Page 50 - 2020 Sustainability Report

ENVIRONMENTAL STEWARDSHIP

Waste Management

We are committed to improving resource efficiency Notwithstanding these important differences, we attempt
through reuse, recovery and/or recycling of waste materials to minimize the need to store and/or dispose of aggregates
in our businesses. We also dispose of waste using safe and waste products at our facilities by selling the fine material
responsible methods. from our processes for reuse in other commercial activities.
We often sell fine material as a replacement for natural
In recent years, following the failure of the Brumadinho sand where customer specifications allow. To the extent
Dam at a Vale iron mine in Brazil, there has been increased that we maintain settling basins for fine material on our
attention by regulators and the public to the environmental mine sites, these are generally constructed below grade in
and safety risks associated with the storage and disposal of mined out areas of our pits or in specially engineered
mine tailings. Although our aggregates operations result in settling basins.
certain waste products, ours are meaningfully different
than tailings produced through metals mining. Whereas, in These pits and basins are regulated by MSHA, as well as
a metals mine, a very high percentage of the mined various state laws, and are subject to multiple inspections
material becomes waste or tailings (e.g., some copper each year. Further, to the extent water is discharged from
mines waste in excess of 80 percent of their raw material), 7 a pit or basin, it is regulated by the CWA and various state
the waste fraction in our quarries and mines is generally laws and subject to periodic monitoring.
less than 20 percent of the mined stone.
These pits and basins often serve as more than simply a
Further, tailings in metals mines can release toxic metals, place to collect the fine rock fraction. As an adequate
such as arsenic and mercury, and may lead to acid mine supply of water is essential at any aggregate mining
drainage (caused by microbial action on sulfide ores) which operation for processing and dust control, water from our
can result in significant environmental impacts, particularly settling basins is reintroduced to our process. This reduces
in the case of a sudden release. Our operations, on the our reliance on other water sources and lessens stress on
other hand, involve mining limestone and granite; the local aquifers and surface water bodies.
resulting fines are non-hazardous.

The 282-foot-high Brumadinho Dam in Brazil was built using
the “upstream” method in which terraced embankments are
constructed successively higher on the upstream side of the dam
as the impoundment fills with tailings. Thus, it was not a single
engineered structure. Brazil has now banned new upstream
tailings dams and ordered the removal of existing ones. None of
Martin Marietta’s 34 dams, all of which are located in the United
States, were constructed using the upstream method. The vast
majority of our dams are under 30 feet, and none exceeds
70 feet in height. All of our dams are designed and operated in
compliance with stringent U.S. regulations, including those
of MSHA, various states and the Army Corps of Engineers.
Additionally, these structures are regularly inspected by our
A below ground level settling pond qualified personnel. The majority of our dams are maintained
in connection with fresh water ponds.

7 D. R. Nagaraj “Minerals Recovery and Processing” in Kirk-Othmer Encyclopedia of Chemical Technology,
Wiley-VCH doi:10.1002/0471238961.1309140514010701. a01.pub2

48 2020 SUSTAINABILITY REPORT