1984-03-21 Regular Meeting - Laserfiche WebLink

Browse Search

r • ~_ 7 • `*s 7 DISCUSSION OF CASED PIPELINE CROSSING ROADS OR STREETS VERSE UNCASED PIPELINES CROSSING ROADS OR STREETS Although cased pipelines have been used for many years, updated technology has brought forth better conditions and safer aspect to pipelines as shown below. The U.S. Department of Transportation, Title 49 C.F.R. Parts 195, State Department of Transportation and Safety, American National Standard Institute (ANSI), American Petroleum Institute (API), Harris County Commissioners are some of the governing organizations under which pipelines are designed that allows pipeline to cross roads and street without casing but requires different types of protection. Although we respect the requirements and ordinances of the City of LaPorte, Texas we sincerely request that the replacement pipeline be installed across city street as shown on the attached plats without casing but coated with 1" layer of concrete reinforced with wire mesh- over the bitumastic coal tar coating. Even if requirements for non-casing calls for additional foot of cover or installation of reinforced concrete slab in the drainage ditches below grade we think more would be accomplished than casing the pipeline. It is thought that the city of LaPorte would be best served giving the safest means living with the pipeline industry. 1. The most important aspect for non-cased road is that the carrier pipe (pipe which contains the liquid) will be cathodically protected by magnesium anodes or electrical rectifiers. With the bitumastic coal tar or epoxy coatings a minimum of cathodic protection will be required. With casing, the carrier pipe cannot be cathodic protected since the casing will prevent the carrier pipe from receiving the cathodic protection current. 2. Also it is very difficult with expansion of the pipe and casing due to wetting and drying of the soil as well as temperature changes the casing and carrier pipe become in contact with each other causing damage to the coating and shorting the casing and carrier pipe. When shorting the pipe and casing occurs, the cathodic protection is partly lost. To correct this shorting of the pipe and casing they must be excavated to remove the short. If the short is not removed additional cathodic protection must be applied and even then the pipe may require removing or replaced if damages are sever. 3. The casing will give a certain amount mechanical protection from external outside forces depending on the type of equipment is used and the experience of the equipment operator. A tooth of a backhoe or a plow installing cable would probably puncher both the casing and carrier. The 1" concrete coating would offer just as much protection as the casing. 4. Lowering the carrier pipe would probably help the chances of less damage of the pipe. Additional cover-in drainage ditches would be beneficial to prevent ruptures. 1 ~ /6