should be moderate to rapid, allowing a percolation rate of at least 

 1 inch per hour [103]. 



Normally, septic systems should be avoided where there is a high 

 water table (typically, if closer to the surface than about 10 feet). If 

 the groundwater beneath the septic tank absorption field rises to the 

 level of the discharge pipes, the saturated soils cannot absorb the 

 effluent. The groundwater may become grossly polluted. In the worst 

 situations the unpurified effluent may even rise to the surface, where it 

 will drain directly into an adjacent water body. 



Properly spaced septic tanks on slopes of less than 15 percent 

 usually do not create serious problems if soil properties are adequate 

 for sewage absorption; however, on steeper slopes, controlling the down- 

 hill flow of the effluent may be difficult. Steep slopes can allow 

 improperly filtered effluent to reach and contaminate receiving 

 waters [103]. 



Several other precautions may also be observed. Overflow pipes, which 

 convey sewage directly to the water basin when the septic tank fills, 

 should be prohibited. Seepage pits should be discouraged in favor of 

 septic drainage fields. Finally, septic tanks and similar private sewage 

 treatment facilities should be inspected on a regular basis by the local 

 health department to ensure proper working order and adequate treatment. 



4.11 OVERLAND TRANSMISSION SYSTEMS - SUBPROJECT 11 



Overland transmission systems are a natural outgrowth of OCS-related 

 community and industrial development. Transmission lines for oil, gas, 

 electricity, water, sewage, and telephones and various booster or pump- 

 ing stations are the primary system components. Proper location and 

 construction of these components can reduce their impact upon both the 

 narrow utility corridors they occupy and the entire inland ecosystem. 

 This subproject covers only buried (or underground) transmission systems 

 onshore. 



4.11.1 Summary 



Overland transmission systems serve as linkages between onshore 

 facilities and community growth areas. Oil and gas-related facilities, 

 such as oil refineries, petrochemical plants, gas processing plants and 

 market terminals are linked to each other and to their source of oil or 

 gas by pipelines. These originate at oil tank farms near marine terminals, 

 LNG regasification plants, or landfalls of marine oil or gas pipelines. 

 All 3f these facilities are also served by utility transmission lines for 

 phones, electricity, water and sewage, and possibly natural gas. Addition- 

 ally, induced growth in nearby communities creates a demand for these 

 utility services and transmission lines. 



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