for.

BF: It really makes a lot of sense when you explain it in that way. Any other benefits of pavement management?

MR: I mentioned it above, but predictability is invaluable. There are huge capital investment benefits to implementing a pavement management plan.  It helps with budgeting, planning for development and growth and also can increase property values. I recommend any community, regardless of size, consider pavement management in the future.

By Sheue Torng Lee, Graduate Engineer, WSB

As a city leader you are responsible for many things; managing budgets, people, community needs, city assets, and the list goes on. What if there were a system in place for managing one of your largest assets, the city streets?

A pavement management program provides a systematic method of inspecting and rating the pavement condition of your roads; including the analysis of various maintenance and rehabilitation strategies. As part of the program, we use pavement forensics to identify the pavement structure and condition underneath the visible surface of the pavement. We look at the depths and condition of the pavement layers, signs of bonding or de-bonding, and distresses that may not be visible from the surface. Data collected from the pavement cores during forensics, provides a better understanding of the roadway sections and allows us to determine cost-effective and appropriate pavement rehabilitation techniques. The program is designed to help you get the most out of your available resources.

The collected data is used to evaluate funding needs and, in some cases, implement new funding tools such as franchise fees. We conduct analysis on various budget scenarios to help you forecast the funding required to maintain your network of roadways. The inspection results are useful for talking with residents and City Council Members regarding necessary road improvements and are vital in justifying the funding needed to maintain city streets as part of your Capital Improvement Plans. 

However, when streets have deteriorated and demand more extensive repair, your pavement management program allows you to plan for those projects and minimize the risks of having to make extensive changes to the project. By successfully implementing a pavement management program, you can improve the overall performance and life of your roads, saving the city and taxpayers time and money.

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.