Concrete C&G vs. Asphalt Wedge Curb 2

[packgrad98]

The municipality that I work for is considering the possibility of changing our development standards to allow the use of asphalt wedge curbing instead of concrete C&G. While this is definitely not my recommendation, I have been assigned the task of locating any studies that may have been done comparing the two alternatives. More specifically, the maintenance costs associated with each alternative. I have searched the internet high and low and have not been able to find anything (including the APWA site, etc.)

Does anyone have any information or ideas. Any comments concerning pros and cons of each alternative would be helpful also.

Thanks in advance.

 

[KRSServices]

As with most municipalities, budgets for infrastructure is always tight.

To properly answer you thread, I must point out that ACP is designed to support traffic, not act as a channel for water. Over the past 18 years, I have seen many cases where ACP was used to channel water, as a swale or wedge curbing. In those cases where streamflow is quite prevalent, the surfacing quickly ravels and segregation of aggregate causes widespread failure of the channel, which than leads to costly repairs.

On channels where there is only periodic flow, the ravelling process is not as rapid.

Because of the very nature of concrete, it is ideal for applications as a channel. What is precipitating the need to change the development standards?...Is it pressure from the developers through the Council?...Is this a smaller community?

Normally, when a change such to development standards (for a lower standard) is considered, the future cost to the municipality must be factored into the equation presented by the proponents. Their initial savings will result in a horrible mess to clean up at some point in the future.

KRS Services

http://www.krs-services.com

 

[jheidt2543]

I agree with KRSServices, particularly with respect to doing a life cycle cost study. Concrete is definetly the way to go. One other thing to consider is the suseptablility of the curb to damage from traffic and, if you are in a snow area, damage due to snow removal. I've seen private developments here in the upper midwest where asphalt curbs didn't last the first winter because of damage from snow plows.

Another knock on asphalt curbs is I've never seen a straight one, they are always wavey. At least concrete is straight for the 8', 10' or 12' length of the forms. Or, if you are slipforming, the concrete pavers seem to have a straighter eye than the asphalt guys. Just my unscientific observation.

 

[erikfinley]

Stick with concrete. Asphalt reduces construction costs, but I can't think of any other benefit.

REDUCED R/W WIDTHS
As I recall, at a 35 mph design speed vertical concrete curb has a minimum clearzone requirement of 1.5 to 2 feet; by comparison clear zone for a rolled edge is 10 feet. With an asphalt rolled edge, hydrants should be placed at least 10 feet back from the traveled way.

 

[packgrad98]

I am very familiar with the cons against using asphalt c&G as opposed to concrete. I have spoken my piece on that to the planning department on several occasions and expressed my opposition to "lowering" the standard. As suggested by KRS, this is definitely developer driven. This came about as a part of discussions to drum up support for an extremely large forced annexation. This change is included with several other items, primary of which is a set of drainage design standards that have been non-existant to date. It is hard to believe that a city of 100K+ has absolutely no drainage standards in place.

The worst part about this situation is that, now that this has been taken before the City Council, everyone is questioning the knowledge and ability of the planning and engineering staff. This was a decision that was brought about by the City Manager. That, in part, is why I am looking for some sort of comparison studies to see if anyone had something that could help justify their decisions.

 

[jheidt2543]

I'm not aware of any studies comparing asphalt curbs with concrete but, if you are in snow country and can find any asphalt curbs, I'll bet they aren't whole anymore. Snow plows really tear them up. Take a look around and see if you can find any in your area to look at and show the "powers that be" what they look like after 4 or 5 years.

I know that planning departments can take a lot of heat for some of their recommendations and regulations. I bitch about a number of their goofy requirements too but, sometimes they do protect developers from themselves. Concrete curb and gutter is the way to go, they last longer and require a lot less maintenence.

 

[roncity]

I'm not aware of any formal studies on asphalt vs. concrete curb performance, in part because there are so few asphalt curbs out in actual roadway conditions. I suggest doing a local inspection tour & study of your area and photograph asphalt and concrete valley gutters in parking lots , parks, and roadways to show how fast asphalt deteriorates when subjected to a constant water flow . Don’t forget to look for areas where air conditioners and roof drains discharge across asphalt and eroded it. You won't see that in concrete valley gutters
Also check roadway and parking lot construction sites, where temporary asphalt curbs are occasionally used. You’ll find that any over two or three years old have cracked, sagged, or settled.
Also, it takes a lot of hand labor and skill to place hot asphalt and stack it up into a curb shape and compact it before it cools down. It’s very hard to get a smooth finish, with accurate edge lines, on a vertical asphalt surface. I suspect you’ll find very few if any contractors that can do a good job with asphalt curbs.
If you do find an asphalt curb contactor, you’ll find that an asphalt curb is not that much cheaper than concrete. A lot of the cost of curb work is in the grade control and the hand finishing. Any savings in asphalt is offset by the time delay and difficulty in getting small batches of hotmix. If asphalt curbs were a " good thing", you would see them used in private parking lots and shopping centers.
Finally, there is a lot of pressure from developers to build cheap and pass increased maintenance cost onto future generations. Ask these developers if they will warranty asphalt curbs for 5 years.

 

[KRSServices]

packgrad,

You just provided me with the insight necessary to fully comprehend and provide you with some advice on your thread.

You mentioned the City Manager, how is he or she fitting into the picture? The item is before Council, I am assuming that it is an agenda item put forth by the Planning Department. Since you stated that no development standard exists with respect to stormwater management, I am assuming that at least there are precedent policies in place.

From what you have wrote, it appears as though the Council may be frustrated with the Administration of the municipality in general. If the staff recommended against ashpalt curbing and gutters, and the developer is presenting counter arguements, which is par for the course, it is up to the manager to and the administrative staff to present clear and concise arguements. Be careful not to ensue into a debate because generally, staff will lose.

If the City Manager is siding with the developer, then the engineering and planning departments, particularly thier managers, MUST do a better job to provide facts. They must present future costs and dilemmas that will be faced by the municipality and it must be presented in a very concise and short report. In my experience, Couoncils make better decisions with abreviated facts rather than long winded techno-verbage. It may be well advised to bring in someone whom has some key municipal experience to provide a "third" party presentation to the Council,developer and Manager in a three hour "retreat" session. I have done this and it works, particulalrly if some of the parties are adversarial.

One thing to remember, most Councils are untrained in the intracacies of stormwater management (they only hear about it when things go wrong) and have a variety of backgrounds. They must be dealt with in that manner, never ever bury them in technology. Most City managers have financial backgrounds, MBA's, etc. They too, get quickly frustrated when staff throw road blocks to percieved growth (large developments). In my experience, I see many solutions that could resolve your issues, the least of which is getting comparisons or finding studies. The issues that I see are way deeper than that.

If you wish further information or want to discuss in greater detail, please do not hesitate to contact me (780)573-1884.

KRS Services

http://www.krs-services.com

 

[ndpw]

Please allow me to stir the pot a little and make a case against concrete curbing.

1. Concrete curb is not infallible to the effects of snowplowing. I see many, many examples of eyesore concrete curbs that have not fared well through New England winters. Did I mention the effects from salting the streets and sidewalks?

2. Each year municipalities overlay X number of miles of streets as part of capital improvements. In the municipality I work for, there has been a movement over the last 5-10 years to opt for concrete and/or granite curbing. Well, now some of the streets that have these types of curbing need to be overlayed. Because such an investment was made to place this curbing with a specified reveal height, we end up having to mill either all or part of the road prior to overlaying to save curb reveal!! This adds significant time and cost to our overlay program which means we overlay less streets per year which means we fall behind our target lifecycles (heaven knows we're not going to get more money) which means the public has more reason to question their public works dept. With asphalt, we either ignore the lost reveal (if gutter flows aren't a concern) or replace the curb at $3/ft vs $15-$25/ft for concrete/granite. As far as placing the asphalt... one respondent mentioned the hand work required to place asphalt curb, well the contractors I've recently worked with have a mold machine that allows them to lay several thousand feet per day (try doing that with concrete). As far as paying extra for small loads... the plants aren't going to charge extra for municipalities and/or contractors that purchase tens of thousands of tons per year.

3. The last point I'll make is in regards to claims against municipalities. In this ever increasing litigious world in which we live I regularly am made aware of what I'd consider ridiculous claims against our City. Mr. and Mrs. BMW can't parallel park or cut the right turn on red a little too close and bang their rims and cut their tires on concrete/granite curb and claim the City is responsible for the $800 in parts and $300 in labor required to fix it when if there was asphalt they'd just have climbed the curb a little before gravity straightened them out. (Do I sound frustrated?)

There are many good reasons against asphalt, many of which were listed in previous replies to this thread. There's no doubt that they get banged up and break far more easily than concrete/granite. I think in high profile areas concrete/granite has its place, but I wouldn't opt for them everywhere within a municipality. Asphalt has its place in rural areas. I've personally never had a big problem with gutter scour, but we're not prone to high frequency rain events here in New England. My ranking of curbing preference is 1. None (roadside ditches) 2. Asphalt 3. Granite 4. Concrete

Enough stirring….