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The urban quarry: the former Stapleton Airport in Denver becomes a high-profile recycling project. (C&D Series).

The scope of the project is overwhelming. Six million tons of runway, taxiway and concourse concrete and asphalt. Fleets of trucks, loaders and several pieces of recycling and screening equipment. Hundreds and hundreds of feet of conveyors. Six years to process the material and 10 years to use and market it.

There were probably dozens of reasons why Recycled Materials Co. (RMC), Arvada, Colo., could have backed off from its proposal to recycle the runways, taxiways and parking lots of the former Stapleton International Airport in Denver.

But CEO Ken Buesing, president Mark Wachal, general manager Rick Givan and the company's other leaders didn't back away from the project. Instead, they have followed up on every commitment and turned the former airport into a bold experiment in urban quarrying.

In the second half of 2002, RMC entered its fourth year of concrete and asphalt recycling at Stapleton, continuing on a project that produces up to 5,000 tons of secondary aggregates each day.


Very few new airports have been built in the U.S. in the past two decades, and thus very few old airports have been taken out of service.

But civic planners in the Denver area made the decision to build a major new airport at a greenfield site and to close operations at the former Stapleton International Airport.

While commercial airport closings are rare, the scaling back of the number of military bases that has taken place in the past 10 years has resulted in several military airfields being de-commissioned.

One of the de-commissioned sites was Lowry Air Base, also in Denver. When this Air Force training center and airstrip was closed and re-developed, Recycled Materials Co. was a key part of the demolition and development process.

"Lowry was a major military base that was scheduled to shut down," says RMC general manager Rick Givan. "At the time it happened, the company was involved in several contracting segments, but the one our president Mark Wachal wanted to focus on was concrete recycling," he adds.

The company was the winning bidding for several contracts at the Lowry site, eventually recycling parts of runways and roadways and builing a sports complex and some of the new roads in the neighborhood being developed at the former air base site.

Givan says the company's experience with the Lowry project helped prepare RMC for the Stapleton project. "We learned a good deal about government applications and proposals, about working with future users and about finding applications for recycled concrete and asphalt," notes Givan.

In the mid-1990s, as construction of the new Denver International Airport proceeded, the City of Denver formed a committee to begin making plans and holding public forums concerning the redevelopment of the seven square miles of land comprising Stapleton Airport.

The committee and the resulting Stapleton Development Foundation consisted of elected officials and citizens from surrounding neighborhoods as well as business owners and executives with land planning experience.

Mark Wachal, with his Lowry redevelopment experience and knowledge of materials recycling techniques, attended the public forums and eventually served with the foundation. His involvement with the foundation ensured that the recycling of demolition materials generated at the airport remained on the redevelopment agenda.

Ultimately, Recycled Materials Co. had to bid against several major contracting and engineering firms in 1998 for the right to remove and recycle the estimated 6 million tons of concrete contained in Stapleton's runways, roadways and parking lots.

"We made a presentation going up against a multi-billion firm that could buy us out with the money in their coffee fund," quips Wachal of the nerve-wracking proposal stage. "They had a nifty PowerPoint presentation; we had some transparencies on an overhead projector, and unfortunately the bulb burned out on the projector."

But David defeated Goliath, with the RMC proposal being accepted. Now, the company was committed to a 6-year demolition project with a 10-year marketing timeframe and to finding a home for 6 million tons of recycled concrete and asphalt.

"We had a public persona of confidence, but, sure, we lost some sleep over committing to finding end markets for 6 million tons of material," says Wachal.

The company was very careful in negotiating the terms of its contract, Wachal says. "It was important to have clearly defined contracts, due to changing administrations and staffs within the City of Denver," he notes.

Despite the contract caution, RMC has assumed a significant risk with its arrangement. "We were the only company who said we view the concrete and asphalt as resources," says Givan. "We aren't charging the city to remove the material, but we needed to have the time and the space to produce and market the materials."


The redevelopment of the former Stapleton land has been a playground for Urban planners, who seldom have a seven-square mile parcel of land within a major city to redevelop.

Foundation leaders and lead developer Forest City Enterprises, Cleveland, eventually sculpted a master plan for a community simply called Stapleton, with a mix of housing, retail, recreation and office space plotted out.

But before the new homes and shops could go up, work would have to start on removing the runways, taxiways and roads of the former airport. Recycled Materials Co. moved into the site of the Stapleton urban quarry with an arsenal of equipment.

The company is now in its third year of tearing up runways (which in some places have layers of concrete and asphalt up to four feet deep), transporting material to on-site and off-site crushing plants for selling or stockpiling.

At the runway sites, large Caterpillar loaders with 12-yard buckets scoop up chunks of runway into 26-ton trailer trucks dedicated to moving the runway material to recycling plants.

Before the runway is scooped up, it is broken with a guillotine or gate breaker made by Walker Equipment Mfg., Moriarty, N.M. The device is capable of cracking all the way through the paved taxiway and runway layers, which usually range anywhere from 12- to 36-inches deep, according to RMC project superintendent Myron Saylor.

Shallower surfaces, such as parking lots and roadways, are broken up with a roll-behind rotary impactor made by Impact Roller Technologies, Omaha, Neb.

The asphalt or concrete rubble can be destined for one of several crushing plants that handle the several thousand tons of material generated daily at the Stapleton site.

Two of those, plants are on-site at Stapleton, while five RMC mobile plants can be located at various sites, including at a nearby landfill and across town at an RMC property in Arvada.

One of the on-site plants features a large Nordberg (now known as Metso) jaw crusher that serves as the first step in creating a 12-1/2-inch minus product that is being stockpiled for a nearby federal government facility involved in a land remediation effort. This large-spec material is being moved via a 1,300-foot conveyor system that stockpiles it on the edge of the Stapleton property.

While this product is one important end market, the other materials created during the recycling process are also sorted, washed and prepared for sale as various gravel or sand grades of material. Virtually nothing is wasted.

After large chunks of runway leave the jaw plant, a magnet pulls out re-enforcing steel for the scrap market, the government-spec material heads down its long conveyor path, and smaller concrete pieces are screened into a 2-1/2-inch minus and 3/8-inch sand and gravel grades.

The end result of material passing through the crusher, a trommel, several screens, and (in some cases) a wash plant are seven grades of saleable material, plus the scrap steel.

According to RMC plant superintendent Jack Heard, the thick runway concrete has been an ideal feedstock for the 12-1/2-inch minus material desired by the government end user. "I don't think we could make this material out of highway concrete--it's not as thick," he notes.

The material stream is also clean, although one contaminant that has to be watched for is the fiber PetroMat moisture barrier that is often installed beneath runway surfaces. The company has used both manual pickers and air jets to remove fiber from the stream.

The other on-site plant includes a HazMag primary impactor that processes concrete rubble initially, before sending material on one of several paths that may involve a secondary impactor and a series of screens.

Among the key products made at this plant are roadbase materials and a Spec #57 coarse aggregate. Smaller materials are sent to a wash plant where sand and #8 gravel grades are produced.

A key offsite plant has been sited at the Denver Arapahoe Disposal Site (DADS) landfill run by Waste Management Inc. Recycled Materials Co. has sub-leased land at the site and placed a scale house to accept both material generated at Stapleton and brought in by customers who generate concrete and asphalt at construction and demolition sites. (Washout material from ready-mix contractors is also accepted at the site.)

Material is processed periodically by one of RMC's five mobile Hartl crushing and screening plants. One of the RMC Hartl plants is often kept busy in Arvada (which is about 15 miles from the Stapleton neighborhood). The RMC facility in Arvada features a mobile Hartl plant on tracks, which is operated by remote control, producing a specification concrete road base product and screened rock that is used in both municipal and private markets.


The array of plants and equipment that RMC deploys in and around Denver can only remain in service as long as there are end markets for material.

One of the keys to RMC's success has been the tireless efforts of Mark Wachal to preach, lobby and cajole for the cause of recycled aggregates.

Ken Buesing and Wachal started RMC in 1987, entering the business with a background in grading, paving and rock crushing. From the beginning, Wachal says his focus was on "value engineering--using waste to make products for on-site or to sell off-site."

Wachal has become a leading advocate for the production and marketing of high-quality secondary aggregates. "As a company, we object to giving recycled products a lesser standard to meet," he remarks. "It can meet the highest standards."

Building product acceptance has become a vital part of RMC's business plan and Wachal's role in the company and the industry. "We are dedicated to the belief that you never make a product you have to apologize for," he says. "A lot of people are looking for reasons for us to fail; they have the mindset that, `It's recycled, it's second rate.' But we have disarmed some of the naysayers by meeting and exceeding the quality expectations of our customers."

The keys to building market acceptance include careful operations practices, making sure transportation agency specs include recycled aggregates as an option and consistently knocking on contractor and engineering firm doors and letting them know the material is available.

"We were able, in 1988, to get asphalt and concrete rubble accepted by the State of Colorado as a source of material," Wachal notes. He worked with the Colorado School of Mines, Golden, Colo., to produce technical data supporting recycled aggregates in ready-mixed concrete materials applications.

Wachal has been able to stay in front of contractors via his long-time volunteer involvement with the Colorado Contractors Association Inc. (CCA). The Englewood, Colo.-based group is the state chapter of the Associated General Contractors of America. After serving in several posts and on several committees, Wachal is currently chairman of the CCA.

RMC is also a long-time member of the Construction Materials Recycling Association (CMRA), Lisle, Ill.

Contacts made via his CCA work have helped Recycled Materials Co. build a bank of more than 800 customers in the Rocky Mountains and Great Plans regions. In addition to its Lowry Air Base and Stapleton Airport projects, RMC has also been the pavement removal and recycling contractor for several major interstate highway projects.

What has helped distinguish RMC has been its ability to work within Colorado to build higher-end markets for recycled aggregates. "We couldn't make a living just making fill materials," says Wachal. "We needed to make higher-end-use products. As a result, I think Colorado is ahead in its acceptance of recycled products in ready-mix and asphalt paving applications."

But lobbying on behalf of recycled materials and commissioning studies is only the first part Of the acceptance process. It is then up to the company to make products that are consistent and clean enough to keep customers happy. "There is a psychological objection contractors have to seeing a piece of metal, wood or plastic in a pile of aggregate. A piece of plastic can be just 1/200th of a percent of a load--well within the material spec--but its visibility within a pile can turn a customer off. It's our job to keep that plastic out of there," says Wachal.

The massive volume of the Stapleton project has tested RMC's ability to meet its quality standards and to find sufficient end markets.

Without wanting to sound too optimistic (a sure way to jinx something that is running smoothly), Givan is pleased with the end market arrangements that have been made for the projected 6 million tons of material at Stapleton.

The projected need for the 12-1/2-inch minus material at the federal government site has been one key end market component. The runway-derived product has proven ideal for the civil engineering application, and RMC and the federal government were able to negotiate a contract that provides a profit margin for the company.

Another major step was taken with the DADS arrangement. This not only provided RMC with an additional staging area for processing, but it also allowed it to work with a major aggregates producer that is using recycled asphalt and concrete as part of its material blend in both asphalt and ready-mix concrete paving materials.

"This was important, because we really didn't want to get into the ready-mix business ourselves to prove that these materials could work as aggregate in concrete and asphalt mixes," says Wachal.

And finally, the nature of the project has allowed RMC to work on-site with a range of contractors, sub-contractors and developers to provide material as it is needed in the redevelopment of Stapleton Airport's land into residential neighborhoods, commercial shopping centers, a golf course and other uses.

"We're very pleased with our relationship with the lead developer, Forest City Enterprises of Cleveland," says Givan. "They have really been supportive in urging the use of our materials by other developers and contractors involved in the redevelopment."


It seems hard to fathom, but RMC may actually be past the mid-way point in terms of removing and crushing Stapleton's runways.

The company is certainly at a point where it has to consider its future beyond the Stapleton project. "We have experienced tremendous personal satisfaction in making materials that have met or exceeded specs and been accepted by end users," says Givan. "This project and concept is so successful, it's going to be unfortunate when we run out of materials. Our customer base will miss the material."

Wachal and Givan believe they can duplicate the effort at other major demolition and decommissioning sites, and they are looking at other opportunities in California, Texas and other states where projects of similar scope could present themselves.

"The concept of an urban quarry has proven successful," says Givan. "We think it sets the tone for large urban projects from here on out."

While projects that can yield 1.3 million tons of concrete and asphalt in one year (that was Stapleton's 2001 yield) are rare, RMC is keeping tabs on major projects that could allow them to stay in the urban quarrying business.


Mark Wachal, president of Recycled Materials Co. (RMC), Arvada. Colo., does not tolerate closed doors for recycled aggregates.

Wachal has been aggressive in pushing for the acceptance of recycled concrete and asphalt as a paving material aggregate, and he has spent his time, energy and money to make sure that the state of Colorado has not put up barriers to the use of the material.

Through his involvement with the Colorado Contractors Association Inc. (CCA), Englewood, Colo., Wachal has made friends with the contractor community that is the ultimate customer for secondary aggregates.

Wachal is currently chairman of the CCA, which is the state chapter of the Associated General Contractors of America. During his several years of involvement with the group, he has been able to vouch for the quality and legitimacy of secondary aggregates and to help ensure that RMC does not portray an image of a fly-by-night company that is desperately trying to find a destination for its products.

To help overcome technical objections, Wachal has worked with the Colorado School of Mines, Golden, Colo., to provide the data to contractors that recycled aggregates could be made with the surface qualities and the consistency they need. "Their researchers couldn't find a reason why recycled materials are considered inferior." says RMC general manager Rick Givan. "In fact, in many applications they are superior due to their residual cementitious content"

Wachal's efforts have helped make Colorado a model state in terms of its acceptance of recycled aggregates within paving materials. "If all 50 states had someone like Mark Wachal producing and then lobbying for high-quality secondary aggregates, our industry would benefit tremendously," says William Turley, executive director of the Construction Materials Recycling Association, Lisle, III. While Wachal cannot be cloned and sent to each state, his work provides a model for other recyclers to follow.


For decades, airplane engines roared and taxis and shuttle buses poured in and out of bustling Stapleton Airport, located in the northeast corner of Denver.

When the last airplane departed from Stapleton in 1995, the silence was probably eerie to surrounding residents.

The lack of activity was also noticed by surrounding wildlife, which has quickly made itself at home in the seven square miles of the former airport.

A wildlife census would reveal a considerable population of prairie dogs, the ubiquitous ground squirrels of western North America. The dogs can be seen leaping from burrow to burrow at grassy areas throughout the site.

Fewer in number but more noticeable are the coyotes re-populating the airport land. Truck drivers working on the site are frequently challenged to races by playful coyotes sprinting over and across the idled runways.

As the land is redeveloped into residential neighborhoods, shopping centers and office parks, much of the wildlife will once again be on the lookout for new territory. But for now. the Stapleton land has reverted to its pre-urbanization days as part of the Western Prairie.


Recycled Materials Co. is entering the second half of the Stapleton concrete recycling project. Read more in an exclusive online sidebar at

The author is editor of Recycling Today and can be contacted via e-mail a
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Title Annotation:Recycled Materials Co.
Comment:The urban quarry: the former Stapleton Airport in Denver becomes a high-profile recycling project. (C&D Series).(Recycled Materials Co.)
Author:Taylor, Brian
Publication:Recycling Today
Geographic Code:1U8CO
Date:Dec 1, 2002
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