SWRs: for Aesthetics, Diversity and Protection

Compiled by Larry Shield, regional editor

The use of the retaining wall system has allowed landscape contractors to build sites that were unbuildable in the past. It has allowed them to shape the landscape and to beautify hardscape projects in the commercial and residential markets. It also gives landscape architects creative lines and options in which to design award winning projects!

This wall is built on standard footings of crushed and compacted limestone road-base material. In this case, the engineering advantages of building terraced walls over a single-tired wall are minimal. Slightly less geogrid reinforcing material is required, but that isn?EUR??,,????'???t a major consideration. It?EUR??,,????'???s likely that this wall was built with terraces for the aesthetics of green-scaping alone.

Advancements

Since their introduction in the mid-1980s, Segmental Retaining Wall systems (SRWs) have made many advancements, acquiring wide use across the country.

SRW buyers now have at their disposal a wide selection of unit sizes, face types, colors and textures. In addition, a new generation of SRW has three finished faces (like Keystone Retaining Walls Country Manor), making possible freestanding walls and other above-grade landscaping accents. Retaining walls aren?EUR??,,????'???t just for holding back earth any more!

A segmental retaining wall with an exposed height of 50' and a length of 1200' is monitored for movements by surveyed prisms, and has been through two earthquakes. Due to use of the right wall system and proper installation there have been no movements or problems.

Versatility

The HartmanEW system is more than just an endwall or headwall for storm drainage pipe. This product has been adapted to construct small retaining structures, benching structures for planting on hillsides, benches, stream and swale crossings. It?EUR??,,????'???s also a beautiful and cost effective means of installing endwalls and headwalls for storm drains.

With relative ease these blocks are installed. The Komatsu 128 excavator does the work while the man on the ground merely guides the block into place.

Another application for the sectional risers is as a small retaining structure for planting areas on slopes. One riser anchored to the ground with reinforcing rods and filled with soil creates a perfect planting area for trees or shrubbery planted along the slope.

Design Capabilities

At 5.75 square feet of face on each block, Redi-Rock is one of the largest retaining wall blocks available today. These massive concrete blocks, averaging between 1,500 and 2,500 lbs., can achieve heights up to 75 percent higher than other retaining wall systems without using expensive geo-grid or tie back systems. The utilization of equipment for installing these massive blocks replaces the need for an army of manual labor. This fact reduces installation time and labor expense. Size is not the only advantage: the natural rock appearance, nearly indistinguishable from quarried stone, makes structural retaining walls (SRWs) a favorite among landscape architects, engineers and landscape contractors.

The structures before the establishment of vegetation. The walls pictured here at the Five Canyons project in Castro Valley, Calif. utilized GEOWEB sections with black colored facias.

Vegetated Retaining Walls

In addition to economic and aesthetic advantages, Geoweb walls provide a superior system for earth retention structures located in an area noted for seismic concerns. Presto Products confinement systems provide flexible retention structures, capable of tolerating large deformation without loss of structural integrity or adversely affecting the aesthetics, especially with vegetated facing treatment.

Allow for Proper Drainage

When you change the landscape with any retaining wall system, there are concerns about erosion and runoff water. The landscape contractor must use precautionary measures to insure a proper install. These potential problems can be solved by using the standards of the industry and the manufacturer?EUR??,,????'???s recommendations. The gravel back-fill and drainage piping are essential in runoff areas. If this part of the installation isn’t done correctly, the wall will surely fail.

This 2,517 square foot wall was installed in 2 1/2 weeks with a crew of four, a Caterpillar 320A and a Bobcat skid-steer. No soil reinforcement was used adding considerable cost savings to the project because the underground utilities from the parking lot above did not need to be relocated. The wall was completed and stained to match existing buildings.

Select Construction Products provides the proper aggregates needed to allow the wall to drain correctly. The most common material used in the Southeast is generally crusher run base (GAB) for the footings of the first course of modular block. The widely used product is #57 Type Stone. This product varies in size from 1 inch to 1 1/2 inches in size. This is generally, backfilled behind the wall 12 inches for drainage. This is the trickiest part of the project. If you skimp on the backfill the project may have problems in the future.

Rising to the Challenge

What do you do when you want to build a new Granite City Restaurant, need a 12-foot high gravity wall, cannot disturb the nearby shopping malls underground utilities, sidewalk or parking lot and need a wall built quickly? You call in Stone Strong Systems retaining wall block to save the day.

Risi Stone Retaining Wall Systems DuraHold3 geogrid-reinforced vertical wall surrounds a grocery store. An 8-foot wood acoustical fence was attached to the top of the wall to further reduce the impact of the new building on the neighboring residences.

The 2,517-square-foot wall was necessary to separate the shopping malls parking lot rising 12 feet above the grade of the new restaurant, in Lincoln, Neb. Buried utilities made it impossible for any type of soil reinforcement such as mechanical tiebacks or geo-grid tiebacks. The developers needed a gravity wall that could erected at a competitive price.

A crew of four workers completed the wall quickly. On-site soils were used to back-fill the wall, avoiding the cost of expensive imported fill. The installer completed the wall at a cost savings of 40 percent versus a cast-in-place wall.

Cost-Effective Systems

One of the major benefits of machine-installed systems is to increase efficiency and productivity. These larger systems allow you to place more square footage per day when compared to hand-placed installation, due in part to the larger actual unit size, but also because of the increased speed of the machines. This means less dependence on the energy and physical strength of your employees ?EUR??,,????'??? factors that often will slow a project down and waste valuable time, and in turn, money.

This cross section of the DuraHold??????oe concrete pier connection and dowel bar layout features: A) reinforced concrete pier by others (dowels to extend into pier as required by pier design); B) exterior face brick; C) DuraHold coping unit ensures level bearing surface, correct with concrete formwork; D) minimum of 19 1/2 inches depth; E) geogrid reinforcement (type and placement as required by design); F) 15M dowel grout solid using the Epcon A7 concrete adhesive (typical).

Reliance on the energy level/capacity of your workers adds another level of variability to estimation, speed of installation and scheduling. Remember that simplicity reduces variability ?EUR??,,????'??? if you eliminate some of the more difficult and time-consuming tasks from the shoulders of your employees, it is easier for you to estimate the speed and therefore the cost of construction. To give you an idea of how reducing labor costs can reduce the total project cost, a recent article in an industry publication estimated labor as 55-65 percent of the total cost of a hand-placed SRW installation.

A Complex Business

Soil Retention Systems has as its goal, the perfection of SRW systems, producing blocks that go into the system and installing the blocks to create grade-transitioning structures. This seemingly straightforward business requires almost daily contacts with potential customers. They include landscape architects, civil engineers, soils engineers, wall designers, material suppliers, general contractors, grading contractors, landscape contractors, other site-development related subcontractors, operating engineers, labor crews, unions, special inspectors, soil technicians, plan checkers, building inspectors, developers, homeowners and other end users. Any and all of which make the business far from straightforward. Producing blocks and buying geosynthetics are among the easier tasks.

In this business, the material suppliers drive the SRW business; a young, isolated and small segment of the construction industry. At its current level of industry maturity, those driving the SRW business focus on square meters of wall facing and geosynthetics sold. Those driving the business also seek out small landscape contractors that can be encouraged to build walls in accordance with the system providers?EUR??,,????'??? specific installation requirements and at their direction.