Page 68 - 2022 Sustainability Report
P. 68

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), 1  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.



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


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