Section 4: Planning and Contracting
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.
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.
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:
- Any special site-specific requirements that need to be addressed?
- Any repairs and patching that need to be part of the project plans?
- Any “no-work areas” that need to be shown on plans including whether bridge decks are to be seal coated?
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
. This report can be found through the TxDOT website.