Fred Creek Wall in Tulsa, Oklahoma

Large Block Systems, Redi-Rock
By Doug Blackburn
Jan 5, 2009 - 6:39:12 AM

Project Name

Phase 1: Fred Creek Drainage Improvements at the Oral Roberts University Campus

Customer Name

City of Tulsa, Oklahoma

Design / Specifying Engineer

Project Engineer Ryan Mittasch, P.E.

Block Manufacturer

SI Precast

Wall Installer

Crossland Heavy Construction

Project Location

Tulsa, Oklahoma

Year Built

2007, 2008

Project Scope:

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When the natural banks of Fred Creek, a storm water runoff channel near the campus of Oral Roberts University (ORU) in downtown Tulsa, began eroding and threatening the stability of the banks and associated utilities, the city needed to stabilize the stream banks while providing an attractive green area for jogging trails and parks.

As the city of Tulsa has grown and become more urbanized, the Fred Creek drainage has had to accept an increasing amount of storm water.

"When ORU was built, this area was natural hillside and grass," Special Projects Coordinator for ORU Ron Lee said on the ORU website. "Urbanization and development increases the speed at which the water runs off as we develop, build, pave the streets and put in parking lots."

Fred Creek has velocities of 12-15 ft. per second along the nearly half-mile stretch of drainage slated for improvement. Along the drainage near the ORU campus, two to four bridge abutments were being undermined by erosion, along with footings for utility lines crossing the creek. Rip rap had been placed in several isolated locations but was not proving successful in halting the erosion issue.

Inadequacies with the Fred Creek drainage have caused flooding problems on the 263 acre ORU campus for years. Most notable was the May 2000 flooding that caused more than $5  million worth of damages to the university’s Learning Resources Center. Water submerged the facility to depths of 4 in. to 8 ½ ft., damaging departments including biology, chemistry, engineering, physics, the MultiMedia Institute and more.

University students campaigned by phone and foot throughout the city for the Tulsa “GO” bond, which city residents approved in April 2005. The bond issue, which passed by almost 25,000 votes, supports infrastructure improvements throughout the city and set aside almost $33 million for flood control improvements, including $15 million for Fred Creek improvements.

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Considering the Options   

Natural stone was considered in conceptual phases of the project but was quickly ruled out as too expensive. Instead, the engineers turned to large block precast retaining walls to provide an engineered yet attractive solution to erosion control.

“We have found in the past on similar projects that the smaller retaining wall blocks just won’t handle the velocity of the water,” said Bill Robinson P.E., project manager and then-Senior Engineer in Stormwater Design for the city of Tulsa. “This is one of five projects that are either been done or are under construction in Tulsa right now using Redi-Rock or equal products.”

This is the first phase of the project to improve the Fred Creek Drainage. The 9” setback Redi-Rock retaining walls stand 18-19 ft. at the tallest point and encompass a total 68,000 sq. ft. The project contains both gravity and reinforced walls that are placed atop a concrete footing and are buried five feet on average. The walls are limestone texture, with 15 percent of the face area composed of half-blocks to “break up” the look of the walls.

The City of Tulsa wanted the contours of the renovated channel to follow the natural slope of the existing channel to create a more natural look as well as providing a more hospitable environment for wildlife and plants and a safer escape route in the event that a person might fall in.

“A strong selling point for Redi-Rock is its ability to offer creative solutions in storm water applications and the flexibility of the system to create different shapes that can match the natural lay of the land,” said Steve Browne of SI Precast, the Redi-Rock dealer in Tulsa.

Redi-Rock’s 26.6 degree batter angle created by Redi-Rock’s 9 in. setback retaining wall series allowed the flood channel batter to approximate the natural channel of the creek.

Also unique to Redi-Rock is the retaining wall system’s ability to build serpentine curves using the standard retaining wall blocks. Inside and outside curves allow walls to follow the natural lay of the land and also slow water to prevent erosion.

The Redi-Rock retaining wall system consists of massive precast concrete blocks that interlock using a patented knob and groove system often likened to giant Lego blocks. The blocks capture “the essence of natural rock” in natural-looking cobblestone and limestone textures that can be stained any color to match local environments. Redi-Rock blocks average more than one ton each, which allows Redi-Rock walls to be built up to 13 ½ ft. without reinforcement and in excess of XX ft. with reinforcement. Redi-Rock’s 9 in. setback blocks allow walls to be built even taller. Blocks are installed by a small installation crew and a piece of heavy equipment, saving time and labor costs.

Another benefit of for the city of Tulsa choosing the Redi-Rock system is that the blocks are manufactured locally by SI Precast, located approximately 10 miles (CHECK) from the construction site, cutting the freight cost and delivery times. The scale of the project required a block manufacturer that could keep up with the production schedule and SI Precast was prepared for the challenge.

A Natural Look

“Appearance at this site was especially important because it goes right through an urban campus with walking trails. We needed a natural looking material that’s also functional, which is where Redi-Rock fit in,” said Mike Peters, Landscape Architect with Alaback Design Associates in Tulsa.

Since construction of the retaining walls was completed, Allaback has installed lighting throughout the project and landscape plantings to give a natural look to the project. The firm has also worked to restore creek bed habitat including landscape plantings along the creek bottom. Landscaping is still in process currently.

"This project will create a park-like atmosphere along the banks of Fred Creek through the entire campus," Ron Lee said on the ORU website. "The new retaining walls in the creek channel and the landscaping will be easier to maintain and will give this area of the campus a cleaner look."

The second through sixth phases of the $15.25 million Fred Creek Drainage Improvements project are expected to require extensive retaining walls, rip rap, landscaping and new bridge construction. SI Precast is currently supplying blocks for Phase 2 of the project.

Robinson, the project manager for the Fred Creek project, has since been promoted to Lead Engineer for Stormwater Planning for the City of Tulsa. He says the city will continue working with large block retaining walls for their erosion control needs throughout the city.