Barrier Removal Sediment Barrier Removal Sediment Management - - PowerPoint PPT Presentation

Barrier Removal Sediment Barrier Removal Sediment Management Management

Presentation to the Rivers Management Advisory Committee Presentation to the Rivers Management Advisory Committee May 9, 2011 May 9, 2011

General Dam Information General Dam Information

• New Hampshire has more than 5,100 active and inactive

New Hampshire has more than 5,100 active and inactive dams that have been inventoried by the DES Dam dams that have been inventoried by the DES Dam Bureau. Bureau.

• Over 75% are privately owned.

Over 75% are privately owned.

• The impoundments created by dams may enable and/or

The impoundments created by dams may enable and/or enhance recreational uses such as boating, fishing and enhance recreational uses such as boating, fishing and

• swimming. They may also provide fire protection,
• swimming. They may also provide fire protection,

hydropower production, water supply, and flood control. hydropower production, water supply, and flood control.

The Benefits of Dam Removal The Benefits of Dam Removal

• Eliminates a public safety hazard.

Eliminates a public safety hazard.

• Provides cost savings to dam owners and tax payers.

Provides cost savings to dam owners and tax payers.

• Improves water quality.

Improves water quality.

• Eliminates barriers to fish and other aquatic species.

Eliminates barriers to fish and other aquatic species.

• Restores river habitats.

Restores river habitats.

• Reestablishes normal sediment dynamics.

Reestablishes normal sediment dynamics.

Dam Removal in New Hampshire Dam Removal in New Hampshire

• The NH River Restoration Task Force was formed in

The NH River Restoration Task Force was formed in 2000 with the goal of exploring opportunities to remove 2000 with the goal of exploring opportunities to remove dams primarily to restore rivers and eliminate public dams primarily to restore rivers and eliminate public safety hazards. safety hazards.

• In 2001 DES created the Dam Removal and River

In 2001 DES created the Dam Removal and River Restoration Program within the Dam Bureau to assist Restoration Program within the Dam Bureau to assist dam owners with technical, regulatory and financial dam owners with technical, regulatory and financial aspects of dam removal. aspects of dam removal.

Dam Removal in NH continued… Dam Removal in NH continued…

• Since 2001, 14 dam removal projects have been

Since 2001, 14 dam removal projects have been completed. completed.

• The most recent was the Homestead Woolen Dam in

The most recent was the Homestead Woolen Dam in West Swanzey in 2010. West Swanzey in 2010.

• Currently there are nearly a dozen other dams under

Currently there are nearly a dozen other dams under consideration for removal. consideration for removal.

Primary Issues Facing Dam Removal Primary Issues Facing Dam Removal Projects Projects

• Fisheries and wildlife

Fisheries and wildlife

• Funding

Funding

• Historic resources

Historic resources

• Hydrology and hydraulics

Hydrology and hydraulics

• Sediment

Sediment

Why Develop a Sediment Assessment & Why Develop a Sediment Assessment & Management Protocol? Management Protocol?

• Sediment management methods have been inconsistent

Sediment management methods have been inconsistent and handled on a project and handled on a project-

• by

by-

• project basis.

project basis.

• Uncertainty for dam owners and consultants, often

Uncertainty for dam owners and consultants, often leading to significant additional effort and expense. leading to significant additional effort and expense.

• Need a standardized, science

Need a standardized, science-

• based methodology that

based methodology that can be applied to any dam removal project in the state. can be applied to any dam removal project in the state.

• Provide consistency for dam owners, consultants and

Provide consistency for dam owners, consultants and regulatory agencies, and reduce project costs. regulatory agencies, and reduce project costs.

Contributors to the Protocol Contributors to the Protocol

• DES (Dam Bureau, 401 Water Quality Program, Rivers

DES (Dam Bureau, 401 Water Quality Program, Rivers Management Program, Wetlands Bureau, Waste Management Program, Wetlands Bureau, Waste Management Division and Coastal Program) Management Division and Coastal Program)

• New Hampshire Fish & Game Department

New Hampshire Fish & Game Department

• Massachusetts Department of Fish & Game

Massachusetts Department of Fish & Game

• National Marine Fisheries Service

National Marine Fisheries Service

• American Rivers

American Rivers

Assumptions

1. Barrier removal is beneficial to river health. 2. The total volume of potentially mobile impounded sediment is critical to the sediment management process. As such, the level

• f sediment contaminant testing should be commensurate with

the volume of potentially mobile impounded sediment. 3. Projects with small amounts of potentially mobile impounded sediment and no or limited due diligence issues should be able to proceed with no contaminant testing. 4. Sediment assessment and management protocols should not always be determined on a case-by-case basis. A standardized sediment assessment and management protocol should be utilized until specific sediment volume or contamination thresholds are exceeded. 5. Natural erosion of the potentially mobile impounded sediment should be the preferred sediment management alternative unless conditions/ factors dictate otherwise.

Conduct due diligence review

Determine quantity and potential mobility of impounded sediment, and assess whether mobile portion of sediment is likely to “cause problems” downstream

Does due diligence review suggest contaminant or other issues? Is mobile portion of impounded sediment likely to “cause problems” downstream? No contaminant testing or sediment management required DRAFT Barrier Removal Sediment Assessment & Management Protocol Flow Chart

#1 #2 #3 #5

No Yes No Yes

#4

Yes

Due Diligence Information Due Diligence Information

• Dam specific (i.e., current and historical purposes of

Dam specific (i.e., current and historical purposes of dam and impoundment, assessment of dam’s structural dam and impoundment, assessment of dam’s structural integrity, has dam been breached?, has impoundment integrity, has dam been breached?, has impoundment been dredged?) been dredged?)

• Hydrological (i.e., stream gage data, FEMA flood maps)

Hydrological (i.e., stream gage data, FEMA flood maps)

• Natural Resource (i.e., aquatic resources,

Natural Resource (i.e., aquatic resources, rare/threatened/endangered species, exemplary natural rare/threatened/endangered species, exemplary natural communities) communities)

Due Diligence Information cont… Due Diligence Information cont…

• Waterbody and watershed (i.e., current and historical

Waterbody and watershed (i.e., current and historical land use activities at site and upstream, presence of land use activities at site and upstream, presence of downstream infrastructure, recreational, commercial and downstream infrastructure, recreational, commercial and

• ther uses of impoundment and downstream channel).
• ther uses of impoundment and downstream channel).
• Contamination (i.e., hazardous waste sites, landfills

Contamination (i.e., hazardous waste sites, landfills and/or solid waste disposal sites, oil/toxic spill sites, and/or solid waste disposal sites, oil/toxic spill sites, NPDES outfalls, and Superfund sites). NPDES outfalls, and Superfund sites).

Conduct due diligence review

Determine quantity and potential mobility of impounded sediment, and assess whether mobile portion of sediment is likely to “cause problems” downstream

Does due diligence review suggest contaminant or other issues? Is mobile portion of impounded sediment likely to “cause problems” downstream? No contaminant testing or sediment management required DRAFT Barrier Removal Sediment Assessment & Management Protocol Flow Chart

#1 #2 #3 #5

No Yes No Yes

#4

Yes

Fundamental Questions Fundamental Questions

• 1. How best to determine potential mobility of impounded
• 1. How best to determine potential mobility of impounded

sediment? sediment?

• Wisconsin method?

Wisconsin method?

• 2. How to assess whether the mobile portion of impounded
• 2. How to assess whether the mobile portion of impounded

sediment is likely to “cause problems” downstream? sediment is likely to “cause problems” downstream?

• OK if quantity of mobile sediment is

OK if quantity of mobile sediment is ≤0.5 times the ≤0.5 times the annual sediment load of the waterbody. annual sediment load of the waterbody.

Conduct due diligence review

Determine quantity and potential mobility of impounded sediment, and assess whether mobile portion of sediment is likely to “cause problems” downstream

Does due diligence review suggest contaminant or other issues? Is mobile portion of impounded sediment likely to “cause problems” downstream? No contaminant testing or sediment management required DRAFT Barrier Removal Sediment Assessment & Management Protocol Flow Chart

#1 #2 #3 #5

No Yes No Yes

#4

Yes

Conduct grain size analysis

• f potentially mobile sediment

Does >10% by weight of potentially mobile sediment pass the No.200 sieve? Is quantity of potentially mobile sediment >10,000 cubic yards? Consult with DES for site specific sediment contaminant testing protocol Conduct sediment screening

• f potentially mobile sediment
• 2 samples within impoundment

Do any chemical constituents exceed thresholds? Conduct sediment contaminant testing as follows:

• 1 core per 1,000 cubic yards of

potentially mobile sediment within impoundment*

• at least 2 cores downstream
• 1 core upstream

*Contact DES if >10,000 cubic yards of potentially mobile coarse-grained sediment

Yes Yes No No Yes No

#6 #7 #8 #9 #10 #11 #12

Yes

No further contaminant testing required Go to Box #17 Do any of the sediment samples from the impoundment exceed contaminant thresholds? Conduct additional risk investigation Consult with DES! No Is the mobile portion of sediment likely to “cause problems” downstream? (per Box #4) Allow natural erosion of sediment via slow drawdown of impoundment

#13

No

#15

Do any of the sediment samples from the impoundment exceed background levels from the downstream sample? Yes No

#14 #16a

No

#17 #18

Yes

• OR -

Sediment exceeding downstream background levels must be capped, stabilized, dredged or excavated! Consult with DES!

#16b

Yes

Dredge/excavate portion of mobile sediment and allow remainder to naturally erode (via slow drawdown of impoundment) Consult with DES! Natural erosion of sediment not allowed Cap, stabilize, dredge or excavate contaminated sediment Consult with DES! Less Problematic* More Problematic**

#19 #20

*Less Problematic – moderate sediment quantity concerns and no sediment quality concerns

**More Problematic – significant sediment quantity concerns and moderate sediment quality concerns

Next Steps Next Steps

• Review the sediment assessment and management

Review the sediment assessment and management protocol with professionals with expertise in sediment protocol with professionals with expertise in sediment management, geomorphology, aquatic risk assessment, management, geomorphology, aquatic risk assessment, aquatic biology, and dam removal. aquatic biology, and dam removal.

• “Test Drive” the protocol using data from recently

“Test Drive” the protocol using data from recently completed dam removal projects here in NH. completed dam removal projects here in NH.

• Develop a guidance document.

Develop a guidance document.

Contact Information: Contact Information:

Chris Williams Chris Williams NH Coastal Program NH Coastal Program christian.williams@des.nh.gov christian.williams@des.nh.gov 603 603-

• 559

559-

• 0025

0025

Questions? Questions?