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Licensed for the sole use of the purchaser. See license agreement penalties for distribution. PAGE 4 COMPRESSEp GAS ASSOCIATION INC. CGA G-1.8-2017 5.2 Carbide lime ponds Carbide lime co-product from the acetylene manufacturing process is often stored and/or processed in lime ponds before sale. In some cases, the lime pond may be regulated through a federal or state storm water or na- tional/state pollution discharge elimination system (NPDESISPDES) permit. These permits can have require- ments to retain all lime and water in the pond.They may also have pH,total suspended solids,and/or biochemical oxygen demand discharge limits and monitoring requirements for any waters released from the pond. Occasionally states have regulated lime ponds through a groundwater discharge permit. However, when a layer of lime of at least 12 in (30 cm) is retained undisturbed on the pond bottom, percolation to groundwater is unlikely to occur. Studies conducted at various undisturbed lime ponds have typically shown that the pH of soil beneath a lime pond is not affected below 5 ft (1.5 m). 5.3 Canadian regulations In Canada, the issues covered by 5.1 and 5.2 are generally addressed by provincial regulations. Operators and handlers of lime ponds and lime should consult the regulations of the province in which they are working. Federal requirements are usually only applicable(except Transportation of Dangerous Goods Regulations requirements) when material crosses provincial or international boundaries [8], 6 Potential environmental issues If not operated and maintained properly, lime ponds can impact the environment. The nature and extent of the potential impact is dependent on the site conditions,construction of the ponds, and maintenance and operational practices. In general,the primary environmental concern associated with lime is its relatively high pH as described in 5.1. 6.1 Soil Typically, only the soil immediately adjacent to a lime pond is impacted by lime.The pozzolanic effect of lime and certain soils at the bottom of the pond forms a relatively impermeable barrier to the migration of high pH water. The thickness of the lime-impacted soil beneath the pond depends primarily on the soil type but typically extends only a few feet below the bottom of the pond. Impacts to soil are evidenced by an elevated pH relative to the background. It is important to characterize background pH levels because some soils are naturally alkaline. 6.2 Groundwater Unless lime ponds are in direct contact or in very close proximity with groundwater, few groundwater impacts occur.The hydraulic"head pressure"caused by a large impoundment can affect the flow of lime or lime migration to groundwater, especially near a surface water body. Impacts of the lime on groundwater are characterized by elevated pH (above background) and an increase in calcium salts. Soil type also affects the migration of lime. Soil predominately comprised of sands and gravel enables the lime to migrate more readily. Since carbide lime is a slurry of solids that dewaters as it sets,the lime often provides a self-lining barrier to inhibit the migration of lime or lime water. In certain soils,a pozzolanic barrier forms in the bottom and sides of the pond to further inhibit the migration of lime or lime water. 6.3 Surface water Surface water can be impacted if lime is released from a pond and migrates over land through storm drains or ditches into surface waters. Release of lime or high pH water can result if sufficient freeboard is not maintained and lime escapes the containment berm or sidewall. Lime can also escape from ponds through cracks or breaches in the containment berm or sidewall. Evidence of impacts can include elevated pH levels and increased turbidity. 6.4 A i r Although carbide lime has a characteristic odor, impacts to air quality are negligible.When excavating limo from ponds, dust is generally not a problem. However, water can be used to suppress dust if it becomes an issue. Ensure that water used as a dust suppressant is captured to prevent any off-site impacts. This document licensed for the sole use of the purchaser. It may not be shared with any other person or used after the expiration date without the express written permission of the CGA. Any unauthorized use, reproduction. distribution, or modification of this printed page will result in a$5,000 liquidated damages fee plus loss of access to GGA publications for one year for your company.