206Excavation and Backfill for Culverts and Minor Structures

206.1 Description

This Work consists of excavati ng, placing and compacting selec t backfill, bedding, and flowable fill Materials, and disposing of Material related to c onstruction of Minor Structures. Excavation includes dewatering, pumping, bailing, draining, she eting, bracing, and Incidentals required for proper execution of the Work. Ditches required at Culvert inlets and outlets, and other loca tions indicated in the Contract are included under the it em for Unclassified Excavatio n.

206.2 Materials

206.2.1 Select Backfill

The Contractor shall furnish a suitable, well-graded, compacti ble Material free of Recycled Asphalt Pavement (RAP), organic matter, clay balls, lu mps, rock fragments that may degrade with time such as shale or gypsum and other Deleterious Materials. Select backfill Material shall conform to the following and be placed in accord ance with the Contract: 1. For structures and pipes other than plastic pipe: a. Maximum particle size: two (2) inch; b. Soil classification, AASHTO M 145 A-1 or A-2-4; 2. For plastic pipe: a. Maximum particle size: 1½ inch; and b. Soil classification, AASHTO M 145 A-1 or A-2-4. All Backfill Material shall meet the electrochemical criteria where specified in the Contract.

206.2.2 Flowable Fill

The Contractor may substitute flowable fill for select backfil l in accordance with Section 516, “Flowable Fill,” at no addi tional cost to the Department. The Contractor shall secure Culverts and minor Structure s to prevent flotation.

206.2.3 Bedding

The Contractor shall furnish a suitable, well-graded, non-plas tic, free draining Material, free of Recycled Asphalt Pavement (RAP), organic matter, clay b alls, lumps, rock fragments that may degrade with time such as shale or gypsum and other De leterious Materials. Bedding Material shall conform to the following and be placed i n accordance with the Contract: 1. Maximum particle size: ½ inch or half the corrugation depth , whichever is smaller; and 2. Material passing No. 200 (75-µm) sieve: ten percent (10.0%) max AASHTO T 27 and AASHTO T 11. All Bedding Material shall meet the electrochemical requiremen ts where specified in the Contract.

206.2.4 Unsuitable Material

Section 206: Excavation and Backfill for Culverts and Minor St ructures Page 117 Unsuitable Material includes or ganic Materials, frozen lumps, i ce; soils such as peat, shale, gypsum or other Materials that may degrade with time, or are contaminated soil. Suitable Material that is unstable may be reworked to create a stable platform as directed by the Project Manager. Material below minor Structures and areas identified by the Pr oject Manager, determined to be unsuitable shall be excavated and disposed of in accordan ce with Section 107, “Legal Relations, Environmental Requirements, and Responsibility to th e Public” unless otherwise specified in the Contract. When unsuitable Material is remo ved and disposed of, the resul ting void shall be filled with Material suitable for its planned use as directed by the P roject Manager. Such suitable Material shall be placed and com pacted in accordance with this Specification.

206.3 Construction Requirements

206.3.1 General

The Contractor shall remove unsuitable foundation Material bel ow the specified bottom- of-structure elevation and replac e with approved Material, as d irected by the Project Manager. The Contractor shall use backfil l Material to backfill Culverts in accordance with Section

206.2 1, “Select Backfill,” or Section 206.2.2, “Flowable Fill, ” unless otherwise shown on the

Plans. The Contractor shall ensure the moisture content of the soil; at the time of compaction is not less than five percent (5%) below optimum moisture conte nt or greater than optimum moisture content. The Contractor shall compact the top six (6) inches of existing ground to at least 95% of maximum density in accordance with AASHTO T 180 (M odified Proctor), Method A or D (TTCP Modified). The Contractor shall maintain the dens ity, approved surface elevation, and shape of the founda tion immediately before placi ng Structures and forms. The Contractor shall distribute backfill Material in uniform l ayers, each no more than eight

206.3.2 Pipe Culverts, Storm Drains, and Structural Plate Pipe

For preparation and installation of pipe culverts, storm drain s, and structural plate pipes with bottoms the Contractor shall remove rock and other unyield ing foundation Material a minimum of four (4) inches (maximum 12 inches) below the bottom of the Structure. The Contractor shall backfill this added depth with an approved Mat erial as identified in the Contract. The Contractor shall excavate trenches as described in the Contract to allow for pipe joining and compaction of the bedding and backfill Materia l under and around the pipe in accordance with Section 206.3.1, “ Construction Requirements, Ge neral.” The Contractor shall Section 206: Excavation and Backfill for Culverts and Minor St ructures Page 118 ensure that the trench width for pipes and Culverts conforms to the trench widths requirements in Section 570.3.2, “Excavation and Backfill.” The Contractor shall uniformly compact the trench for its full length and width. If specified in the Cont ract, the Contractor shall provide the longitudinal camber of the specif ied magnitude for cross drains .

206.3.3 Box Culverts and Other Drainage Structures

For preparation and installation of box culverts and other dra inage structures the Contractor shall excavate Material to the elevations establishe d by the Contract. The Contractor shall not remove Material, except unsuitable Materia l, below the final grade, if placing footings on excavated surfaces other than rock. The Co ntractor shall remove rock and other unyielding foundation Material a maximum 12 inches below the bottom of the Structure. The Contractor shall clean rock seams and cavities, and fill wi th concrete or grout. If the Contractor’s excavation extends beyond the neat lines shown in the Contract, the Contractor shall use concrete (of the same class as the footing) to backfi ll these areas, at no additional cost to the Department. The Contractor shall notify the Project Manager after each foo ting excavation. The Contractor shall not place footings until the excavation depth and foundation Materials are approved by the Project Manager. The Contractor shall maintain the moisture and density and the approved surface elevation and shape of the foundation befo re installing reinforcing steel.

206.4 Method of Measurement

The Project Manager will measure the void created by the remov al of Unsuitable Material Excavation below the bottom-of-structure elevation.

206.5 Basis of Payment

Pay Item Pay Unit Unsuitable Material Excavation Cubic Yard The Department will pay for rock excavation in accordance with Section 203, “Excavation, Borrow, and Embankment.”

206.5.1 Work Included in Payment

Excavation, disposal of unsui table Material, bedding, backfill and select backfill Materials, placement and compaction of bedding and select backfill Materia ls for Culverts, storm drains, other drainage Structures, box Culverts, and minor Structures s hall be included in the Contract unit price per linear foot of Structure identified in the Contr act. Excavation shall include all dew atering, pumping, bailing, dra ining, sheeting, bracing, and Incidentals required for proper execution of the Work. Select backfill shall include the use of Section 516, “Flowable Fill.” Backfilling with concrete of the same class as the footings where the Contractor excavates below the established final elevation for bottom of footings or beyond the neat lines of the footings in rock or other hard foundation Material shall be included in the Contract unit price per linear foot of Culvert. Unrippable roc k or unyielding Material will be defined and paid for as covered in Section 203, “Excavation, Bo rrow, and Embankment.” Section 207: Subgrade Preparation Page 119