SECTION 02201
SUBGRADE PREPARATION
PART 1 GENERAL
1.01
WORK INCLUDED
1.
Preparation of the existing ground surfaces under all embankment, structure and
crushed aggregate base course, and high density polyethylene pond liner
construction areas that are required by these Specifications or so indicated on the
Drawings.
2.
In the event that materials beneath the existing ponds are too wet to obtain the
densities required by this section, work will be suspended until such time that the
requirements can be met. There will be no additional payments made to the
contractor for any costs associated with work stopping and restarting as a result of
this delay.
1.02
RELATED WORK
1.
Section 01410: Testing Laboratory Services
A.
Section 02120: Temporary Water Pollution and Erosion Control
B.
Section 02200: Clearing and Grubbing
C.
Section 02220: Excavation and Backfill
D.
Section 02601: Sewer Manholes
1.03
REFERENCES
1.
American Society for Testing and Materials:
1.
ASTM D-422, “Particle Size Analysis of Soils”.
2.
ASTM D-698, “Test for Moisture-Density Relations of Soils (Standard
Proctor) Using 5.5-lb Hammer and 12-in Drop”.
3.
ASTM D-1556, “Density of Soil in Place by the Sand-Cone Method”.
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4.
5.
6.
7.
8.
9.
1.04
ASTM D-1557, “Test for Moisture-Density Relations of Soils (Modified
Proctor) Using 10-lb Hammer and 18-in Drop”.
ASTM D-2216, “Laboratory Determination of Moisture Content of Soil”.
ASTM D-2167, “Density and Unit Weight of Soils in Place by the Rubber
Balloon Method”.
ASTM D-2922, “Density of Soil and Soil-Aggregate in Place by Nuclear
Methods (Shallow Depth)”.
ASTM D-3017, “Moisture Content of Soil and Soil-Aggregate in Place by
Nuclear Methods (Shallow Depth)”.
ASTM D-4318, “Standard Test Method for Liquid Limit, Plastic Limit,
and Plasticity Index for Soils”.
QUALITY ASSURANCE
A.
Contractor shall provide material testing for quality control during subgrade
preparation at the following frequencies:
1.
Structures and Crushed Aggregate Base Course Construction Areas
1.
One in-place soil density per 2500 square feet of structure or
CBAC subgrade area or as requested by the Engineer according to
ASTM D-1556, ASTM D-2167, or ASTM D-2922, and ASTM D3017.
2.
One sieve analysis and plasticity index per each type of subgrade
material encountered per ASTM D-422 and ASTM D-4318.
3.
One moisture density curve per each type of subgrade material
encountered according to ASTM D-1557.
2.
Embankment and HDPE Pond Liner Construction Areas
1.
One in-place soil density per 9000 square feet of embankment or
HDPE pond liner subgrade area or as requested by the Engineer
according to ASTM D-1556, ASTM D-2167, or ASTM D-2922,
and ASTM D-3017.
2.
One sieve analysis and plasticity index per each type of subgrade
material encountered per ASTM D-422 and ASTM D-4318.
3.
One moisture density curve per each type of subgrade material
encountered according to ASTM D-698.
B.
Following approval by the Engineer of clearing activities and initial cross section
data, subgrade elevations required by these Specifications or as indicated by the
Drawings shall be approved by the Engineer prior to the commencement of any
subgrade preparation activities.
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1.05
SUBMITTALS
1.
Moisture Density Curve: For each type of material encountered per ASTM D-698
or ASTM D-1557.
B.
Sieve Analysis and Plasticity Index Test Results: For each type of material
encountered per ASTM D-422 and ASTM D-4318.
3.
In-Place Field Density Test Results for all subgrade preparation areas per ASTM
D-1556, ASTM D-2167, or ASTM D-2922 and ASTM D-3017.
PART 2 PRODUCTS
2.01
SUITABLE MATERIALS
A.
Suitable materials shall consist of materials encountered at the site and are subject
to approval by the Engineer.
B.
Any underlying soft or otherwise unsuitable material shall be removed and
replaced with suitable material as directed by the Engineer.
2.02
WASTE
A.
Disposal of excavated materials shall be the responsibility of the Contractor.
PART 3 EXECUTION
3.01
GENERAL
1.
Subgrade preparation activities are to be performed on approximately horizontal
surfaces that terrace up the native slopes, at the elevations set forth in these
Specifications and as indicated by the Drawings.
1.
Perpendicular to the embankment the horizontal benches shall be terraced
into the native slope with elevation changes per step not to exceed twenty
four (24) inches.
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2.
2.
3.02
Parallel to the embankment the horizontal benches shall be terraced into
the native slope with elevation changes per step not to exceed thirty six
(36) inches.
Surfaces requiring subgrade preparation activities shall be exposed by the
overexcavation of native materials to the required depths below existing grades
obtained from approved cross section data, below bottom of structures, CABC,
and as approved by the Engineer.
EXECUTION
1.
3.03
Prior to the commencement of any fill activities the following subgrade
preparation activities shall be performed:
1.
Scarify and blend the subgrade material to a depth of eight (8) inches and a
moisture content to within + or - 2% of optimum.
2.
Begin compaction efforts immediately after obtaining a uniform subgrade
material blended to the required depth and at the required moisture
content.
COMPACTION REQUIREMENTS
1.
Beneath structures and CABC construction areas, a minimum of 95% of Modified
Proctor (ASTM D-1557) is required.
2.
Beneath embankment a minimum of 95% of Standard Proctor (ASTM D-698) is
required.
3.
Compaction areas shall be kept separate, and no lift shall be covered by another
until the proper density is obtained.
4.
The Contractor shall make the necessary corrections and adjustments in methods,
materials or moisture content in order to achieve the specified compaction
requirements.
END OF SECTION
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