DuraHold2 - Hammersmith Parking Lot

Retaining Wall System : DuraHold2
Owner: Parking Authority of Toronto
Structural Engineer: Cole, Sherman Engineers, Architects, Planners Thornhill, ON
Geotechnical Engineer: VA Wood Associates Ltd. Scarborough, ON
Contractor: Gazzola Paving – Adrian Niekirk, Aldo Da Silva Toronto, ON
Geogrid Manufacturer: Conwed Strata Systems Minneapolis, MN

During the latter part of 1992, the Parking Authority of Toronto commissioned Cole, Sherman to design a retaining wall for a parking lot project. The wall was required to protect a parking area located at Hammersmith Ave. and Queen St. E. in Toronto, Canada. Cole, Sherman had orginally specified a conventional concrete reinforced retaining wall which was over budget. Gazzola Paving was then asked to recommend another cost-effective solution. The resulting proposal was a DuraHold2 wall with Stratagrid 500 and Risigrid reinforcement. The supply and install price was then to the Parking Authority’s approval.

The DuraHold2 system has a random block face pattern based on units 12” high, 12” deep, and 72” long. It is a high strength system with quick and easy installation - in this case, facilitated by a concrete pad with appropriate stepped-up footings. The concrete pad also ensured a good, solid base. The wall is eleven feet at the highest point, requiring layers of Stratagrid 500 on the top two courses, as well as five layers of Risigrid. The first three courses did not require the use of any grid. Aldo Da Silva of Gazzola Paving assessed the existing site material and used the superior quality free-draining sand and imported Granular A as needed. At present there is only five to six feet of the wall exposed, as the future plans for the neighbouring apartments and stores may require that the entire area be demolished and the new grade lowered by three to four feet.

The Hammersmith Avenue parking lot took five days to construct and is a total of 1300 square feet. All parties involved - the owner, contractor, and even the neighbours - are pleased with the results.

DuraHold - To the Rescue

Retaining Wall System: DuraHold with Stratagrid 500 geogrid reinforcement
Owner : Oakville Fire Department
Contractor : Tarrascape Innovations Inc., Hamilton, ON
Wall Design : RisiStone Systems, Thornhill, ON
Retaining Wall Manufacturer : Unilock Ltd., ON

In the summer of 2000, the City of Oakville, Ontario completed construction of a new, state-of-the-art training center for its emergency services. In order to be fully equipped for fire and rescue simulations, it was necessary to install a retention pond immediately adjacent to the new training facilities. The design had to take into account the issue of vehicle accessibility. So that emergency vehicles (fire pumping trucks) could park immediately adjacent to the deepest water, the architect’s design called for the application of vertical retaining walls running along two sides of the pond.

Through the efforts of Unilock Territory Manager Dave Laurie, the DuraHold geogrid reinforced segmental retaining wall system was approved and a sealed RisiStone Systems design was completed.

The substantial loading and potential hydrostatic effects posed a number of unique design challenges. In order to account for the effects of a significant drop in the water level due to pumping, the wall analysis incorporated the AASHTO recommendations for rapid draw-down conditions. With a maximum design height of 4.0m (13.0ft), vertical orientation, and significant potential loading, the DuraHold wall design required a heavy-duty geogrid reinforcement to do the job. The Stratagrid 500 geosynthetic was utilized for its high tensile strength and durability. As well, in order to facilitate the dissipation of hydrostatic forces immediately behind the wall face, a ¾” clear stone drainage layer wrapped in filter cloth was incorporated into the design.

The Contractor, Tarrascape Innovations Inc., employed time-saving techniques to maintain an efficient rate of installation. On top of the standard 300mm (12”) granular base, reinforced 2x2 patio slabs were used to provide an even leveling pad for the base course to be placed. As the site consisted mainly of a clay material, a pond liner was not required to contain the water. This proved to be an asset during construction.

Once the walls were completed and grading of the pond finalized, the “pit” was flooded to the design elevations. With the addition of creative landscaping, the result is an aesthetically pleasing water feature, designed and constructed with the structural stability to provide years of use as an effective training tool. This project emphasizes the applicability of the DuraHold retaining wall system when a variety of challenging design conditions are presented.

SienaStone - Colonial Creek

Wall System : SienaStone with Stratagrid 500 Geogrid Reinforcement
Owner: City of Waterloo, Waterloo, ON
Contractor: Gateman Milloy, Kitchener, ON
Designers: Layout: MTE Consultants Inc.
Structural Design: RisiStone Systems
Geotechnical Engineering: Naylor Engineering Associates
Wall Certification/Project Engineers: MTE Consultants Inc.
Manufacturer: Unilock Ltd., Glenn Wiley,Territory Manager

As part of an ongoing project to extend University Avenue, one of the main arteries in Waterloo, Ontario, the City recently completed construction of the Bridge at Colonial Creek. In response to environmental concerns, MTE Consultants designed the bridge to minimize the impact of the roadway on the existing creek.

The bridge deck and abutments are constructed of reinforced concrete and are abutted on all sides by SienaStone geogrid reinforced wing-walls. The four wing-walls run nearly parallel with the existing watercourse, perpendicular to the bridge.

Based on the location and proposed use, the design of the SienaStone geogrid reinforced walls had to comply with several additional criteria. Acting as bridge wing-walls, the analysis and design was conducted in accordance with the Ontario Highway Bridge Design Code, which currently calls for slightly higher margins of safety than the NCMA Design Manual. The presence of a creek in front of the wall required that special attention be paid to drainage at the wall face, scour protection, and depth of embedment. Finally, in an effort to minimise overall costs, the geogrid reinforcement design was optimised to allow reduced lengths as the walls tapered down to grade.

At the maximum height, the SienaStone wing-walls stand approximately 7.7m (25ft), then taper down rapidly (2.5H:1V) to near grade. For erosion protection, rip-rap is positioned in front and at the ends of the walls. The total face area of the walls is approximately 3500 square feet.

These walls highlight the capacity of the SienaStone system to combine rugged performance with an aesthetic quality rarely found in heavy highway and bridge applications. With aesthetics becoming an increasingly important issue in large commercial and government projects, the solid strength and lasting beauty of the SienaStone system will surely prove to be an attractive option to consultants and specifiers alike.

DuraHold - Canal Ponds

Wall System : DuraHold
Owner: Pioneer Developments, Rochester, NY
Landscape Architect : E D R, Syracuse, NY
Retaining Wall Engineer : InterSol Engineering, Milton, ON
Installation Contractor: Camful Industries, Syracuse, NY
Retaining Wall Manufacturer: Binghamton Precast and Supply, Binghamton, NY

During the month of June 1993, installation of vertical DuraHold and DuraHold2 retaining walls began at the new Canal Ponds business park near Rochester, NY. Pedestrian and bike paths wind around the development to guide people to a central green space. This combination of bridges, piers and walkways located around the ponds, constructed using the DuraHold system, creates a serene and beautiful waterfront environment.

The DuraHold retaining wall system was selected partially because of the system's high strength, quick and simple installation, but mostly because DuraHold possessed aesthetic qualities similar to the quarried limestone blocks used in the nearby Old Erie Canal. After the walls were installed, this look was enhanced with sandblasting, giving the facing a mottled, weathered appearance.

The DuraHold system has a random block pattern based on units 12" high, 24" deep, and 72" long with a weight of 1740 lbs each. Special coping units were manufactured for this project to provide extra overhang of the top course and a keyway to receive the poured in place concrete sidewalk above the wall. The DuraHold2 system, also used on the site, is based on a unit that is half the depth of the DuraHold unit. This allows it to be used at a significant cost savings in locations that are less demanding.

The site plans required vertical retaining walls to be constructed that would support pedestrian bridge structures, walkways and planting beds. For most of the installation, the retaining wall was 7 ft high, with the foundation of the wall 3 ft below the water line. In these locations, the DuraHold system utilizing two layers of Stratagrid 5033, was constructed. At the inlet structures the walls were 13 ft high with 7 ft below the water line. This required the DuraHold system, again with two layers of Stratagrid 5033, and an additional three layers of Stratagrid 9027. For the areas retaining the planting beds, walls 3 ft in height were built. Here the DuraHold2 system was used. The site plans also called for three-foot-wide accent walls at the entrances to the business park. These were constructed using DuraHold and DuraHold2, placed back-to-back, with a specially manufactured three-foot-wide coping unit.

Throughout the construction approximately 11,000 square face feet of DuraHold and 5,000 square face feet of DuraHold2 were installed on the site. All the material was placed by a five-person crew over a period of three months, with a materials cost of less than $11.00 per square face foot.

“The final outcome produced excellent retaining walls.”
Joe Alberti, Pioneer Developments

“This project required minimal site cutting, which made manufacturing very intricate, but it produced very nice results.”
Jay Abbey, Binghamton Precast & Supply

“It was a clean and quick installation. The DuraHold system is an enjoyable system to work with.”
Peter Iwanicki, Camful Industries

“All walls went together smoothly and there have been no problems to date.”
Dan Reeder, E D R

Pisa2 - Byrd Park

Wall System : Pisa2
Owner: City of Richmond, VA
Landscape Architect : Higgins Associates, Inc.,Richmond, VA
Structural Engineer : Mr. Mike Matthews, P.E.,The Structures Group, Inc.
Contractor: Mid Atlantic Retaining Wall Systems,Inc.
Materials Supplier: Custom Concrete, Inc., Williamsburg, VA
Geogrid Manufacturer : Conwed Strata Systems

In 1992, the City of Richmond, VA selected a Pisa2 / Risigrid reinforced retaining wall system to protect the lakefront surrounding a large municipal retention pond. The size of the wall was approximately 6 ft high and 2,350 ft long. The pond was pumped dry for cleaning and general rehabilitation. A stable footer/leveling pad was constructed to provide a firm foundation for the base course of blocks. Due to the soft foundation in the lake bed, all materials were “handed down” from the top of the excavation using a pair of Skytrack 6036’s. Number 10 manufactured crushed stone was specified as infill material for its high internal angle of friction and compactability properties.

The geogrid specified was Risigrid with a long-term allowable design strength of 541 lbs/ft (ultimate strength = 1,979 lbs/ft). Two six-foot-long layers were required to satisfy minimum factors of safety against failure by sliding,overturning, overstressing, and pullout. There were 22 pipes which penetrated this wall, ranging from 8 to 36 inch drainage outfalls. The Pisa2 blocks were field-cut to fit snugly around the pipes and the annulus was grouted.

The construction of the wall began on April 11th, 1992 and was completed on May 22nd. Not including rain days, an average of 470 square ft per day was realized. All granular backfill was placed with a Case 621 wheelloader and compacted to 95% Standard Proctor with two Case 900 plate compactors. This retaining wall adds outstanding aesthetic appeal to this neighbourhood lake. Most importantly, it has stabilized the shoreline against erosion for its 75-100 year design life. The project was completed on time and under budget.

“This wall looks great and is performing better than expected. We are very pleased.”
Mr. Saeed Rabie, City Engineer, City of Richmond

“The experience we had on the Byrd Park Project with Risigrid gives us a lot of confidence in its future use for soil reinforcement.”
Mr. Bill Spell, ASLA, RLA, Higgins Associates, Inc.

"From the manufacturing and installation aspect, Pisa2 with geogrids are a joy to work with. The solid Pisa2 wall units provide superior strength and durability in comparison to other hollow units available. Their performance will secure much more work for us in this field."
Mr. Bob Swope, Custom Concrete