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February 27, 1998 <br />WQCD Letter <br />Page 4 <br />rainfall event occurred that resulted in an out-of-compliance discharge, the discharge <br />might have been in compliance had the pond not had its capacity reduced with pit- <br />pumped water. Pit pumpage (and vehicle washwater) scenarios must therefore be <br />accounted for in a pond's design. We recommend Colowyo be required to install, <br />maintain and monitor continuous flow recorders for any pit pumped or wash water, <br />to document the volume of these waters that or maybe introduced into a pond. <br />8. DMG suggested that as it is stated in the draft individual WQCD permit that "all <br />manual dewatering of ponds that are .equipped with automatic dewatering systems <br />must meet TSS and total iron limitations" (page 5, "Burden of Proof Requirements"), <br />the WQCD permit should also require sampling of each manual discharge to <br />demonstrate compliance with th(s permit requirement. The reason DMG feels that <br />this is important is that surface runoff could be contained for 2-3 days, sampled and <br />found to meet primary limits, then discharged. Later in that same month, a second <br />pond inflow volume could be held for only a few hours, then discharged out of <br />compliance but in accordance with the approved sampling frequency. Without the <br />WQCD permit requiring a sample for each manual discharge, a manual discharge <br />that exceeded effluent limits could occur without either regulatory agency (WQCD or <br />DMG) being aware of it. <br />A further point for requiring samples of each manual discharge is that while <br />automatic dewatering is modeled to meet effluent limitations (with ponds being <br />subsequently designed in accordance with the model and constructed in accordance <br />with the design), manual dewatering is not so modeled. As we stated on our <br />comments at B.2., "discharge though manually-operated dewatering tubes are not <br />currently designed to meet any effluent limitations." Colowyo agreed with this point <br />in their February 9, 19981etter (page 1 1, paragraph C.1.). <br />WQCD responded, saying it will evaluate our request. We would appreciate being <br />informed of WQCD's decision. <br />9. DMG suggested that the WQCD permit be revised to contain language requiring the <br />dewatering of sediment ponds "be achieved in accordance with applicable state <br />laws". We felt this was important because our rules at 4.05.6(3)(c) state this, and <br />because the Colorado Division of Water Resources publication "Synopsis of <br />Colorado Water Laws" (May 1991) contains language specific to the construction of <br />erosion control reservoirs with regard to dewatering capability. <br />Colowyo, in its February 9, 1998 letter, responded that its ten sedimentation ponds <br />are "sediment control ponds which are designed to "settle" out solids before <br />discharging the clear water to waters of the state", rather than erosion control <br />reservoirs. While we at this point disagree with Colowyo, the company makes a point <br />that we will discuss with the Colorado Division of Water Resources before we feel <br />we can say our concern is resolved on this issue. <br />