Combined Sewer System Long Term Control Plan - DC Water

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Selection of Draft LTCP The monthly fecal coliform geometric mean is most affected by the boundary conditions. Transient wet weather pollution sources like CSOs have less impact on the geometric mean. This is particularly true because the magnitude of CSO discharges to Rock Creek is small. Rock Creek is predicted to exceed the Class A standard every month of the year. Providing a high degree of CSO control of between zero and 12 overflows per year still will not enable the standard to be met. CSO control does not have a large effect on the geometric mean. In May (the wet month), the predicted fecal geometric mean at the zoo is 1313. Reducing overflows to 12 and 2 per year change the predicted geometric mean to 1,276 and 1,233, respectively. CSOs can affect the hourly or daily concentrations of fecal coliform in Rock Creek. Because the travel time in Rock Creek is so short, the number of days CSOs impact the Creek is a function of the number of overflows. As shown in the table, reducing overflows to 4 per year, reduces the number of days of impact to 3 days. Reducing overflows to 2 per year, reduces the days of impact to 2 days per year. Separation produces worse water quality than a high degree of CSO control because a large amount of storm water is treated in the combined sewer system. 9.6.4.2 E. Coli As with fecal coliform, the effect of varying levels of CSO control on e. coli concentrations was analyzed. Complete data is presented in Appendix D, while selected results are shown in Table 9-15. The e. coli and fecal coliform results track each other very closely and the observations made for fecal coliform apply to e. coli. \\Gh-wash\ENG 1160\LTCP\LTCP Final\Sec 9.doc 9-40 FINAL - July 2002
Table 9-15 Effect of CSO Control On E. Coli in Rock Creek Existing SSWS and Upstream Loads Selection of Draft LTCP M Street Zoo DC/MD Boundary Reduced SSWS and Upstream Loads 1 Existing SSWS and Upstream Loads Reduced SSWS and Upstream Loads 1 Existing SSWS and Upstream Loads Reduced SSWS and Upstream Loads 1 All Year May to Sept. All Year May to Sept. All Year May to Sept. All Year May to Sept. All Year May to Sept. All Year May to Sept. Parameter # Months Exceeding 126/100 ml Geometric Mean No Phase 1 Controls 12 5 12 2 12 5 12 3 12 5 0 0 Phase 1 Controls 12 5 12 2 12 5 12 3 12 5 0 0 Pump Sta. Rehab. 12 5 12 2 12 5 12 3 12 5 0 0 12 Overflows/yr 12 5 12 2 12 5 12 3 12 5 0 0 8 Overflows/yr 12 5 12 2 12 5 12 3 12 5 0 0 4 Overflows/yr 12 5 12 2 12 5 12 2 12 5 0 0 2 Overflows/yr 12 5 12 2 12 5 12 2 12 5 0 0 0 Overflows/yr 2 12 5 12 2 12 5 12 2 12 5 0 0 Separation 12 5 12 5 12 5 12 5 12 5 0 0 # Days E. Coli > 126/100 ml No Phase 1 Controls 331 132 169 75 362 153 171 75 365 153 4 2 Phase 1 Controls 331 132 169 75 362 153 171 75 365 153 4 2 Pump Sta. Rehab. 331 132 169 75 362 153 171 75 365 153 4 2 12 Overflows/yr 331 132 168 75 362 153 170 75 365 153 4 2 8 Overflows/yr 331 132 168 75 362 153 170 75 365 153 4 2 4 Overflows/yr 331 132 168 75 362 153 170 75 365 153 4 2 2 Overflows/yr 331 132 168 75 362 153 170 75 365 153 4 2 0 Overflows/yr 2 331 132 168 75 362 153 170 75 365 153 4 2 Separation 337 135 232 99 363 153 220 95 365 153 1 1 # Days E. Coli CSO Impact (>126/100 ml) No Phase 1 Controls 26 18 N/A N/A 23 14 N/A N/A 0 0 N/A N/A Phase 1 Controls 26 18 N/A N/A 23 14 N/A N/A 0 0 N/A N/A Pump Sta. Rehab. 26 18 N/A N/A 23 14 N/A N/A 0 0 N/A N/A 12 Overflows/yr 10 7 N/A N/A 12 8 N/A N/A 0 0 N/A N/A 8 Overflows/yr 7 5 N/A N/A 7 5 N/A N/A 0 0 N/A N/A 4 Overflows/yr 4 3 N/A N/A 4 2 N/A N/A 0 0 N/A N/A 2 Overflows/yr 3 2 N/A N/A 2 1 N/A N/A 0 0 N/A N/A 0 Overflows/yr 2 0 0 N/A N/A 0 0 N/A N/A 0 0 N/A N/A Separation 0 0 N/A N/A 0 0 N/A N/A 0 0 N/A N/A # Days E. Coli CSO Impact (>576/100 ml) No Phase 1 Controls 16 11 N/A N/A 14 9 N/A N/A 0 0 N/A N/A Phase 1 Controls 16 11 N/A N/A 14 9 N/A N/A 0 0 N/A N/A Pump Sta. Rehab. 16 11 N/A N/A 14 9 N/A N/A 0 0 N/A N/A 12 Overflows/yr 9 6 N/A N/A 10 7 N/A N/A 0 0 N/A N/A 8 Overflows/yr 6 4 N/A N/A 6 4 N/A N/A 0 0 N/A N/A 4 Overflows/yr 2 1 N/A N/A 2 1 N/A N/A 0 0 N/A N/A 2 Overflows/yr 2 1 N/A N/A 2 1 N/A N/A 0 0 N/A N/A 0 Overflows/yr 2 0 0 N/A N/A 0 0 N/A N/A 0 0 N/A N/A Separation 0 0 N/A N/A 0 0 N/A N/A 0 0 N/A N/A Notes: 1. Separate storm water load reduced by 40%. Upstream nutrients reduced by 40%. Upstream fecal coliform reduced to 80% of water quality standards or 160 organism/100ml. 2. Zero overflows for all storms during analysis period 1988-1990. There will still be overflows under other climatic conditions. \\Gh-wash\ENG 1160\LTCP\LTCP Final\Sec 9.doc 9-41 FINAL - July 2002
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DISTRICT OF COLUMBIA WATER AND SEWE
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Acknowledgments The following Distr
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Table of Contents 3.2.1 Collection
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Table of Contents 9.6.1 Sensitive A
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Table of Contents SECTION 14 - WATE
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Table of Contents LIST OF TABLES Ta
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Table of Contents LIST OF FIGURES F
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Table of Contents LIST OF FIGURES F
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Executive Summary this condition, D
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Executive Summary relatively small
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Executive Summary Table ES-2 Recomm
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Executive Summary WASA would also b
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Executive Summary Table ES-3 CSO Ov
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Executive Summary Table ES-4 Compar
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Executive Summary 18% Figure ES -3
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Executive Summary Table ES-6 Cost I
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Executive Summary Develop compl
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Introduction 1.2 HISTORICAL BACKGRO
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Introduction CSOs. The inflatable d
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Introduction Public Participation
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Existing Conditions Table 2-1 Water
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Existing Conditions Table 2-3 Recei
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Existing Conditions The policy is b
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Existing Conditions during a single
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Existing Conditions 2.4.3 Use Attai
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Existing Conditions Government (not
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Existing Conditions Table 2-7 Compa
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Existing Conditions Anacostia River
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Existing Conditions Rock Creek As
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Existing Conditions be classified a
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Existing Systems NPDES Outfall No.
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Existing Systems Table 3-1 Summary
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Existing Systems Under the Intermun
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Existing Systems The capacities of
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Existing Systems Table 3-3 Inflatab
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Existing Systems 3.4.2 Existing Con
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Existing Systems 3.4.2.5 Control Of
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Sewer Systems Characterization Sect
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Sewer Systems Characterization 4.3
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Sewer Systems Characterization Tabl
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Sewer Systems Characterization At
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Sewer Systems Characterization Two
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Sewer Systems Characterization Para
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Sewer Systems Characterization Sinc
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Sewer Systems Characterization Wast
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Sewer Systems Characterization sele
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Sewer Systems Characterization Loca
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Receiving Waters Characterization S
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Receiving Waters Characterization 5
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Receiving Waters Characterization m
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Receiving Waters Characterization T
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Receiving Waters Characterization P
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Receiving Waters Characterization 5
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Pollutant Loads and Predicated Wate
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District of Columbia Water and Sewe
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Screening of CSO Control Technologi
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Preliminary Control Program Alterna
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Selection of Final LTCP % Imperviou
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Selection of Final LTCP Cost-benefi
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Selection of Final LTCP Table 11-10
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Selection of Final LTCP Washington
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Selection of Final LTCP Rate) treat
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Selection of Final LTCP Alternative
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Parameter Table 11-13 (continued) F
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Parameter Table 11-13 (continued) F
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Selection of Final LTCP Table 11-14
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Selection of Final LTCP Pump Statio
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Selection of Final LTCP CSO NPDES N
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Financial Capability Section 12 Fin
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Financial Capability controls. Next
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Financial Capability Percent of Hou
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Financial Capability of the financi
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Financial Capability Table 12-6 Sum
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Financial Capability Over half of
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Financial Capability The 15 and 20-
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$35 Financial Capability Figure 12-
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Financial Capability behavior. Alth
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Recommended Control Plan Section 13
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Recommended Control Plan 13.2.1 Sys
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Recommended Control Plan Regulator
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Recommended Control Plan Descriptio
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Recommended Control Plan 13.2.3 Roc
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Recommended Control Plan the case w
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Recommended Control Plan 13.2.8 Oth
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Recommended Control Plan weather, m
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Recommended Control Plan Table 13-6
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Recommended Control Plan While othe
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Recommended Control Plan Location T
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Recommended Control Plan Item Draft
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Recommended Control Plan 18% Figure
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Recommended Control Plan 13.6 SCHED
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District Columbia Water and Sewer A
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District Columbia Water and Sewer A
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Recommended Control Plan 3. The BOD
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Recommended Control Plan Figure 13-
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Water Quality Standards Review Thes
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Water Quality Standards Review Crit
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Water Quality Standards Review CSO
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Water Quality Standards Review CSO
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Water Quality Standards Review two
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Water Quality Standards Review prop
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Section 15 Post Construction Monito
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Post Construction Monitoring disbur
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Post Construction Monitoring Rainfa
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Table 15-3 Phase 3 Monitoring Post
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Post Construction Monitoring CSO Ou
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References Engineering Program Mana
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References Limno-Tech, Inc (LTI), 1
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References U.S. Environmental Prote
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Glossary Glossary A Activated Sludg
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Glossary DOH: District of Columbia
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Glossary O Operation and Maintenanc
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Glossary T TDS: Total Dissolved Sol
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41. Study Memorandum LTCP-8-5: Fina
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Appendix E - Basis for Cost Opinion
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Responses to Comments Appendix F Re
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