EGGW Groundwater Impacts Hi, my name is Mark Bixby and I’m here to talk about groundwater impacts. Mark Bixby – 06/01/09

Sheet Piling – January 2008 CP Last year the county installed emergency sheet piling in the Wintersburg north levee from Graham downstream to the oil road bridge.

CP Groundwater – 03/30/07 Parkside EIR 97-2 found CP wetland groundwater to be QUOTE “tidally influenced” UNQUOTE from channel seepage. We see from this March 2007 bike jump photo that groundwater was about a foot below the surface prior to sheet piling installation.

Permeable Joint Design The sheet piling was designed to use special joints to allow continued seepage in order to protect CP.

Initial Monitoring Wells Three wells were installed to collect before/after data to see if the sheet piling would have impacts on groundwater.

Initial Monitoring Data ENV-1 Sheet Piling And boy oh boy were those impacts immediate and dramatic. The water level at well ENV-1 on the CP-side of the sheet piling declined by four to five FEET in less than three weeks.

Additional Monitoring Wells The county then started monitoring four previously existing Shea LSA wells.

Additional Monitoring Data Sheet Piling All four wells were either dry or near-dry when the monitoring started, and after a brief rise in water after significant rain in February, all four wells soon ran dry as indicated by the red arrows. Several years of prior data exist for these wells, and they had never ever all run dry in the past, not even during drought conditions.

CP Groundwater – 03/30/07 The preceding slide showed indisputably that significant impacts have occurred. The groundwater is now more than seven feet below ground surface, whereas prior to the sheet piling it was only about a foot below as shown here.

More Monitoring Wells Recently more well data came to light in a Shea grading report.

Adjacent to Channel (Shallow) More Monitoring Data Adjacent to Channel (Shallow) Sheet Piling Water levels in all wells adjacent to the channel dropped steeply and immediately after the sheet piling.

More Monitoring Data (cont.) North Boundary (Shallow) Sheet Piling MW-5 Apr-Dec Peak-to-Ebb Delta 2006 -1.25ft 2007 -1.50ft 2008 -2.50ft MW-5 near Graham & Kenilworth registered its biggest seasonal decline in recent years.

More Monitoring Data (cont.) 200-300 feet from Channel (Shallow) MW-13 Previous Minimum MW-13 New Minimum Sheet Piling MW-13 located in the south eucalyptus grove ESHA north of CP dropped steeply and is now more than two feet lower than the previous minimum. So the ESHA is being impacted as well.

Significant Impacts To-Date The red arrows indicate the areas of significant groundwater impact as determined from all data currently available to the public.

The Problems Could Worsen Completed by OCPW To be completed by Shea Channel Shea property The WRC report warns that completing the levee work may further reduce permeability and increase groundwater impact unless the design is re-thought.

County Data Coming in July The county considers all of this to be a very serious problem and is monitoring several dozen wells throughout the area. Preliminary results will be published in July.

Too Many Unanswered Questions Why did the sheet pile fail to allow seepage as intended? How far away from the channel do the impacts and risks extend? How will current impacts be mitigated? How will the design be changed to avoid future impacts? There are still too many unanswered questions. We don’t know why the original design failed. We don’t know the full scope of the impacts. We don’t know how those impacts will be mitigated. And we don’t know how the design must be changed to avoid future impacts.

A Subsequent EIR is Required Given the significance of these groundwater impacts and the other impacts in the Land Trust letter, please continue this hearing until an SEIR can be prepared, circulated and approved as required by CEQA. Thank you.