Planning Assistance to States Study for MADEP Brief of Assabet - - PowerPoint PPT Presentation

Planning Assistance to States Study for MADEP Brief of Assabet River Sediment and Dam Removal (for Sediment P-flux Reduction) Feasibility Study DECEMBER 2, 2009

EPA (Clean Water Act) Requires States to: EPA (Clean Water Act) Requires States to:

Set Limits on Pollutants Set Limits on Pollutants Total Maximum Daily Load (TMDL) Total Maximum Daily Load (TMDL)

Maximum amount of pollutant that can enter a Maximum amount of pollutant that can enter a water body water body … …and still meet water quality and still meet water quality standards standards

PHOSPHORUS TMDL FOR PHOSPHORUS TMDL FOR ASSABET RIVER ASSABET RIVER

• Developed in 2004

Developed in 2004

• Requires reductions of P loadings from four treatment plants to

Requires reductions of P loadings from four treatment plants to 0.1 mg/L during the growing season 0.1 mg/L during the growing season

• 90% reduction in sediment phosphorus load

90% reduction in sediment phosphorus load

Wastewater Treatment Plants Wastewater Treatment Plants will meet 0.1 seasonal limit will meet 0.1 seasonal limit with new facilities with new facilities

• Westborough

Westborough

– – Includes Shrewsbury & Hopkinton Includes Shrewsbury & Hopkinton – – Construction underway Construction underway

• Hudson

Hudson

– – Construction almost complete Construction almost complete

• Marlborough West

Marlborough West

– – Includes Northborough Includes Northborough – – Plans approved Plans approved – – Awaiting permit modification from Awaiting permit modification from EPA EPA

• Maynard

Maynard

– – Construction contract signed Construction contract signed

Corps Planning Assistance to States Study

MADEP requested the Corps provide information on sediment and dam removal:

– relative to the TMDL goal of 90 % reduction in phosphorus release from the sediments

NOTE: The Corps is not involved in permitting the WWTFs discharges to the river - EPA and MADEP permit the WWTFs on the river

CDM assisted Corps in Study Technical Reports prepared by CDM for this study are:

• Modeling Report – June 2008
• Sediment Management Plan – Dec 2008

Available at: http://www.nae.usace.army.mil/projects/ma/assab etriver/assabetriver.htm

There several Communities located along the ~32 mile river and the Communities share this resource

Dams create manmade impoundments along the Assabet River

Dams Sites Date from 1700 and 1800s

pre-1835 1924 (being rebuilt) Acton Powdermill 1850 1850 Maynard Ben Smith 1750 1924/1883 Stow Gleasondale 1860 Repaired 1987 Hudson Hudson 1720 1900 Northborough Allen Street pre-1900 1925 Northborough Aluminum City Dam site dates from Year Built Town Dam Name

Dam Dam Structural Height (ft) Estimated Extent of Dam influence

Aluminum City

8.5 About 0.1 mile in Northborough

Allen Street

12 About 0.6 miles to River St. in Northborough

Hudson

15 About 1.2 miles to Chapin Rd. in Hudson

Gleasondale

12 About 1.5 miles to Cox Rd. in Hudson

Ben Smith

9 About 5 miles to Route 62 in Stow

Powdermill

13 About 1 mile to Crane Ave in Maynard

The extent of influence of a Dam on water levels The extent of influence of a Dam on water levels extends beyond the visual pool extends beyond the visual pool

CDM Modeling Methodology CDM Modeling Methodology

Watershed and river water quality model Sediment transport model Water surface / hydraulic model

• > River bed profile and

sediment movement

Revised XS Revised hydraulics

• > Water surface

profiles and river hydraulics

Sediment P fluxes

Phosphorus flux model

• > Water quality

benefits

• > Sediment P fluxes

Scenarios Analyzed Scenarios Analyzed

Scenario Wastewater Treatment Plant Improvements River Sediment Removal Dam Removal Existing conditions (2000) Planned WWTF improvements

√

Dredging √ 3 ft from each impoundment Full dam removal √ all 6 dams Partial dam removal √ Hudson, Gleasondale, Ben Smith Partial dam removal √ Ben Smith

Findings Findings – – WWTF Improvements WWTF Improvements

( (2005 NPDES Permits of 1.0 TP winter and 0.1 TP growing season)

2005 NPDES Permits of 1.0 TP winter and 0.1 TP growing season)

• Reducing phosphorus discharges from the

Reducing phosphorus discharges from the WWTFs has several impacts on water quality: WWTFs has several impacts on water quality:

• Lower instream P concentrations in river

Lower instream P concentrations in river

• Lower algal counts

Lower algal counts

• Improved DO

Improved DO

• Less algal settling

Less algal settling

• Reduced P flux from sediment due to lower algal

Reduced P flux from sediment due to lower algal settling settling 60% reduction in P flux 60% reduction in P flux

Note: Note: high summer P fluxes are due not only to algal settling high summer P fluxes are due not only to algal settling and cycling through sediment, but also the high P in the and cycling through sediment, but also the high P in the sediment during sediment during winter winter time time

Findings Findings -

• Sediment Removal/Dredging

Sediment Removal/Dredging

• Based on USGS study, total P sediment

Based on USGS study, total P sediment concentration in the impoundments was highest in concentration in the impoundments was highest in top 3 ft of sediment top 3 ft of sediment

• Removing the top 3 ft of sediment from each

Removing the top 3 ft of sediment from each impoundment results in the following water quality impoundment results in the following water quality impacts: impacts:

• Reduced

Reduced sediment phosphorus flux lasts only for a sediment phosphorus flux lasts only for a few years few years; as dredged areas fill back in, P flux will ; as dredged areas fill back in, P flux will increase back to previous levels increase back to previous levels

• Dredging increases residence time in impoundments

Dredging increases residence time in impoundments

• Reduces reaeration and dissolved oxygen

Reduces reaeration and dissolved oxygen

• Increases algal growth from deeper impoundments

Increases algal growth from deeper impoundments Dredging does not improve water quality Dredging does not improve water quality

Findings Findings – – Dam Removal Dam Removal

• Dam removal results in the following water

Dam removal results in the following water quality impacts: quality impacts:

• Reduced residence time

Reduced residence time

• Reduced biomass production

Reduced biomass production

• Improved DO

Improved DO

• Less algal settling

Less algal settling

• Reduced P flux from sediment due to lower algal

Reduced P flux from sediment due to lower algal settling settling Additional 20% reduction in P flux from dam Additional 20% reduction in P flux from dam removal for a total 0f 80%. removal for a total 0f 80%. Note: Note: Removing the dams for the larger Removing the dams for the larger impoundments has the greatest benefit impoundments has the greatest benefit

Estimated P-Flux Reduction

~ 70% reduction (Ben Smith and Powdermill impoundments only ~ 60% reduction (Gleasondale and u/s impoundments) D/S: 6.5 U/S: 4.8 Planned Improvements plus Dam Removal – 1 dam (Ben Smith) ~ 80% reduction (Hudson and d/s impoundments only) ~ 60% reduction (u/s impoundments) D/S: 4.3 U/S: 4.8 Planned Improvements plus Dam Removal – 3 dams (Hudson, Gleasondale, Ben Smith) ~ 80 % reduction D/S: 4.3 U/S: 2.4 Planned Improvements plus Dam Removal – 6 dams ~ 60 % reduction D/S: 8.6 U/S: 4.8 Planned Improvements (WWTP TP @ 0.1 mg/l – summer @ 1.0 mg/l - winter) No Change D/S: 21.6 U/S: 12.0 Base Condition (2000)

P Flux Change P-Flux (mg P/m2-day) Scenario

Although WWTF permitting is not part of this study - The P-flux model based on limited laboratory data indicated that winter instream P concentration may have an effect on summer sediment flux rates – reductions in phosphorus levels in WWTF discharges during the non-growing season may make a significant contribution toward achieving water quality standards – this contribution could not be quantified in this study MADEP is gathering additional data to help them assess this contribution as part of their Assabet River monitoring program

Summary of P-Flux Seasonal Analysis (using P-flux model only)

Considerations for Dam Removal Cost, Impacts, Permits

* Modeling used to determine volumes that would move downstream * Modeling used to determine volumes that would move downstream

Dam Sediment volume to be managed/dredged to prevent downstream movement of sediment with dam removal * (CY)

Aluminum City 1,300 Allen Street 2,230 Hudson 71,560 Gleasondale 27,860 Ben Smith 67,600 Powdermill 65,830

Dam removal Dam removal -

• sediment behind dams will

sediment behind dams will need to be managed to prevent downstream need to be managed to prevent downstream sediment movement sediment movement

Sediment Management with Dam Sediment Management with Dam Removal: Removal:

• Evaluation of sediments behind dams based

Evaluation of sediments behind dams based

• n 2003 USGS sediment core data
• n 2003 USGS sediment core data –

– 185 cores 185 cores

• Data review noted in some areas the presence

Data review noted in some areas the presence

• f chemicals that may effect reuse and
• f chemicals that may effect reuse and

disposal options disposal options

• Additional sampling and analysis is

Additional sampling and analysis is recommended recommended

Develop Dam Removal Estimate – Construction Cost to Remove Dam

Dam Removal and Sediment Management Costs

0.72 0.28 42,713,140.00 11,840,680.00 Total All Six Dams 0.85 0.15 11,802,180.00 1,764,890.00 Powdermill 0.64 0.36 12,840,300.00 4,559,430.00 Ben Smith 0.59 0.41 5,882,950.00 2,428,450.00 Gleasondale 0.85 0.15 9,404,000.00 1,440,640.00 Hudson 0.43 0.57 1,773,380.00 1,007,780.00 Allen Street 0.37 0.63 1,010,330.00 639,490.00 Aluminum City % % ($) ($) Sediment Management Cost Dam Removal Construction Cost Dam Removal and Sediment Management Dam Removal Only * Dam Name Assabet River Dam Removal Construction Cost Estimates, provided for general planning purposes only

Without Dams water levels in the Without Dams water levels in the impoundments will decrease impoundments will decrease

Dam Summer Average flow Scenario Change in Water Surface if Dam Removed (ft)*

Aluminum City

• 4.8

Allen Street

• 3.5

Hudson

• 6.9

Gleasondale

• 4.5

Ben Smith

• 7.4

Powdermill

• 7.6

*Note: Value shown is just a few feet upstream of the Dam.

100 150 200 250 300 350 5 10 15 20 25 30 River Station (miles) Elevation (ft) WSEL (Base Condition) WSEL (Remove 6 Dams) Thalweg (Remove 6 Dams) Aluminum City Dam Allen Street Dam Hudson Dam Gleasondale Dam Ben Smith Dam Powdermill Dam Water Surface Profile 7Q10

Impacts to Existing Uses

Allen Street Dam – some recreation Hudson Dam – recreation Gleasondale Dam – recreation, water source

for building fire protection and water source for fire protection in town of Stow

Ben Smith Dam – recreation, impoundment

used for water supply for fire protection in Stow, potential hydroelectric production

– Mill pond is water supply for building fire protection, Mill pond important cultural feature in Maynard Powdermill Dam – hydroelectric production

Recreation includes canoeing, kayaking, fishing, hiking, bird wa Recreation includes canoeing, kayaking, fishing, hiking, bird watching tching

Ben Smith Dam and Mill Ponds

Water flows from the River to the Mill Ponds due to the water surface elevation gradient created by the Ben Smith Dam.

Wetlands behind dams will change due to lower water levels with out dams

Fish Community Analysis - Habitat Use and Pollution Tolerance: Existing community composition

consists primarily of microhabitat generalists and pollution tolerant species

Fish Community Findings

Removing dams and restoring water quality

will provide habitat that will support the TFC for the river with expected increases in fluvial dependent and fluvial specialist fish species for example native brook trout

The USFWS long term objective is to restore

anadromous fish such as alewife to the Assabet - Dam removal is consistent with this goal

River was moderately used by prehistoric groups for resource procurement, and seasonal or short-term

• settlement. The potential exists for prehistoric sites to

be identified in the floodplain, on terraces or surrounding wetlands adjacent to the river. Further archaeological studies will be needed as part of environmental assessments of a dam removal project. Assabet River Archaeological Resources Powdermill Dam is located at the site of historic manufacturing activity, so removal of the dam could possibly effect significant cultural resource Powdermill Dam Removal of the dam would constitute an adverse effect to a NR eligible historic resource and an adverse effect on the Assabet Mills Historic District Ben Smith Dam Dam is a contributing element of a NR eligible historic district, village of Gleasondale. Dam removal will have an adverse effect on the NR eligible district Gleasondale Dam Dam is a contributing structure to the Silas Felton Historic District. Dam removal will have an adverse effect on the NR district Hudson Dam As part of the Woodside area appears to be potentially eligible for the NR. Allen St. Dam Does not appear to be eligible for the NR. Aluminum City Dam Findings relative to the National Register (NR) of Historic Places

Cultural Resources

Dam Removal Permitting includes:

Local Permits MA Wetlands Protection Act - Notice of Intent and project approval from local conservation commissions Local Building or other local permits State Permits MEPA – ENF and EIR as applicable - EOEA Chapter 91 waterways license (for projects with dredging) - MADEP 401 Water Quality Certificate - MADEP Section 106 Historical Review/Certificate - MHC Chapter 253 Dam Safety dam removal permit - DCR Massachusetts Endangered Species Act filing/permit - NHESP Beneficial Use of Solid Waste Permit - MADEP Federal Permits United States Army Corps of Engineers 404 permit- NEPA process National Pollutant Discharge Elimination System (NPDES) for discharges from construction sites as applicable. FERC approval if hydropower dam regulated under FERC

General Summary Dam Removal

Benefits:

• improve water quality, decrease sediment P-flux (CDM studies)
• improve aquatic habitat

restore habitat for native fluvial dependent and fluvial specialists species

and future migratory corridor for anadromous fish Costs/Impacts:

• costs for dam removal including sediment management costs
• change from impoundment to free flowing river will effect existing uses
• changes to wetlands
• cultural resource impacts

Permits:

• Multiple permits and environmental assessments would be needed

Community Concerns:

• loss of recreation
• change to viewscape
• loss of historic/cultural value
• disruption during construction

All comments must be submitted in writing to MADEP, preferably in an electronic format, and must be received by December 21, 2009 MassDEP - Division of Watershed Management 627 Main Street Worcester, MA 01608 Attention: Alice M. Rojko E-mail: Alice.Rojko@massmail.state.ma.us

Comments on Draft Report Dec 2009. Final Report Jan/Feb 2010. End of Corps Study.

http://www.nae.usace.army.mil/projects/ ma/assabetriver/assabetriver.htm Copies of Draft Report can be downloaded at: