6-196
D.Design computations prepared, checked, and sealed by a licen sed Professional Engineer.
E.Prior to the beginning of cons truction, the contractor shall supply the Resident with two copies of the design-supplier’s Installation Manual. In ad dition, the Contractor shall have two copies of the Installation Manual on the project site.
673.06 Construction Requirements The Wet Cast Small Landscape Block Wall shall
have the following construction requirements:
A.Excavation The excavation and use as fill of all excavated material shall meet the requirements of Section 203 -- Excavation and Embankment, excep t as modified herein.
B.Foundation The area upon which the Wet Cast Small Landscape Block Wall structure is to rest, and within the limits shown on the submit ted plans, shall be graded for a width equal to, or exceeding, the length of the bl ocks. Prior to wall and leveling pad construction, this foundation material shall be co mpacted to at least 95 percent of maximum laborat ory dry density (AASHTO T-180 Method C or D). Frozen and unsuitable soil shall be removed and replaced with g ravel borrow compacted to 95 percent of AASHTO T-180, or as shown on the pla ns. A concrete leveling pad shall have a minimum thickness of 4 inc hes and shall be constructed a minimum width of 6 inches beyond the front and ba ck of the concrete wall units, or as indicated on the plans. Dimensions may be mo dified per the wall supplier’s recommendations, with written approval of the Geotec hnical Engineer. The leveling pad shall be cast to the design elevati ons as shown on the plans, or as required by the wall supplier upon written approva l of the Geotechnical Engineer. The allowable elevation tolerances from the design elevations a re +0.01 ft and -0.02 ft. Leveling pads which do not meet this requirement shall be repaired or replaced as directed by the Resident at no additional cost to the Departmen t. Placement of wall units may begin after the strength of the concrete leveling pad reaches 1000 psi or is adequate to support the proposed loads. Contractor may begin p lacement of concrete block units after 12 hours at their own risk.
C.Method and Equipment Prior to e rection of the wall, the Con tractor shall furnish the Resident with detailed information concerning the proposed cons truction method and equipment to be used. The erection procedure shall be in accor dance with the manufacturer’s instructions. Any units that are damaged due to handling will be replaced at the Contractor’s expense.
D.Installation of Concrete Wall Units A field representative from the wall system being used shall be available, as needed, during the erection of the wall. The services of the representative shall be at no additional cost to the project. 6-197 The contractor shall place the first course of wall units direc tly on the leveling pad and check for level and alignment. Adjacent units should be in contact. The prefabricated concrete wall units shall be installed to a toler ance of plus or minus 3/4 inch in 10 ft in vertical and horizontal alignment. Fill all voids between and within the wall units with drainage stone as described in this specification. Stone infill shall be compacted by hand ta mping with a rod. The drainage stone fill shall extend a minimum of 6 in behind the t ails of the wall units unless a geotextile filter is placed over the inside joint at t he back of adjacent wall units. If used, the drainage geotextile shall conform to the r equirements of Section 722.02. Geogrid reinforcement, if required, shall be placed at the loca tions and elevations shown on the Plans on level fill compacted to the requirements of this Specification. Geogrid reinforcem ent shall not be visible at t he finished face of the wall. The top course of blocks and all coping units shall be installe d using adhesive or other method of permanent attachment as recommended by the manu facturer.
E.Backfill Placement Backfill pl acement shall closely follow the erection of each row of prefabricated wall units. The maximum lift thickness shall be 8 inches loose. The Contractor shall decrease the lift thickness if necessary to ob tain the specified density. The backfill shall be compacted in accordance with Section 203. 12 except that the minimum required compaction shall be at least 92 percent of max imum density as determined by AASHTO T-180 Method C or D. Backfill compaction shall be accomplished without disturbance or displacement of the concret e wall units. Sheepsfoot rollers will not be allowed. Whenever a compaction test fails, no additional backfill shall be placed over the area until the lif t is recompacted and a passing test achieved. The moisture content of the backfill material prior to and duri ng compaction shall be uniform throughout each layer. Backfill material shall have a placement moisture content less than or equal to the optimum moisture content. Ba ckfill material with placement moisture content in excess of the optimum moisture co ntent shall be removed and reworked until the moisture content is uniform and acceptable throughout the entire lift. The optimum moisture content shall be determined in accordance with AASHTO T-180, Method C or D. At the end of the day’s operations, the Contractor shall shape the last level of backfi ll so as to direct runoff of rainwater away from the wall face.
F.Construction Certification Letter The Contractor shall furn ish the Resident a Construction Certification Letter describing how adequate compa ction of the block infill material was accomplished and what QA/QC procedures were followed to ensure that this effort was continued throughout construction o f the wall. 6-198
673.07 Method of Measurement Wet Cast Small Landscape Block W all will be
measured by the square foot of fr ont surface not to exceed the dimensions shown on the Contract Plans unless authori zed by the Resident. Vertical and horizontal dimensions will be from the edges of the blocks. No field measurements for com putations will be made unless the Resident specifies, in writing, a change in the limi ts indicated on the Plans.
673.08 Basis of Payment The accepted quantity of Wet Cast Sma ll Landscape Block
Wall will be paid for at the contract unit price per square foo t complete in place. Payment shall be full compensation for furnishing geotechnical design a s required, all labor, equipment and materials including all precast concrete units, a ggregate fill, hardware, joint fillers, geosynthetic, drainage pipe, and technical field repre sentative. Excavation, foundation material and backfill material will all be incidenta l to the Wet Cast Small Landscape Block Wall. Cost of cast-in-place concrete for leveling pad will not be pa id for separately, but will be considered incidental to the Wet Cast Small Landscape B lock Wall. There will be no allowance for excavating and backfilling for the Wet Cast Small Landscape Block Wall beyond the limits shown on the approved su bmitted plans, except for excavation required to remove unsuitable subsoil in preparation for the foundation. Payment for excavating unsuitable subsoil shall be full compens ation for all costs of pumping, drainage, sheeting, bracing and incidentals for proper execution of the work, and will be paid as common excavation in accordance with Section 20 3. Payment will be made under: P a y I t e m P a y U n i t
673.10 Wet Cast Small Landscape Block Wall S q u a r e F o o t
SECTION 674 - PREFABRICATED CONCRETE MODULAR GRAVITY WALL
674.01 Description This work shall consist of designing, fabric ating, furnishing, and
constructing a prefabricated modular reinforced concrete gravit y wall in accordance with these specifications and in reasonably close conformance with t he lines and grades shown on the Plans, or established by the Resident. Included in the scope of the Pre fabricated Concrete Modular Gr avity Wall construction are: all grading necessary for wall construction, excavation, compaction of the wall foundation, backfill, construction of leveling pads, place ment of geotextile, segmental unit erection, and all incidentals necessity to complete the wo rk.
Source: Maine Standard Specifications for Road and Bridge Construction, 2020 Edition. Pages 666–668 of 817.