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Natalia Subbotnikova [EH] From: DelFrate, Todd@Waterboards <Todd.Del Frate@waterboards.ca.gov> Sent: Thursday,January 22, 2015 11:19 AM To: Taj Bahadori Cc: Robert McClellon [EH]; Natalia Subbotnikova [EH]; Michael Kith [EH];Joyesh Chandra; Michael Carroll; 'Isham,Julian'; Hold, Howard@Waterboards; Moody, John@Waterboards; Hartzell, Marty@Waterboards; DelFrate, Todd @Waterboards Subject: RE: Foothill Landfill - Compliance Well MW-6 Taj, staff approves the revised design discussed in this email with the following conditions. • Construct the well with 30 feet of well screen. To account for possible rebound of water levels, allow for 5 feet of well screen above first encountered water and 25 feet below • Collect split spoon samples every five feet through the saturated zone • If high plasticity clay or similar low-permeable material is encountered in the saturated zone at a thickness resembling an aquitard, drilling shall cease and the well shall be constructed • Centralizers should be used to properly install the well casing • Well shall be constructed to DWR well standards Please proceed with your schedule to install well MW-6. Staff will prepare a brief letter to formalize this approval. Also, please provide a start date a minimum of 48 hours in advance of the drilling. Any questions do not hesitate to call. From: Taj Bahadori [mailto:tbahadori@sjgov.org] Sent: Thursday, January 22, 2015 9:53 AM To: DelFrate,Todd@Waterboards Cc: 'Robert McClellon [EH]'; 'Natalia Subbotnikova [EH]'; 'Michael Kith [EH]'; Joyesh Chandra; Michael Carroll; 'Isham, Julian'; Hold, Howard@Waterboards Subject: Foothill Landfill - Compliance Well MW-6 Hello Todd, The County has received your letter response to our revised workplan for Well MW-6.Thank you for a quick turn-around on this,the County appreciates the CVRWQCB efforts to meet our schedule. I have discussed your response with our consultant CB&I and we have the following concerns: • It appears that the Water Board's prediction of annual water level decline is based on an average over an extended time period,as much as 17 years (1997 to 2014)for some wells. The concern for the review of that extended period of time, is the fact that the greatest annual degree of decline has occurred within the most recent period of time. This is due to the pronounced drought that has occurred in the Central Valley,which in some locations have caused recent annual water declines of over 10 feet. Attached is a spread sheet that calculates the annual water level decline between 2013 and 2014. During that period of time the annual rate of decline varied from about 2 to 2%feet. The County has proposed the multi-screen well design to take into account this ominous recent water level decline. The County's concern for future water level decline at their Foothill Landfill is not that much different from the concerns that the State Resource Control Board appears to be taking in making water allocations within the Central Valley. • The prediction of well longevity could be significantly reduced below the Water Board's prediction. It is very difficult to predict the future climate patterns for California. The County's proposed well design is based on a more conservative approach than that taken by staff of the Central Valley Water Board. 1