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