1 discussion points for ima participants – flow studies december 19, 2006 district of columbia...

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Discussion Points for IMA Participants – Flow Studies

December 19, 2006

District of ColumbiaWater and Sewer Authority

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Agenda

Flow Studies Nitrogen Update

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Suburbs Flow

Largest storm in 3-yr design period

Excess Vol. above flow produced during largest storm in3-yr

design period

Complete Treatment• an. avg.• 2 x an. avg, 4 hrs• 1.38 x an. avg thereafter

Capacity that suburbs have in complete treatment at

Blue Plains

Volume exceeding treatment capacity =

39 mg

Vol. produced by flow from suburbs that

exceeds capacity that suburbs have in Blue

Plains

DC Flow

Largest storm in 3-yr design period

Tunnels

Complete Treatment• an. avg.• 2 x an. avg, 4 hrs• 1.38 x an. avg thereafter

Blue Plains

Excess Flow Treatment (336

mgd)

Remaining CSOs (Allowed)

Outfall 001Outfall 002

Separate Systems: Capacity Requirements for Largest Storm in 3-Year Design Period (‘88-’90)

Volume exceeding treatment capacity =

269 mg

Total volume exceeding treatment capacity = Suburbs (39 mg) + DC (269 mg) = 308 mg

Suburban Share = 39/308 = 12.7%

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Suburbs Flow DC Flow

DC Collection System

Blue Plains

Complete Treatment Excess Flow Treatment (336 mgd Capacity)Outfall 002 Outfall 001

Tunnels (194 mg)

CSOs

Overflow volume (64 mg+/-)

LTCP capacity

370 mgd an. avg.2 x an. avg, 4 hrs

1.38 x an. avg thereafter

Flow from DC & Suburbs is for largest storm in Avg year

Benefits of Collective System

Volumes exceeding treatment capacity:

Collective system: 194 + 64 = 258 mg

Separate Systems: 269 + 39 = 309 mgCollective system less than separate systems

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Summary of Storage/Equalization Volumes for Regional WWTPs

WWTPUtility

Collection System

Avg Design Flow (mgd)

Peak Design Flow (mgd)

Storage Volume

(mg) Storage Type

Storage/ Avg

Design Flow

(mg/mgd)

Storage/ Peak

Design Flow

(mg/mgd)

Blue Plains after LTCP Built

DC WASACombined 370 1076 194 LTCP tunnels 52% 18%

Noman ColeFairfax CountySeparate 67 134 34.9

On-site equalization 52% 26%

ArlingtonArlington CntySeparate 40 75 16.3


H.L. MooneyPrince William CntySeparate 18 36 10.8


Richmond, VACity of RichmondCombined 45 90 57

Off site CSO storage 127% 63%

Alexandria

ASA- Serves City of Alexandria & Fairfax County/Separate 54 108 0 None SSO issues

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Summary of Flow Studies

Percent Use in LTCP

Storage Volume

(mg)Suburban Cost ($2001

dollars)

1. Difference in Tunnel Storage Volume Required 6% N/A 0.06 x $1.265 B = $76 M

2. Difference in Annual CSO Overflow Volume (Avg year) 9.4% N/A 0.094 x $1.265 B = $110 M

3. Annual Wet Weather Volume Handled (Avg Year) 24% N/A 0.24 x $1.265 B = $304 M

4. Separate Handling by Suburbs

a. LTCP Design (Largest storm in 3-year design period) 12.7 % N/A 0.127 x $1.265 B = $161 M

b. Based on Feb 2003 storm N/A >60 mg 60 x $10/gal = >$600 M

c. 2-yr 24 hr storm N/A 82 82 x $10/gal = $820 M

d. On-site equalization based on comparable WWTPS N/A108 mg

( 51%1 ) 108 x $10 = $1080 M

Notes:

(1) Average of Noman Cole, Arlington and Mooney plants

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Current Status of Negotiations

EPA has public noticed modified permit with 4.86 mil. lb TN limit on 12/14/06 30 day comment period

Intent: WASA to prepare TN removal/wet weather plan ~ draft to

EPA Jan 2007 Modify LTCP consent decree to include TN/wet weather

projects Finalize permit and modify LTCP consent decree at the

same time

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Months After Reaching Agreement with EPA

Activity 1 2 3 4 5 6 7 8 9 10 11 12

1. Blue Plains TN Removal/ Wet Weather Plan (WWP)

2. TN Removal and WWP Compliance Schedule

3. Permit Reissuance Application

4. Develop LTCP Wet Weather Supplement

5. Develop Consent Decree Modification

6. Public Participation Program

7. Reissue Permit w/ Final TN Limit

8. Lodge Consent Decree Modification

Draft Final

Draft Final

Draft Final

Hold Pub Mtg Respond to CommentsPublish Draft Plans

Permit and Consent Decree Schedule

Entry

Pub Notice

Pub Notice

12/20/20069/30/2007

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Alternative: B-1BP: 740 mgd to ENR (C.T.), no ECFLTCP: TDPS at Poplar Point

Outfall 002

Prim & Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

BypassNew Poplar

Point PS45 mgd

336/336/336/0

740/511/450/450

4 New Clar.

Off SiteBPWWTP Site

TDPS 170 mgd

Tunnel OF

RFK Stadium

Main & O Pumping Stations

S & F

S & F

Tunnel OFAnacostia River

SCR

GR

IT

Headworks

Anacostia River Tunnel

Branch Tunnel

Northeast Boundary Tunnel

Complete Treatment

Poplar Point

Existing Sewers up to 1076 from all

sources

LEGENDExisting facilitiesJoint Use – split based on 370 mgdJoint Use – split based on agreed LTCP splitJoint Use - split based on flow proportion

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Alternative: C-1BP: 555 mgd to C.T.+ 521 mgd ECFLTCP: TDPS at Poplar Point

Outfall 002

Prim &

Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

Bypass

Low Lift Pumps

521/521/521/336

555/511/450/370

New ECF521 mgd

521/521/521/0

Off SiteBPWWTP Site

Force Main in Tunnel - 336 mgd Capacity

S & F


New PoplarPoint PS45 mgd

170 mgd

Tunnel OF

S & F

Headworks

To Secondary

RFK Stadium



Branch Tunnel


Poplar PointComplete Treatment

Up to 1076 from all sources

TDPS 336 mgd

166 mgd


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Alternative: C-2BP: 555 mgd to C.T. + 521 mgd ECFLTCP: TDPS at BP, Clear Poplar Point

Outfall 002

Prim &

Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

Bypass

Low Lift Pumps

Modify O St to replace Poplar

Point P.S.

521/521/336/336

555/511/450/370

New ECF 521 mgd

521/

521/

521/

0

Off SiteBPWWTP Site

Main Pumping Sta.

Gravity Tunnel - 336 mgd Capacity

S & F

Tunnel OFPoplar Point cleared of major facilities

Shaft

S & F

Tunnel OF

Anacostia River

Headworks

To Secondary

RFK StadiumAnacostia River Tunnel

Branch Tunnel



Up to 1076 from all sources

170 mgd

TDPS 336 mgd

166 mgdLEGENDExisting facilitiesJoint Use – split based on 370 mgdJoint Use – split based on agreed LTCP splitJoint Use - split based on flow proportion

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Alternative: C-3BP: 555 mgd to C. T. + 521 mgd ECFLTCP: TDPS at BP, Clear Poplar Point

Outfall 002

Prim &

Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

Bypass

521/521/521/336

555/511/450/370

555/511/450/370

New ECF

Off SiteBPWWTP Site


S & F

Tunnel OFPoplar Point cleared of major facilities

Shaft

S & F

Tunnel OF

Anacostia River

521/

521/

521/

0

Headworks


To Secondary


Branch Tunnel


Point P.S.

Main Pumping Sta.


Spills to Tunnel if > 555

mgd


mgdUp to 1076

from all sources

170 mgd

TDPS 521 mgd

351 mgd


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Alternative: D-1BP: 555 mgd C.T., 336 mgd ECF, Equiv. to 740 C.T.LTCP: TDPS at BP, Clear Poplar Point

Outfall 002

Prim &

Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

Bypass

336/336/336/336

555/511/450/370

New ECF

521/

521/

521

Off SiteBPWWTP Site


S & F

Tunnel OF

Poplar Point cleared of major facilities

Shaft

S & F

Tunnel OF

Anacostia River

336 185/4 hrs

Maintains 511/450 to C.T.

Maintains 511/450 to C.T.

555/511/450/370

Headworks

To Secondary


Branch Tunnel



Point P.S.

Main Pumping Sta.



mgd


mgdUp to 1076

from all sources

170 mgd

TDPS 336 mgd

166 mgdLEGENDExisting facilitiesJoint Use – split based on 370 mgdJoint Use – split based on agreed LTCP splitJoint Use - split based on flow proportion

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Alternative: E-1BP: 555 mgd to C. T. + 521 mgd ECF LTCP: TDPS at Poplar Point

Outfall 002

Prim & Sec

West P.S.

East P.S.

BNRFilters

& Disinf.

Disinf.

Outfall 001 CSO

BypassNew Poplar

Point PS45 mgd

521/521/521/521

555/511/450/450Existing

Sewers up to 1076 from all

sources

Off SiteBPWWTP Site

Tunnel OF

RFK Stadium


S & F

S & F


Headworks


Branch Tunnel


Low Lift Pumps

New ECF521 mgd

Grit

Fine SCR


To Secondary

170 mgd

TDPS 250 mgd

80 mgd


1 discussion points for ima participants – flow studies december 19, 2006 district of columbia...

Documents

treatment capacity

mgd ecfltcp

mgd capacityoutfall

east p

suburbs flowlargest

ltcp capacity370 mgd

prim secwest p

bnrfilters disinf