United States Environmental Protection Agency Municipal Environmental Resean Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-81 -113 July 1981 Project Summary Combined Sewer Overflow Abatement Program, Rochester, N.Y.—Volume I. Abatement Analysis Frank J. Drehwing, Cornelius B. Murphy, Jr., David J. Carleo, and Thomas A. Jordan CSO locations within the Rochester, New York, Pure Waters District served as the basis for network modeling studies. The USEPA Stormwater Management Model—Version II, Simplified Stormwater Model, and receiving water models were used to evaluate various CSO pollution abate- ment alternatives. Nonstructural, minimal structural, and structurally intensive alternatives were defined and evaluated by these models. The nonstructural approach applied Best Management Practices (BMP). Structural alternatives in- volved evaluation of conventional storage and treatment options. Cost benefit analyses of all structurally intensive alternatives were conducted using optimum treatment process train configurations developed from pilot plant evaluations, as reported in Volume II.* Preliminary analysis of BMP and minimal structural alternatives indica- ted that by addressing the major sources of pollution and by elimina- ting throttling constraints within the existing sewerage system, a substan- "Combmed Sewer Overflow Abatement Program, Rochester, N Y Volume II Pilot Plant Evaluations F J. Drehwing, C B.'Murphy, Jr., S R. Carver, D F Geisser, and D Bhargava EPA-600/2-79-031b NTIS Order No PB 80-159 262 (also available from the Storm and Combined Sewer Branch, MERL USEPA, Edison, NJ 08837) tial decrease in the total annual load of contaminants to the receiving waters from rainfall-induced CSO can be achieved for relatively small capital expenditures. These measures can be initiated within a short period of time, thereby immediately reducing pollu- tion to the receiving waters, while long term design and construction of more structurally intensive alterna- tives are undertaken. This Project Summary was develop- ed by EPA's Municipal Environmental Research Laboratory, Cincinnati, OH, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering information at back). Introduction In response to the transient water quality problems induced by periodic overflows from the Rochester Pure Waters District's combined sewer system, a project was undertaken to develop an abatement and manage- ment program necessary to achieve a cost effective solution to the CSO induced impairment of the Genesee River, Irondequoit Bay, and Lake Ontario. Other aims of the project were to demonstrate the usefulness of mathe- matical models (the Simplified Storm- ------- water Model (SSM) developed by Metcalf & Eddy, Inc., and the USEPA Stormwater Management Model— Version II (SWMM)) simulating both the urban rainfall/runoff process and the subsequent stormwater flows within a large combined sewer system; present the merits of implementing the BMP program to abate CSO; and evaluate source and collection system manage- ment options. The developed management program (including the methodology of approach, urban stormwater mathematical model- ing, and abatement alternative analysis that involved both structural and BMP measures) lead to the formulation of a master plan for CSO pollution abate- ment within the Rochester Pure Waters District. Problem Definition All programs adopted by Monroe County for the Rochester Pure Waters District are directed at meeting state and federal water quality standards established for the Rochester, NY, area. These programs specifically address the problem of receiving water quality degradation due to urban storm runoff and subsequent CSO. The study area including the major receiving water bodies, intercepting sewer network, and significant overflow relief points are shown in Figure 1. Present CSO directly contravenes established water quality standards for the Genesee River, imposes heavy nutrient and chemical loadings on Irondequoit Bay, and causes bacterial contamination of the public bathing beaches along the Rochester Embay- rrient of Lake Ontario. The latter has resulted in periodic beach closing days during the summer months. Aside from such direct impacts as ob- jectionable floating material and high bacteria loadings, the settling of oxygen demanding materials discharged during overflow events contribute to contra- vening stream standards in the lower reaches of the Genesee River under dry- weather conditions. Previous studies of the District's combined sewer system cited major deficiencies in the existing sewer system and identified the effects of CSO on the area receiving waters. Project Elements The project was divided into three basic elements: a CSO monitoring and assessment program, a CSO mathe- matical modeling program, and a pilot plant demonstration program. The monitoring and modeling programs are described in detail in Volume I (summar- ized here) and the pilot plant studies, in Volume II. As part of the overflow monitoring program, an intensive CSO flow record- ing and sampling system was imple- mented to define the frequency, volume, and pollutant characteristics associated with the District's CSO dis- charges. A drainage basin field investigation was conducted to define those basin parameters that affect the urban stormwater runoff process. These two programs provided the necessary data sets, including repre- sentative CSO hydrographsandpolluto- graphs, drainage basin characteristics, and sewer system inventory, to facili- tate model calibration and verification. Included in the modeling effort was the refinement and verification of the previously developed Genesee River Water Quality Model. The pilot plant program involved designing and constructing a pump sta- tion and pilot treatment facilities to evaluate the effectiveness of eight unit processes: high-rate flocculation/sedi- mentation, swirl degrittmg, swirl primary separation, high-rate dual- media filtration, granular activated carbon adsorption, high-rate disinfec- tion using chlorine, high-rate disinfec- tion using chlorine dioxide, and micro- screening. These results were used to develop process models and associated cost effectiveness relationships. Conclusions 1. A rigorous defining of the existing system of CSO and stormwater facilities is fundamental for devel- oping an abatement program. This definition includes identifying major drainage basins, major trunk and intercepting sewers, and CSO and stormwater relief points. 2. Installing and properly maintain- ing overflow monitoring instru- mentation are essential for both receiving water problem defini- tion and any subsequent sewer network and water quality model calibration and verification. 3. Collecting accurate rainfall data and subsequent statistical analyses, including defining the design storm, are essential in evaluating the response of the existing system as well as the ef- fectiveness of various abatement alternatives. 4. Developing a methodology of approach and defining applicable abatement alternatives early in the program will ensure that the purpose of the study is not lost and all data collection activities are conducted according to the required analyses. 5. SSM is capable of providing a preliminary screening of potential abatement alternatives involving a balance between storage and treatment. 6. SWMM can project the urban storm runoff andquantitieswithin acceptable confidence limits but is presently limited in its ability to simulate overflow quality. 7. Overflow quality can be better t simulated by applying statistical * techniques using actual moni- tored overflow data. 8. The ability to abate CSO pollution may require implementing structurally-intensive facilities. In Rochester, one structural alterna- tive involves grit removal, in con- junction with the optimized operation of the F. E. Van Lare Treatment Facility. 9. In many situations, significantly reducing the total annual load of contaminants discharged to receiving waters because of CSO can be reduced through minimal structural improvements to the existing sewer system. In Rochester, minimal structural abatement alternatives include removing three throttling con- straints, modifying or adjusting overflow weirs and regulators, and using inflatable dams for increased in-system storage. 10. Implementing nonstructural abatement alternatives (BMP)can reduce the annual load of pollu- tants discharged by CSO and A stormwater. Implementing inflow fl ------- restriction regulations(e.g., use of porous pavement) in select areas and more intensive street clean- ing and sewer maintenance can alleviate a portion of CSO induced water quality degradation. 11. Based on projections using a simplified mathematical storm- water model, the nonstructural and minimal structural abatement alternatives are expected to reduce significantly the existing volume of CSO and the average annual BODsand TSS loadings to the Genesee River. Recommendations It is recommended that: 1. Network models, such asSWMM, be relied on, mostly, for determin- ing runoff and overflow volumes for selected storm events and less for estimating the quality of the runoff. Use statistical analyses of actual field monitored data to estimate surface runoff quality. 2. Initial screening, planning, and designing of storage and treatment abatement alternatives be made with a simplified continuous simulation model to avoid the prohibitive computer costs associated with many de- tailed hydraulic models. Use only a model that will satisfy the ob- jectives of a study at the least possible cost. 3. Hydraulic analysis and design of sewer systems be conducted with a detailed network model such as SWMM. 4. Rainfall characterization be based, primarily, on the use of historical precipitation data, although the design storm ap- proach may have to be applied in certain situations. More research should be conducted on the con- cept of design storms to establish design rainfall hyetographs that could be applied with mathe- matical network runoff models. 5. Models not be used to predict runoff/overflow quantities or qualities without proper field cali- bration and verification. A rela- tively detailed field monitoring program is essential in providing the background data for proper model calibration and verification. 6. More statistical analyses be con- ducted to better establish the correlation between runoff quality and parameters such as rainfall and land use characteristics. 7. Detailed hydraulic analyses be conducted to better define inter- ceptor throttling constraints, regulator/weir modifications, and control structure locations. SWMM is capable of providing the required analyses. 8. BMP be considered when conduc- ting any CSO abatement program. In many instances implementing BMP, possibly in conjunction with minimal-structural alternatives, can alleviate many problems associated with frequent CSO discharges. Failure to investigate their effects could severely limit establishing cost effective abate- ment solutions. 9. A program be initiated to investi- gate the effectiveness of in- creased street sweeping on reducing the pollutant loadings to the sewer system. Include provisions for correlating the effects of increased street sweep- ing operations, types of equip- ment used, street parking use and restrictions, and program costs for reducing surface pollutants avail- able for washoff during storm events. 10. A master plan for CSO pollution abatement be developed and implemented that follows a sequence of phasing of required system improvements according to their projected cost effective- ness. 11. Scheduled reviews be included in any CSO abatement program to periodically evaluate the effec- tiveness and cost/benefits asso- ciated with alternative imple- mentation. This periodic review will ensure that previously defined objectives are being met and, if not, changes to the program can be made to better solve the initial problems. The full report was submitted in ful- fillment of Grant No. Y-005141 by O'Brien & Gere Engineers, Inc., under the partial sponsorship of the U.S. Environmental Protection Agency. 6 U&QCNEftNMEHtmKnNaOFFICE W1 .T57-OU/7239 ------- Frank J. Drehwing, Cornelius B. Murphy, Jr., David J. Carleo, and Thomas A. Jordan are with O'Brien & Gere Engineers, Inc., Syracuse, NY 13201. Richard Field, Anthony Tafuri, and Lawrence Moriarty (retired) are the EPA Project Officers (see below). The EPA Grant Officer is Ralph G. Christensen (see below). The complete report, entitled "Combined Sewer Overflow Abatement Program, Rochester. N.Y.: Volume I. Abatement Analysis," (Order No. PB 81'-219 602; Cost: $15.50, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield. VA 22161 Telephone: 703-487-4650 The EPA Project Officers can be contacted at: Storm and Combined Sewer Section Municipal Environmental Research Laboratory-Cincinnati U.S. Environmental Protection Agency Edison, NJ 08827 The EPA Grant Officer can be contacted at: Great Lakes National Program Office USEPA. Region V Chicago, IL 60604 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 RETURN POSTAGE GUARANTEED Third-Class Bulk Rate ------- |