No preview available
2013-26 TETRA TECH April 25, 2013 Mr.James Kinzler City of Clermont East Side Water Reclamation Facility 3335 Hancock Road Clermont,Florida 34711 Subject: City of Clermont Professional Services Proposed for the Eastside Chlorine Decay and Disinfection By-Product Study Tt#: 200-BP08310 Dear Mr. Kinzler: Tetra Tech is pleased to furnish this proposal for professional services for the chlorine decay and disinfection by-products study of seven (7) wells in the eastern distribution system. Additional details along with a cost breakdown have been included in the detailed scope of services attached. As requested the proposed fee of $19,918 for this scope of service will be funded from the remaining unbilled budget in the Westside WTP Project. The total fee for the final design task of the Westside WTP Project will be reduced from $280,844 to $260,926. The $19,918 will be reallocated to a new Task No. 13: Eastside Water Quality Study and will be invoiced through the Westside WTP Project. Tetra Tech looks forward to serving the City of Clermont on this project. If you should have any questions,please do not hesitate to contact me at 407-839-3955. Very truly yours, Approved: Tetra Te_c_h2 . City of Clermont .��. Jon D.Fox,P.E. By: iA. A Vice President I . Date: 0 l 2D13 Attachments BAF/BP08310/Kinzler Eastside WQ C: Brian Foulkes,P.E.,Tetra Tech Tetra Tech, Inc. 201 E Pine Street.Suite 1000,Orlando,FL 32801 Tel 407 839 3955 Fax 407 839 3790 www tetratech corn ATTACHMENT "A" SCOPE OF SERVICES Eastside Water Distribution System Chlorine Decay and Disinfection By-Product Study A. BACKGROUND In the final design stage of the Westside Water Treatment Plant (WTP), water quality samples from the Disston Well indicated high levels of total organic carbon (TOC). Due to increased treatment costs associated with removal of TOC, Tetra Tech performed an analysis to determine the feasibility of eliminating substandard wells in the western water distribution system and supplying water from existing wells in the eastern distribution system. A computer model was used to simulate existing conditions in the City's system and determine deficiencies and required improvements under various conditions. Based on the analysis and relying upon the accuracy of the initial hydraulic model provided it appears to be feasible to combine the east and west distribution systems to meet existing maximum day demands (MDD) plus fire flow delivery requirements. Water age scenarios were set up to estimate the age of the water in existing 2013 average day demand (ADD) and existing 2013 MDD simulations for a combined system. It was observed that in the existing ADD condition the average water age in the system is 60 hours and the maximum water age is 106 hours. During the simulation for the existing MDD condition the average water age in the system is approximately 31 hours with a maximum water age of 74 hours. This increased water age could impact both chlorine residual and disinfection by-product formation (DPB). Prior to implementing a combined system the City requested Tetra Tech perform a water quality analysis on the seven (7) wells in the east water distribution system to identify any potential issues associated with increased water age. B. SCOPE OF SERVICES Task 1—Raw Water Collection and Testing Seven(7)existing wells serving the Eastside distribution system will be sampled. Samples will collected by Tetra Tech staff at each well under supervision of City personnel. Additionally, basic water quality analysis (conductivity, temperature, and pH) will be performed on-site to characterize the raw water samples. The water samples will be transported back to the Tetra Tech Laboratory to conduct the bench scale testing. One(1) sample from each well will be sent to the laboratory to test for alkalinity,TOC,and total sulfides. Task 2—Chlorine Demand/Decay and Disinfection By-Product Formation Bench Scale Testing Each of the seven (7) water samples will be analyzed during a chlorine demand/decay (CD/D) test and a disinfectant by-product formation (DBPF) test. The primary goal of the CD/D testing is to evaluate the free chlorine demand and chlorine residual decay of the groundwater to determine the necessary chlorine dosage to maintain a residual in the distribution system over a period of 7 days. The CD/D test involves dosing chlorine solution into amber glass bottles containing water samples, and measuring the loss of chlorine residual over time. Several initial chlorine dosages will be analyzed for each sample, in order to determine the target chlorine dosage for the DBPF testing. These results can then be compared to the anticipated water age from the hydraulic model to see if there are any potential concerns with maintaining BAF/Scope 041013(2) © TETRA TECH Tt#200-BP08310 -1- 041013 chlorine residuals in the system. The CD/D study will be performed in accordance with Standard Methods Procedure 2350 B. To determine the disinfection byproduct formation (DBPF) potential in the eastern wells, a Simulated Distribution System DBPF (SDS-DBPF) study will be performed in accordance with Standard Methods Procedure 5710-C. The primary goal of the SDS-DBPF study is to evaluate the rate of formation of THMs and HAA5s in the samples when exposed to a free chlorine residual. Aliquots of raw groundwater from each well will be added to amber glass bottles and will be dosed with the target chlorine residual from the CD/D study. Bottles will be dechlorinated and preserved at pre-selected chlorine contact times, and then sent to a certified commercial laboratory to determine the THM and HAA5 concentrations. A THM and HAA formation curve will be constructed for each well from the DBPF results. Each curve will consist of at least six(6) samples so that a correlation between DBP formation and water age can be derived. The results will be compared to the anticipated water age from the hydraulic model to see if there are any potential concerns of DBP formation with respect to the Stage II DBP rule maximum contaminant limits(MCLs)and other requirements. Task 3—Final Report The previously submitted Combined System Feasibility Study will be updated to contain a summary of CD/D and DBPF studies and the effects on the combined system. The report will contain the conclusions and recommendations as they relate to water quality issues associated with combining the east and west distribution systems. Four draft(4) copies of the Memorandum will be forwarded to the City for review. Following a review meeting to discuss any comments, four (4) copies of the final memorandum will be delivered to the City. C. COMPENSATION SUMMARY The proposed Lump Sum compensation for the Scope of Services described above is $19,918 as described in Section B. A task breakdown of labor hours and fees is provided in Attachment B. D. SERVICES NOT INCLUDED All outside laboratory testing will be paid directly by the City. The laboratory fees for this assignment are estimated at approximately$13,000. BAF/Scope 041013(2) © TETRA TECH Tt#200-BP08310 -2- 041013 0, 0 E 1 $ ICI i F. , I tr a. W 0 in q a p p S N N .n 2 .0 12 I WI C �� a N , 1 1 Il ♦ f i ue tnsl wpupp',spud fuJo4ae19)Al C Z, s d � •� a§ 3 ' " s ~ cue � '° S me) »feat i ua(u.d _ I O ^I f n O ) !✓b fauna 'aim-peat U91dpI10 e3 31:41§ m - ' 3 3 1 • '7 7 r.• N a _ o x CO C E ul go Id O ego O CL c d •• O u o V u ~ ei © W Q vii o I 1 F