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 The
soil is finely divided clay about 1000 feet deep, the water table is about
35 feet below the surface. Conditions ideal for both building and gardening.
Because of its composition, seismic soil liquefaction is not considered
to be probable. The site is behind the Sepulveda Dam in the Sepulveda
Flood Control basin which could impound 17,300 acre feet of water in about
2.25 square miles. The dam is earthen, 57 feet high, and located at the
Northwest corner of the San Diego and Ventura Freeways. The basin is roughly
bounded by Balboa and Victory Blvds. In 1980 the TWRP-JG was built near
the basin's Northeast corner at an altitude of 706 feet. According to
the Army Corps of Engineers this was safe from the "100 years" flood,
whenever that might happen. The Army has since revised its estimation
of safety (in part due to the extensive paving of the Valley), and an
altitude of 714 feet is now considered the minimum for flood safety. The
TWRP-JG engineers are working on plans to conform, probably with walls
and berms. The basin was selected for the TWRP-JG on the basis of six
considerations. -
1.
Availability of land. About 90 acres are now involved. As Los Angeles
increases in population, TWRP must increase in size - the land need
becomes formidable. 2.
Forestalling disruption to the community. As almost continuous construction
over two decades was planned, the TWRP site had to have substantial
distance from residences and a clear shot at freeways. 3.
Proximity to the main sewage line. The Valley's main sewage disposal
line, built in the early l950's, roughly begins in Canoga Park and traverses
Eastward alongside the River, through the basin to Toluca Lake where
it abruptly turns South and dives under the Santa Monica mountains en
route to El Segundo. The TWRP-JG site is right above this line. 4.
Altitude. For both reliability and economy disposing of sewage demands
the use of gravity. While possibly TWRP could have been located at a
higher altitude, e.g. Tarzana, this would have severely restricted the
area it could serve. There is no site at a lower altitude. 5.
The river. Catastrophes do happen. TWRP has to have some last resort
dumping facility. While certainly a final option, dumping sewage in
the river is better than dumping it in the streets. TWRP is next to
the river. 6. Donald C. Tillman. The City Engineer was determined in his desire that Los Angeles have the best and most beautiful sewage processing plant in the world. |
