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<br />London Mountain Clean Up <br />July 2025 <br /> <br /> <br />G2-4 <br /> <br />Support potential delisting from 303(d) impaired waters list following demonstrated compliance <br />with standards over a 2-3 year post-remediation monitoring period, as typically required by <br />Colorado Water Quality Control Division protocols. <br /> <br />5. Data Quality and Limitations <br />Data Completeness <br />The monitoring network shows significant temporal gaps, with CDPHE data from 1998-1999 (3 <br />sampling events), a data gap of over a decade, and DRMS data from 2011-2012 (3 sampling <br />events). The USGS station provides the most consistent long-term record (1998-present) but <br />lacks chemical analysis for metals. This temporal inconsistency limits trend analysis but <br />provides adequate characterization of existing conditions. <br />Parameter Coverage Variability: Not all stations monitor the same parameters. The USGS <br />station focuses on physical parameters (flow, temperature, conductivity) while the Colorado <br />state agencies (CDPHE and DRMS) provide metals analysis. Some key parameters show data <br />limitations - cadmium and copper at the CDPHE station had no numeric values, likely indicating <br />concentrations below analytical detection limits. <br />Quality Assurance <br />Multi-Agency Monitoring: Data quality is enhanced by collection from three different agencies <br />(USGS, CDPHE, and Colorado DRMS), each following their respective QA/QC protocols. The <br />USGS data represents federal water quality monitoring standards, while Colorado agencies <br />follow state-specific protocols for mining impact assessment. Cross-validation between <br />agencies shows consistent patterns for overlapping parameters. <br />Analytical Detection Limits: Some measurements are reported as less-than values or method <br />detection limits (MDL), particularly evident in the older CDPHE dataset. Specific analytical <br />methods include ICP-MS for trace metals analysis with typical detection limits of 0.001 mg/L for <br />cadmium and lead, and 0.005-0.010 mg/L for copper and zinc. The DRMS dataset (2011-2012) <br />generally shows improved analytical sensitivity compared to earlier CDPHE monitoring, <br />reflecting advances in analytical chemistry methods. Sampling protocols should be confirmed <br />with respective agencies, though standard grab sampling procedures appear to have been used <br />consistently across all monitoring events.