Evaluation and Reporting on Contaminant Hydrogeological
12-12-01
Conditions at the Tajiguas Landfill
Page 22 of 24
preventing the high water table from intersepting the landfill mass.
Maps and crossection of the bottm of the
2) Provide a detailed study of the faults at the site evaluating the potential impact on
the existing landfill and on the proposed landfill expansion.
3) Special attention needs to be given to all potential point sources. A historical
environmental audit of the types of waste that may have been placed in the
landfill may yield specific point source locations of gasoline and solvent related
constituents within the landfill to be investigated. The landfill operator has 90
days to perform subsurface investigations to define the point sources of all
releases as well as the characteristics of all constituents of concern after a release
has been confirmed (Article 4, §20425. (b) & (e)) . The VOCs identified in
groundwater are from unauthorized release(s) from point sources(s) which have
not been delineated.
4) Establish a groundwater monitoring well network curtain between the landfill
waste and the Arroyo Quemada Community which intercepts all subsurface
conduits that may exist between the source and the receptor.
5) Perform a water budget for each individual water body and each
hydrostratigraphic unit as well as for the whole watershed.
6) Analyze the collection trench’s effectiveness. The water balance must include a
determination as to how much water is used for irrigation, what types of earth
materials are undergoing irrigation, all methods of distribution and application of
irrigation water, and where and when the irrigation is performed.
7) Perform a subsurface investigation which isolates all discrete water flow regimes
from the landfill mass through the alluvium and beyond the interceptor trench as
well as for the portion of the groundwater flow within the Vaqueros Formation
which allegedly flows eastward and may discharge to the Arroyo Quemado
alluvium. Geophysical methods like areal and vertical temperature surveys can be
effective for this purpose. After these hydrogeological flow regimes have been
defined through subsurface investigations, their characteristics should be
evaluated by fate and transport modeling.
8) Collect continuous information on the water flow through the culvert systems
including the total amount of water discharged at the surface water discharge
point. Hydrographs and flow recorders will be suitable.
