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• have submitted technical revisions to incorporate CKD disposal standards into their reclamation permits. The technical revisions detail the geochemistry of the CKD. ,round water protec[ion measures and monitoring, dust control, and closure and reclamation. The procedure being followed by the DMG is to incorporate the CKD disposal standards into the permit through the technical revision process. then to include all areas of the operation where CKD is generated, temporarily stored, or transported inro the permit through an amendmen[. From a regulatory standpoint, approval of the amendment makes the CKD an onsue rather than an imporred waste. From a technical standpoint, the cement plant must be included in the reclamation permit area m order to provide regulatory controls over the generation of the CKD, e.g., the types of fuel or chemicals used in [he kilning process, which may effect the geochemistry of [he CKD. In particular. if a cement plan[ were to begin using alternative fuels such as wood, tires, or waste oil, the potential changes to the nature of the CKD should be evalua[ed. This memo discusses some of the details of CKD generation and disposal at the three Colorado cement plants. A discussion of the geochemistry of cement and CICD are provided for background. The Holnam-Boettcher operation and the Southdown-Lyons operation have completed waste characterization studies and have established groundwater monitoring programs. The Holnam- Portland operation has completed waste characterization and some groundwater monitoring, and the Division is processing a TR for continued CKD disposal at [he Portland plant. Based on (a) leach test results, (b) chemical analysis of pit water adjacent to one of the quarries, and (c) CKD waste handling commitments, groundwater monitoring may be perfunctory in some cases because the potential for off-site damage is limited. The latter point - "GIGO waste handling comritments" -was most important in reaching that determination and is discussed in the following sections. PRODUCTION, CHENIISTRY, AND PROPERTIES OF CEMENT Cement is produced by burning limestone and clay at around ?700°F in a horizontal, inclined rotary kiln. It can take up to 2 hours for the raw materials to pass through the kiln depending on its length. Moving down the cylinder, the mixture progresses through four stages of transformation. Initially, free water is driven off. Next, calcination occurs as bound water and carbon dioxide are liberated. After calcination, the limestone has been converted to lime (Ca0). in the third or clinkering stage, lime and decrepitated clay combine to Form calcium silicates and calcium aluminates (see equations following). The fourth stage involves cooling of the clinker. In some cement plants, the firs[ three steps all occur in the same kiln; in other plants, the process occurs in separate calciners and cement kilns. CaCO; + [SiO, + AhO; + Fe,O} + H,O(bound)] + n (limestone) (clay) (heat) -~ 3CaO~SiO, + 2CaO SiO, + 3CaO A1;03 + =4CaO AhO; Fe;O; (mcatcium silicate) + (dicalnum silicate) + Qncalaum aluminate) + (tetracalcium aluminokniie) Compounds on the product side of the above equation comprise about 90 percent of portland cement. The two calcium silicates form approximately 75 percent of cement by weight. When water reacts with the two calcium silicates, tobermorite gel and calaum hydroxide are produced. 3