Page 35 - 2019 Sustainability Report

WASTE MANAGEMENT

We are committed to improving resource efficiency
through reuse, recovery and/or recycling of waste
materials in our businesses. We also dispose of waste The 282-foot-high Brumadinho Dam in Brazil
using safe and responsible methods. was built using the “upstream” method in which
terraced embankments are constructed successively
In recent years, following the failure of the Brumadinho higher on the upstream side of the dam as the
Dam at a Vale iron mine in Brazil, there has been increased impoundment fills with tailings. Thus, it was not
attention by regulators and the public to the environmental a single engineered structure. Brazil has now
and safety risks associated with the storage and disposal of banned new upstream tailings dams and ordered
mine tailings. Although our aggregrates operations result the removal of existing ones. None of Martin
in certain waste products, ours are meaningfully different Marietta’s 34 dams, all of which are located in the
than tailings produced through metals mining. Whereas, in
a metals mine, a very high percentage of the mined material United States, were constructed using the upstream
becomes waste or tailings (e.g., some copper mines waste method. The vast majority of our dams are under
in excess of 80 percent of their raw material), the waste 30 feet, and none exceeds 70 feet in height. All of
7
fraction in our quarries and mines is generally less than 20 our dams are designed and operated in compliance
percent of the mined stone. with stringent U.S. regulations, including those
of MSHA, various states and the Army Corps
Further, tailings in metals mines can release toxic metals, of Engineers. Additionally, these structures are
such as arsenic and mercury, and may lead to acid mine regularly inspected by our qualified personnel. The
drainage (caused by microbial action on sulfide ores) which majority of our dams are maintained in connection
can result in significant environmental impacts, particularly
in the case of a sudden release. Our operations, on the other with fresh water ponds.
hand, involve mining limestone and granite; the resulting fines
are non-hazardous.

Notwithstanding these important differences, we attempt Below grade settling pond at
to minimize the need to store and/or dispose of aggregates Medina Rock & Rail.
waste products at our facilities by selling the fine material
from our processes for reuse in other commercial activities.
We often sell fine material as a replacement for natural sand
where customer specifications allow. To the extent that we
maintain settling basins for fine material on our mine sites,
these are generally constructed below grade in mined out
areas of our pits or in specially engineered settling basins.
These pits and basins are regulated by MSHA, as well as
various state laws, and are subject to multiple inspections
each year. Further, to the extent water is discharged from
a pit or basin, it is regulated by the CWA and various state
laws and subject to periodic monitoring.

These pits and basins often serve as more than simply
a place to collect the fine rock fraction. As an adequate
supply of water is essential at any aggregate mining
operation for processing and dust control, water from our
settling basins is reintroduced to our process. This reduces
our reliance on other water sources and lessens stress on
local aquifers and surface water bodies.

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

35 / MARTIN MARIETTA / SUSTAINABILITY REPORT / 2019