Evaluation and Reporting on Contaminant Hydrogeological

12-12-01

Conditions at the Tajiguas Landfill

Page 16 of 24

presence of MTBE is somewhat odd at a landfill. MTBE is a compound used as a

gasoline additive. We typically find it along with BTEX compounds at our LUFF

projects, but not at landfills. Since it has not been consistently present in MW-4

several potential sources are possible. Gasoline may have been recently spilled at

the equipment service area or during the construction of the collection

trench.................MTBE should be evaluated since it is inconsistent with typical

landfill impacts.” No effort has been made to define the source of MTBE at the

landfill.

(94 Correspondence.tif, Images 30 thru 33)

A February 1, 1996 County letter to the Regional board reports that the December

11, 1995, fourth quarter sampling event, had the following compounds identified in

groundwater monitoring wells:

1) LCRS @ Tank

chlorobenzene @ 1.1 ppb

chlorodifluoromethane @ 5 ppb

fluorotrimethylsilane @ 13 ppb

trimethylsilane (2~methoxyethyl) @ 1 ppb

2) MW#2

chlorodifluoromethane @ 4 ppb

fluorotrimethylsilanevc @ 2 ppb

3) MW#3

chlorodifluoromethane @ 3 ppb

fluorotrimethylsilane @ 1 ppb

4) MW#4

vinyl chloride @ 0.54 ppb

trans-1,2-dichloroethene @ 0.69 ppb

1,1-dichloroethane @ 0.7 ppb

chlorodifluoromethane @ 6 ppb

fluorotrimethylsilane @ 9 ppb

2-methylbutane @ 1 ppb

methoxytrimethylsilane@ ? Ppb

5) MW#12 - unknown hydrocarbon @ 5 ppb