**Minnesota Construction Specification 24---Drainfill**

**1. SCOPE**

The work shall consist of furnishing, placing and compacting drainfill
required in the construction of structure drainage systems.

**2. MATERIALS**

Drainfill materials shall conform to the requirements of Material
Specification 521. At least 30 days prior to delivery of the materials
to the site the Contractor shall inform the Engineer in writing of the
source from which he intends to obtain them. The Contractor shall
provide the Engineer free access to the source for the purpose of
obtaining samples for testing.

**3. BASE PREPARATION**

Foundation surfaces and trenches shall be clean and free of organic
matter, loose soil, foreign substance, and standing water when the
drainfill is placed. Earth surfaces upon or against which drainfill will
be placed shall not be scarified.

**4. PLACEMENT**

Drainfill shall not be placed until the subgrade has been inspected and
approved by the Engineer. Drainfill shall not be placed over or around
pipe or drain tile until the installation of the pipe or tile has been
inspected and approved.

Drainfill shall be placed uniformly in layers not more than 12 inches
deep before compaction. When compaction is accomplished by manually
controlled equipment, the layers shall be not more than 8 inches deep.
The material shall be placed in a manner to avoid segregation of
particle sizes and to insure the continuity and integrity of all zones.
No foreign materials shall be allowed to become intermixed with or
otherwise contaminate the drainfill.

Traffic shall not be allowed to cross over drains at random. Equipment
crossovers shall be maintained, and the number and location of such
crossovers shall be established and approved prior to the beginning of
drainfill placement. Each crossover shall be cleaned of all
contaminating materials and shall be inspected and approved by the
Engineer before additional drainfill is placed.

Any damage to the foundation surface or the sides or bottoms of trenches
occurring during placement of drainfill shall be repaired before
drainfill placement is continued.

The upper surface of drainfill constructed concurrently with adjacent
zones of earthfill shall be maintained at an elevation at least one foot
above the upper surface of the adjacent fill.

Drainfill over or around pipe or drain tile shall be placed in a manner
to avoid any displacement in line or grade of the pipe or tile.

Drainfill shall not be placed adjacent to structures until the concrete
has attained the strength specified in Section 8 of this specification.
The strength shall be determined by compression testing of test
cylinders cast by the Engineer for this purpose and cured at the work
site in the manner specified in ASTM Method C 31 for determining when a
structure may be put in service.

When the required strength of the concrete is not specified as described
above, placement of drainfill adjacent to structures shall not be
started until the following item intervals have elapsed after placement
of the concrete.

> [Structure]{.underline} [Time Interval (Days)]{.underline}
>
> Retaining walls and counterforts (impact basins) 14
>
> Walls backfilled on both sides simultaneously 7
>
> Conduits and galleries, cast-in-place (with inside forms in place) 7
>
> Conduits and galleries, cast-in-place (inside forms removed) 14
>
> Conduits, precast, cradled 2
>
> Conduits, precast, bedded 1
>
> Cantilever outlet bents backfilled on both sides simultaneously 3

**5. CONTROL OF MOISTURE**

Control of moisture content will not be required.

**6. COMPACTION**

Drainfill shall be compacted according to the following requirements for
the class of compaction specified:

*Class A compaction*. For drainfill materials with more than 70 percent
passing the 3/4 inch sieve, each layer of drainfill shall be compacted
to a minimum dry density of not less than the density specified in
section 9 of this specification as determined by ASTM D 698. For
drainfill materials with 70 percent or less passing the 3/4 inch sieve,
each layer of drainfill shall be compacted to a relative density of not
less than 70 percent as determined by ASTM D 4254.

*Class I compaction*. Each layer of drainfill shall be compacted by at
least 2 passes, over the entire surface, of a steel-drum vibrating
roller weighing not less than 5 tons and exerting a vertical vibrating
force of not less than 20,000 pounds at least 1200 times per minute, or
by an approved equivalent method.

*Class II compaction*. Each layer of drainfill shall be compacted by one
of the following methods or by an approved equivalent method:

> a\. At least 2 passes, over the entire surface, of a pneumatic-tired
> roller exerting a pressure of not less than 75 pounds per square inch.
> A pass is defined as at least one complete coverage of the roller
> wheel, tire or drum over the entire surface of the layer.
>
> b\. At least 4 passes, over the entire surface, of the track of a
> crawler-type tractor weighing not less than 20 tons.
>
> c\. Controlled movement of the hauling equipment so that the entire
> surface is traversed by not less than one tread track of the loaded
> equipment.

*Class III compaction*. No compaction will be required beyond that
resulting from the placing and spreading operations.

When compaction other than Class III compaction is specified materials
placed in trenches or other locations inaccessible to heavy equipment
shall be compacted by means of manually controlled pneumatic or
vibrating tampers or by approved equivalent methods.

Heavy equipment shall not be operated within 2 feet of any structure.
Vibrating rollers shall not be operated within 5 feet of any structure.
Compaction by means of drop weights operating from cranes or hoists will
not be permitted.

**7. TESTING**

The Engineer will perform such tests as are required to verify that the
drainfill materials and the drainfill in place meet the requirements of
the specifications. These tests are not intended to provide the
Contractor with information he needs to assure that the materials and
workmanship meet the requirements of the specifications, and their
performance will not relieve the Contractor of the responsibility of
performing his own tests for that purpose.

**8. CONSTRUCTION DETAILS**