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Michael Riddel -2- 21 October 2015 City of Riverbank 1 • The workplan indicates that following installation of the well casing and screen that the I` filter pack, bentonite seal, and neat cement will be installed. However, the workplan does not describe the method(s)to be used to install these well materials. Be advised that the California Water Well Standards Bulletin 74-94 requires that filter pack material and annular seals should be installed using a tremie pipe or equivalent method. • The workplan indicates that development of the replacement monitoring well will consist of i. pumping and surging, and that development will be completed when pH, electrical conductivity, and turbidity have stabilized. The workplan does not discuss the collection frequency for these parameters. Please be advised that well development may only terminate after turbidity is measured at five Nephelometric Turbidity Units(NTUs) or less. The workplan indicates that the coordinates for the center of the top of the casing of the replacement well will be to the nearest 0.01 feet. However, the workplan does not provide information indicating that vertical elevation data to the nearest 0.01 foot will be obtained. Please be advised that the well survey shall include the collection of vertical elevation data. Following initial sampling of MW-5R, the well shall be sampled in accordance with the Monitoring and Reporting Program. The data collected from the initial sampling event shall be submitted with the December 2015 monthly monitoring report which is due by 1 January 2016. The Groundwater Monitoring Well Installation Report shall also be submitted by 1 January 2016, and include the information listed in the second section of the enclosed attachment, and shall describe the abandonment of MW-5. Finally, as a reminder,we have transitioned to a paperless office. Therefore, all documents including monitoring reports shall be converted to a searchable Portable Document Format(PDF) and submitted by email to centralvalleysacramento@waterboards.ca.gov. The e-mail shall contain the following information: (a)The City of Riverbank, (b) Riverbank WWTF, (c)Title and Date of the Report, and (c) CIWQS Place ID No: 2441143. Documents that are 50 MB or larger should be transferred to a CD, DVD, or flash drive and mailed to our office, attention "ECM Mailroom." If you have any questions regarding this letter or submitting documents, please contact me at (916) 464-4648 or at gchilds@waterboards.ca.gov. A AA111 GUY CHILDS, P.G. Engineering Geologist Waste Discharge to Land Compliance Unit. Encl: Requirements for Monitoring Well Installation Workplans and Monitoring Well Installation Reports cc: Bella Bedal, Stanislaus County Environmental Health Department, Modesto Neal Colwell, Kjeldsen, Sinnock & Neudeck, Inc., West Sacramento gjc:21 Oct-15