in which case a full brick shall be used at the corner and the bat in the interior of the course.

In case any brick is moved, or a joint broken during laying, the brick shall be taken up, the mortar thoroughly cleaned from the brick, bed, and joints, and the brick relaid in fresh mortar. In hot and dry weather, or when directed, the brick masonry shall be protected and kept moist for a period of at least forty-eight (48) hours after laying of the brick.

The inside and outside surfaces of brick masonry shall be neatly plastered with mortar to a thickness of not less than one-half (1⁄2) inch, and the mortar shall be finished to a true and uniform surface. The mortar shall be protected and kept moist for forty-eight (48) hours after completion.

Brick masonry shall not be constructed in freezing weather or when bricks contain frost, except by written permission of the engineer and subject to such conditions for protection against freezing.

751-3.3 CONCRETE STRUCTURES. The structures shall be constructed of concrete, built on prepared foundations, conforming to the dimensions and form indicated on the plans. The construction shall conform to the methods, forms, mixture, placement, and curing, as specified in Item P-610. Any reinforcement required shall be of the kind, type, and size, and shall be furnished, located, spaced, bent, and fastened as indicated on the plans; it shall be approved by the engineer before the concrete is poured.

All invert channels shall be constructed and shaped accurately so as to be smooth, uniform, and cause minimum resistance to flow. The interior bottom shall be sloped downward toward the outlet.

751-3.4 INLET AND OUTLET PIPES. Inlet and outlet pipes shall extend through the walls of the structures for a sufficient distance beyond the outside surface to allow for connections, but shall be cut off flush with the wall on the inside surface unless otherwise directed. Concrete or brick and mortar shall be constructed around the pipes so as to prevent leakage and form a neat connection.

751-3.5 PLACEMENT AND TREATMENT OF CASTINGS, FRAMES, AND FITTINGS. All castings, frames, and fittings shall be placed in the positions indicated on the plans or as directed by the engineer, and shall be set true to line and to correct elevation. If frames or fittings are to be set in concrete or cement mortar, all anchors or bolts shall be in place and position before the concrete or mortar is placed. The unit shall not be disturbed until the mortar or concrete has set.

When frames or fittings are to be placed upon previously constructed masonry, the bearing surface or masonry shall be brought true to line and grade and present an even bearing surface in order that the entire face or back of the unit will come in contact with the masonry. The unit shall be set in mortar beds or anchored to the masonry, as indicated on the plans or as directed and approved by the engineer. All units shall set firm and secure.

763591°-48-26

After the frames or fittings have been set in final position, and the concrete or mortar has been allowed to harden for seven (7) days, the grates or covers shall be placed and fastened down.

751-3.6 INSTALLATION OF STEPS. The steps shall be installed as indicated on the plans, or as directed by the engineer. When the steps are to be set in concrete they shall be placed and secured in position before the concrete is poured. When the steps are installed in brick masonry they shall be placed as the masonry is being built. The steps shall not be disturbed or used until the concrete or mortar has hardened for at least seven (7) days. After this period has elapsed, the steps shall be cleaned and painted, unless they have been galvanized.

751-3.7 BACKFILLING. (a) After a structure has been completed, the area around it shall be filled with approved material, in horizontal layers not to exceed eight (8) inches in loose depth, and compacted to the density specified. The fill shall be made to the elevation shown on the plans, or as directed by the engineer.

(b) No backfilling shall be placed against any structure until permission is given by the engineer. In the case of concrete, such permission preferably shall not be given until the concrete has been in place fourteen (14) days, or until tests made by the laboratory, under the supervision of the engineer, establish that the concrete has attained sufficient strength to withstand any pressure created by the methods used and materials placed without damage or strain beyond a safe factor. Adequate provisions shall be made for thorough drainage.

(c) Fill placed shall be deposited all around a structure at the same time and to approximately the same elevation. Especial care shall be taken to prevent any wedging action against the structure, and all slopes bounding or within the areas to be backfilled will be stepped or serrated to prevent wedge action.

(d) All backfill shall be compacted to the density as required in Item P-152, and as determined by CAA compaction control tests T-611 for the class of airport involved.

(e) Backfill shall not be measured for direct payment. Performance of this work is not payable directly, but shall be considered as a subsidiary obligation of the contractor, covered under the contract unit price for the structure involved.

751-3.8 CLEANING AND RESTORATION OF SITE. After the backfill is completed, the contractor shall dispose of all surplus material, dirt, and rubbish from the site. Surplus dirt may be deposited in embankment, shoulders, or as ordered by the engineer. Except for paved areas of the airport, the contractor shall restore all disturbed areas to their original condition.

After all work is completed, the contractor shall remove all tools and other equipment used by him, leaving the entire site free, clear, and in good condition.

Performance of the work described in this section is not payable directly, but shall be considered as a subsidiary obligation of the contractor, covered under the contract unit price for the structure.

METHOD OF MEASUREMENT

751-4.1 The number of brick manholes, catch basins, inlets, or inspection holes shall be counted for each type and size of structure and listed as the number of units complete in place and accepted.

751-4.2 The number of concrete manholes, catch basins, inlets, or inspection holes shall be counted for each type and size of structure and listed as the number of units complete in place and accepted.

751-4.3 Manholes, catch basins, inlets, or inspection holes shall be measured for payment by the vertical foot for each type and size of structure and for brick or concrete construction, complete, in place, and accepted. The number of vertical feet for a structure shall be defined as the vertical distance to the nearest one tenth of a foot from the bottom of the footing to the top of the rim. The units of structures of approximaely equal size shall be divided into groups by depth measurements between the following limiting figures, as for instance: 0 to 6 feet; 6 feet to 10 feet; 10 feet to 12 feet, etc.

BASIS OF PAYMENT

751-5.1 The number of units of brick structures, determined as provided in Section 4.1, shall be paid for at the contract unit price per each for "Brick Manholes, Catch Basins, Inlets, or Inspection Holes," respectively, as called for in the bid schedule, which prices and payment shall constitute full compensation for furnishing all materials; for placing and finishing; for all connections to drainage pipe; for all excavation and hauling; for all backfilling; for setting and anchoring any frame, grate, cover, or fitting necessary to complete structure; for finishing flow line; for placing steps; for plastering brick surfaces as required; and for all labor, equipment, tools, and incidentals necessary to complete the units.

751-5.2 The number of units of concrete structures, determined as provided in Section 4.2, shall be paid for at the contract unit price per each for "Concrete Manholes, Catch Basins, Inlets, or Inspection Holes," respectively, as called for in the bid schedule, which prices and payment shall constitute full compensation for the concrete; for furnishing all materials; for placing and finishing; for all reinforcing; for all connections to drainage pipe; for all excavation and hauling; for all backfilling; for setting and anchoring any frame, grate, cover, or fitting necessary to complete structure; for finishing flow line; for placing steps; and for all labor, equipment, tools, and incidentals necessary to complete the units.

751-5.3 The linear feet of manholes, catch basins, inlets, or inspection holes, as provided in Section 4.3, for either brick or concrete

construction, shall be paid for at the contract unit price per vertical foot for "Manholes, Catch Basins, Inlets, or Inspection Holes" as called for in the bid schedule, which prices and payment shall constitute full compensation for furnishing all materials; for placing and finishing; for all reinforcing; for all connections to drainage pipe; for all excavation and hauling; for all backfilling; for setting and anchoring any frame, grate, cover, or fitting necessary to complete structure; for finishing flow line; for placing steps; for plastering brick surfaces where applicable; for concrete where applicable; and for all labor, equipment, tools, and incidentals necessary to complete the units. Payment will be made under:

Item D-751-5.1 Units of Brick Structures (Manholes, Catch Basins, Inlets, or Inspection Holes)-per each. Item D-751-5.2 Units of Concrete Structures (Manholes, Catch Basins, Inlets, or Inspection Holes) -per each. Item D-751-5.3 Vertical Linear Feet of Brick or Concrete Structures (Manholes, Catch Basins, Inlets, or Inspection Holes) -per vertical foot.

ITEM D-752 CONCRETE CULVERTS, HEADWALLS, AND MISCELLANEOUS DRAINAGE STRUCTURES

DESCRIPTION

752-1.1 This item shall consist of concrete, both plain and reinforced, culverts, headwalls, and miscellaneous drainage structures constructed in accordance with these specifications at the locations and in conformity with the lines, grades, and dimensions shown on the plans or required by the engineer.

752-2.1

MATERIALS

CONCRETE. Plain and reinforced concrete shall meet the requirements of Item P-610.

752-2.2 BACKFILLING. The material used for backfill shall be selected material from the excavation or borrow. All excavated material, so far as suitable, shall be utilized as backfill or embankment.

CONSTRUCTION METHODS

752-3.1 UNCLASSIFIED EXCAVATION. (a) Trenches and foundation pits for structures or structure footings shall be excavated to the lines and grades or elevations shown on the plans or as staked by the engineer. The excavation shall be of sufficient size to permit the placing of the full width and length of the structure or structure footings shown. The elevations of the bottoms of footings, as shown on the plans, shall be considered as approximate only; and the engineer may order, in writing, such changes in dimensions or elevations of footings as may be deemed necessary to secure a satisfactory foundation. (b) Boulders, logs, or any other objectionable material encountered in excavation shall be removed. All rock or other hard foundation material shall be cleaned of all loose material and cut to a firm surface either level, stepped, or serrated, as directed by the engineer. All seams or crevices shall be cleaned out and grouted. All loose and disintegrated rock and thin strata shall be removed. When concrete is to rest on a surface other than rock, special care shall be taken not to disturb the bottom of the excavation, and excavation to final grade shall not be made until just before the concrete or reinforcing steel is to be placed.

(c) The contractor shall do all bracing, sheathing, or shoring necessary to perform and protect the excavation and the structure; also as required for safety or to conform to governing laws. The cost of brac