humboldt bay maintenance dredging &...
TRANSCRIPT
Humboldt Bay Maintenance Dredging &
Disposal PUBLIC MEETING
MAY 3, 20175:30-7:30 PM
Agenda• Dredging Goals and History
• Efforts Taken Since Previous Dredge Cycle
• Disposal Opportunities Evaluation
• Potential Hybrid Approach
• Next Steps and other options
Dredging Goals & HistoryHISTORY:
• Three Previous Maintenance Dredging Projects• Cutter Head Suction Dredge/Samoa Beach Disposal
• Nearshore Subtidal and Intertidal Habitat Monitoring
• January-March 1988• 131,000 cubic yards
• January-May 1998• 226,238 cubic yards
• November 2006-March 2007• 230,065 cubic yards (contract dredging $3.2 million,
included $600k mobilization)
GOALS:
• Maintain safety and usability of various recreational and commercial fishing waterfront facilities.
• Break the cycle of 7-10 year dredging. Annually dredge smaller volumes to upland sites for beneficial reuse.
IMMEDIATE NEEDS:• Remove ~ 40-50,000 cubic yards
from Eureka Public Marina
Efforts Taken• Samoa Beach Surf Zone Monitoring (2006-2009)
• Samoa Lagoons dredge disposal site development (2006-2017)
• Annual meetings with US Army Corps about flow lane disposal (2008-2017)
• Coastal Regional Sediment Management Plan (CRSMP) (2011-2017)
• Dredge purchase and implemented marina dredge surcharge (2014)
• Bathymetric Survey (2014) and Sediment Sampling and Analysis Plan (SAP) (2015)
• Beneficial Reuse of Dredge Materials for Marsh Restoration and Sea Level Rise Adaptation in Humboldt Bay (July 2015)
• King Salmon Fisherman’s Channel Beneficial Reuse – White Slough (Nov 2015-July 2016)
• Infrastructure Reuse Evaluation – filtration plant modifications and ocean outfall (2015-16)
• Vibracore Purchase (2016) and sediment sampling (2016-17)
• Super Bowl botanical survey (2016-2017)
• Updated research and findings (2017)
Samoa Beach Monitoring History and Results
• Impacts of beach disposal operations are temporary and localized to the pipeline transect.
• Sediment composition and biological communities returned to pre-project conditions within three to four months.
• The effects on ocean water quality are considered less significant than other disposal alternatives.
• A majority of the dredge material is fine grain (80% - 90% silt and clay).
• Fines are transported offshore and settle on the continental margin.
• Disposal operations during the winter months disperse material due to large swells, high tides, and strong currents.
USGS Fine-Grained Sediment Research• 2008-2009 Tijuana River Demonstration Project
• Majority of fine sediment moved far offshore of the project site due to waves and currents. (50% fines/50% sand)
• 2009 Santa Cruz Harbor Demonstration Project• No significant net deposition on the seabed in or near the project site, no shift to a
finer grain-size class along the beach or on the inner shelf (considered “in-bay” disposal, not ocean disposal).
• Fine sediment discharged to the coastal ocean:• Did not result in observable deposition of fine-grained sediment on the beach or inner-
continental shelf.
• Resulted in turbidity values significantly lower than those values observed during a large wave event or small flood of the San Lorenzo River.
In-House SamplingVibracore
In-House Dredge
• Purchased 2014
• 13,000 feet of pipe
• Booster pump and barge
• Work boat and skiff
• Floats, weights, anchors
• New Tier 3 engines
• Invested ~$1.3M into dredge and equipment
• Eureka Public Marina and Woodley Island sediment sampling conducted 2016-17
• Contaminants of concern have decreased over time and are below residential screening levels
Based on review of feasibility, scientific data, environmental impacts and fiduciary responsibility.
1. White Slough2. Flow Lane - In-Bay Disposal3. ACOE Ocean Disposal (HOODS)4. RMT II - Beach/ Ocean Outfall5. RMT II - Clarifiers6. Super Bowl7. Samoa Lagoons8. Samoa Beach
Disposal Options Evaluated
Potential Disposal Option Costs
White SloughPros
• Beneficial re-use• Mid-range cost ($10-15 per cubic yard)• White Slough unit needs material - Good
option for South Bay if sediment is acceptable reuse.
Cons• Very limited on-site capacity• Off-site dewatering significantly raises costs
and environmental impacts• Distance very far for middle and North Bay
– 8-9 miles and logistically difficult• High capital costs – $1 million (1st year -
pipe and booster pumps)
Flow Lane (In-Bay) or ACOE Ocean Disposal (HOODS)
(Flow Lane = in navigation channel on outgoing tide)
(HOODS = existing ACOE ocean disposal site)
Pros
• Low to mid-range cost ($10-$11 per cubic yard)
Cons
• No beneficial re-use and debris difficult to remove
• Flow Lane considered “In-bay disposal” (ACOE mandated to reduce in-bay disposal in San Francisco Bay)
• Regulatory hurdles (3 years and $3 million)
• Requires ACOE approval – In discussions since 2008. Harbor District offered to reimburse costs of removal to HOODS; told too difficult to permit material removed from non-jurisdictional area.
Redwood Marine Terminal II - Options 1, 2
Pros• Low to mid-range cost ($11 per cubic
yard)
Cons• Compliance with Ocean Plan
• No beneficial re-use if outfall used
• High capital costs - $500,000 1st year
• Modification could damage or plug pipe eliminating other important uses
Option 1) Beach disposal with debris clean-up on beach
Option 2) Mud pond debris clean-up with outfall discharge
Redwood Marine Terminal II – Option 3, Clarifiers
Pros• Man made dewatering option, no sensitive
habitat issues• Potential for beneficial re-use• Possible use with dewatering belt press or
geotubes• Possible use to clarify decanted water from
other upland dewatering sites
Cons• Extensive modifications to clarifiers and
plumbing – high capital costs ($300,000 1st
year)• High costs ($27 per cubic yard – includes
sediment transportation)• Limited volume (15-20k cubic yards
maximum)• Beneficial re-use raises costs and
environmental impacts from trucking
Super Bowl - Upland Site
Pros• Low to mid-range cost ($11 per cubic yard)
• High capacity (~100k cubic yards)
• Potential for beneficial re-use
Cons• 1998-CCC stated that use of this site would not be a
less environmentally damaging alternative to beach disposal
• Recent botanical survey identified protected species (Layia carnosa and Erysimum menziesii )
• Expensive mitigation costs – take permit
Used by Army Corps and Simpson in the 1980’s
Samoa Lagoons –Upland SitePros
• Low to mid-range cost ($11 per cubic yard)
• Potential for beneficial re-use
Cons• Limited volume
• Beneficial re-use raises costs and environmental impacts from trucking
• Contamination of freshwater lens – current testing to determine sustainability of freshwater lens
• Water board stopped use in 2010 requiring a membrane liner be installed
Option 1 - Temporary Off-shore Outfall
• Pros• Low to mid-range costs ($11 per cubic yard)
• Cons• Compliance with Ocean Plan
• Outfall monitoring issues – removal of marine debris
• No beneficial re-use
• Maintaining pipe anchoring system
Samoa Beach Options
• Pros• Low cost ($7 per cubic yard)
• Accommodates high volume locations, lessening environmental impacts
• Beach nourishment
• Cons• Compliance with Ocean Plan
• Compliance with Special Condition 17 of 2006 CDP
• Public concerns
Option 2 – Beach Disposal
Potential Hybrid Approach
• Samoa Lagoons for debris removal and sediment settling
• Pump decanted water to RMT II clarifiers for further treatment
• Discharge water through RMT II ocean outfall or back to Bay
Next Steps
• Receive public input
• Continue coordination with regulatory agencies
• Determine path forward for immediate needs (Eureka Marina), prepare CEQA document and submit permit applications
• Continue to pursue potential upland sites and wetland restoration/ beneficial reuse opportunities