30 Sep 01
(1) General. Borrow sites may be investigated during either the pre-design or design phases.
The investigations should determine if adequate borrow material is available for the various layers of the
cover. It is important to ensure that an excess of each borrow type is available in case some of the
material at a borrow site later proves to be unacceptable or investigations indicate the landfill cover is
larger than anticipated. Borrow sources are required for topsoil, select fill, random fill, clay, and
granular materials. Granular materials are required for drainage layers, gas collection layers, and road
surfacing. Larger diameter materials may also be required for ditch linings, gabion structures, and stilling
basins. The availability of both on-site and off-site borrow should be evaluated. On-site borrow will
normally result in substantial cost savings over off-site materials. Off-site materials must be purchased
by the contractor and hauled to the project. If on-site borrow is available, investigations are required to
define the nature and extent of the borrow source. On-site borrow areas can be used for wetland
mitigation if needed. A borrow area grading plan is sometimes required along with profiles showing
excavation limits and subsurface features. Access and haul roads from a borrow source to the landfill
location must also be assessed. Hauling activities may damage access roads and may be a concern to
the public owing to increased traffic volume.
(2) Design Criteria. Potential borrow sites should be characterized by determining material
types and their extent, natural water content, and depth to ground water. In addition, soil samples
should be collected from all materials that will be used in construction. These samples will be used to
determine specific geotechnical engineering properties of the soils. The type of sample and amount of
material required depends on the type of testing that will be done. Samples should also be taken from
each borrow site to verify that the soils are not contaminated. The chemical testing required should be
as outlined in Paragraph B-2e(2) Borrow Soil Testing.
e. Ground Water Monitoring.
(1) General. Closure requirements mandate that the upper aquifer beneath the landfill be
monitored to determine if it is causing degradation of ground water quality. Ground water monitoring
wells are placed both up- and down-gradient from the landfill and are sometimes located within the
landfill footprint. Before the cover is constructed, all existing monitoring wells should be evaluated to
see if they would be useful for long-term monitoring. If any monitoring wells are located within the limits
of construction, it will be necessary to protect, raise, abandon, or relocate the wells. If wells are to be
abandoned, well abandonment procedures required by the state or other government agencies should
be described in the specifications.
(2) Design Criteria. The requirements for monitoring ground water at solid waste management
units, such as hazardous waste landfills, are described in 40 CFR 264 Subpart F--Releases from Solid
Waste Management Units. Ground water monitoring well design criteria are described in EM 1110-
1-4000. Guide Specification CEGS-02522 should be used in contract documents to specify
construction requirements for monitoring wells.
f. Cover Grading Requirements. Development of the grading plans for the various layers is an