Evaluation and Reporting on Contaminant Hydrogeological

12-12-01

Conditions at the Tajiguas Landfill

Page 5 of 24

movement and juxtaposes the Rincon and Monterey rocks. The projected trace of

this fault would cross the canyon bottom. This fault has not been mapped directly on

the site. (D&M, 1988)

S

ECTION

A

Groundwater in contact with landfill waste

A pumping system removes water coming from the upper canyon area behind

the landfill in the canyon bottom in attempt to reduce inflows into the landfill bottom.

Some surface water and groundwater however, enters the landfill along several

paths, the most important of which may be the streambed and the streambed

alluvium left in place under the landfill. Another source of recharge for the water

table in the landfill would be direct infiltration of the rainfall.

The basal groundwater table (see September 2001 Hydrologic Investigations

Status Report by ARCADIS G&M, page 15 of 17, Image 110) within the Tajiguas

Landfill waste mass has been defined by the groundwater present in monitoring and

dewatering wells located throughout the landfill (see

GeoSolv cross section

, based

upon well data from the July 2001 SEMI-ANNUAL WATER QUALITY MONITORING

REPORT PREPARED BY COUNTY OF SANTA BARBARA PUBLIC WORKS

DEPARTMENT SOLID WASTE & UTILITIES DIVISION). This is a clear violation of the

5-foot separation rule which states that the bottom of the landfill waste mass must

be five or more vertical feet above the highest seasonal groundwater table.

(Combined SWRCB/CIWMB Regulations Division 2, Title 27, Article 3, §20240 and

Title 23, Divison 3, Chapter15, Article 3, §2530)

A review of the Collection Trench Profile and Details in the June 17, 1998

Corrective Action plan shows that the original trench excavation was founded in at

least eight (8) feet of unweathered Rincon to intercept some of the underflow of

groundwater contaminated by the landfill from exiting the confines of the landfill and

migrating offsite to the beaches and ocean. Although, this implies that the

unweathered Rincon is impermeable, the Environmental Impact Report, TABLE 3.2-3

STRATIGRAPHY OF TAJIGUAS LANDFILL PROJECT SITE) states that the “The

unweathered Rincon is mainly massive, but zones of intensely fractured rock have

been observed.” The Environmental Impact Report, page 3.3-9 states, “The

groundwater flows from topographically high areas downward to stream channels,

where the flow emerges as discharge to the streams if the water level is high