The Kennedy Space Center is a unique facility and an extremely difficult one to maintain. Built between 1949 and 1963, primarily on Everitt Island, all but operational areas are designated as a wildlife refuge, containing over 500 species of birds, reptiles, and animals, many of them on the endangered spices list. The center runs 34 miles north to south and is 10 miles at its widest point. The center averages 5 ft about sea level, and contains 157 miles of paved roads and 87 mile of dirt or gravel roads.
Operating this high tech center and adhering to deadlines and launch schedules while maintaining harmony with the environment is no easy task for NASA Center Director Robert Crippen nor the base operations contractor, EG & G Florida. Special Maintenance headaches exist in a facility that must work around launch deadlines and obtain environmental approval for literally every maintenance problem that affects drainage, soil, disturbance or removal. The center's infrastructure and aging highways built in the 1940 to 1970 period are subject to severe loads caused by heavy equipment, the never ending tour buses that are a part of one of America's most popular attractions, heavy fuel trucks, and a continuous stream of traffic. Roads and culverts are aging and require a lot of maintenance. The center is faced with tight budgets that are constantly reviewed to keep costs low. Base operations are managed under contract by EG & G Florida, a subsidiary of EG & G Inc. EG & G is responsible for all building and grounds maintenance including roads and railroads, security, even fuel handling.
Rodger Sorey, branch manager for EG & G, has been at the center 32 years. He and his staff must be innovative in highway maintenance. "We need products and maintenance procedures that reduce costs and make roads last longer," states Sorey. "We need product maintenance procedures that reduce costs and make roads last longer," states Sorey. "Maintenance must be considerate of the environment since we work in the center of a national wildlife preserve. Still, runoff into the waterways must be avoided." The culverts are a special problem. Both bituminous coated corrugated mental and concrete culverts are 35 to 50 years old and many have reached the end of their useful life. Because of security considerations and difficult time schedules, EG & G and its on-base road subcontractor, USIA, do the majority of their own maintenance work. Occasionally specialized work is bid and let to outside contractors.
Culverts a Special Problem
Each year the center is forced to replace a growing number of aging culverts. Once a road is cut open to replace a culvert, the road invariably settles for three to four years no matter how well the fill is compacted, resulting in a series of patches. Each culvert replacement must be considered to determine how dewatering or siltation would affect the environment. Dewatering and building a stable base in swamp-like environment is quite a challenge. To prevent danger to workers, the cut must be tapered back to a 2 or 3 to 1 slope, resulting in a wide, deep hold. Excavations must be well below the culvert bottom to build a stable base for the replacement culvert. This requires deeper than normal excavations.
In the fall of 1994, Sorey and 8000 Departments engineer Andy Minor decided to try a cost saving alternative to culvert replacement that would not disrupt base traffic flow nor disturb the environment. "Culvert Renew" a profile wall, high density, high molecular weight culvert liner was chosen to rehabilitate two test culverts. "Culvert Renew" is manufactured by Poly Systems Inc. of Steelville, Missouri. The liner has a 100-year design life with very high abrasion and chemical resistance. The decision to use this material instead of other liners or polyethylene pipes was based on three factors:
The liner has a minimum pipe stiffness of 46 psi in all sizes. This high pipe stiffness gives a great deal of resistance to deflection.
It has threaded ends for a positive joint that will not pull apart while winching it through offsets, and the joint is soil tight.
The linter is manufactured from a premium grade resin that is HDB rated (PE 3408). It has very high environmental stress crack resistance to stand up to the gouging and abuse it will recieve when being inserted in a culvert.
Twin 54-in corrugated metal culverts were chosen for the test. The culverts were severly rusted out and on one culvert the bands had bulled apart, creating a severe wash-out on the downstream side that caused the headwall to drop. Both shoulders, which are approximately 20 to 25 feet wide, had experienced severe erosion iorated culvert. The road itself was in danger of collapse. The liner chosen had a 47 .47in OD with a 42in ID. Even though the liner was smaller in size, it would still give 116 percent of the original flow due to the improved manning factor.
However, before the work could begin on the culverts that had been chosen to launch area and the primary road used by the large double-decker tour buses collapsed and was given immediate priority to repair or replace. The twin culverts under the collapsed road were 42in diameter and were installed over 35 years ago. Both concrete and bituminous coated metal culverts were deteriorated due to age, heavy traffic loads, and brackish water. The only liner size that was immediately available was 40.65in OD with a 36in ID. Normally this size would have been unacceptable as a 10 percent clearance is usually required to ensure that the liner would fit through offsets and deterioration in the host culvert pipe. However, due to the emergency, it was decided to use the pipe on hand since the collapsed area would have to repaired in any event, and a point excavation could be easily made.
Pulling heads were made for the pipe by the company. The design is a pie-shaped wedges out of the liner and pulling the nose cone to help the pipe through any offsets. Due to the extremely tight fit, a rear pulling device was designed by EG & G manager Sorey so a cable could be run through the liner pipe and the pipe pulled from both the front and the rear.
First the culvert was cleaned and the bituminous coating removed where possible. The cleaning was accomplished with high pressure washers. Before the cleaning could begin, the "local residents" had to be induced to vacate the culvert. In one culvert, a 6.5ft alligator was chased out, but in the other culvert a 3ft baby alligator was very difficult to chase away. Obviously used to people, and perhaps even fed by the local base personnel, every time he was chased away he would come right back. However the high pressure cleaner scared him and he decided to vacate on the run. The work crews always were quite careful when first approaching a culvert, as an alligator is very fast in the first 10 to 20 ft, and can even catch a dog who gets too close.
After the culvert was cleaned and the nose cone attached to the pipe, the insertion was started. Two winch trucks were used to pull the pipe from both the nose and the rear of the liner. The first 40 ft of liner went in the culvert without too many problems. The next liner section was then rolled down into the ditch and the sections joined together using nylon strap slings tied loosely around the pipe with a long bar, then twisted through the pipe. Since the sections of the liner were 40ft in length and quite heavy, it took two two-man crews to screw it together. it was easier to start the pipe threads if the rear puller exerted a small amount of pressure to pull the pipe tight against the first section while the crews twisted the section to be joined. When both pipe sections were in place, the crews were able to join the two sections in about 15 minutes.
With the sections of pipe joined, the insertion process was started again. this time, however, the winch trucks were unable to pull the liner through a deteriorated section of the culvert. A Gradall bucket crane was then positioned above the culvert, partially on the road and partially on the road and partly on the shoulder. A choke chain was looped around the pipe and the crane's hydraulic arm was used to help pull the liner into the culvert. The wooden rear puller plate, which was made from four pieces of 3/4in plywood, cracked in half and wrinkled the threads on the end of the pipe, but finally the liner went all the way into the culvert.
On the second culvert the same insertion procedure was used with the expectation that the rear wooden pulling plate was replaced with a metal one, and a Caterpillar tractor was used to replace the smaller winch truck. Since space was not a factor it was decided to join the two liner section along the roadway. Once joined, the 80ft section was rolled down into the ditch and the cables, the pulling head, and rear pulling plate were attached. Insertion in the second culvert was anticipated to be more difficult as the top of the culvert was partially missing, and a point excavation at the collapse are was used to pull the top of the deteriorated culvert up so that the liner could get through. When the liner reached the area of the collapse, the 1 1/3in clearance was not sufficient to allow it to pass though the partially collapsed culvert. Again the Gradall bucket crane was used to help force the liner into the culvert. The pipe was deformed about four inches before it finally freed itself and passed though the collapse area. The work crew was amazed at the abuse that the liner received by forcing it though the culvert, and came to the conclusion that it really is almost indestructible. The final section of the pipe was then added and pulled though the culvert.
The entire operation for lining the two culverts had taken a day and a half. This unusually long installation time was due to the collapsed culvert and the small amount of clearance between the liner and the culvert. Had the normally recommended size of liner been available, the time of insertion would have been less than two hours for both culverts and cleaning time would have been reduced. Once the liner pipes had been cut off at the headwall, a hydraulic grout was used to seal the annular space at the ends of the liner to prevent any soil migration through the space. The collapsed area was then filled, compacted, and a new six inch cap put on the collapsed area. The road was immediately opened again to traffic, much to the relief of all concerned.
Back To The Planned Test
When the emergency was over, attention turned to the original demonstration culverts. The section of headwall that had cracked and dropped had to be removed to allow for the "Culvert Renew" liner to be inserted. Also, the collapsed area of pipe on the shoulder was removed. A base fire truck was then used to flush out approximately 19 inches of mud in it. The pipe was then assembled on the bank of the downstream ditch, which was more like a small lake than a ditch. In all, 90Ft of the liner pipe was threaded together then rolled down the bank with a rope attached to the nose cone to guide it into the culvert. The rope was removed and replaced with the pulling cable. This time the Caterpillar tractor easily pulled the liner completely though the deteriorated culvert in less than 20 minutes. The second culvert was assembled on the bank and pulled though the culvert easily in similar fashion. Once the liners had been inserted, the broken headwall was repaired and since the original culvert was in such poor condition, the annular space was grouted to prevent any road collapse due to soil migration.
According to Sorey, "relining culverts rather than replacing them has several advantages. Cost savings average about 65 percent versus replacement. With the age of the base's culverts, many will have to be replaced or relined, so cost savings become a significant consideration. It is also important not to have to disrupt traffic on the heavily traveled roads. Detours are very difficult since in many cases there is no convenient detour route. Closing some roads on the congested base would have been next to impossible. This problem is solved by relining rather than replacing the culverts. "Calculating the flow gave us a big surprise too. The manning factor of the polyethylene liner is much better than either concrete or corrugated metal. In many cases flow capacity remains the same as the original culvert and often flows can be increased by the lining procedure. "Environmentally we are better off any time we do not have to do major excavations. In our environment with brackish water and heavy traffic loads, the 100 year design life is a big plus. Overall, I would have to say we were pleased with the lining procedure and as required, hope to do many more in the future."
The proceeding article was based on information submitted by Steve Campbell of Poly Systems, INC., and republished by Public Works issue of March, 1995.
POLY PROFILES TECHNOLOGY, INC
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