312316_Struct_Excavation_Backfill.pdf

LOST LAKE CAMPGROUND 312316-1

WATER SYSTEM STRUCTURAL EXCAVATION,

BACKFILL AND COMPACTION

SECTION 312316

STRUCTURAL EXCAVATION, BACKFILL AND COMPACTION

PART 1 - GENERAL

1.1 SUMMARY

A. Includes excavation, special fills, backfill, and compaction. Work also includes borrow excavation, drainage excavation, removal of slide material, excavation of unsuitable material, embankment construction, and disposal of all excavated material necessary for the completion of the work. Work items include, but are not limited to, the hydrant concrete pads, water treatment building, and all other miscellaneous structures as shown on the drawings.

1.2 PROTECTION

A. Protect excavations from accumulation of water. If clay soil becomes saturated, compact after it has dried as specified herein.

B. Protect excavations from freezing. If frost action occurs, compact ground after thawing as specified herein.

C. Provide shoring and bracing as necessary to protect structures, employees, and the public.

1.3 REFERENCES

A. Standard Moisture Density Test AASHTO T-99, Method C or D.

1.4 TESTING FREQUENCY

A. Testing frequency shall be as indicated below. Repeat tests shall be conducted in any areas where test results indicate noncompliance with specification requirements. All tests shall be conducted under the direction of a registered engineer or certified testing laboratory. The Contracting Officer shall choose locations for the tests.

Type of Test Frequency

Density of Soil In-Place 1 at the Hydrant Concrete Pads

Density of Soil In-Place 1 at the Water Treatment Building

1.5 APPROVALS

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BACKFILL AND COMPACTION

A. The Contractor shall notify the CO when excavation is complete. Approval shall be obtained prior to placing any bedding or forms.

PART 2 - PRODUCTS

2.1 BACKFILL AND FILLS

A. Use the excavated material as specified below:

1. Remove rocks over 8 inches in maximum dimension, ice or frozen earth, muck, debris, and earth with high void content.

2. Remove rocks over 4 inches in maximum dimension for backfill placed within

12 inches of foundation.

3. Materials removed in stripping shall not be used for backfill.

4. If additional material is required to complete the backfill requirements of this section, the Contractor shall use excess excavated material from other operations required by this contract or from an approved off-site source.

2.2 AGGREGATE BASE

A. Aggregate base course material under the hydrant concrete pads, treatment building, storage tank and solar systems shall be CDOT Class 6, ¾” minus as specified in

Section 321123.

PART 3 - EXECUTION

3.1 EXCAVATION

A. Perform to the lines, grades, and elevations indicated. Extend excavation a sufficient distance from walls and footings to allow for safety, placing and removal of forms, installation of services, and for inspection. Provide proper depth with allowance made for gravel fills, formed voids, and concrete flatwork.

1. Bottoms for footings and concrete slabs shall be level, clean, true to size, and clear of loose materials.

2. Footing excavations shall be drilled or otherwise accurately formed.

3. If excavations for foundations are carried below the specified levels, extend the foundation to the excavated level.

4. If rock is encountered, remove it for a depth of six (6) inches below footing elevation.

3.2 BACKFILLING

A. Place and compact fills and backfills adjacent to structures in such a manner as to prevent wedging action or eccentric lodging upon or against the structures.

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BACKFILL AND COMPACTION

1. Remove forms and clean the excavation of trash and debris prior to backfilling.

2. Do not place backfill against any concrete footings or slab without prior approval of the Contracting Officer and in no case less than 7 days after completion of the wall or footings.

3. Place backfill in horizontal layers not more than 12 inches (loose measure) with the proper moisture content for the required degree of compaction. Compact each layer as specified. Backfill layer thickness under concrete flatwork limited to 6 inches maximum.

4. Heavy equipment for spreading and compacting backfill shall not be operated closer to a slab than a distance equal to the height of the backfill above the top of the footing.

5. Provide for anticipated settlement and shrinkage of the backfill and for the finished grades required, including topsoil grading.

6. Excavated areas shall be dry and free of standing water before placing initial backfill and subsequent backfill material.

7. Puddling or water flooding for consolidating backfill shall not be allowed.

Addition of water shall be limited to that needed to obtain optimum density of backfill material.

8. Prepare subgrades for gravel fill areas level and free from soft spots. Place and compact earthfill where required to raise subgrade. Place gravel to the lines and grades shown. Compact the gravel sub-base as specified until a smooth, uniform use surface is obtained.

3.3 COMPACTION

A. The minimum degree of compaction required shall be a percent of the maximum laboratory density obtained by the standard proctor test AASHTO T-99 or ASTM

D698. The in-place field density shall be determined by AASHTTO T238 or ASTM

D2922. The minimum compaction requirements are:

1. Under structures, footings and concrete slabs scarify and re-compact top 12 inches of existing subgrade and each layer of backfill or fill material at 95 percent.

2. Under concrete flatwork or walkways, scarify and re-compact top 6 inches below subgrade and compact each layer of backfill or fill at 90 percent.

3. All other areas: 85%.

4. Crushed Stone bedding shall be compacted with a minimum of three passes per lift over the entire surface area with a mechanical vibrating tamper.

5. Aggregate shall be moistened or dried to uniform moisture content suitable for compaction. Additional water needed to increase the moisture content for suitable compaction shall be incidental.

3.4 MATERIAL STOCKPILING

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BACKFILL AND COMPACTION

A. The Contractor may stockpile crushed stone and/or special bedding provided the location and method of stockpiling are approved by the Contracting Officer.

Stockpiling shall employ such protective measures as necessary to hold segregation, intermixing and waste to a practical minimum.

3.5 TESTING FOR QUALITY COMPLIANCE

A. It shall be the sole responsibility of the Contractor to provide quality control to ensure that compaction of backfill material complies with this section. The Contractor shall perform, or cause to be performed, the sampling and testing required to substantiate that compliance.

B. Results of compaction tests shall be submitted to the Contracting Officer within 24 hours of testing. If compaction is less than specified in this section, the Contractor shall re-excavate and re-compact, at the contractor's expense, to obtain the percent compaction required.

C. Compaction testing shall not be required for undisturbed soils, gravel bedding, special bedding or other material that, in the opinion of the Contracting Officer, exhibits poor or low cohesive characteristics.

D. Test locations shall be selected at random within the limitations specified here.

E. The CO may reduce the testing frequency contingent upon the uniformity of material at the project site, compactive effort put forward by the Contractor, and previous test results for similar materials and compactive effort.

F. The Government may conduct additional sampling and testing that the Contracting

Officer deems reasonable and prudent at no additional cost to the Contractor.

However, if such tests confirm compaction does not comply with this section, the

Contractor shall remove, replace and recompact the affected area at his expense.

END OF SECTION