78 section furnished by the Users which permitted the ray of light to be split by means of mirrors into 1812 and then continue to 1813. The “Y” section was mounted on two 6’ x 18’ x 12’-high steel frames set on concrete bases. Station 1815 consisted of three steel towers approximately 7’ x 8’x 25’ high using standard 6”-pipe for its legs, which were enclosed with weatherproof plywood houses having plexiglass windows. The User-furnished mirrors were mounted on the steel towers. Station 1816 consisted of two L-shaped 4’ thick reinforced concrete blast walls set on a 4’ thick reinforced crete slab in which the Station 1819 pipe abfied. Located at intervals along the pipelines were the pumping stations (Station 1818.01 through 1818.09, 1817.02 and 1841) containing User-furnished pumps for producing the re- quired vacuum. The pumps were mounted on 16’ x 21’ x 4”-thick concrete slabs with a ply- wood house for cover. + . Figure 2-95. CHAPTER I!, SECTION 3 Project 18 pipelines were essentially a long laboratory quality vacuum chamber design to maintain close alignment and be gas tight. Alignment was assured by roller supports that were adjustable in both horizontal and vertical directions. Gas tightness resulted from incorporating approximate 700’ lengths of welded spool, which had bolted flange joints with OTing gaskets to all metal bellows expansion joints. Fixed anchors midway between the expansion joints maintained the position of each pipe spool. Pump stations and junction points along each line also had expansion joints on both sides of each station and the pipe at these same locations was rigidly anchored. The pipeline supports consisted of welded steel “A” frames spaced 20 feet on center and were constructed of 6-inch pipe columns and angle bracing. The supports were braced one to the other and supported on 2’ x 2’ x 6’ isolated concrete footings. Support heights varied from approximately 3 to 13 feet to allow for grade variation. All of these stations were located and oriented by the Users, and from their infor- wots Stations 1815 Mirror Towers Page 2-105