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Figure 1-2 were located to provide at least one up gradient and two down gradient monitoring points at the facility with respect to this gradient. Local groundwater gradient direction within the immediate vicinity of the wastewater facility has generally trended southward and westward,both toward and in the downstream direction of the Stanislaus River. In 1991,four 4"diameter groundwater monitoring wells(MW-1 through MW-4)were installed to a depth of 27.5 to 40 feet below ground surface. An additional 4"monitoring well,MW-5,was installed to a depth of 27.5 feet in February, 1995,as detailed in a report regarding this installation dated March, 1995. In 2000,the monitoring well network was expanded by installing MW-6,to a depth of 42 feet. In 2003,the monitoring well network was expanded by installing MW-7,8&9 to depths of 26.7 to 32.5 feet. In 2006,the monitoring well network was expanded by installing MW-10& 1 I to depths of 40 to 41.5 feet. The monitoring well installation report for these wells indicated sandy gravel and gravelly sands between a 5 to 20 foot depth between ponds T-1,T-2 and P-2. In order to gain a further understanding of groundwater gradient and chemistry,the monitoring well network was further expanded by installing offsite wells MW-12& 13 in December,2012,to depths of 60 to 65 feet. 1.3 PROJECT PURPOSE Prior to July 2014 eleven of the City's thirteen monitoring wells indicated one or more total coliform results exceeding 2.2 MPN/100ml, leading the City to perform well chlorination. Well chlorination was conducted under the speculation that prior sampling techniques,or other factors,could have contributed to formation of coliform organism population growth in the wells not necessarily associated with the wastewater treatment and disposal operations. Following the July 2014 chlorination,all but one of the site wells has consistently indicated total coliform level sat 1.1 MPN/100 ml or less, indicating that the presumption that the source of higher colform results were indeed not of wastewater treatment and disposal operation origins. Monitoring well MW-5,however, has inconsistently indicated total coliform levels exceeding 2.2 MPN/I OOml,albeit at levels significantly less than the high historical results in 2013 and early 2014. Recent,since from I'quarter 2012,groundwater total coliform results indicating the above are depicted in Table 1-1. July 2015 Conformed wM 21 October 2015 Conditional Approval 3 VW-5 Replacement City of Riverbark WWTF Monitodrg Well Installation Workplan