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Home My WebLink About3. L16 Emergency Operating Plan StudyLift Station L16 Emergency Operating Plan WSB Project No. 1975 -000 I A /[+® 701 Xenia Avenue South, Suite 300 Minneapolis, MN 55416 763.541.4800 & Associates. Inc. LIFT STATION L16 EMERGENCY OPERATING PLAN FINAL REPORT FOR THE CITY OF SHAKOPEE, MINNESOTA July 25, 2011 Prepared By: WSB & Associates, Inc. 701 Xenia Avenue South, Suite 300 Minneapolis, MN 55416 763 -541 -4800 763 - 541- 1700(Fax) Final Report Lijt Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 July 25, 2011 Mr. Bruce Loney Director of Public Works /City Engineer Public Works Department 400 Gorman Street Shakopee, MN 55379 Re: Lift Station L16 Emergency Operating Plan Dear Mr. Loney: Transmitted herewith is the final report of the Lift Station L16 Emergency Operating Plan Study. WSB has evaluated potential lift station and force main failure situations and has outlined an emergency operating plan that addresses them. We have also evaluated the lift station and force main to identify desirable measures to improve their reliability or minimize down -time should a failure occur. We would be happy to discuss the final report with you at your convenience. Please do not hesitate to contact me at 763 - 287 -7195 if you have any questions regarding the report. I look forward to presenting the report to the City Council. In closing, we would like to thank you for your friendly and able assistance and that of your staff throughout the study. Sincerely, WSB & Associates, Inc. Thomas A. Roushar, PE Senior Project Manager Enclosure srb wsa &AsxoekW. Ins. Engineering r Planning a Environmental n Construction 701 Xenia Avenue South Suite 300 Minneapolis, MN 55416 Tel: 763 - 541 -4800 Fax: 763 -541 -1700 July 25, 2011 Mr. Bruce Loney Director of Public Works /City Engineer Public Works Department 400 Gorman Street Shakopee, MN 55379 Re: Lift Station L16 Emergency Operating Plan Dear Mr. Loney: Transmitted herewith is the final report of the Lift Station L16 Emergency Operating Plan Study. WSB has evaluated potential lift station and force main failure situations and has outlined an emergency operating plan that addresses them. We have also evaluated the lift station and force main to identify desirable measures to improve their reliability or minimize down -time should a failure occur. We would be happy to discuss the final report with you at your convenience. Please do not hesitate to contact me at 763 - 287 -7195 if you have any questions regarding the report. I look forward to presenting the report to the City Council. In closing, we would like to thank you for your friendly and able assistance and that of your staff throughout the study. Sincerely, WSB & Associates, Inc. Thomas A. Roushar, PE Senior Project Manager Enclosure srb CERTIFICATION I hereby certify that this plan, specification or report was prepared by me or under my direct supervision and that I am a duly Licensed Professional Engineer under the laws of the State of Minnesota. Thomas A. Roushar, PE Date: July 25, 2011 Lie. No. 12084 -- Final Report Lift Station L16 Emergency Operating Plan City ofShakopee, MN WSB Project No. 1975 -000 TITLE SHEET LETTER OF TRANSMITTAL CERTIFICATION SHEET TABLE OF CONTENTS 1 . EXECUTIVE SUMMARY ............................................................................... ..............................1 2 . BACKGROUND INFORMATION ................................................................. ..............................3 2.1 History of Shakopee Interceptor ................................................................ ..............................3 2.2 Existing Shakopee Interceptor ................................................................... ..............................3 2.3 Shakopee Interceptor Capacity .................................................................. ..............................5 2.4 Infiltration .................................................................................................. ..............................7 3. RELIABILITY AND DEFICIENCY EVALUATION ................................... ..............................8 3.1 Lift Station L16 ......................................................................................... ..............................8 3.2 SCADA System ......................................................................................... ..............................8 3.3 Pump Plugging .......................................................................................... ..............................9 3.4 Single Programmable Logic Controller ( PLC) .......................................... ..............................9 3.5 Back -up Pump Control System ................................................................. ..............................9 3.6 Monitoring Discharge Pressure ................................................................. ..............................9 3.7 Force Main and Gravity Sewer ............................................................... ............................... 11 4. DISCUSSION OF RECOMMENDED RELIABILITY EVIPROVEMENTS ..........................13 4.1 Lift Station L16 ........................................................................................ .............................13 4.2 SCADA System ........................................................................................ .............................13 4.3 Pump Plugging ......................................................................................... .............................14 44 Single Programmable Logic Controller ( PLC) ......................................... .............................14 4.5 Back -up Pump Control System ................................................................ .............................14 4.6 Monitoring Discharge Pressure ................................................................ .............................14 4.7 Force Main and Gravity Sewer ................................................................. .............................15 5. EMERGENCY OPERATING PLAN ............................................................. .............................16 5.1 Scope of Emergency Operating Plan ........................................................ .............................16 5.2 Format of Emergency Operating Plan ...................................................... .............................16 6 . COST ESTIMATES ......................................................................................... .............................18 APPENDICES Appendix 1 Chapter 1, Section 7.0 Emergency Response Program Appendix 2 Chapter 1, Section 2.0 Personnel Appendix 3 Chapter 1, Section 5.0 Response Times Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, PIN WSB Project No. 1975 -000 1. EXECUTIVE SUMMARY WSB interviewed City staff, toured Lift Station L16 and reviewed the construction drawings for both the lift station and the Shakopee Interceptor downstream of the lift station. In addition, the lift station electrical equipment shop drawings were reviewed. These efforts allowed us to gain a full understanding of the reliability characteristics of the station and interceptor downstream of the station. The lift station is in excellent condition and has sufficient reserve capacity to serve the City for years into the future. The station has multiple pumps and on -site standby electrical power which provide it with a high level of reliability. The dike surrounding the lift station was raised to an elevation of 724 feet mean sea level (MSL) prior to this spring's flood. The 100 -year flood elevation is 721 feet MSL. Therefore, the lift station is protected to three feet over the 100 -year flood. Although the lift station has a high level of reliability, WSB identified four potential failure scenarios which could render the lift station inoperable. These failure scenarios were then addressed by the Emergency Operating Plan. The failure scenarios include: • Discharge header failure • Natural disaster such as a tornado rendering the station inoperable • Failure of the single force main • Pump control system failure WSB also evaluated the lift station to identify deficiencies that could be corrected to improve its reliability. The identified deficiencies include: • Unreliable supervisory control and data acquisition ( SCADA) system • Pumps prone to plugging • Single programmable logic controller (PLC) for automatic operation of the pumps • No back -up pump control system • No means of determining discharge pressure Improvements to correct the deficiencies were evaluated and cost estimates were prepared for implementation of the improvements. Correction of the following deficiencies was recommended at this time: • Single programmable logic controller (PLC) for automatic operation of the pumps • No back -up pump control system • No means of determining discharge pressure Although the existing SCADA system is unreliable, it is not recommended that it be replaced at this time due to the high cost ($110,000) of replacement. It is recommended that City staff continue to work with the SCADA vendor over the next year to determine if low -cost improvements can be implemented to improve its reliability. If the existing system cannot be made more reliable, its replacement should be part of the 2013 Capital Improvement Plan (CIP) Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page I The pumps in the lift station are prone to plugging due to an excessive number of rags in the wastewater. A sewage grinder would eliminate the pump plugging problem. However, due to its high cost ($100,000), a sewage grinder is not recommended at this time. Rather, City staff should continue their efforts to determine the sources of the rags (likely commercial or industrial sewer users) and to direct that these users discontinue their practice of flushing rags down the sewer. If the sources of the rags cannot be identified and the rag problem persists, a sewage grinder should be part of the 2013 CIP. A sewage grinder would be cost - effective compared to the cost of staff time to clear plugged pumps and the additional electrical costs of operating partially plugged pumps. In addition, WSB recommended and provided cost estimates for repair parts and piping related to the force main. Finally, the old lift station building serves no purpose and has deteriorated. WSB prepared a cost estimate for its demolition. The Emergency Operating Plan is attached as an appendix to the report. Cost estimates for the recommended improvements can be found in Section 6. Cost Estimates. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 2 � .ITN 1cHtZeI11 ►1171i,i0T1]wR111F[/3 i 2.1 History of Shakopee Interceptor The City of Shakopee owned and operated a wastewater treatment facility (WWTF) from the early 1960s to 1971. Many of the buildings and facilities of the WWTF, which was located at the end of Marschall Road, still exist and are now owned by the Shakopee Valley RV Park. In 1971, the South Suburban Sanitary District constructed an interceptor sewer from Shakopee to the Blue Lake WWTF and the City's WWTF ceased operating. The WWTF lift station was retained by the sanitary district. The Metropolitan Council was created by the state legislature in the late 1960s and subsequently acquired the assets of the South Suburban Sanitary District which ceased to exist. From 1971 to 1998, the Metropolitan Council owned and operated the Shakopee Interceptor including the old lift station. Then, in 1998, the Metropolitan Council constructed a new lift station —Lift Station L16 as it currently exists, which they operated from 1998 to approximately four years ago when they transferred ownership of the Shakopee Interceptor to the City of Shakopee. In addition to Lift Station L16, the Metropolitan Council also transferred ownership of the old lift station to the City. 2.2 Existing Shakopee Interceptor Lift Station L16 Lift Station L16 is a modern, submersible lift station that is in good condition despite the fact that it has been in service for 12 years. The major components of the lift station include: • Wet well with three 2,200 gallon -per- minute (gpm), 125 horsepower, submersible sewage PUMPS. • Valve vault below the control room that contains the pump discharge header, check valves and shut -off valves for each of the three pumps. The vault also contains an ultrasonic flow meter to meter the flow that is being pumped. • Control room that houses the motor control center including variable frequency drives (VFDs) and across - the -line bypass starters for each of the pumps. • Generator /equipment room that houses the standby generator, generator switchgear, and the I1VAC equipment for the station. The old lift station is immediately north of Lift Station L16. No mechanical or electrical equipment is housed in it. The old lift station's only remaining function is to provide emergency storage, should an emergency interrupt pumping by Lift Station L16. A 24- inch - diameter overflow line runs from the wet well of Lift Station L16 to the old lift station. If the level in the wet well should rise to the invert elevation of the 24 -inch overflow line, wastewater would be diverted to the old lift station for temporary storage. A site piping drawing for Lift Station L16 appears on the following page. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 3 Pv >MAZ� 0 FT 15 30 701 Xenia Avenue South, Suite 300 WSB Minneapolis, MN 55416 wvxi,=beng.com ANEENEEM also ;ate=, ® 763.111 - F.763fiJ1'1700 a PLANNING a CONSTRUCTION SITE PIPING WSB Project No. 01975 -000 Date CITY Project No. LIFT STATION L16 ENCY OPERATING PLAN FIGURE 1 K: \01975 - 000 \Gd \E hlbl6 \fig IW.dw , fig 1, 7/26/20113:41:14 PM Force Main and Gravity Sewer Lift Station L16 pumps wastewater flow through the Shakopee Interceptor to the Metropolitan Council Blue Lake WWTF for treatment. The interceptor sewer consists of approximately 8,400 linear feet of single 16 -inch diameter force main which, in turn, discharges to a single 36 -inch to 42 -inch diameter gravity sewer that is approximately 10,000 feet long. The existing force main replaced the previous 14 -inch diameter one that had become unreliable due to corrosion. Approximately 1,500 linear feet of the existing force main was constructed in 1992 with the remainder of the force main constructed in 1995. Therefore, the force main is 16 to 19 years old, but is in good condition. The gravity sewer downstream of the force main was rehabilitated before ownership was transferred to the City. Therefore, it is also in good condition. A schematic drawing of the Shakopee Interceptor system appears on the following page. 2.3 Shakopee Interceptor Capacity The Shakopee Interceptor was designed to convey a peak flow of 4.5 million gallons per day. However, since its construction, the following factors have dramatically reduced the peals flow rate: • Rahr Malting Company no longer discharges process wastewater to the City system • The East and West River Interceptors have been replaced Previously, Rahr Malting Company discharged approximately 1.0 million gallons of process wastewater per day. They now treat the process wastewater in their own WWTF and discharge the treated effluent directly to the Minnesota River. The original East and West River Interceptors were constructed in 1960. Over time, the interceptors developed leaks that allowed infiltration of clear ground water through bad joints in the pipe or manholes, or through broken pipes. The volume of infiltration into these interceptors peaked during Minnesota River flood stage conditions and contributed to the previous 4.5 million gallon - per -day peak flow. Because they were in poor condition and allowed ground water to enter, both the East and West River Interceptors were replaced. On an average day, the Shakopee Interceptor conveys approximately 800,000 gallons of wastewater to the Blue Lake WWTF for treatment. During recent flood events — spring and fall of 2010 and this spring, the peak flow was approximately 2.0 million gallons per day which is a reduction of 2.5 million gallons per day from the previous flood event peak of 4.5 million gallons. Because the capacity of the Shakopee Interceptor is 4.5 million gallons per day, there is now 2.5 million gallons per day of reserve capacity to accommodate future growth. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 5 F \\ z RELEAS o LIFT 0. 1 STA' AIR L16 COUNTY w STR COUNTY z B 11 N @1 2 EDEN PRAIRIE \\ AIR & VAC RELEAS r STRUCTUR 0. 1 \ AIR VACUUM RE STR TURE NO. 2 EDEN PRAIRIE i6 15 NO. 5 AIR 8 END 16" ` °4p DIAMETER J INSPEC'.,QN STRUCTURES FORCEMAIN N0. 3 &L NO. 4 A 4 r 16" DIAMETER INS! NO. 7 F , V �JL � I FORCEMAIN 36 "x42" � GRAVITY o `"CASH y �b nM-r y I SEWER ( jq J�LJ�' E iW�AY A /% � / y N \�"A • jY T 9A sT I9 AE n , NEpIN Cp S COT T Un 'T Y C oUN � Y zI DISCHARGE TO PRIOR LAKE INTERCEPTOR n I \I B a p PLACE I2, A. t] h n CIR P. !t! 701 Xenia Avenue South, Suite 300 WSB Minneapolis, MN 55416 www.wsheng.com & Associates, Inc. TB1b/1d9W -FU id4541.1N0 INFRASTRUCTURE R ENGINEERING a PLANNING 2CONSTRUCTION uu T � XjA•�d5�re'(P" / R CXELLE 1]TH AVE E FAIRBAULI �� 8 }� CUfl �Ci Q FflENCH iRA Q ' 12 ANION VE �� 6 P 4 h 0 FT 1000 2000 SHAKOPEEINTERCEPTOR LIFT STATION L16 EMERGENCY OPERATING PLAN i )) No. 01975-000 Figure Number 2 \01975- W0\QdvNhIbl6 \FfG 2.dw , layouth 7/27/201173]9h AN 2.4 Infiltration As noted above, the peak flow during recent flood events was approximately 2.0 million gallons per day. The conclusion reached by subtracting 800,000 gallons of average day flow from the 2.0 million gallons of peals flow is that there is still 1.2 million gallons per day of infiltration entering the system during flood events. During this spring's flood event, City staff took the opportunity to investigate potential infiltration sources. A large infiltration source was identified at the Mobile Home Park near Lift Station L16. Also, another infiltration source was identified at the Shakopee Valley RV Park. These sources will be further evaluated and corrected. Although the Shakopee Interceptor has capacity to convey the volume of infiltration, the City must pay the Metropolitan Council for the additional flow. The infiltration from last fall's flood event was estimated at 18 million gallons and resulted in $35,735 in additional treatment charges. Correcting the infiltration sources that have been identified will save the City a portion of this amount during the next Minnesota River flood event. Final Report Lift Station Ll6 Emergency Operating Plan City ofShakopee, AIN WSB Project No. 1975 -000 Page 7 3. RELIABILITY AND DEFICIENCY EVALUATION 3.1 Lift Station L16 Reliability The peak flow pumped by Lift Station L16 during recent flood events was approximately 2.0 million gallons per day which equates to an average daily flow of approximately 1,400 gallons per minute (gpm). Each of the three pumps in the lift station has a capacity of 2,200 gpm. So, even under maximum flow conditions, a single 2,200 gpm pump was adequate. With three 2,200 gpm pumps, the lift station has redundant pumping capacity and is reliable from a pumping capacity standpoint. The lift station has two electrical feeds - normal power from the Shakopee Public Utilities and an emergency on -site standby generator. The standby power system includes an automatic transfer switch that continuously monitors normal power. Should normal power fail, the transfer switch will start the standby generator and transfer the station operation from normal to standby power. Because of the dual power system, the lift station is reliable from a power standpoint. Despite having redundant pumping capacity and two sources of power, the lift station pumps into a single discharge header. Should the discharge header fail, the lift station could not pump wastewater flow. Eventually wastewater would back -up into the lowest -lying basements. In addition to a discharge header failure, a natural disaster such as a tornado could render the lift station inoperable for an extended period of time. Deficiencies During interviews with City staff, the following deficiencies that diminish the reliability of the lift station were identified: Supervisory control and data acquisition (SCADA) system doesn't always accurately report alarm conditions Pumps that are prone to plugging with rags 3.2 SCADA System When the Metropolitan Council owned and operated Lift Station L16, it was monitored by their SCADA system. Prior to the City assuming ownership and operation of the lift station, the current Omni SCADA system was installed which, in essence, is a cell phone system that relies on cell phone technology. City staff has noted that alarm conditions aren't always being reported by the system and sometimes the system does not notify the correct duty person of the alarm condition. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 8 3.3 Pump Plugging Although there are three pumps in the lift station that provide redundant pumping capacity, the pumps often operate partially plugged with rags which reduces their pumping rate and increases electrical costs. City staff is attempting to identify the sources of the rags. Once the sources of the rags have been identified, the responsible parties will be directed to quit disposing of rags in the sanitary sewer. The measure will reduce the rag plugging problem from a chronic to occasional situation. WSB toured the lift station and reviewed the electrical plans for the station and the electrical equipment shop drawings. This review identified the following deficiencies that also reduce the reliability of the lift station: Single programmable logic controller (PLC) No back -up pump control system No means of monitoring discharge pressure 3.4 Single Programmable Logic Controller (PLC) The PLC controls the automatic starting and stopping of pumps. Because there is only one PLC and no back -up control system, the lift station could not be operated automatically if it failed. The PLC is 13 years old and is out -dated compared to current technology. Although parts should still available for the PLC, they would take time to get. During the period of time that the PLC is inoperable, the lift station would have to be manned 24 hours per day and the pumps started and stopped manually. At some point, parts will no longer be available and the PLC will be obsolete. 3.5 Back -up Pump Control System Lift Station Ll6 is a major lift station. Best design practice is to equip a station of its size with a back -up pump control system to automatically control the starting and stopping of pumps in the event of PLC failure. However, WSB's review of the electrical plans and electrical equipment shop drawings revealed that there is no back -up control system. As noted above, the lift station would have to be manned 24 hours per day and operated manually during the period of PLC failure. A back -up pump control system would eliminate manual operation even if he PLC failed. 3.6 Monitoring Discharge Pressure The lift station was not furnished with either a pressure transducer or pressure gauge to permit monitoring discharge pressure. Either a pressure transducer or a pressure gauge is desirable to detect partial plugging of the force main. A sketch of a pressure gauge installation appears on the following page. -" Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 9 701 Xenia Avenue South, Suite 300 WSB Minneapolis, MN 55415 ww,v ws6eng•oorn AMMENEEW iH5N14000 Fm�iB'W/17iN INFRASTRUCNRE s ENGINEERING a PLANNING a CONSTRUCTION K: \01975400\Ced\ &h0i6 \fig 1&3.dwg, flg 2, 6130/20113:12;56 PM 02" PRESSURE GAUGE (1'2" BOTTOM CONNECT) SNUBBER GLYCERIN FILLED DIAPHRAGM SEAL BLEED SCREW QUICK CONNECT Y2" VALVE (TYP) WET TAP Y2" GALVANIZED STEEL PIPE 16" DIP DISCHARGE HEADER PRESSURE GAUGE LIFT STATION L16 ENCY OPERATING PLAN CITY Project No, FIGURE 3 Date Old Lift Station Building Although it doesn't affect the reliability of Lift Station L16, the old lift station building which dates back to 1960 is in poor condition. The masonry has started to spall, steel lintel plates are corroding, and the doors and windows are in poor condition. Because the building serves no useful purpose, it should be demolished. In conjunction with the demolition, the open stairwells from the ground floor level to the lower level which serves as emergency storage should be closed in with hatches. 3.7 Force Main and Gravity Sewer Lift Station L16 pumps wastewater flow via the Shakopee Interceptor to the Blue Lake W WTF for treatment. As previously noted, the Shakopee Interceptor consists of approximately 8,400 feet of single 16 -inch diameter force main which, in turn, discharges to a single gravity sewer ranging from 36 inches to 42 inches in diameter that is approximately 10,000 feet long. Gravity sewer pipes are very reliable and are not prone to failure. So, only a single pipe is provided. Force mains, on the other hand, convey flow under pressure and can fail. Therefore, the reliability of the Shakopee Interceptor is reduced because of the single force main. Although best engineering practice does not dictate that a second, redundant force main be provided, a dual force main system would provide additional reliability. WSB. evaluated the 8,400 -foot force main. Most of the force main was constructed of polyvinyl chloride (PVC) pipe meeting the requirements of American Water Works Association (AWWA) Standard C905. PVC pipe meeting this standard is corrosion -proof and impervious to virtually any type of chemical attack. Further, because it is a water main pipe, it has a pressure rating well above the low pressure in the force main. Although most of the force main was constructed of PVC pipe, there are three sections of force main that were constructed of ductile iron pipe (DIP). These sections are as follows: Approximately 200 feet below the Mill Pond Approximately 1,500 feet in the vicinity of Murphy's Landing Last nine feet of force main upstream of the gravity sewer pipe Although DIP is a very durable pipe with a pressure rating well in excess of the low pressure in the force main, unlike PVC pipe, it is potentially susceptible to corrosion. Of the three sections of DIP, the 1,500 -foot section in the vicinity of Murphy's Landing is the greatest concern from a corrosion standpoint. That section was installed in 1992 to replace the cast iron pipe force main that had been installed in 1970 and failed due to external corrosion. Encasing DIP in polyethylene is a very effective means of preventing external corrosion. However, the Metropolitan Council could not confirm whether the 1,500 foot section was installed with polyethylene encasement. To determine the potential for that section of pipe to corrode through, the City should consider the following investigations: • Excavation to determine if the force main is polyethylene encased • Soil resistivity survey Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 11 The excavation should be conducted first. If the force main is polyethylene encased, it is protected from external corrosion. However, if the excavation determines that it is not polyethylene encased, a soil resistivity study should be conducted to determine the potential for external corrosion. If the soil resistivity survey indicates a high corrosion potential, it is reasonable to expect that leaks may begin occurring in the near future considering that the existing force main is now 19 years old and the original force main had to be replaced after only 22 years. If a leak develops due to corrosion, the force main will have to be excavated to expose the leaking section. If it is an isolated corrosion pit, the pipe can be repaired with a repair clamp. If the corrosion is extensive, the pipe section or sections will have to be replaced with new pipe connected to the existing pipe with repair couplings. A recommended spare parts inventory for the force main is presented in Section 4. Discussion of Recommended Reliability Improvements. If leaks begin to develop frequently, the 1,500 -foot section of DIP force main should be replaced with C905 PVC. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 12 4. DISCUSSION OF RECOMMENDED RELIABILITY IMPROVEMENTS 4.1 Lift Station L16 Discharge Header As noted in the previous section, there is a single discharge header. Should the header break or develop a major leak, the lift station could not be operated. Considering that the discharge header was constructed of a very substantial material —Class 53 DIP with a pressure rating well in excess of the low discharge pressure, failure of this header is a very remote possibility. Therefore, installation of a second, redundant header is not recommended. In the unlikely event that the header should fail, a temporary pumping system would have to be installed. The Emergency Operating Plan addresses installation of a temporary pumping system. Natural Disaster A natural disaster such as a tornado could render the lift station inoperable for an extended period of time. Obviously, there are no improvements that could be implemented to reduce this risk. Should a natural disaster strike, it would be necessary to install a temporary pumping system. The Emergency Operating Plan addresses installation of a temporary pumping system. Deficiencies In the previous section, the following deficiencies that reduce the reliability of the lift station were identified and discussed: • Unreliable SCADA system • Pump plugging • Single programmable logic controller (PLC) • No back -up pump control system • No means of monitoring discharge pressure 4.2 SCADA System The Omni SCADA system doesn't always report alarm conditions and, at times, notifies the wrong duty person. As noted, the system is a cell phone -based system with the Omni server located in Greenwood, Indiana. Because it is cell phone- based, cell towers and perhaps even satellites are on the communication path. This long communication path could be the cause of some of the unreliability. A radio -based SCADA system owned and operated by the City of Shakopee would eliminate the potential communication failures of a cell phone -based system. However, the cost of a radio -based SCADA system would be approximately $110,000. Replacement of the Omni SCADA system is not recommended at this time because of the cost of doing so. City staff should continue working with Omni to overcome the reporting failures. If the failures can't be either eliminated or significantly reduced, the Omni SCADA system should be replaced with a radio -based SCADA system in the future. Final Report Lift Station L16 Emergency Operating Platt City of Shakopee, AIN WSB Project No. 1975 -000 Page 13 4.3 Pump Plugging On occasion, rags are accidentally flushed down a sewer system. However, the pumps in Lift Station L16 are chronically plugged with rags leading to the conclusion that someone must be intentionally flushing the rags down the sewer. Too much City staff time is being spent pulling pumps and clearing them of rags. Also, the City is incurring additional electrical costs because of the reduced pumping rate of a partially plugged pump. A grinder could be installed to grind the rags into small pieces that would pass through the pumps without plugging them. However, installation of a grinder would cost approximately $100,000 and would increase the cost of operating Lift Station L16 because of the additional power and maintenance requirements. Installation of a grinder is not recommended at this time because of its cost. Rather, it is recommended that City staff continue to investigate the sources of the rags. Eventually the sources of the rags can be identified and the problem eliminated by directing the responsible parties to quit flushing rags down the system. 4.4 Single Programmable Logic Controller (PLC) As previously discussed, the reliability of the lift station is compromised because there is only a single PLC with no back -up pump control system. Although the lift station could continue to operate should the PLC fail, it would have to be operated manually. During the period of time that the PLC is inoperable, the station would have to be manned 24 hours per day. Installation of a second, redundant PLC in parallel with existing PLC is not recommended because of the complexity in doing so. However, a back -up pump control system is being recommended as discussed below. Lift Station L16 went into service in 1998. Therefore, the existing PLC has been in service for 13 years. Because of the rapid evolution of PLC technology, the existing one is out - dated. Replacement parts will become more difficult to obtain in the future. The PLC will become obsolete when parts are no longer available. Because of the age of the existing PLC, the City should give strong consideration to replacing it in conjunction with installation of the back -up pump control system recommended below. A cost estimate for a replacement PLC appears in Section 6. Cost Estimates. 4.5 Back -up Pump Control System If the single PLC should fail, Lift Station L16 could not be operated automatically. To eliminate having to operate the lift station manually, a back -up pump control system is recommended. A cost estimate for the back -up pump control system appears in Section 6. Cost Estimates. 4.6 Monitoring Discharge Pressure Currently there is no means of monitoring discharge pressure. Discharge pressure should be monitored and recorded periodically. Increasing discharge pressure would provide an indication that the force main is starting to plug. Installation of a pressure gauge on the discharge header is recommended. A cost estimate for the pressure gauge installation appears in Section 6. Cost Estimates. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 14 4.7 Force Main and Gravity Sewer As previously discussed, the Shakopee Interceptor downstream of Lift Station L16 consists of a single 8,400 -foot force main and single gravity sewer downstream of the force main. A second, redundant force main would increase the reliability of the interceptor. However, installation of a second force main would cost in excess of $ 1 million. Because of its cost, installation of a second force main is not recommended. The force main was constructed of water main material with pressure ratings well in excess of the low pressure in the force main. Therefore, rupture of the force main is highly unlikely. Two potential failure mechanisms for the force main are corrosion of the DIP sections or damage due to an excavator inadvertently hitting it. The Emergency Operating Plan addresses emergency repair of the force main. To minimize the time that it would take to repair the force main, it is recommended that the City purchase and maintain repair parts on hand. Cost estimates for the repair parts appear in Section 6. Cost Estimates. Approximately 200 feet of the force main was installed on the bottom of the Mill Pond. Because it is below water, it should never be inadvertently damaged by an excavator. However, because it was constructed of DIP, it could corrode through and begin leaking. Due to the fact that it is under water, it would be time - consuming to either repair it or replace it. Inspection structures that provide access to the force main exist on either side of the Mill Pond. In the event of a failure of the force main under the pond, a temporary force main could be laid over the ground between the structures which would alleviate the need to immediately repair or replace the failed force main. Installation of a temporary force main between the structures is addressed in the Emergency Operating Plan. WSB recommends that the City purchase the piping assemblies for the inspection structures to minimize the time that it would take to install a temporary force main. One of these assemblies could also be used if it were ever necessary to install a temporary pumping system for Lift Station L16. A cost estimate for the piping assemblies appears in Section 6. Cost Estimates. Final Report Lift Station L16 Emergency Operating Plan Ciry of Shakopee, MN WSB Project No. 1975 -000 Page 15 5. EMERGENCY OPERATING PLAN 5.1 Scope of Emergency Operating Plan WSB evaluated the following emergency conditions and developed an emergency operating plan for each. • Discharge header failure • Natural disaster • Force main failure • Pump control system failure The emergency operating plan addresses both flooding and non - flooding conditions of the Minnesota River. 5.2 Format of Emergency Operating Plan The Metropolitan Council prepared a detailed three volume operation and maintenance (O &M) manual for Lift Station L16 which was turned over to the City at the time ownership of the lift station was transferred. Because much of the O &M manual remains equally valid despite the change in ownership, WSB concluded that the existing O &M manual should be updated rather than complete the Emergency Operating Plan as a free - standing document. Volume I — Facility Management, Operations & Maintenance of the three - volume O &M manual includes the following chapters: • Chapter 1: Facility Management — Section 1.0 - Introduction — Section 2.0 - Personnel — Section 3.0 - Records — Section 4.0 - Reporting — Section 5.0 - Spill Reporting — Section 6.0 - Response Times — Section 7.0 - Emergency Response Program — Section 8.0 - Monitoring Plan — Section 9.0 - Safety — Section 10.0 - Utilities • Chapter 2: Operations — Section 1.0 - Introduction — Section 2.0 - Project Design Criteria — Section 3.0 - Collection System — Section 4.0 - Lift Station — Section 5.0 - Force Main Final Report Lift Station L16 Emergency operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 16 Chapter 3: Maintenance — Section 1.0 - Introduction — Section 2.0 - Maintenance Management — Section 3.0 - Equipment Maintenance Requirements — Section 4.0 - Valve, Gate, Other — Exercise Schedule — Section 5.0 - Spare Parts — Section 6.0 - Lubricants — Section 7.0 - Painting Revisions to the O &M manual are summarized below: 0 Chapter 1: Facility Management, Section 7.0 —Emergency Response Program was revised to include the Emergency Operating Plan which appears in the Appendix. Chapter 1: Facility Management, Section 2.0 — Personnel was outdated because the City of Shakopee now owns and operates the lift station. This section was revised with an updated listing of key personnel that also appears in the Appendix. The revised personnel section also lists the contact information of local contractors or vendors who agreed to be on -call for emergency repairs. 0 Chapter 1: Facility Management, Section 5.0 —Response Times was also outdated because Rabr Malting Company is no longer on the system and infiltration has been reduced. Rahr leaving the system and the reduced infiltration have increased response times. A new table of response times appears in the Appendix. Chapter 2: Operations, Section 1.0 — Introduction includes a schematic of the lift station influent piping, the overflow piping from the wet well to the old lift station, and the discharge force main. Neither the record drawings of the lift station construction nor this schematic adequately show the piping. WSB prepared a drawing of the piping at the lift station shown as Figure No. 1. The drawing was delivered under separate cover. A laminated copy of the drawing should be hung on the wall of the lift station control room for reference, particularly during emergencies. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Page 17 6. COST ESTIMATES Cost estimates will now appear for the recommendations made in Section 4 — Discussion of Recommended Reliability Improvements. Description Cost Estimate ($) Radio -based SCADA System ........................ ..............................$ 110,000 SewageGrinder .............................................. ..............................$ 100,000 NewPLC ........................................................ ..............................$ 45,000 Back -up Pump Control System ...................... ..............................$ 20,000 Discharge Header Pressure Gauge ................. ..............................$ 2,000 Force Main Repair Parts ................................ ..............................$ 5,000 Inspection Structure Piping Assemblies ........ ..............................$ 2,000 Demolition of Old Lift Station Building ........ .............................. 50,000 TOTAL $ 334,000 Notes: 1. The radio -based SCADA system should only be installed if the reliability of the existing Omni SCADA system cannot be improved. 2. The sewage grinder should only be installed if the sources of the rags cannot be identified. 3. The force main repair parts include two 20 -foot lengths of PVC pipe, two repair couplings and two repair clamps (sleeves). 4. The inspection structure piping assemblies consist of a flanged by plain end thimble, gaskets, and bolts. Final Report Lift Station L16 Emergency Operating Plan City ofShakopee, MN WSB Project No. 1975 -000 Page 18 APPENDICES F1nal Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 APPENDIX 1 CHAPTER 1, SECTION 7.0 - EMERGENCY RESPONSE PROGRAM (EMERGENCY OPERATING PLAN) Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 SECTION 7.0 EMERGENCY RESPONSE PROGRAM The following section should be added at the end. 7.5 EMERGENCY OPERATING PLAN 7.5.1 General This emergency operating plan will address actions that should be taken in the event of one of the following emergencies: • Discharge header failure • Natural disaster • Force main failure • Pump control system failure 7.5.2 Discharge Header Failure Lift Station Ll6 includes three submersible pumps that are located in the wet well. Piping from each of the pumps conveys pumped flow to the single common discharge header located in the valve vault below the control room. The valve vault contains a sump pump with a pumping capacity of approximately 60 gpm. A leak in the discharge header or a discharge header break resulting in leakage greater than this rate will cause the valve vault floor flooding switch to activate and sound an alarm. Eventually the valve vault will be flooded and wastewater will begin flowing into the control room. At this point, the lift station pumps will have to be turned off to prevent flooding of the control room. Repair of a major leak or discharge header break will take several hours and could even be days depending on how quickly replacement piping and fittings can be obtained. As noted in Appendix 3, the response time for average day wastewater flow is 400 minutes or approximately 6 11 /2 hours before basement back -ups will begin. For peak flow during a flood event, the response time will only be 200 minutes or approximately 3 hours. It is not reasonable to expect that a major leak or discharge header break can be repaired in 3 hours or even 6 1 /2 hours. Consequently, a temporary pumping system would be required to pump wastewater around the lift station until the leak or break can be repaired. Northern Dewatering and Rain for Rent both offer temporary pumping services. Also, each has the capability of laying a temporary force main between Lift Station L16 and Air and Vacuum Release Structure No. 1 which is approximately 100 feet from the wet well of the lift station. Both firms have 24 -hour answering services. Northern Dewatering is located in Rogers and Rain for Rent is located in Elk River. Contact information on both firms appears in Appendix 2. Both Northern Dewatering and Rain for Rent indicated approximately 3 hours to mobilize and travel to Shakopee and another 3 hours to get the temporary pumping system installed and operating. -- Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 Both Northern Dewatering and Rain for Rent have self - priming centrifugal pumps that could be used for this temporary pumping application. Both firms indicated that they can lift wastewater from a depth in excess of 20 feet. This depth is well below the assumed 708' MSL elevation of the lowest -lying basement. Therefore, no piping would be required in the wet well. The temporary pump suction line could be lowered through an open hatch into the wet well. A temporary force main would be required between the temporary pump and Air and Vacuum Release Structure No. 1. Both Northern Dewatering and Rain for Rent have the capability to install the temporary force main. Connection of the temporary force main to the existing force main would involve removing the blind flange with air and vacuum release valve from the tee in the structure and installation of a piping assembly (flanged by plain end thimble) on the tee that the temporary force main would connect to. Both Northern Dewatering and Rain for Rent indicated approximately 6 hours from the time that they receive a call to the time that the temporary pumping system would be operable. The estimated response time is only 6 '/2 hours even under average day flow conditions from the time a valve vault floor flooding alarm is received. Considering that the duty person will first travel to the lift station and diagnose a major leak or break in the discharge header before calling either of the firms, it can be concluded that the temporary pumping system will likely not be operable in time to prevent basement back -ups from occurring. The release of raw wastewater is prohibited by the Minnesota Pollution Control Agency (MPCA). However, they recognize that it is better to release raw wastewater to the environment than to damage private property or expose people to the health risk that would occur with basement back -ups. The assumed elevation of the lowest -lying basement is 708' mean sea level (MSL). To prevent basement back -ups, the bolted, gasketed cover should be removed from Manhole No. 2 on the West River Interceptor to allow wastewater flow to be relieved. That manhole has the lowest rim elevation (702.43 feet MSL) and would, therefore, offer the greatest protection against basement back -ups. The manhole is north of the flood protection dike around the lift station and is approximately 140 feet north of the toe of the dike. The Minnesota Department of Natural Resources owns the property in question. If acceptable to them, depression storage could be created around the manhole to prevent wastewater flow directly to the Minnesota River. This would permit recovery of much of the raw wastewater released which could then be pumped back into the interceptor after the lift station is again operable. Whenever the Minnesota River is above 702.43 feet MSL, opening Manhole No. 2 to relieve wastewater will not be an option. Rather, wastewater would have to be pumped from either Manhole No. 7 or the lift station wet well over the flood protection dike surrounding the lift station site. As noted above, Northern Dewatering and Rain for Rent have both indicated that it would take approximately 6 hours from the time they received a call to the time that they could have an emergency pumping system in operation. During flood stage, basement back -ups will begin occurring in less than 6 hours due to the higher wastewater flow rate as the result of infiltration/inflow into the sewer system. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 The City owns an emergency, engine - driven, trailer- mounted pump that has the capability of pumping wastewater from either Manhole No. 7 or the lift station wet well over the flood protection dike. Currently the pump is inoperable because the engine failed. However, City staff is planning to convert the pump to run off a tractor power take -off. After this conversion, the pump will again be operable. During peak flow conditions, basement back -ups will begin occurring in approximately 3 hours. However, it should be possible to deliver the emergency pump to the lift station and have it in operation within this period of time. Therefore, the City's emergency pump could be used as a stop -gap measure to prevent basement back -ups until either Northern Dewatering or Rain for Rent could install a temporary pumping system. Release of wastewater from Manhole No. 2 or pumping wastewater from either Manhole No. 5 or the lift station wet well would constitute a spill. The spill should be reported immediately to the State Duty Officer at 651/649 -5451. The officer will ask the caller the following questions: • Name of caller • Date, time and location of spill • Telephone number for call - backs at the spill location • Whether local emergency officials (fire and police) have been notified • Volume involved in the spill • Responsible party for the spill and telephone number • Whether surface waters have been impacted • Cause of spill and current situation 7.5.3 Natural Disaster Because Lift Station L16 is protected from flooding, the natural disaster that could render it inoperable would either be a tornado or high straight line winds that would seriously damage the lift station building and its electrical systems. Should either occur, installation of a temporary pumping system as discussed above would be necessary. Assuming serious damage to the building, it is doubtful that the SCADA system would be operable and the City's duty person would receive a high wet well level alarm. Rather the duty person would likely be informed of the situation by one of the City's emergency services' personnel. With this delay, there would be less time to open a manhole to relieve wastewater flow or set up an emergency pumping system before basement back -ups begin to occur. However, the emergency operating procedures would be identical to those described above for a discharge header break. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 7.5.4 Force Main Failure Because the force main was constructed of water main pipe —DIP and AWWA C905 PVC, the pipe has a much higher pressure rating than the low pressure in the force main. Therefore, pipe rupture should not be a major concern. The biggest threat of a force main break is felt to be an excavator inadvertently hitting it. Also, the DIP sections of force main could corrode and begin to leak. In the event of a force main break or leak, one of the emergency underground contractors should be contacted to excavate down to the problem and the City should furnish the items required to correct the problem — either repair clamps or new pipe and repair couplings if the contractor does not have the required materials on hand. Installing a repair clamp around a leak should only require that the lift station be shut down for a short period of time, well within the 6 'h hours of response time during average day flow and 3 hours available during flood event peak flow. Assuming a break due to excavator damage, the damaged pipe will have to be exposed, the damaged section removed and the replacement section installed with repair couplings. This procedure will take longer but should be achievable even during the shorter 3 hour response time during flood event peak flow. During lift station shut down, the wet well level and rise rate should be continuously monitored by a staff person in phone contact with the repair crew who should provide on -going estimates of the remaining time required to complete the repairs. If the wet well level and rise rate indicate that the level may rise to the 708' MSL basement back -up elevation before the lift station can be turned back on, Manhole No. 2 should be opened on the West River Interceptor to relieve wastewater flow or the City's emergency pump should be set up as described in Section 7.5.2. With one exception, installation of a temporary force main to pump around the repair area would likely require an equally long or longer lift station shut -down period to install than to make the force main repairs. The exception is the Mill Pond crossing. Because the force main is under water, a cofferdam and dewatering system would have to be installed to expose the force main for repair. Or, a parallel force main would have to be installed and the existing force main abandoned. In either case, it would take several days to facilitate repairs or replacement. In the event of a force main failure under the Mill Pond, a temporary force main should be installed. There are inspection structures that allow access to the force main on either side of the Mill Pond crossing. A temporary force main could be laid on the ground between the inspection structures. The temporary force main could be connected to the existing force main by removing the blind flanges from the tees in the inspection structures and then bolting a piping assembly (flanged by plain end thimble) to each of the tees. The temporary force main would then be connected to the plain ends of the thimbles. Both Northern Dewatering and Rain for Rent have the capability to install the temporary force main. By laying the temporary force main first and making the connections last, it should be possible to install it even within the 3 hour response time available during flood event peak flow. To speed the installation of the temporary force main, the City should keep two piping assemblies on hand. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 7.5.5 Pump Control System Failure The pumps in Lift Station L16 are controlled automatically by the PLC. There is no back -up control system. If the PLC fails, the pumps will not operate automatically. In the event of PLC failure, the pumps would have to be controlled manually. The pumps should be switched from the VFD position to the bypass contactor position. The wet well level would then be monitored by viewing the gauge on the bubbler panel which is to the left of the Omni panels. When the wet well level reaches the "on" level, one of the pumps should be switched to the "hand" position. After the wet well reaches the "off' level, the pump should be switched to the "off' position. To avoid too many starts and stops, the pumps should be alternated. Pump no. 1 should be started and stopped followed by Pump no. 2 and then Pump no. 3. Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 APPENDIX 2 CHAPTER 1, SECTION 2.0 - PERSONNEL Fina[Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 The following table should be substituted for existing TABLE I -1 -2 -1 Key Facility Personnel in Chapter 1, Section 3.0 — Personnel of the O &M manual. That table included the names of several Metropolitan Council staff members. However, now that ownership and operation of the lift station has been transferred to the City, only City and SPUC personnel have been listed. TABLE I -1 -2 -1 (REVISED) KEY FACILITY PERSONNEL NAME TITLE AND RESPONSIBILITY PHONE EMERGENCY PHONE ORGANIZATION Bruce Loney DPW /City Engineer 952- 233 -9361 612 - 369 -7488 City of Shakopee Mike Hullander Public Works Superintendent 952- 233 -9554 612 - 369 -7096 City of Shakopee Dave Rutt Street Supervisor Lift Station Operator 952- 233 -9556 612 - 369 -7694 City of Shakopee Lon Schemel Water Superintendent Mater 952- 233 -1504 952- 445 -6681 SPUC Joe Adams Electric Superintendent Electricity 952- 233 -1501 952- 445 -6681 SPUC Jeff Tate Police Chief Law Enforcement 952- 233 -9421 952- 292 -9529 City of Shakopee Rick Coleman Fire Chief Fire 952- 233 -9579 612 - 490 -9501 City of Shakopee Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 The following table of emergency contractor contracts should be added to Chapter 1, Section 3.0 — Personnel of the O &M manual. These contractors have indicated their willingness to be on call for emergency pumping or emergency repair of the lift station and force main. TABLE I -2 -la (NEW) EMERGENCY CONTRACTORS NAME ORGANIZATION RESPONSIBILITY PHONE EMERGENCY PHONE Erin O'Brien Northern Dewatering Emergency Pumping or Temporary Force Main 763- 428 -2616 763- 428 -2616 Art Martinez Rain for Rent Emergency Pumping or Temporary Force Main 651- 755 -6006 763- 323 -2085 Mark Houser Choice Electric Electric Failure 952- 445 -2625 612 - 363 -8326 Ken Kawiecld In Control PLC Failure 763 - 783 -9500 763- 783 -9500 Kyle Higdem Quiring Excavating Force Main Repair 952- 496 -0151 612 - 490 -8111 Steve Ingram Valley Rich Force Main Repair 952- 448 -3002 612 - 839 -8502 Jeremy Gylland Northwest Asphalt Force Main Repair 952- 445 -1003 952- 292 -8368 Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 APPENDIX 3 CHAPTER 1, SECTION 5.0 - RESPONSE TIMES Final Report Lift Station L16 Emergency Operating Plan City of Shakopee, MN WSB Project No. 1975 -000 The following table should be substituted for existing TABLE I -1 -6 -1 Emergency Response Time Estimates in Chapter 1, Section 5.0 — Response Times. The response times represent the number of minutes that can elapse between high wet well level alarm and when pumping of the lift station must be restored to prevent back -up into the lowest -lying basement. Because Rahr Malting Company no longer discharges process wastewater to the system and infiltration has been reduced, current flow rates are lower than when the lift station first went into service. The reduction in flow rate has had the effect of increasing response time. TABLE I -1 -6 -1 (REVISED) EMERGENCY RESPONSE TIME ESTIMATES SYSTEM STORAGE (gallons) FLOW FLOW WET WELL OLD INTERCEPTOR RESPONSE CONDITION RATE (gpm) STATION SYSTEM TIME (minutes) Flood Peak 1,700 gpm 64,000 114,000 173,000 200 Average Day 850 gpm 64,000 114,000 173,000 400 Notes: 1. System storage is based on a 708 MSL elevation which was assumed to be the elevation of the lowest -lying basement. There are manholes on the West River Interceptor with lower elevations. However, these manholes have gasketed, bolted, covers. Therefore, wastewater flow will not flow out of them. 2. Total system storage is 351,000 gallons. 3. The flow rates reflect the higher flow rates during day -time hours. Final Report Lift Station LI6 Emergency operating Plan City of Shakopee, MN WSB Project No. 1975 -000