CATEGORY 200 GRADING SECTION 212 — SUBGRADE DRAINAGE BLANKET
212.01 Description
Construct subgrade drainage blankets (SDB). Do not construct SDB in stormwater management (SWM) facilities or as drainage blankets for SWM facility embankments.
212.02 Materials
Graded Aggregate Base 901.01 No. 57 Aggregate 901.01 Securing Pins or Staples 919.03 Geotextile 919.01, Class SD Type II
212.03 Construction
212.03.01 Preparation. In the area where the SDB is to be placed, excavate 12 in. below the
elevation of the proposed bottom of the Graded Aggregate Base or as directed. If directed, adjust the depth or footprint of the SDB beyond the limits shown in the Contract Documents. Establish the grade to the line, grade, and cross section specified on the plans and to the satisfaction of the Engineer. Construct the grade as smooth as practical and free of debris. Minimize construction traffic on the grade. Remove ruts and reshape areas affected by construction traffic to the satisfaction of the Engineer. Do not overwork the grade to avoid causing further saturation or pumping of the subgrade. Maintain adequate surface drainage as specified in 208.03.03. Compaction and moisture requirements for the underlying soil on which the SDB is to be placed will be waived.
212.03.02 Geotextile Placement. Place a bottom layer of geotextile Class SD Type II on the
prepared surface prior to placement of 12 in. of No. 57 aggregate. Place a top layer of geotextile Class SD Type II after the No. 57 aggregate has been placed. Place the geotextile for the full width of the area to be treated. Unroll the geotextile on the grade parallel to the baseline. Do not drag the geotextile across the grade. Remove wrinkles and folds in the geotextile by stretching and pinning. Overlap the geotextile at roll edges and ends. Overlaps at the end of the roll are to be in the direction of aggregate placement with the previous roll on top. The minimum overlap is to be 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 30 in. Pin roll ends and roll end overlaps a minimum of 5 ft on-center. Pin roll edges and roll edge overlaps a minimum of 50 ft on-center. Provide enough material at each edge of the geotextile to allow a 36 in. fold over the top layer of geotextile. For curves, fold or cut and overlap the geotextile in the direction of the turn. Pin the folds in the geotextile a minimum of 5 ft on center. Repair any damage to the geotextile immediately at no additional cost to the Administration. Repair geotextile as directed by the Engineer. Overlap geotextile patches a minimum of 3 ft into undamaged geotextile. Do not allow traffic, including construction equipment, on the bare geotextile. 212.03.03 No. 57 Aggregate Placement. Place 12 in. of No. 57 aggregate as specified in Section 501 with the following exceptions:
a.Spreading. Place No. 57 aggregate the same working day as the geotextile placement. Place the No. 57 aggregate as a single lift in the thickness required to provide the specified full depth of material thickness. Increase the thickness of the No. 57 aggregate if the excavation depth was increased in the Grade Preparation. Place the No. 57 aggregate by end dumping and spreading. Construct parallel to the baseline. Keep the turning of construction equipment on the No. 57 aggregate to a minimum.
b.Density Requirements. Compaction requirements will be waived for the No. 57 aggregate.
c.Roll. Roll with a static steel drum roller prior to placing the top layer of geotextile.
212.03.04 Graded Aggregate Base Placement. Place the pavement section graded aggregate
base course after the top layer of geotextile has been placed and as specified in Section 501 with the following exceptions:
a.Spreading. Place the graded aggregate within three working days of geotextile placement. Place the graded aggregate base as separate lifts in the thickness required to provide the specified compacted depth. Place the graded aggregate base by end dumping and spreading. Construct parallel to the baseline. Keep the turning of construction equipment on the graded aggregate base to a minimum.
b.Density Requirements. Immediately after placement, compact the graded aggregate base material to the required density. Compact the top lift of the graded aggregate base to a minimum of 95 percent of maximum dry density according to T 180. When compacting, maintain the resultant moisture content within two percentage points of optimum. Measure in-place density according to MSMT 350 or MSMT 352. Compaction requirements will be waived for the graded aggregate base material below the top lift.
c.When directed, do not use vibratory compaction on the graded aggregate base. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
212.04 Measurement and Payment
yard as specified in Section 501. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS Subgrade Drainage Blanket will be measured and paid for at the Contract unit price per cubic yard. The payment will be full compensation for furnishing and placing geotextile; furnishing, placing, and spreading No. 57 aggregate; compaction; and for all material, labor, equipment, tools, and incidentals necessary to complete the work. Excavation will be measured and paid for at the pertinent class of excavation as specified in 201.04. Graded Aggregate Base course will be measured and paid for at the Contract unit price per square 301 — CLASS 3 EXCAVATION FOR INCIDENTAL CONSTRUCTION CATEGORY 300 DRAINAGE SECTION 301 — CLASS 3 EXCAVATION FOR INCIDENTAL CONSTRUCTION
301.01 Description
Excavate below the specified elevation when unsuitable subgrade material is encountered.
301.02 Materials
Not applicable.
301.03 Construction
Excavate to the length, width, and depth at authorized locations. Handle excavated material as specified in 402.03.01.
301.04 Measurement and Payment
Class 3 Excavation for Incidental Construction will be measured and paid for at the Contract unit price per cubic yard. The payment will be full compensation for all material, labor, equipment, tools, and incidentals necessary to complete the work. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 310–312 of 1,113.