Private well/spring position paper, Rifle, Colorado, sites

This report describes the hydrogeochemical relationship between the New and Old Rifle processing sites and 15 domestic wells in their vicinity. The relationship of the domestic wells to the Old and New Rifle tailings sites requires clarification due to recent advances in understanding of Rifle site conceptual models. In order to form a bridge from the Rifle remedial action plan (RAP) and the recent baseline risk assessment to this position paper, several issues require discussion. First, through analysis of long-term ground water level data, the hydraulic gradient between the former tailings and private wells and springs was assessed. Second, in the Rifle RAP there was not a strong emphasis placed on describing regional influences on water quality in the vicinity of the processing sites. This document uses available information coupled with theory of regional ground water flow to describe regional flow systems north of Rifle. Third, the definition of background water quality from the RAP has been refined in several ways. Also, for the recent baseline risk assessment, all alluvial wells used to define background for the sites were located east of Old Rifle. In the RAP, alluvial background wells were also placed between the sites (downgradient of Old Rifle). Two additional wells were installed for the recent baseline risk assessment upgradient of Old Rifle which verified that several of the older wells (RFO-01-0597 and -0598) were in locations representative of background