Waste Management 2007 Annual Report Download - page 39

stable, solid form, which meets regulatory requirements, can be deposited in our secure disposal cells. In some
cases, hazardous waste can be treated before disposal. Generally, these treatments involve the separation or removal
of solid materials from liquids and chemical treatments that transform waste into inert materials that are no longer
hazardous. Our hazardous waste landfills are sited, constructed and operated in a manner designed to provide long-
term containment of waste. We also operate a hazardous waste facility at which we isolate treated hazardous waste
in liquid form by injection into deep wells that have been drilled in rock formations far below the base of fresh water
to a point that is separated by other substantial geological confining layers.
We owned or operated 271 solid waste and six hazardous waste landfills at December 31, 2007 and we owned
or operated 277 solid waste and six hazardous waste landfills at December 31, 2006. The landfills that we operate
but do not own are generally operated under a lease agreement or an operating contract. The differences between the
two arrangements usually relate to the owner of the landfill operating permit. Under lease agreements, the permit
typically is in our name and we operate the landfill for its entire life, making payments to the lessor based either on a
percentage of revenue or a rate per ton of waste received. We are usually responsible for the closure and post-closure
obligations of the landfills we lease. For operating contracts, the property owner owns the permit and we operate the
landfill for a contracted term, which may be the life of the landfill. The property owner is generally responsible for
closure and post-closure obligations under our operating contracts.
Based on remaining permitted airspace as of December 31, 2007 and projected annual disposal volumes, the
weighted average remaining landfill life for all of our owned or operated landfills is approximately 30 years. Many
of our landfills have the potential for expanded disposal capacity beyond what is currently permitted. We monitor
the availability of permitted disposal capacity at each of our landfills and evaluate whether to pursue an expansion at
a given landfill based on estimated future waste volumes and prices, remaining capacity and likelihood of obtaining
an expansion permit. We are currently seeking expansion permits at 54 of our landfills for which we consider
expansions to be likely. Although no assurances can be made that all future expansions will be permitted or
permitted as designed, the weighted average remaining landfill life for all owned or operated landfills is
approximately 37 years when considering remaining permitted airspace, expansion airspace and projected annual
disposal volume. Remaining permitted airspace and expansion airspace are defined in the Management’s Dis-
cussion and Analysis of Financial Condition and Results of Operations section of this report under “— Critical
Accounting Estimates and Assumptions.” At December 31, 2007 and 2006, the expected remaining capacity in
cubic yards and tonnage of waste that can be accepted at our owned or operated landfills is shown below (in
millions):
Remaining
Permitted
Capacity
Expansion
Capacity
Total
Capacity
Remaining
Permitted
Capacity
Expansion
Capacity
Total
Capacity
December 31, 2007 December 31, 2006
Remaining cubic yards ..... 4,265 944 5,209 4,255 1,037 5,292
Remaining tonnage ........ 3,787 893 4,680 3,760 959 4,719
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