The plume of Chromium 6 contamination in Hinkley groundwater stemming from its use at a Pacific Gas & Electric compression station in the 1950s and 1960s has spread. The regional water board last week ordered more investigations. \u201cWe need to know what is going on,\u201d said Lauri Kemper, Lahontan Regional Water Board assistant executive director. There are no plans to slap a violation order on PG&E \u201cas verbal enforcement for this ongoing violation has already been given, and PG&E has responded by presenting plans for addressing the plume expansion,\u201d according to a Nov. 2 board memo. The carcinogenic substance has been found in some residential water supply wells not previously impacted and for the first time also in the region\u2019s lower aquifer. The plume is two miles long and one mile wide, which violates the regional water board\u2019s Cleanup and Abatement order. The migration and spread of the hexavalent chromium is attributed to the natural flow of the groundwater and pumping activities. \u201cIt all influences the shape of the plume,\u201d according to Kemper. PG&E sent a letter Nov. 17 to about 100 property owners in Hinkley, offering to buy them bottled water and to let them know the utility\u2019s property purchase program has been expanded. Reaching an agreed upon price in the economic downturn is likely to be tricky. The letter from Rich Echols, PG&E land acquisition supervisor, states that bottled water will be provided to residents whose wells have chromium levels above natural background concentrations; to those using wells that have steadily increasing levels of chromium; and those \u201cwho are concerned about future chromium elevation of their water supply.\u201d By November 30, 2010, the regional water board staff had planned to order PG&E to provide replacement drinking water for those well owners where water samples contain concentrations that exceed maximum background concentrations of hexavalent chromium where the water is near the PG&E contamination plume. The contamination levels do not exceed drinking water standards set for total chromium, which is 50 parts per billion. Currently, there is no drinking water standard for hexavalent chromium, which is the most toxic form of chromium. The state Office of Environmental Health Hazard Assessment has proposed 0.06 parts per billion as the safe limit for hexavalent chromium in drinking water. According to Kemper, the proposed standard is well below naturally occurring levels in Hinkley. PG&E has installed treatment wells at the center of the plume, and installed 300 monitoring wells. More monitoring wells are being drilled, said Jeff Smith, PG&E spokesperson.