Evaluation and Reporting on Contaminant Hydrogeological

12-12-01

Conditions at the Tajiguas Landfill

Page 13 of 24

All groundwater samples should be analyzed for all gasoline constituents as well

as for all oxygenates and lead scavengers by EPA Method 8260b. All groundwater

samples should also be analyzed utilizing EPA Method 8260b for all constituents,

including but not limited to, all chlorinated solvents as well as 1,4, dioxane. In

addition, all groundwater and surface water samples should be analyzed for total

and fecal coliform and enterococus bacteria. Finally, all chemicals, identiyed in the

groundwater in the past must be analysed as well.

All potential point sources of contamination which were burried in the landfill

such as barrels of solvents should also undergo point source subsurface

investigations.

The scale house and maintenance shop should undergo an immediate point

source subsurface investigation based upon a complete Phase I Environmental audit

to identify gasoline, chlorinate solvents and other VOCs commonly associated with

this type operation.

H

OLOCENE

F

AULTING AND

P

OTENTIAL FOR

S

URFACE

R

UPTURE

For the 1988 Expansion EIR, an acceleration number of 0.39g was used. They

then revised their number to 0.354g but still claimed that the slopes were still stable

at 2/1. The EIR consultant, Geologic Associates, performed the new slope stability

analysis using a maximum probable earthquake ground acceleration of 0.21g. This is

the original number used in the same consultant’s projection for benchfill stability.

The slope stability analysis was done under the assumption that the landfill mass is

not saturated. Their disclaimer states that if the landfill was saturated then they

would not be held to their stability analysis projections.

Another issue is whether or not the proposed expansion is resting upon a

Holocene fault. The draft EIR makes no mention as to whether or not the proposed

landfill expansion will overly an active fault. On page 3-1 of the September 2001

SLOPE STABILITY EVALUATION, no mention is made as to whether or not local

faults may cause surface rupture in the future which may impact the landfill and/or

landfill expansion. Also, there is no mention as to whether or not these local faults

are Holocene. Furthermore, the text refers to the Dames and Moore, 1995 report, yet

does not expressly concur with the reports findings nor does it state specifically that

the Dames and Moore report verifies that the faults in questions are Holocene or not.