TAB_4_-_3-Sprep.CoG.New_Sunshine_Civil-Drainage_Phase.pdf

City of Gallup

New Sunshine Substation

SITE PREPARATION SPECIFICATIONS

(Civil Grading & Drainage Phase)

June 2024

Issued for Bid Not for Construction

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The intent of these specifications is to establish the minimum acceptable quality and requirements of materials and workmanship for the switch station site preparation.

GROUP M - SITE PREPARATION AND ACCESS ROAD

I. Preparation

A. Protect and maintain benchmarks and survey control points from disturbance

B. Flag any trees, shrubs and other vegetation that is to remain or to be relocated.

C. Protect existing site improvements to remain from damage during construction.

Restore damaged improvements to their original condition, as acceptable to the owner.

II. Clearing & Grubbing

Prior to site grading, all borrow areas and areas to receive fill shall be stripped of vegetation and deleterious materials. Strippings shall be hauled off-site of stock piles for subsequent use in landscaped areas or for non-structural fill areas as designated by the

Owner. Coordinate with the Owner regarding any spoils.

III. Explosives and Blasting No blasting is allowed on this project.

IV. Grading After clearing is complete, rough grade the area. Cut and fill operations shall then proceed. Grading the station site to a uniform sloped surface that will drain in accordance with the plans provided. The subgrade shall not vary more than 1” from the established elevations.

Spread unsuitable material as directed by the Owner. Perform compaction while the material has the optimum moisture content for maximum compaction. Reseeding and/or stabilization of the soils may be required to coordinate with the overall site SWPPP.

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V. Excavation Make excavations to the full dimensions called for and finish to the prescribed lines and grades as required by the geotechnical report and foundations details. Before and during the compaction operations, the soil shall have the optimum moisture content required for compaction. The moisture content shall be uniform. After the moisture content is proper, compact it with tampers or vibratory rollers as to 95%.

Mine tailings are spread across the site appropriate care shall be exercised to control blown dust. Coal ore mined adjacent to Gallup is a high silica low calcium deposit, appropriate personal protective gear shall be worn.

At least one unmarked mine shaft is likely located within the project site, see geotechnical report Appendix C, Geotechnical Logs and Geophysics.

The potential mine shafts can be seen on Seismic Refraction LINE SL-1 and SL-2, they can be inferred by changes in velocity running vertically.

VI. Stock Piling Existing site soils are partially composed of mine tailings from nearby historic coal mines, as such smoking, hot work, and spark making activities shall not be performed next to stock piles that contain visible amounts of coal mine tailings.

VII. Backfill Backfill shall include material placed around concrete footings and foundations and elsewhere, as directed by the Geotechnical report. The Engineer may review the materials used for backfill, the amount, and the manner of depositing the materials.

Obtain as much backfill as possible from suitable material moved in excavating. When sufficient suitable material is not available from this source, obtain additional materials from sources approved by the Engineer. Backfill shall not contain cobbles larger than three (3) inches in diameter that may damage conduits or leave voids when compacted.

The material to be compacted shall consist only of approved selected materials. Deposit the backfill in horizontal layers having a thickness of not more than 6" after being compacted. Before and during the compaction operations, the backfill material shall have

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the optimum moisture content required for compaction. The moisture content shall be uniform throughout the layers. The Contractor shall provide a proctor for the compacted backfill.

Condition the material as specified, and compact it with tamping machines or vibratory rollers to 95%. Compaction and Density tests shall be performed at the Contractor’s expense, and the results reviewed by the Engineer. The Contractor shall refill and compact the excess excavation at his expense.

VIII. Disposal of Material Waste material shall be removed in accordance with the Owner’s recommendations and desires. Leave the waste area with reasonably even and regular surfaces.

IX. Access Roads Paved access is available to the southern edge of the station location. Adjacent to the substation pad there are multiple off-road tracks present, these shall be left in a passible condition no worse than the beginning of construction with all drainage features in good working order per the overall site grading and drainage plans.

X. Culverts Culverts and culvert end sections shall be submitted to the Engineer for approval.

Culverts shall conform to the NM DOT 2019 Master Specification section 570 for

Corrugated HDPE Storm Drain Culverts. Generally pre-formed or pre-cast culvert end sections are desirable.

XI. Riprap Riprap and wire mesh shall conform requirements of the NM DOT 2019 master specification section 602.2.1 Class A or B as required by the construction plans and

602.2.2.2.1 respectively.

Contractor shall submit riprap and wire mesh to the engineer for approval prior to commencing construction.

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NPDES COMPLIANCE

PART 1 - GENERAL

1.01 - SCOPE OF WORK

The work under this section includes compliance with the U.S. Environmental Protection

Agency (EPA), National Pollutant Discharge Elimination System (NPDES) Regulations for Storm Water Discharges from construction sites. This work consists of developing a site specific Storm Water Pollution Prevention Plan (SWPPP) and/or abiding by the overall SWPPP in place for the larger construction project. Contractor is to Coordinate with the Owner regarding the SWPPP and any best practices needed for the specific substation location of the project. Routine inspection of erosion control measure will likely be required by the Contractor in accordance with the overall SWPPP to control erosion, pollution, sediment and runoff during the construction of the project.