212.8 -PREPARATION OF FOUNDATIONS : Rock or other hard foundation material shall be free from all loose material, cleaned and cut to a firm surface, stepped or serrated as directed by t he Engineer. All seams shall be cleaned and filled with concrete, mortar, or grout. Excavation in rock shall be made to the neat lines of the footing as nearly as practicable and the concrete placed against the rock without forming. When masonry is to r est on an excavated surface other that rock, special care shall be taken not to disturb the bearing surface, and the final removal of foundation material shall not be made until just before masonry is to be placed. 212.9 -DRAINAGE : Adequate drainage for the backs of retaining walls, abutments and wing walls shall be provided by outlet tile or pipe drains extending through the walls at the ground line or as indicated on the Plans. In case the outlet end of these drains is below the g round line or would be covered by fill material, the drains shall connect to pipe outlets or be extended to the toe of the slope of the fill. When drain pipes are not called for or indicated on the Plans for these drains, the drains shall be constructed t o a minimum sectional area of twenty -four ( 24) by twenty -four ( 24) inches and shall consist of sand, crushed stone, or gravel. Excavation and backfilling shall conform to the requirements of this Specification. When underdrains with pipe are shown or in dicated on the Plans and there are bid items for the same, they shall conform to the applicable requirements of Section 606. The back of retaining walls, abutments and wing walls shall have porous drains, one (1) foot thick or as shown on the Plans, place d on the back side of the walls and abutments for the entire length and height of the same, beginning at the elevation of the outlet drains.
212.10 Backfilling :
Backfill material shall be sui table random material, controlled low strength material or select backfill material. Random material shall be free from particles larger than three ( 3) inches, frozen lumps, wood, or other extraneous material. Unless otherwise specified in the plans, any of the types of controlled low strength material may be used and shall be an alternative to random material at the contractor’s option. Select backfill material shall be in accordance with Section 212. Controlled low strength material shall be in accord ance with Section 219. All spaces excavated and not occupied by abutments, piers, or other structures shall be backfilled to the surface of the surrounding ground. All backfill, except controlled low strength material, shall be thoroughly compacted by ro lling or tamping as prescribed below and the top surface neatly graded. Random material and select backfill material behind and around abutments, wingwalls, piers, bents, pedestals and all other structures, including those inaccessible to a roller, shall be compacted in layers not to exceed four ( 4) inches after compaction. Controlled low strength material shall be placed according to Section 219. The quality control and acceptance of controlled low strength material shall be in accordance with Section 219. The quality control and acceptance for compaction of random material shall be in accordance with applicable sections of 207 and 716. Five density tests shall be performed for quality control. The target percentage of dry density shall be 95%. Spec ial precautions shall be taken to prevent any wedging action against the masonry and the slope bounding the excavation for abutments and walls. Such condition shall be prevented by stepping or serrating to destroy wedge action. Jetting of fill behind ret aining walls, abutments, 136 and wing walls will not be permitted. Backfill over and around abutments, culverts, arches, and columns shall be brought up uniformly to avoid bending or distortional stresses in the structures, shall be made as soon as practicabl e after forms are removed, and shall be sloped to drain. The four ( 4) inch layer requirement and compaction for backfill in water will be waived. The testing of backfill compaction, at piers or other structures, which will not become part of an embankmen t or highway pavement or shoulder area will be waived. Select backfill material shall be place d behind abutments, wingwalls, retaining walls, and box culverts to the dimensions shown on the Plans. The material shall be placed in horizontal layers not to exceed four ( 4) inches compacted. The quality control testing and acceptance for the select backfill material shall be in accordance with applicable sections of 207 and 716. A lot shall normally consist of the quantity of backfill material required to fil l behind and around abutments, wingwalls, piers, bents, pedestals and all other structures as approved by the Engineer. The select backfill materials shall be tested according to MP 700.00.24. Five density tests shall be performed for quality control. T he target percentage of dry density shall be 95%. In all areas where select backfill will contact random material, engineering fabric shall be placed in accordance with the last paragraph of Subsection 207.9.
212.11 Method of Measurement :
The quantity of work done for Item 212001 -*, "Structure Excavation", Item 212002 -*, "Wet Excavation", Item 212003 -*, "Rock Excavation" and Item 212005 -*, "Select Material for Backfilling", will be the number of cubic yards measured. Any additional work be yond the scope of the Plans, authorized by the Engineer, will be measured in cubic yards for the excavated material removed or Select Backfill in place and paid for in accordance with the Subsection and 109.2. Measurement for "Structure Excavation" and "We t Excavation" will be limited to the volume bounded by vertical planes eighteen ( 18) inches outside the neat line of footings and parallel thereto; "Rock Excavation" will be limited to the volume bounded by the neat lines of the footings. When an increase in depth of foundation has been ordered by the Engineer, the excavation for the first five ( 5) feet or fraction thereof below the elevation shown on the Plans will be paid at the unit bid price. The Engineer may require the Contractor to make excavation to a depth greater than five ( 5) feet below Plan elevation in accordance with Subsection 104.3. All excavation performed under this section will be classified as "Structure Excavation", except as stated. When the Plans specify "Rock Excavation", all material encountered in the excavation requiring blasting for its removal and al l boulders greater the 1/2 cu. y d. in volume will be considered as "Rock Excavation" and be paid for as such. When a quantity of "Wet Excavation" is shown on the Plans, and a normal pool elevation is indicated, excavation below the normal pool elevation, except that classified as "Rock Excavation", will be considered "Wet Excavation" and will be measured below normal pool elevation from the stream bed to the bottom of the footings. The cost of bracing, shoring and supporting excavation adjacent to railroad tracks and other structures shall be included in the unit price bid for "Structure Excavation", "Wet Excavation", or "Rock Excavation". Structural excavation for old structures requiring removal will be limited to the outside dimensions of the structure. Excavation for the d rains specified in Subsection 212.9 will be paid as Item 212001 -*, "Structure Excavation", and the cost of backfilling drains with sand, crushed stone or gravel shall be included in the price bid for "Structure Excavation".