As a former Public Works Director, I notice infrastructure wherever I go. I do my best to not bother Kent Public Service crews with too many of my “observations” about Kent’s infrastructure but I’m sure there are days when they wish I was a former police or fire chief. I have never been a big fan of chip seal on city streets and I must admit I cringed when I heard we pay the country each year to come in and lay down chip seal on certain Kent streets. Chip seal has its place — but that’s usually on old country roads not city streets — so I couldn’t help but ask Gene Roberts (Kent Public Service Director) why he continues to pay the county for this stuff. He gave a good explanation, and even though I still don’t like chip seal, at least I understand Gene’s recommendation to continue to use it. I’ve included Gene’s explanation for your review.
Date: June 27, 2007
To: David Ruller, City Manager
From: Gene Roberts, Service Director
Chris Tolnar, City Engineer
Subject: Seal Coat Program
By Agreement, the Division of Engineering with the Portage County Engineer’s office has completed the seal coat treatment work for 2007. The following streets have received the maintenance treatment:
–Garrett Street from South End to West Main Street.
–Glad Boulevard from Rhodes Road to North end of Cul-de-Sac.
–East Hall Street from South Water Street to Vine Street.
–Hudson Road from Fairchild Avenue to the North Corp. Limit.
–Irma Street from End of Construction Limits to West Main Street.
–Louise Street from Parmalee Street to West Main Street.
–Meloy Road from South Water Street to the East Corp. Limit.
–Parmalee Street from Deidrick Road to Garrett Street.
–Sunnybrook Road the South Corp. Limit to SR261.
The City of Kent historically has maintained a portion of the roadway system network with seal coat surface treatment (also known as chip-seal or bituminous surface treatment). In the Division of Engineering’s pavement network index, approximately 26% of the City street centerline miles are identified as seal coat surface treatment streets. These roads were gravel and non-improved pavement roadway sections and over time were treated with seal coat due to dust and wet weather rutting complaints. A large portion of the seal coat treatment streets were added to the City’s inventory through annexation that included existing township streets but many have always existed as seal coat treatment streets considering this technique is one of the oldest forms of roadway maintenance.
The seal coat maintenance operation is comparable to other methods in durability and effectiveness, but costs far less. This allows the City to improve conditions on more square yards of improved roadway. The advantages of seal coat treatment operations are:
- Improved skid resistance of pavement surface
- Quick placement and cure time – Reduces inconvenience to traveling public
- Provides a protective coating over the existing roadway to reduce the deteriorating effects of the sun and water penetration, through oxidation of the existing asphalt and moisture penetrating into the base and creating premature pavement failure
- Less expensive than other options
- Seal Coat Cost $1.70/Square Yard (2007 dollars, Single Coat)
- 2-inch Asphalt Overlay $6.20/Square Yard (2006 dollars, Overlay only)
- Typical 2-inch Mill & Resurface $8.70/Square Yard (2006 dollars, Mill, Pavement Fabric & Asphalt)
- The program for 2007 encompassed 37,870 square yards of roadway to be treated. The approximate cost for 2007 was $79,000 due to several roads receiving a double coat of the treatment for added durability. For the same 37,870 square yards of roadway with 2-inchs of asphalt placed over the seal coat surface treatment would cost approximately $235,000 or if it was milled and resurfaced the cost could be around $330,000.
- The life expectancy of a newly treated seal coat roadway is anticipated to last between 5 and 7 years, while the life expectancy of an asphalt resurface is between 10 to 12 years. Of course there are many variables that can extend or shorten the expected life of a road, however even if the seal coat lasts half as long as the asphalt, the cost is one quarter of asphalt resurfacing, resulting in an appreciable cost savings to the city and permitting other improvements to be undertaken with the already strained resources.
Typically, asphalt overlays are not effective on existing seal coat surface treatment roadways. The nature of the seal coat roadway is to be relatively flexible and self-healing. When a layer of asphalt, which is less flexible than seal coat, is placed on top of a seal coat pavement section the resulting asphalt surface will typically exhibit premature cracking and rutting as the base seal coat moves or deforms as it is intended. Additionally, milling (the grinding of the existing asphalt surface) does not perform well because the seal coat roadways have more bituminous material (the liquid part of the asphalt pavement) and sticks to the drum of the milling machine and/or rips out in large chunks. Consequently, in order to improve a surface treatment roadway into an asphalt section the entire roadway material should be removed and replaced with a proper asphalt section (typically 6-inches of stone sub-base, 5-1/2-inches of base course asphalt and 1-1/2-inches of surface course asphalt).
The following information is provided to provide some scale to the reader relative to the quantity and cost associated with the City of Kent’s inventory of seal coat surface treatment roadways. Table No. 1 describes the quantity and type of pavements in the City of Kent. Table No. 2 indicates the cost to convert the chip and seal streets in the City to Asphalt pavement. The cost in 2007 dollars to single coat every chip and seal street in the City is $578,660 and with an estimated life cycle of 7-years has an annualized cost of $82,666. Conversely, the cost to convert all the chip and seal streets in the City’s inventory to asphalt would cost $7,351,436 in 2007 dollars with an estimated life cycle of 10-years with an annualized cost of $735,144. The cost reported for converting seal coat surface treatment roadways to asphalt does not include the cost necessary to upgrade storm water and utilities, which typically are required.
Table No. 1
City of Kent
Pavement Type by Length and Area
Length Area Pavement Type Length Length Area Area % Total % Total Ft. Mi. SF SY Network Network Asphalt Pavement 297,726 56.39 7,805,101 867,233 65.14% 66.14% Brick 2,859 0.54 82,173 9,130 0.63% 0.70% Gravel 10,335 1.96 139,820 15,536 2.26% 1.18% Concrete 27,265 5.16 710,366 78,930 5.97% 6.02% Surface Treatment (Chip Seal) 118,888 22.52 3,063,491 340,388 26.01% 25.96% Totals: 457,073 86.6 11,800,951 1,311,217
Table No. 2
Pavement Cost to Change all Chip & Seal Streets to Asphalt
Description Unit Cost Unit Unit Cost Cost Surface Treatment City Wide 340,388 SY $ 1.70 $ 578,659.60 Replace Surface Treatment with Asphalt (maintaining existing alignments) Excavation (13-inches) 122,918 CY $ 6.50 $ 798,967.00 Subgrade Compaction 340,388 SY $ 0.50 $ 170,194.00 Subbase (6-inces) 56731 CY $ 15.00 $ 850,965.00 Asphalt Base (5.5-inches) 52,004 CY $ 90.00 $4,254,840.00 Asphalt Surface (1.5-inches) 14,183 CY $ 90.00 $1,276,470.00 Total: $7,351,436.00
The final issue, which must be addressed regarding improving seal coat surface treatment roadways, is related to adjoining property owner equity. A property that is purchased on a fully improved asphalt street typically cost more versus a similar property that is purchased on seal coat surface treatment street. Additionally most seal coat surface treatment streets do not have the same type and kind of storm water improvements that are typically found on fully improved asphalt streets.
In the past when the City improved streets from seal coat surface treatment to asphalt or even concrete the adjoining property owners were asked to pay for a portion of the improvement through an assessment thus offsetting the improved value of their property. The last time the City upgraded its assessment ordinance (Chapter 925) relative to what is charged for each type of improvement was for 1996. When originally written the assessment ordinance was based on the adjoining property owner(s) paying approximately one third (33-percent) of the cost of the improvement. In current dollars, a typical improvement assessment equates to approximately 20-percent and in some cases less, of the actual construction cost.
While seal coat maintenance has many advantages, it does present some inconveniences during and immediately after application. This includes temporary dustiness (reduced greatly with slag as recommended by the County) as well as short-term presence of wet emulsion (typically called tar, but it is actually a polymer modified bituminous asphalt cement) and loose aggregate. To minimize the inconveniences the Division of Engineering contracts with a sweeping company to have the loose aggregate removed the same day or the following day, allowing the fresh stone material to embed as much as possible into the asphalt cement. The City’s Central Maintenance Division temporally places Loose Stone signs to warn the motoring public of the inconvenience.
Therefore, while there is some short-term inconvenience with seal coat surface treatment the amount of work that can be conducted in a short time along with the cost saving benefits it is anticipated that the Division of Engineering will continue to recommend the use of seal coat maintenance in the City’s annual street programs.