513.03 CONSTRUCTION

513.03.01 Proprietary Retaining Walls

A. Working Drawings. At least 30 days before beginning the work, submit working drawings for approval that include, at a minimum, the following:

1. Design calculations giving complete information as to the proposed method of fabrication and erection of precast units and related components.

2. General notes, design parameters, soil characteristics, and factors of safety.

3. An elevation view of the wall showing elevations at the top of the wall, the beginning, and at the end.

4. Plan view of the wall showing the offset from the construction baseline to face of wall units at all changes in horizontal alignment.

5. Distance from front of wall to the extreme limit of module. 6. Typical sections of the wall indicating how internal drainage and

surface drainage behind the wall is handled. Typical cross-sections of cut and fill sections. Limits and extent of select granular backfill material placed above original ground. Location of proposed ground line.

7. Panel or unit length and size and designations.

8. A numbered panel layout for fabrication and erection purposes.

9. Typical panels, as well as special panels, such as at bends; dimensions necessary to construct the member; the location of reinforcement steel in the member; and the location of reinforcement attachment devices that are embedded in the panels.

10. Designation of breaks in vertical alignments and elevations at whole stations and at 25-foot increments and treatment.

11. All details for footings and leveling pads, including step details, locations, and elevations, and actual maximum bearing pressure. 12. Architectural details, such as special facing finish, texture, and color. 13. The location of the proposed final ground line.

14. ROW limits and their relationship to the wall, with offsets and stations to corners.

15. Location of any noise walls or sign structures near the wall by station and offsets.

16. Centerline of any drainage structures or utilities behind and passing through or under walls.

17. Location of all piles on any adjoining structure’s foundation plans with details to avoid any conflict.

18. Connections to barriers, copings, signs, lights, railing, fences, noise barriers, or any other element.

19. Details for the construction of walls and soil reinforcement around obstructions including bridge supports, drainage facilities, sign footings, or any other element.

20. Details for required electrical systems, including highway lighting bases, junction boxes, and conduit.

21. Limits and extent of common structure volume, such as excavation, volume of concrete, reinforcement steel, and backfill.

22. Numbers and types of precast units/panels.

23. Manufacturer’s recommendations, including suggested sequence of construction.

B. Shipping, Handling, and Storing. Ensure that the precast units have cured for at least 72 hours and have attained the minimum 28-day compressive strength before shipping.

Provide galvanized handling devices according to ASTM A 123. Store, transport, hoist, and handle units to prevent cracking or damage. After galvanizing, coat attachment surfaces not to be embedded in concrete with coal tar epoxy paint. Replace or repair units damaged by improper storing, transporting, or handling.

C. Wall Foundation. Excavate as specified in 202.03.03. Shape and compact the underlying material to produce a firm, even surface. Obtain RE approval before finishing excavation. If the RE determines that the bottom of the excavation is unstable, undercut, backfill, and compact as directed by the RE. Grade the foundation for the structure level for a width that exceeds the length of the soil reinforcement by at least 2 feet.

Place concrete, as specified in 504.03.02.D, for an unreinforced concrete leveling footing, or provide a precast concrete leveling pad according to the manufacturer’s recommendations.

Before placing wall units, install underdrains and drainage pipes.

D. Installing. Provide 2 copies of the manufacturer’s recommendations to the RE. If a section of wall is to be cast-in-place, construct the section as

specified 504.03.02.D. Obtain RE approval of the foundation for the structure before beginning erection. Install the units according to the manufacturer’s recommendations. For erection, handle units with lifting devices set into the upper edge of the panels. Place units in a horizontal course. Do not place the subsequent course until the previous course is backfilled within 2 inches of the top of the course.

Provide external bracing for the initial course. While erecting each course, examine line, and grade, and correct deviations to prevent cumulative inaccuracies in alignment. Vertical tolerance and horizontal alignment tolerance shall not exceed 1/2 inch, when measured along a straightedge. Install joint filler and rubber pads according to the manufacturer’s

Ensure that all wall units above the first course interlock with the lower courses. Vertical joint openings on the wall’s front face shall not exceed 3/4 inch. The front face vertical joints shall have 12-inch wide strips of subsurface drainage geotextile behind each joint starting 2 feet below grade.

E. Back of Wall Drainage. Place a stone pocket, subsurface drainage

geotextile, and an 8-inch corrugated steel underdrain pipe as shown on the Plans.

When constructing weep holes, place ports or vents for equalizing hydrostatic pressure below low water. Use 4-inch PVC or unreinforced concrete drain pipe as forms for weep holes through concrete.

F. Backfilling. For MSE walls, place reinforcement perpendicular to the face of the wall, unless otherwise shown on the Plans or directed. Before placing soil reinforcement, compact the backfill material as specified in 513.03.01.G. For modular bin walls, fill wall units 4 feet or less in height in 1 lift and then thoroughly compact with a vibratory tamping device. Fill wall units more than 4 feet in height in 2 approximately equal lifts and thoroughly compact after each layer is placed.

Backfill after erecting each course of wall units. Verify that the reinforcements and wall units are not damaged, disturbed, or misaligned while backfilling. Correct misalignment and remove and replace damaged units of the wall units before placing the next course. Backfill using 1 of the following materials:

1. Soil Aggregate (I-15) or Soil Aggregate (I-9) and Coarse Aggregate No. 57. For MSE walls, use I-15 soil aggregate. The Contractor may use I-9 soil aggregate or No. 57 coarse aggregate in place of I-15 soil aggregate for modular walls.

Do not exceed 10 inches loose measurement for the maximum lift thickness of the backfill. Decrease this lift thickness to obtain the specified density.

The ME will determine the optimum moisture content as specified in AASHTO T 99, Method C. Ensure that the moisture content of the backfill is uniform throughout each layer and has a placement moisture content that is less than or equal to the optimum moisture content. Remove and rework backfill that has a placement moisture content in excess of the optimum moisture content until the moisture content is uniformly acceptable throughout the entire layer.

Ensure that backfill placed within 1 foot of a drainage structure or utility does not have any particle greater than 3 inches in maximum dimension.

2. Coarse Aggregate. Do not exceed 8 inch lift thickness of coarse aggregate.

Place subsurface drainage geotextile at the interface of the coarse aggregate and regular roadway materials and embankments. At each reinforcement strip level, level and compact the coarse aggregate before placing the reinforcement.

G. Compacting. Compact backfill material without damaging, disturbing, or misaligning the wall units before placing the next block level. Roughly level each course of backfill to an elevation approximately 2 inches above the level of the next course of units. Compact in a direction parallel to the wall. For MSE walls, do not use sheepsfoot or grid-type rollers for compacting backfill within the limits of the soil reinforcement. Compact for the specified material as follows:

1. Soil Aggregate (I-15) or Soil Aggregate (I-9). With the exception of the 5-foot zone directly behind the units, compact I-15 soil

aggregate or I-9 soil aggregate with large, smooth drum, vibratory rollers using the density control method as specified in 203.03.02.D. Within 5 feet of the wall, use small, single or double drum, hand operated, walk-behind vibratory rollers, or walk-behind vibrating plate compactors. Make at least 3 passes.

2. Coarse Aggregate. To provide the proper density of the broken stone, compact by making at least 4 passes with a vibratory roller that has a total operating weight of 8 to 10 tons. Set the roller in the vibratory mode between 1.5 and 2.5 mph.

Within 5 feet of the wall, use small, single or double drum, hand operated, walk-behind vibratory rollers, or walk-behind vibrating plate compactors. Make at least 3 passes.

When there is evidence of wall displacement or disturbance, compact with a smooth drum static roller.

At the end of each day’s operation, slope the last placed layer of backfill away from the wall units to direct runoff of rainwater away from the wall face. Do not allow surface runoff from adjacent areas to enter the work site.

Ensure that the overall vertical tolerance of wall does not exceed 1/2 inch per 10 feet of wall height.

H. HDPE Geomembrane Liner for MSE Walls. Deliver HDPE geomembrane liner systems and store to prevent damage to the material before installation.

Before placing HDPE liner, ensure that the area to be lined is smooth and free of sharp objects or debris. Do not use equipment or tools that may damage the HDPE liner while handling, moving, or installing.

Place the HDPE liner below the pavement and just above the first row of reinforcements. Slope the HDPE liner to drain away from the wall units. Align seams parallel to the line of maximum slope. Overlap seams at least 2 feet and seam according to the manufacturer’s recommendations. Conduct field testing of seams, according to the manufacturer’s specifications, to verify satisfactory seaming conditions.

When backfilling, prevent damage to the HDPE liner system. Do not allow equipment or traffic within 10 feet of the HDPE liner. Slope the last placed level of backfill away from the wall units to direct runoff of rainwater away from the wall face. Do not allow surface runoff from adjacent areas to enter the work site.

513.03.02 Cast-in-Place Retaining Walls

Place reinforcement steel as specified in 504.03.01. Construct concrete as specified in 504.03.02.