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1 Discussion Points for IMA Participants – Flow Studies December 19, 2006 District of Columbia Water and Sewer Authority
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2 Agenda Flow Studies Nitrogen Update
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3 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 001 Outfall 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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4 Suburbs FlowDC Flow DC Collection System Blue Plains Complete TreatmentExcess Flow Treatment (336 mgd Capacity) Outfall 002Outfall 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 mg Collective system less than separate systems
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5 Summary of Storage/Equalization Volumes for Regional WWTPs WWTP Utility 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 WASA Combined3701076194LTCP tunnels52%18% Noman Cole Fairfax County Separate6713434.9 On-site equalization52%26% Arlington Arlington Cnty Separate407516.3 On-site equalization41%22% H.L. Mooney Prince William Cnty Separate183610.8 On-site equalization60%30% Richmond, VA City of Richmond Combined459057 Off site CSO storage127%63% Alexandria ASA- Serves City of Alexandria & Fairfax County/Separate541080NoneSSO issues
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6 Summary of Flow Studies Percent Use in LTCP Storage Volume (mg) Suburban Cost ($2001 dollars) 1. Difference in Tunnel Storage Volume Required6%N/A0.06 x $1.265 B = $76 M 2. Difference in Annual CSO Overflow Volume (Avg year)9.4%N/A0.094 x $1.265 B = $110 M 3. Annual Wet Weather Volume Handled (Avg Year)24%N/A0.24 x $1.265 B = $304 M 4. Separate Handling by Suburbs a. LTCP Design (Largest storm in 3-year design period)12.7 %N/A0.127 x $1.265 B = $161 M b. Based on Feb 2003 stormN/A>60 mg60 x $10/gal = >$600 M c. 2-yr 24 hr stormN/A8282 x $10/gal = $820 M d. On-site equalization based on comparable WWTPSN/A 108 mg ( 51% 1 )108 x $10 = $1080 M Notes: (1) Average of Noman Cole, Arlington and Mooney plants
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7 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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8 Months After Reaching Agreement with EPA Activity123456789101112 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 DraftFinal DraftFinal Hold Pub Mtg Respond to Comments Publish Draft Plans Permit and Consent Decree Schedule Entry Pub Notice 12/20/2006 9/30/2007
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9 Alternative:B-1 BP:740 mgd to ENR (C.T.), no ECF LTCP:TDPS at Poplar Point Outfall 002 Prim & Sec West P.S. East P.S. BNR Filters & Disinf. Disinf. Outfall 001 CSO Bypass New Poplar Point PS 45 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 Tunnel OF Anacostia River SCR GRIT Headworks Anacostia River Tunnel Branch Tunnel Northeast Boundary Tunnel Complete Treatment Poplar Point Existing Sewers up to 1076 from all sources LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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10 Alternative:C-1 BP:555 mgd to C.T.+ 521 mgd ECF LTCP:TDPS at Poplar Point Outfall 002 Prim & Sec West P.S. East P.S. BNR Filters & Disinf. Disinf. Outfall 001 CSO Bypass Low Lift Pumps 521/521/ 521/336 555/511/450/370 New ECF 521 mgd 521/521/521/0 Off SiteBPWWTP Site Force Main in Tunnel - 336 mgd Capacity S & F Tunnel OF Anacostia River New Poplar Point PS 45 mgd 170 mgd Tunnel OF S & F Headworks To Secondary RFK Stadium Main & O Pumping Stations Anacostia River Tunnel Branch Tunnel Northeast Boundary Tunnel Poplar Point Complete Treatment Up to 1076 from all sources TDPS 336 mgd 166 mgd LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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11 Alternative:C-2 BP:555 mgd to C.T. + 521 mgd ECF LTCP:TDPS at BP, Clear Poplar Point Outfall 002 Prim & Sec West P.S. East P.S. BNR Filters & 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 OF Poplar Point cleared of major facilities Shaft S & F Tunnel OF Anacostia River Headworks To Secondary RFK Stadium Anacostia River Tunnel Branch Tunnel Northeast Boundary Tunnel Poplar Point Complete Treatment Up to 1076 from all sources 170 mgd TDPS 336 mgd 166 mgd LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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12 Alternative:C-3 BP:555 mgd to C. T. + 521 mgd ECF LTCP:TDPS at BP, Clear Poplar Point Outfall 002 Prim & Sec West P.S. East P.S. BNR Filters & Disinf. Disinf. Outfall 001 CSO Bypass 521/521/521/336 555/511/450/370 New ECF Off SiteBPWWTP Site Gravity Tunnel - 336 mgd Capacity S & F Tunnel OF Poplar Point cleared of major facilities Shaft S & F Tunnel OF Anacostia River 521/521/521/0 Headworks Northeast Boundary Tunnel To Secondary RFK Stadium Anacostia River Tunnel Branch Tunnel Modify O St to replace Poplar Point P.S. Main Pumping Sta. Poplar Point Complete Treatment Spills to Tunnel if > 555 mgd Up to 1076 from all sources 170 mgd TDPS 521 mgd 351 mgd LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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13 Alternative:D-1 BP: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. BNR Filters & Disinf. Disinf. Outfall 001 CSO Bypass 336/336/336/336 555/511/450/370 New ECF 521/521/521 Off SiteBPWWTP Site Gravity Tunnel - 336 mgd Capacity 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. 555/511/450/370 Headworks To Secondary RFK Stadium Anacostia River Tunnel Branch Tunnel Northeast Boundary Tunnel Modify O St to replace Poplar Point P.S. Main Pumping Sta. Poplar Point Complete Treatment Spills to Tunnel if > 555 mgd Up to 1076 from all sources 170 mgd TDPS 336 mgd 166 mgd LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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14 Alternative:E-1 BP: 555 mgd to C. T. + 521 mgd ECF LTCP:TDPS at Poplar Point Outfall 002 Prim & Sec West P.S. East P.S. BNR Filters & Disinf. Disinf. Outfall 001 CSO Bypass New Poplar Point PS 45 mgd 521/521/521/521 555/511/450/450 Existing Sewers up to 1076 from all sources Off SiteBPWWTP Site Tunnel OF RFK Stadium Main & O Pumping Stations S & F Tunnel OF Anacostia River Headworks Anacostia River Tunnel Branch Tunnel Northeast Boundary Tunnel Low Lift Pumps New ECF 521 mgd Grit Fine SCR Poplar Point Complete Treatment To Secondary 170 mgd TDPS 250 mgd 80 mgd LEGEND Existing facilities Joint Use – split based on 370 mgd Joint Use – split based on agreed LTCP split Joint Use - split based on flow proportion
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