Page 2-26 M 41-102-06 Subgrade Preparation
2-06.1 Description
This Work consists of preparing graded Roadbed for surfacing or surfaced Roadbed for paving.
2-06.2 Vacant
2-06.3 Construction Requirements
2-06.3(1) Subgrade for Surfacing
In preparing the Roadbed for surfacing, the Contractor shall:
1.Remove from the Roadbed, immediately before placing surfacing materials, all brush, weeds, vegetation, grass, and other debris.
2.Dispose of all debris as the Engineer directs.
3.Drain water from all low spots or ruts.
4.Shape the entire Subgrade to a uniform surface running reasonably true to the line, grade, and cross-section as staked.
5.If necessary, the Contractor shall process the Subgrade in cut areas to remove materials too coarse for mechanical trimming and recompaction.
6.Compact the Subgrade to a depth of 6 inches. Compaction shall achieve 95 percent of the maximum density determined under the tests described in Section 2-03.3(14)D . If the underlying material is too soft to permit proper compaction of the Subgrade, the Contractor shall loosen, aerate (or excavate and remove), and compact the Subgrade until the top layer can be compacted as required.
7.Remove excess material that does not drift to low spots during grading and shaping. The Contractor shall dispose of this excess by placing it where the Subgrade lacks material or by wasting it, as the Engineer directs.
8.Add materials as the Engineer directs where the Subgrade needs more to bring it up to grade. The Contractor shall water and compact these added materials as needed to produce a true finished Subgrade. If the Contract requires a trimming machine, it shall:
1.Maintain the grade and transverse slopes automatically through sensors that respond to reference lines on both edges of each Roadway.
2.Create a smooth, uniform surface free from chatter and ripples.
2-06.3(2) Subgrade for Pavement
Before any paving is placed, the Contractor shall bring the Subgrade to the required line, grade, and cross-section. The Contractor shall compact the Subgrade to a depth of 6 inches to 95 percent of maximum density as determined by the compaction control tests for granular materials. The compacted area shall be wide enough to let paving machines operate without visible distortion of surfacing material. The Contractor shall maintain the Subgrade in the required condition until the pavement is placed. The Contractor may remove material just before paving if the Plans require thicker areas of pavement.
2-06.4 Vacant
2-06 Subgrade Preparation
M 41-10 Page 2-272-06.5 Measurement and Payment
2-06.5(1) Subgrade Constructed Under Same Contract
Surfacing or Treated Base – If the Contractor builds a Subgrade for surfacing or treated base, the Contracting Agency will consider Subgrade preparation as part of the construction Work. In this case, measurement and payment will conform to Section 2-03 . Such payment shall be the full price for all Subgrade preparation Work. Pavement – If the Contractor builds a Subgrade for pavement, the Contracting Agency will follow the criteria in Section 5-04 (for HMA pavement) or Section 5-05 (for cement concrete pavement) to measure and pay for materials used to prepare the Subgrade. The Contracting Agency will measure and pay for water as specified in Section 2-07 .
2-06.5(2) Subgrade Not Constructed Under Same Contract
When the Contractor prepares an existing Subgrade for surfacing (one not built under the present Contract), the Contracting Agency will measure and pay for the Work by these criteria:
1.Final Conditioning – All the following Work on the Subgrade shall be included in other Contract Bid items: clearing vegetation and other debris, draining water, smoothing to prepare for staking, grading, shaping, and compacting to a 6-inch depth to final line, grade, and cross-section.
2.Excess Materials – If the Contractor must dispose of excess materials during grading and shaping, the Contracting Agency will measure and pay for the Work as Roadway excavation. If the Contract includes no pay item for Roadway excavation, the Contracting Agency will measure and pay as provided in Section 1-04.4 .
3.Added Materials – If the Subgrade requires more materials, the Contracting Agency will pay the unit Contract price for each kind of material the Contractor provides. The unit Contract price shall be full pay for furnishing, placing, and compacting the materials. When unit Contract prices do not apply, the Contracting Agency will measure and pay for the Work as provided in Section 1-04.4 .
4.Excavation and Backfill – If the Engineer orders the Contractor to excavate unstable spots in the Subgrade, the Contracting Agency will measure and pay for the Work as Roadway excavation. If the Contract does not include Roadway excavation as a pay item, payment will be by agreed price or force account. The Contracting Agency will pay unit Contract prices for suitable backfill material when included in the Contract and will pay as provided in Section 1-04.4 when not included.
5.Subgrade Protection – No payment shall be made for protecting the Subgrade. Subgrade Preparation 2-06
Source: Washington Standard Specifications for Road, Bridge, and Municipal Construction, 2024 Edition. Pages 234–235 of 1,151.