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Section 3 GIS 2012 s t.•mi cx.:r.' Section 3 — Monitoring Well Design and Field Procedures Well Site Selection Rationale Two new background wells (MW-12 & MW-13) are proposed to be installed at the locations illustrated in Figure 1-1 and Attachment A. Monitoring Well 12 will be installed northeast of the WWTF, 2,650 feet north of Henry Road, within the San Joaquin County easement of the South Santa Fe Road right-of-way, near parcel APN# 249-006-013. This location was chosen due to its accessibility and it being the only location in the surrounding northern area fit for drilling a well. Monitoring Well 13 will be installed east of the WWTF, 530 feet south of Henry Road, within the San Joaquin County easement within the South Santa Fe Road right-of-way, near parcel APN# 249-006-012. This location was chosen for its access ability and ease of well drilling. The intent behind the location of the two wells is to extend the groundwater monitoring network of the WWTF by improving information on the groundwater quality conditions in the area and to aid in the City's master planning activities. The new wells included in this plan need to reasonably account for both seasonal and longer term changes in groundwater depths, providing a measure of assurance for their continued use at the WWTF. New Well Design and Construction Details To aid in the proper installation of the groundwater wells, the screen will be submerged a minimum of 10 feet below the first encounter groundwater. This 10 foot buffer will insure that the screen will be submerged during the seasonal variations in high groundwater elevations of the winter/spring months and lower groundwater elevations in the summer/fall months. To help ensure that the groundwater wells will be operational for many years to come, the wells should be designed with maximum of 15 feet of well screen to accommodate normal seasonal variations, and longer term variations of groundwater levels in the area. The proposed groundwater monitoring wells will subsequently be installed using a truck mounted hollow stem auger drill rig. The new monitoring wells will be designed and installed according to the San Joaquin County Well Standards (Ordinance Code Section 9-1115.6) Section 13: Monitoring Wells and permit conditions of the San Joaquin Environmental Health Department with the following specific details: • Borehole Diameter — Nominal 8 inches: allows a nominal annular space of 3 inches surrounding the 2 inch diameter well casing and screen. • Borehole Depth — Estimated to be approximately 60 feet below ground surface based on site depth to groundwater measurements and available borehole logs. Well depth should allow for normal seasonal fluctuations, which generally are on the order of approximately+/- 10 feet. 8 City of Riverbank Waste Water Treatment Facility Background Water Quality Monitoring Well Work Plan