Status of WWTF Nutrient Reduction Efforts For

Narragansett Bay

Angelo S. Liberti, Chief

Surface Water Protection

Office of Water Resources

401.222.4700 ext 7225

angelo.liberti@dem.ri.gov

Surface Water Protection Major Program Responsibilities• Designate Water Quality Classifications

• Establish Water Quality Standards

• Evaluate all waters for Compliance (Integrated Report)

• List Waters in violation of WQS (303d list)

• Develop Restoration Plans (TMDLs)

• Issue Permits Requiring Implementation (RIPDES etc.)

• Review Abatement Plans

State Water Quality Standards

• Reflected in DEM Water Quality Regulations• Subject to EPA approval• Consistent with national guidance; no less

stringent• Site specific criteria are allowed• Criteria can account for naturally occurring

conditions• Current focus: nutrient criteria and biocriteria

development

Current Estuarine DO Criteria

• Above a seasonal pycnocline, not less than 4.8 mg/l at any place or time more than once every three years, except as naturally occurs

• Below the pycnocline, instantaneous values below 4.8 are acceptable provided: – not less than 2.9 for any 24 hour period May 1-October 31– Not less than 1.4 mg/l for more than 1 hour more than twice May

1-October 31– cumulative exposure to DO less than 4.8 mg/l doesn’t exceed

prescribed values.

Use Attainability Analysis

• Mechanism required under the Clean Water Act to reach a decision that a specific waterbody will not be able to achieve its designated uses

• Not widely used in New England

• Key factors in UAAs:

Demonstration of widespread economic harm

UAA Example: Pawtuxet River• Completed in early 1980’s for the Main Stem of

the Pawtuxet River • Revisited in response to a February 16, 1988

letter from the Mayors of Cranston and Warwick and the West Warwick Council President. – “ The theoretical water quality required for this use

[propagation of fish] is impossible to meet …” – “… take whatever other steps are necessary to

eliminate the need for advanced wastewater treatment plants along the Pawtuxet River.”

UAA Example: Pawtuxet River

Water Quality Assessment Process

TMDLs are not a prerequisite for issuance of discharge permits

Framework for Restoring Polluted Waters

Define Assessment Units & Assign Water Quality Standards

Monitor and Assess Standards Attainment

List Impaired Waters

Use all Existing and Readily Available Data

Develop TMDL, Determine Allowable Loading and Allocate Loading Reductions Needed

Problem Identification

Issue Point Source Permits Must Comply with Water Quality Standards

Problem Solving

Control Non Point Source

BMPs, Technical Assistance, Money, etc.

Estuarine Waters Listed as Impaired (DO)

• Providence and Seekonk Rivers (since 1994)

• Potter Cove (1998)• Greenwich Bay & Coves (1998)• Upper Narragansett Bay (2000)• East &West Passages (2008)

•Palmer River (1992)

•Wickford Harbor (1994)

•Pawcatuck (1994)

•Mt. Hope Bay (1998)

•Greenhill Pond (2002)

2008 Expansion of DO Impairment

• In its Intergrated Report on statewide water quality conditions, DEM expanded the area in the mid-bay designated as impaired due to low DO.

Current TMDL ScheduleEstuarine DO Impairments

Waterbody First listed

Target for TMDL

Palmer River 1992 2016

Providence and Seekonk Rivers 1994 2016

Wickford Harbor 1994 2012

Pawcatuck River 1994 2010

Mt. Hope Bay 1994 2012

Potter Cove 1998 2016

Greenwich Bay & Coves 1998 2016

Upper Narragansett Bay 2000 2016

Green Hill Pond 2002 2008

West & East Passages 2008 2016

Early Focus: Providence and Seekonk Rivers

• “Available data show a marked lowering of dissolved oxygen levels in surface and bottom waters in the Providence River at least during the warmer months Reduced oxygen levels at times extend down Bay. (Olsen and Lee 1979)

• “The lowest oxygen values throughout the channel bottom were recorded on the August 8, 1980 sampling, those values were 0 to 3 mg/l all the way to Conimicut Pt.” (Oviatt 1979-1980)

• SPRAY& SQUIRT Cruises – 7 surveys (high and low tide samples), 3 summer surveys of DO, June and August 1987, September 1989 Ave bottom oxygen all Providence and Seekonk River Stations: 3 mg/l –4 mg/l

Expanded Data Collection Efforts• DEM – 1995 1996 Total of 11 High and low tide surveys.

– 1995 extreme variations in oxygen and chlorophyll, periods where entire area is <4mg/l, bottom waters in significant portions of the Seekonk and Providence frequently 0-1 mg/l. 1996 mid June-late September bottom DO rarely above 4 down to Conimicut Point, typically near 0 down to Sabin Pt.

• Insomniacs – multi-agency, monthly, overnight surveys 1999-2003, 2005 and continuing

• Fixed-Site Monitoring Network Expansion: DEM, in partnership with NERRS, the NBC and URI-GSO added stations: from 7 to 9 stations during the summer of 2003; from 9 to 12 summer of 2005; from 12 to

• NOAA- Bay Window – shuttle surveys; 1998-present, monthly bay-wide transects

Prior Modeling Efforts – Providence &

Seekonk Rivers• July -December 1989 – Narragansett Bay Project formed a Water Quality

Model Technical Advisory Group and hired Limno-Tech to provide recommendations to the group.

• January 1990 – NBP held a workshop with stakeholders to discuss TAC recommendations and plan for development of a model to establish an abatement strategy.

• 1992-Researchers at EPA Lab in Narragansett produced Providence Seekonk DO and Nitrogen Model (Dettman 1992)

– Collection of additional data to support development of a time dependent model that includes phytoplankton

• 1992 – NBP hired Limno-Tech to enhance the model produced by Dettman (include impacts from phytoplankton and time variable predictions)

– Model not designed to capture variability of short term events observed due to high algal productivity

– Over 50% reduction in Nitrogen needed to produce an observable response (higher levels for significant response)

– To improve model reliability need, additional data, improved understanding of advective flow variations and extend southern boundary of the model.

– Reliability in the current screening model is substantial and provides good indication of the impact of reduced nitrogen loads on phytoplankton levels.

• DEM developed sampling program to support development of a time variable, three dimensional hydrodynamic/water quality model –formed TAC, Tetra Tech was hired to review past modeling efforts and the proposed sampling/modeling strategy.

• DEM engaged ASA to developed a linked hydrodynamics and water quality model. 1997-2001 held TAC meetings regarding model development. Problems encountered when modeling the interaction between the deep channel and shallow flanks of these water bodies, the mass transport component of the model system could not be successfully calibrated and validated.

Preliminary WWTF Nitrogen Reduction Plans

• 1998 - RI WWTF Loading Reduction Analysis

• 7 WWTFs required to reduce ammonia agreed to reduce total N

Current Plan for Managing Nutrients

• Work was already underway

• Greenwich Bay Fish Kill – August 2003

• Draft Plan for nutrient reductions (DEM, Feb. 2004)

• Governor’s Commission Report & Legislation – 2004

• Adoption in law of goal of 50% reduction in N loadings - 2004

• DEM permits issued – June 2005

Revised WWTF Nitrogen Limits• 5 mg/l

– UBWPAD

– Woonsocket– NBC-Fields Pt.– NBC Bucklin Pt.– East Greenwich

– No. Attleborough

– Attleboro

– Grafton

– Uxbridge

– Northbridge

– (max extent)

• Limits May – October, require operation of treatment to remove N to max

extent possible November-April

– East Providence

– Cranston

– West Warwick

– Warwick

– Smithfield (10 mg/l)

– Burrillville (max extent)

- Warren – anticipated to address impacts to the Palmer River

•8 mg/l

Status of Compliance with Revised Permit limits for NRI WWTFs

Limit Status Ave TN (mg/l) 5/07-8/08

Cranston 8 mg/l Construction comp. –1/2006 8.2

Warwick 8 mg/l Construction comp. -11/2004 8.0

West Warwick 8 mg/l Construction comp. -7/2005 9.2 (7.5)*

East Greenwich

5 mg/l Construction comp.–3/2006 4.0

East Providence

8 mg/l Facilities Plan (FP) under DEM Review

Construction Deadline 9/2012

12.3

NBC- Bucklin 5 mg/l Initial Construction Comp. 2006

FP Due 4/2009

7.5

NBC -Field Pt 5 mg/l Design Due 11/2008 13.7

Woonsocket 5 mg/l Construction Comp. 2002 Agreed to complete construction for 3 mg/l by 3/2014

6.7

* Excludes May data (19.5, 13 mg/l)

Status of Compliance with Revised Permit limits for NRI WWTFs (Cont.)

Limit Status Ave TN (mg/l) 5/07-8/08

Burrillville Max extent

TN Reductions since 2002 10.5 (7.7)*

Smithfield 10 mg/l Construction comp. -6/2006 8.3

Warren Anticipated that Warren will need to reduce N to address impacts to the Palmer River

17.7

Westerly Construction comp. 10/03 6.3

* Excludes May data (19.8, 24.0 mg/l)

Status of Compliance with Revised Permit limits for NMA WWTFs

Upper Blackstone

(UBWPAD)5 mg/l EPA issued 8/08; appeals filed.

Attleboro 8 mg/l EPA issued 6/08; appeals filed

North Attleborough 5 mg/l EPA issued 2/08; appeals settled

Grafton 5 mg/l No action to date

Uxbridge 8 mg/l No action to date

Northbridge NA EPA issued 9/06; reduce N to max extent

Significance of MassachusettsWWTFs

• Without reductions at MA WWTFs – Decrease in loading delivered to the Providence

Seekonk River system will change from 59% to 39% below current levels.

– Seekonk River: 57% reduction with full participation (loading factor is reduced from 23X to 10X) only 7% (to 21.5X) without reductions at MA facilities

Nitrogen Reduction Projections•Nitrogen removal at 11 RI WWTFs - reduces their summer season nitrogen loading by 65%, dropping to 48% as WWTF flows reach approved design flows.

Current Status of Load Reduction Efforts

• 8 - WWTFs have complete upgrades • (2 require additional modifications)

• 0 - Under construction

• 3 – Planning Underway• NBC Bucklin Point• Woonsocket• East Providence

• 1 - Design Underway• NBC Fields Point

Things on “Management’s Plate”• What further reductions will be needed and where? “going

to 3 mg/l”

• Establishment of new shellfish closure procedures in response to CSO tunnel.

• How best to update predictive tools to modify shellfish closure area procedures in response to sewer overflows and to develop monitoring strategies.

• How will CSO tunnel operations affect water quality beyond the control of pathogens?

• Manchester Street Power Station permit renewal

Side helpings…

• Need to better understand what is happening in Greenwich Bay; e.g. groundwater inputs.

• Does monitoring need to be modified to better answer questions about how the Bay’s ecology is changing?

Comparison of MERL Experiments to Providence/Seekonk System

Comparison of observed summer loads to the Providence and Seekonk Rivers with MERL tank levels

12

4

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Tank case ("x")

DIN

da

ily lo

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rate

(m

mo

l/m2

/da

y)

Merl N - load (mmol m-2 d-1)

Observed loads

Area North of Fields Point

Seekonk River

Entire Providence- Seekonk River area

Area north of Bullocks Point

Oxygen Minimum 1981-1983

y = 4.56e-0.0361x

R2 = 0.98

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Nitrogen Load (mmol/m2/d)

Ox

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1 X

C

Allowable Loading Condition

WWTF Name

Approved Design Flow

(MGD)

1 CRANSTON 20.2 2 EAST PROVIDENCE 10.4 3 NARRAGANSETT BAY COMM-BUCKLIN 31 4 NARRAGANSETT BAY COMM-FIELDS 65 5 WEST WARWICK 10.5 6 WARWICK 7.7 7 WOONSOCKET 16 8 UBWPAD 56 9 ATTLEBOROUGH 8.6 10 NORTH ATTLEBOROUGH WWTF 4.6

Evaluation of WWTF Load Reductions

Loading Condition Vs. WWTF Load Reductions

Figure 19: Summary of projected DIN loading rates to selected reaches of the Providence and Seekonk Rivers under four scenarios.

Enrichment levels assuming tributary attenuation

4.2

23.2

9.2

5.2

2.6

17.7

7.9

4.1

1.4

10.0

3.9

2.0

0.9

5.9

2.3

1.2

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35

no WWTFs TN = DMR TN = 5 TN = 3

Flow = 95-96 Flow = 95-96 Flow = Design Flow = Design

En

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Seekonk River

Fields Pt

Bullocks Pt

Entire Area

Loading Condition Vs. Cost

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Capital Cost ($M)

Lo

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X)

Seekonk Reach

Fields Point Reach

Bullocks Point Reach

Recommended Option BP, FP, UB, W 5, Others 8

BP, FP, 3 , UB, W 5 Others 8

Anticipated RI WWTF Load Reductions

Average Chlorophyll vs N Load

y = 0.62 x + 6.32

R2 = 0.94

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Nitrogen Load (mmol/m2/d)

Ch

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g/l)

32 X

16 X

8 X

4 X

2 X

1 XC

Allowable Loading Condition