Ponds 6, 7 & 8Ponds 6, 7 & 8Napa Sonoma Marsh Napa Sonoma Marsh

Restoration Group MeetingRestoration Group Meeting

USGS San Pablo Field Station Office, Building 505, Mare IslandUSGS San Pablo Field Station Office, Building 505, Mare Island

September 26, 2006September 26, 2006

Presentation Presentation• Project Overview• Upper Ponds (8 & 7/7A) Goals and Solutions• Ponds 6/6A Goals and Solutions• Geotechnical Investigation and Survey• Schedule

Location MapLocation Map

Existing ConditionsExisting Conditions

• Situated on former Napa River floodplain

• Current Flow from Pond 8 to Ponds 7/7A to Ponds 6/6A

• Pond 7 Bittern

Goals:• Perimeter Levee Improvement• Internal Levee Improvement (wave run-up)• Reduce Pond 7 Salinity to Acceptable Level

– Mix Pond 7 Bittern with Tidal Flows in Mixing Chamber– Increase Tidal Flows to Mixing Chamber

• New Outfall for Mixing Chamber Discharge into Napa Slough

Upper Ponds (8 & 7/7A) SystemUpper Ponds (8 & 7/7A) System

Solution Options:Option 1:

• Increase Flow to Pond 8 From Mud Slough

• Improve System to Allow Increased Flows to Mixing Chamber

Option 2:

• Find Alternate Source for Mixing Chamber Source Water– Mud Slough Finger Into Pond 7A

Upper Ponds (8 & 7/7A) SystemUpper Ponds (8 & 7/7A) System

Design Components:• Perimeter Levee Improvement• Internal Levee Improvement• Mixing Chamber Design• New Discharge Pipe/Control Structure at Napa Slough• New System to Increase Tidal Flows to Mixing Chamber

Upper Ponds (8 & 7/7A) SystemUpper Ponds (8 & 7/7A) System

Goals:• Perimeter Levee Improvement• Internal Levee Improvement• Demolish Siphon from Ponds 7/7A• Decrease Residence Time (one week)

Ponds 6/6APonds 6/6A

Options:• New Intake from Napa Slough• New Intake/Outfall at China Slough (south side)• New Control Structure through Internal Levee• Outfall to Devil’s Slough• Outfall to Little Island Farms

Ponds 6/6APonds 6/6A

Design Components:• Perimeter Levee Improvement• Raise Internal Levee & Fix Breach• Demolish Siphon from Ponds 7/7A• New Systems to Improve Residence Time

Ponds 6/6APonds 6/6A

Geotechnical:• Levee Walk to Assess Conditions

• Geotechnical Scope for Upcoming Investigation

Survey:• Field Survey to obtain Bathymetry and Topography for

Design

Geotechnical and Survey ScopeGeotechnical and Survey Scope

Geotechnical Investigation Pond 8

Geotechnical Investigation Pond 8

Geotechnical Investigation Pond 7/7A

Geotechnical Investigation Pond 7/7A

Geotechnical Investigation Pond 6/6A

Geotechnical Investigation Pond 6/6A

• Finalize Geotechnical and Survey Scope• Alternatives Analyses• Complete Geotechnical Investigation• Complete Survey• Plans to 50% - February 2007

Ongoing TasksOngoing Tasks

QuestionsQuestions