307 - Aggregate Shoulders and Approaches
For all trenching, shoulder and approach operations that cannot be completed at the end of the day, the Contractor will place and maintain traffic control devices per Section 812 of the Standard Specifications for Construction.
All compaction percentages are based on the maximum unit weight of the specified material at moisture content below saturation.
When trenching is proposed, the operations will not be performed beyond the distance that will be backfilled and compacted the same day. The bottom of the trench will be compacted to not less than 95 percent of the maximum unit weight.
The construction of shoulders and approaches will be as specified for the class, width and depth shown on the plans. Shoulder material is to be placed in a way that will not damage an adjacent paved surface.
The compacted shoulder aggregate will be maintained flush with each course of HMA placed. The finished surface layer thickness will be constructed to a tolerance of ± 1/2 inch (15 mm).
For Class I shoulders and approaches, compact the aggregate to not less than 98 percent of the maximum unit weight. For Class II and III shoulders and approaches, compact the aggregate to not less than 95 percent of the maximum unit weight.
Where trenching is required on both sides of the road, each side will be measured separately along the road centerline.
When shoulders or approaches are measured by the ton (metric ton), the pay weight will be the scale weight unless the moisture content is more than the maximum allowable percentage as stated in the MDOT Standard Specifications for Construction. If the moisture exceeds the maximum allowable percentage, then the excess weight will be deducted from the pay weight. The determination of moisture and pay weights will be as specified in Section 109.01 and Section 4 of the MDOT Standard Specifications for Construction.
When payment is by the cubic yards (cubic meters), loose measure, hauling units must be measured, inspected and counted by the Engineer.
Materials paid for by weight are required to be weighed on an approved scale system. There are permanent and portable scale systems.
A permanent scale system is defined as a weighing device that has not been moved from a given location within the last six months. The scale inspections will be conducted by a private scale agency or the Michigan Department of Agriculture. These inspections are valid for one year. The scale owner will provide the Engineer and the regional materials personnel written verification that the scale system has been inspected according to specifications.
For portable scales, the Contractor will obtain scale approval from a local official sealer of weights and measures, or the Engineer may give approval based on verifying the results of the portable scales by passing the loads over another scale that has an official seal.
If the platform scales (permanent or portable) are observed in operation, it is important that the scales are:
- operating freely,
- reasonably clean and
- the approaches are in relatively good condition.
The platform scales need to be balanced at zero and should be periodically checked throughout the day. The Engineer will require a coupled vehicle to be reweighed with each unit being uncoupled at least monthly during its use on the project. The total weight of the uncoupled units will agree with the total weight of the coupled units within ± 0.2 percent.
Tare weights should be recorded at least twice a day, once in the morning and once in the afternoon. It is good practice to ensure that the hauling units are reasonably clean when performing this operation. Aggregates are weighed to the nearest 100 pounds (50 kg), HMA materials to the nearest 20 pounds (9 kg).
Serially numbered tickets will be furnished in triplicate for each load and will have the following information:
- project number
- aggregate source and series
- truck number
- gross, tare and net weights
- signature of a company representative
- basis of aggregate approval.
Moisture checks for determining pay weights should also be performed as described elsewhere in this section.