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Discussion Points for IMA Participants – Flow Studies

This discussion focuses on flow studies and nitrogen update in the separate systems of Blue Plains and suburbs. It explores the capacity requirements for the largest storm in the 3-year design period ('88-'90) and the volume exceeding treatment capacity. The benefits of a collective system and the current status of negotiations are also addressed.

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Discussion Points for IMA Participants – Flow Studies

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  1. Discussion Points for IMA Participants – Flow Studies December 19, 2006 District of Columbia Water and Sewer Authority

  2. Agenda • Flow Studies • Nitrogen Update

  3. Separate Systems: Capacity Requirements for Largest Storm in 3-Year Design Period (‘88-’90) DC Flow Vol. produced by flow from suburbs that exceeds capacity that suburbs have in Blue Plains Suburbs Flow Largest storm in 3-yr design period Largest storm in 3-yr design period Remaining CSOs (Allowed) Volume exceeding treatment capacity = 269 mg Excess Vol. above flow produced during largest storm in3-yr design period Tunnels Blue Plains Complete Treatment an. avg. 2 x an. avg, 4 hrs 1.38 x an. avg thereafter Volume exceeding treatment capacity = 39 mg Complete Treatment an. avg. 2 x an. avg, 4 hrs 1.38 x an. avg thereafter Excess Flow Treatment (336 mgd) Capacity that suburbs have in complete treatment at Blue Plains Outfall 001 Outfall 002 Total volume exceeding treatment capacity = Suburbs (39 mg) + DC (269 mg) = 308 mg Suburban Share = 39/308 = 12.7%

  4. Benefits of Collective System Overflow volume (64 mg+/-) Flow from DC & Suburbs is for largest storm in Avg year CSOs Suburbs Flow DC Flow 370 mgd an. avg. 2 x an. avg, 4 hrs 1.38 x an. avg thereafter DC Collection System Tunnels (194 mg) LTCP capacity Blue Plains Complete Treatment Excess Flow Treatment (336 mgd Capacity) Outfall 002 Outfall 001 Volumes exceeding treatment capacity: Collective system: 194 + 64 = 258 mg Separate Systems: 269 + 39 = 309 mg Collective system less than separate systems

  5. Summary of Storage/Equalization Volumes for Regional WWTPs

  6. Summary of Flow Studies Notes: (1) Average of Noman Cole, Arlington and Mooney plants

  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

  8. Permit and Consent Decree Schedule Draft Final Draft Final Draft Final Hold Pub Mtg Publish Draft Plans Respond to Comments Pub Notice 12/20/2006 9/30/2007 Pub Notice Entry

  9. 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 Alternative: B-1BP: 740 mgd to ENR (C.T.), no ECFLTCP: TDPS at Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks Existing Sewers up to 1076 from all sources West P.S. 740/511/450/450 Outfall 002 Filters & Disinf. Prim & Sec Main & O Pumping Stations BNR 4 New Clar. East P.S. Northeast Boundary Tunnel Branch Tunnel Tunnel OF S & F Outfall 001 CSO Bypass 336/336/336/0 TDPS 170 mgd RFK Stadium GRIT SCR Disinf. Anacostia River Tunnel S & F New Poplar Point PS 45 mgd Tunnel OF Anacostia River

  10. 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 Alternative: C-1BP: 555 mgd to C.T.+ 521 mgd ECFLTCP: TDPS at Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks 555/511/450/370 West P.S. Outfall 002 Prim & Sec Filters & Disinf. Up to 1076 from all sources Main & O Pumping Stations BNR East P.S. Northeast Boundary Tunnel To Secondary Branch Tunnel Low Lift Pumps Tunnel OF S & F 521/521/521/336 521/521/521/0 TDPS 336 mgd Outfall 001 CSO Bypass 170 mgd New ECF 521 mgd RFK Stadium Disinf. Anacostia River Tunnel 166 mgd Force Main in Tunnel - 336 mgd Capacity S & F New Poplar Point PS 45 mgd Tunnel OF Anacostia River

  11. 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 Alternative: C-2BP: 555 mgd to C.T. + 521 mgd ECFLTCP: TDPS at BP, Clear Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks Main Pumping Sta. West P.S. 555/511/450/370 Modify O St to replace Poplar Point P.S. Outfall 002 Prim & Sec Filters & Disinf. Up to 1076 from all sources BNR East P.S. S & F Northeast Boundary Tunnel Tunnel OF Branch Tunnel To Secondary 521/521/521/0 Low Lift Pumps 521/521/336/336 Shaft Outfall 001 CSO Bypass TDPS 336 mgd New ECF 521 mgd RFK Stadium 170 mgd Disinf. Anacostia River Tunnel Gravity Tunnel - 336 mgd Capacity S & F 166 mgd Tunnel OF Poplar Point cleared of major facilities Anacostia River

  12. 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 Alternative: C-3BP: 555 mgd to C. T. + 521 mgd ECFLTCP: TDPS at BP, Clear Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks Spills to Tunnel if > 555 mgd Main Pumping Sta. West P.S. 555/511/450/370 Modify O St to replace Poplar Point P.S. Outfall 002 Prim & Sec Filters & Disinf. Up to 1076 from all sources BNR 555/511/450/370 East P.S. S & F Northeast Boundary Tunnel Tunnel OF Branch Tunnel 521/521/521/0 To Secondary 521/521/521/336 TDPS 521 mgd Shaft Outfall 001 CSO Bypass 170 mgd New ECF RFK Stadium Disinf. Anacostia River Tunnel Gravity Tunnel - 336 mgd Capacity 351 mgd S & F Tunnel OF Poplar Point cleared of major facilities Anacostia River

  13. 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 Alternative: D-1BP: 555 mgd C.T., 336 mgd ECF, Equiv. to 740 C.T.LTCP: TDPS at BP, Clear Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks Spills to Tunnel if > 555 mgd Main Pumping Sta. 555/511/450/370 West P.S. Modify O St to replace Poplar Point P.S. Outfall 002 Prim & Sec Filters & Disinf. Up to 1076 from all sources BNR 555/511/450/370 East P.S. S & F Northeast Boundary Tunnel Maintains 511/450 to C.T. Tunnel OF Branch Tunnel 521/521/521 To Secondary 336/336/336/336 Shaft Outfall 001 CSO Bypass 185/4 hrs TDPS 336 mgd 336 New ECF RFK Stadium 170 mgd Disinf. Anacostia River Tunnel Gravity Tunnel - 336 mgd Capacity S & F 166 mgd Tunnel OF Anacostia River Poplar Point cleared of major facilities

  14. 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 Alternative: E-1BP: 555 mgd to C. T. + 521 mgd ECF LTCP: TDPS at Poplar Point BPWWTP Site Off Site Poplar Point Complete Treatment Headworks Existing Sewers up to 1076 from all sources West P.S. 555/511/450/450 Outfall 002 Filters & Disinf. Prim & Sec Main & O Pumping Stations BNR East P.S. Northeast Boundary Tunnel Grit Branch Tunnel To Secondary Fine SCR Tunnel OF S & F Low Lift Pumps TDPS 250 mgd 170 mgd Outfall 001 CSO Bypass 521/521/521/521 RFK Stadium New ECF 521 mgd Disinf. Anacostia River Tunnel 80 mgd S & F New Poplar Point PS 45 mgd Tunnel OF Anacostia River

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