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Introduction <br />Per the requirements of the Colorado Department of Natural Resources, Division of Reclamation, <br />Mining and Safety (DBMS), this plan has been developed to monitor the effects of dewatering <br />activities on nearby cottonwood trees (Populus deltoides) at the Dillon Ranch Pit near Hermosa, <br />Colorado operated by Elam Construction, Inc. Specifically, there is concern regarding the health <br />of cottonwood trees resulting from dewatering of the aggregate mine pit during the winter months. <br />In a technical memorandum (An in -depth and literature analysis of potential impacts to <br />cottonwood trees due to winter dewatering of the Dillon Ranch Pit, April 29, 2014), it was <br />determined that dewatering of the pit during winter months would have little to no effect on the <br />health of nearby cottonwood trees as this activity would be conducted during the dormant period <br />when little physiological activity is occurring. <br />Monitoring tree health by indicators of stress as well as monitoring groundwater levels during <br />dewatering of the pit and after completion of dewatering activities as groundwater levels recover <br />is a requirement of the (DRMS). This plan describes monitoring activities that will be conducted <br />for cottonwood tree health and groundwater elevations in the area of the mine where trees may <br />be affected by dewatering. <br />Background <br />The growing season for cottonwood trees is from April to October throughout most of their range, <br />and is typically shorter in cooler, higher elevations. It is during this growing season period that <br />the need for water is greatest, and occurs by transpiration of water through the leaves of the tree. <br />Transpiration is the process of water movement through a tree including evaporation from leaves. <br />Generally, cottonwood trees have high rates of transpiration during the growing season due to <br />the trees' access to groundwater and the high evaporative demand of the atmosphere. An <br />important point to note is that the transpiration period for cottonwood trees typically ends in late <br />October, around the first freeze of late autumn, and resumes in April (typically late April) as the <br />new growing season starts. Transpiration will be nominal to non - existent when the trees are <br />dormant during the winter. <br />Monitoring <br />1. Cottonwood Tree Health <br />The primary indicator of cottonwood stress due to a lack of water is leaf scorch. Cottonwood <br />leaf scorch results from drought and environmental stress and leads to yellowing of leaves that <br />quickly turn brown during the normal growing season. Heat stress, water - soaked and oxygen - <br />deprived soil conditions as well as a lack of light or minerals create unfavorable conditions for <br />maintaining chlorophyll production. Leaf scorch will be the primary indicator of cottonwood <br />stress that will be monitored at the Dillon Ranch Pit. Monitoring will be conducted as described <br />below: <br />a) Visually inspect cottonwood trees between the Animas River and the mine pit, or within <br />[750] feet of the dewatered mine pit bi- weekly (every two weeks) during the first three <br />