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Section 4: Planning and Contracting

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Calculate Quantities

One of the first steps in the planning process is to determine the quantity of materials needed. This begins with determining how much roadway is to be covered.

The length and width of roadway to be seal coated must be determined to estimate material quantities. The length of the roadway should be obtained using the station numbers or a distance-measuring instrument (DMI).

Once the longitudinal distance has been determined, the area is computed by multiplying the longitudinal distance (length) by the width of the road, in feet. This total area will be expressed in square feet and must be converted to square yards by dividing the total area by 9. Asphalt application rates are expressed in gallons per square yard, and aggregate application rates are based on cubic yards (of aggregate) per square yard of roadway.

If different materials will be used on the shoulders, they should be calculated separately. To promote cost savings, a TxDOT directive states to limit seal coat on shoulders four feet or greater in width to every other seal coat cycle. Crack sealing on shoulders should be used as part of the overall maintenance plan and is a less expensive means of keeping water out of the substructure.

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Estimate of Materials

An estimate of the material quantities can be made after the roadway area has been computed. It should be understood that the actual application rates of binder and aggregate should be based on a design procedure as described in Chapter 4 after aggregate is delivered and before construction starts. For planning purposes, it is only necessary to estimate the application rates of binder and aggregate. While the actual binder rate may vary in the wheelpath versus outside the wheelpath, and the binder/aggregate rate may vary in the travel lanes versus the shoulders, it is only necessary to use an overall average rate for estimating materials. Application rates for any binder and aggregate combination can vary considerably. The estimated application rates should be based on site-specific conditions and local experience.

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Preparing Plans

For seal coat contracts, plans should include a title sheet, general notes, specification data, a summary of quantities, project location and limits, and standard sheets. Additional decisions regarding plan information may include the following:

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  • Any special site-specific requirements that need to be addressed?
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  • Any repairs and patching that need to be part of the project plans?
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  • Any “no-work areas” that need to be shown on plans including whether bridge decks are to be seal coated?
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Estimating Cost

For estimating seal coat contract costs, review previous unit bid prices and average unit bid prices. Average district and statewide unit bid prices can be obtained from the Construction Division’s (CST) monthly report for construction and maintenance contracts. This report can be found through the TxDOT website.

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