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HomeMy WebLinkAboutAgenda Report - March 21, 2007 E-10AGENDA ITEM So I'D CITY OF WDI i WIL COMMUNICATIC3N TM AGEN13A TITLE: Adopt Resolution Authorizing City Manager to Execute Task Order with Tread mil & Rollo for Groundwater Modeling Work for Lodi Central Plume PCE Remediation Design and Appropriating Funds ($125,000) MEETING DATE: March 21, 2007 PREPAWED BY: Public Works Director RECOMMENDED ACTION: Adopt a resolution authorizing the City Manager to execute a task order with Treadwell & Rollo for groundwater modeling work for Lodi Central Plume PCE remediation design and appropriating funds as shown below. BACKWOUND INFORMAIiON: As presented to the City Council in December 2006, staff has been working with our consultants, Treadwell & Rollo (T&R), to formulate a plan to utilize both existing and new production wells as a major part of the PCE/TCE remediation. There are a variety of technical issues that need to be resolved in order to evaluate and develop this concept in sufficient detail to estimate costs and make a strong proposal to the Regional Water Quality Control Board. T&R has proposed to develop an electronic groundwater model that will allow us to test various pumping configurations, both in terms of number of wells and capacity. In addition, the model has the capability of creating pictorial simulations of the plumes and the effects of pumping to aid in both technical evaluation as well as public presentations. (See attached proposal.) The requested appropriation includes the amount stated in the proposal ($109,400) plus a contingency for additional work and/or meetings, if necessary. FISCAL IMPACT: Doing this work at a comparable level of accuracy and certainty without the model would be cost prohibitive, if not impossible. Without the model, we would rely on judgment and past experience to make our best guesses as to well location and capacity which could either be overly conservative resulting in higher costs, or inadequate, in which case we would need to add additional wells in the future. FUNDING AVAILABLE: Central P4 mqr Trust Fund ($125,000) Kirle`1-vans, Budget MalLager Richard C. Prima, Jr. Public Works Director RCPlpmf Attachments cc: Sieve Schwabauer, City Attomey Wally Sandelin, City Engineer Charlie SvAmley, Water Servi@es Manager Phil Smith, Treadwell & Rollo APPROVED: Blair Oxf, City Manager K'iWPIPRO.ECTSIWAT€R\PCE,TCE\CentratCTreadwellRollo GroundwaterModel.doc 31712007 I March 2007 Project: 3923.12 Mr. Richard Prima Public Works Department City of Lodi 221 West Pine Street Lodi, California 95240 Subject: Proposed Scope, Schedule, and Budget City Groundwater Model Lodi, California Dear Mr. Prima: The City of Lodi (City) is currently considering the development of a comprehensive, City-wide groundwater remediation program that will likely center on the remediation of significant contaminant source areas, combined with the use of relatively high-capacity production wells and possibly lower capacity extraction wells. This approach holds promise to significantly reduce both capital and long-term operations and maintenance costs associated with the groundwater remediation program by using treated groundwater rather than disposing it, and by approaching the contaminant plumes as a single remediation program, not five separate plume - specific programs. Preliminary conversations with the Regional Water Quality Control Board (RWQCB) and other state regulatory agencies suggest that this approach will be acceptable provided that the City can demonstrate that groundwater contamination is being adequately mitigated, and in a timely manner. The RWQCB has, in the past, expressed the opinion that mid -plume extraction wells may be required to expedite remediation, although details of any plan have not yet been formulated or discussed with the RWQCB. Major questions that will likely be asked by the regulators and possibly by the community at large include the following: oo Is groundwater contamination being adequately contained and removed? oo Is the time line for attaining "clear-up" appropriate? oo Does an integrated groundwater extraction remediation program result in the movement of contamination to portions of the aquifer currently not impacted by contamination? oo Does an integrated remediation program that relies on significant groundwater extraction result in additional over -draft of the aquifer, and how would this impact long-term groundwater resources planning for Lodi and possibly Stockton? Treadwell & Rollo, Inc. Environmental & Geotechnical Consultants 555 Montgomery Street, Suite 1300, San Francisco, California 94111 Telephone (415) 955-9040, Facsimile (415) 955-9041 Mr. Richard Prima TnNK1%V1kW%W Public Works Department City of Lodi 1 March 2007 Page 2 oo Can the City "pulse" extraction wells that are used for both remediation and water supply (as supply wells are currently used) without a negative impact on the groundwater remediation program? oo What are the financial risks and benefits associated with this remediation program? To address these questions and prepare a City-wide groundwater remediation program that will be acceptable to the regulatory agencies, T&R has prepared this proposal to develop a flexible, multipurpose three-dimensional City-wide groundwater flow model of the hydrogeologic regime underlying Lodi that can be applied to the following groundwater cleanup and management tasks: oo Evaluate various contaminant source area remedial alternatives, such as soil vapor extraction, the use of injected media to expedite dechlorination, groundwater extraction, etc.; oo Evaluate remedial alternatives for the Central and potential impact to other plumes, including optimizing extraction well designs and locations; oo Develop a City-wide groundwater monitoring program, optimizing the location of new monitoring wells; oo Evaluate modifications to and assist in the management of the City's groundwater supply system including new well design, wellhead protection, groundwater recharge basins, water recycling, aquifer storage and recovery, mitigating potential overdraft, and optimizing system operation. oo Prepare GIS graphics using model results that clearly communicate remediation and water use issues to Lodi citizens, City Council and the regulatory community; oo Demonstrate and support groundwater containment and compliance proposals to the RWQCB in accordance with California legislation A13303, S131938, and AB3030; oo Improve data coordination with the Northeastern San Joaquin Groundwater Basin Groundwater Management Plan; and oo Integrate groundwater cleanup and supply management. We anticipate that the model will cover the area from the Mokelumne River south to at least a half mile south of Harney Lane, approximately 0.75 miles west to Lower Sacramento Road, and east to the CCT railroad. As the focus of the model is groundwater remediation, varying degrees of detail will be input to different portions of the model. Initially, the Central Plume Area will contain the most detail to focus on evaluating and designing extraction scenarios that include source area remediation, the use of production wells and possible mid -plume, lower yield Mr. Richard Prima TnNK1%V1kW%ft Public Works Department City of Lodi 1 March 2007 Page 3 extraction wells. Additional detail would be added to the Busy Bee, Northern, South Central/Western, and Southern plume areas as needed to scope and design remedial approaches for those contaminant plumes. The outer areas of the model would have minimal detail and serve as flow boundaries. The model will include a contaminant fate and transport component to evaluate the migration of contaminants over time. The proposed technical scope and estimated costs for model development are included in the attachment. Our approach will provide flexibility to initially focus on specific issues such as the Central Plume containment while providing a platform for broader planning for City-wide groundwater remediation and groundwater supply and management. By phasing the model construction tasks, the City can determine at several junctures how far to take the model. The model can evolve over time as additional data are obtained and uses are identified to support the City's needs. Finally, we appreciate your need to use the City's financial resotrces effectively and wisely. We share that desire, and believe that the groundwater flow model will be instrumental in achieving that goal. The true value of this model will be in the time saved in: oo Rapidly evaluating multiple remedial alternatives and pumping scenarios, oc Increasing the effectiveness of the chosen remedial alternatives, oo Demonstrating and graphically conveying a high level of understanding of the hydrogeologic regime and its response to pumping and various remedial alternatives, and oo Providing the City with a tool that will integrate operating the overall groundwater remediation program and managing water supply resources. We appreciate the opportunity to assist the City of Lodi and will contact you in a few days to discuss this proposal. Sincerely, TREADWELL & ROLLO, INC. Philip G. Smith, CPGS, REA II Vice President 1.0 GROUNDWATER MODELING TECHNICAL APPROACH 1.1 Data Compilation/ Evaluation Conceptual Hydrogeologic Model Development Prior to development of the groundwater flow model, data (much of which T&R currently has) needed for model input will be compiled, including but not limited to: oo Geologic and topographic maps, and publications pertaining to hydrogeologic features and boundaries, including faults, bedrock, and surface water bodies for establishing the model domain; oo Stratigraphic data including supply well, monitoring well and extraction well lithologic and geophysical logs for wells and test borings, and associated well construction details; oo Historical steady-state and pumping groundwater level data to create a table with the water levels and construct potentiometric maps for dry/wet of years; oo Existing hydrogeologic cross sections; oo Aquifer parameters such as hydraulic conductivity, transmissivity, and storativity from the Well 0-6R and other pumping tests and supply well specific capacity tests; oo Review of existing regional groundwater model for model input parameters; oo Historical production data for supply wells, irrigation wells and other extraction wells including operational data as available; oo Historical water quality data; oo Recharge data for Lodi Lake, and flow and recharge data for Mokelumne River and White Slough Data including any gauging station data, water quality data etc.; and oo Precipitation and irrigation data. Much of these data is already available and can be compiled relatively quickly. It is anticipated that the remaining data can be rapidly obtained and summarized rapidly. 1.2 Model Development and Construction T&R will use the compiled datasets to develop a conceptual hydrogeologic model of groundwater flow conditions for the model domain. The conceptual model, which will be a three-dimensional representation of the groundwater flow system, will be evaluated on the basis of the following components: oo Stratigraphic Analysis; oo Pumpage, Recharge and Discharge Analysis; oo Boundary Condition Analysis; oo Aquifer Parameter Estimation Analysis; and, oo Water Budget Analysis. A 3-D numerical groundwater flow model will be constructed using the conceptual model and the graphical interface modeling platform Groundwater Modeling System (GMS"m). The groundwater flow simulations will be performed using MODFLOW2000, the latest version of the U.S. Geological Survey modular finite - difference groundwater flow code. MODPATH will be used to simulate the particle - tracking and capture zones of the supply / extraction / remediation wells. Grid spacing of the model will be varied to more accurately simulate production wells, observations wells, groundwater flow, and particle tracking, without "over -modeling" the study area. 1.3 Model Calibration — Steady State Following model construction, the model will be calibrated to observed groundwater elevations until a sufficient level of correlation between predicted and observed groundwater elevations is established. During this process, model parameters like hydraulic conductivity, aquifer/ Mokelumne River interaction, aquifer/surface waterinteraction, and recharge from precipitation/infiltration will be adjusted to improve the correlation between predicted and observed water levels. This task will be facilitated using a parameter estimation package (PEST) simulations to enhance the statistical fit to observed water level data. The initial calibration will be conducted under stead) -state conditions until calibration goals are achieved. 1.4 Transient Model CalibrationNerification Following completion of the model calibration phase, transient calibration simulations will be performed. During this phase, pumping and recharge input will be varied with time based on field data, and predicted water levels for each time step will be compared to observed water levels for correlation. For model verification, the constant rate aquifer test performed at water supply Well -06R will be simulated using the groundwater flow model If other similar well data is available, additional verification runs can be performed. Predicted and observed pumping responses observed during the constant rate aquifer test will be compared to assess whether the model is accurately simulating pumping in the vicinity of the extraction wells. If the initial correlation between predicted and observed pumping responses is insufficient, model input parameters will be adjusted and the verification process will be repeated. This iterative process will continue until an acceptable match of calibration and verification data has been achieved. 1.5 Sensitivity Analysis Sensitivity analysis assesses how the model responds to variations in individual input parameters, and the uncertainty of model predictions. During the sensitivity analysis phase the least defined model parameters, such as natural and artificial boundary conditions, unverified pumping rates and poorly constrained aquifer parameters will be varied in a systematic way. Predictive simulations will be repeated with the adjusted model parameters to assess the effects of parameter adjustments on predicted performance. 1.6 Predictive Simulations The initial predictive model simulations will be of the Central Plume source area dual phase extraction system and off-site groundwater plume remedial alternatives. These simulations will be used to evaluate the effectiveness of a full-scale dual phase system and whether a single high-capacity production well in the vicinity Well -06R will adequately capture contamination without the use of up -gradient extraction wells. The potential effect of the Central Plume remediation on the Busy Bee plume will be evaluated. Additional simulations may include multiple extraction well scenarios for the South Central/Western plume, extraction and source area remediation in the Northern Plume Area, and focused in situ remediation in the South Plume. The estimated cost at this task (Section 3.0) includes time to prepare flow and transport simulations of contaminant mitigation over time, and time to prepare a limited number of documents for City use in public presentations. 1.7 Technical Memorandum A technical memorandum will be prepared at the completion of the Central Plume simulations documenting the model development process and results. Results of model calibration, model verification and sensitivity analysis will be presented to demonstrate the ability of the model to predict flow conditions. Results of model calibration, model verification, sensitivity analysis, and predictive simulations will also be presented graphically. Key decisions made during model development will be justified. Results of predictive simulations will be summarized. Recommendations for additional modeling activities made, based on the success of this effort. 1.8 Meetings Prior to start of the groundwater modeling activities, an initial meeting will be held with the City staff to discuss any pertinent issues related to the Project. In addition, all relevant City documents pertaining to the Project will be provided at this meeting. The City will periodically be updated on the progress of the model through brief project updates. Following completion of the groundwater modeling activities, a meeting will be conducted with the City staff to discuss and present the completed model and predictive results. Additionally, a meeting will also be conducted with the RWQCB to discuss and present the completed model and predictive results. Three meetings with City and the RWQCB are anticipated as part of this task. 2.0 PROPOSED SCHEDULE T&R estimates that the scope of services can be completed within approximately two to three months after receiving approval to proceed. A technical memorandum will be submitted to the City following completion of groundwater flow model development activities. T&R will adjust the proposed schedule within reasonable limits to accommodate City needs. 3.0 ESTIMATED COST SUMMARY We propose to perform the work on a time -and -expense basis in accordance with terms similar to our Technical Services Task Order Agreement signed 19 May 2004 with the City of Lodi. We have estimated the following costs for Tasks 1 through 8. Task 1— Data Compilation and Evaluation Task 2 —Model Development and Construction Task 4 — Model Calibration Task 5 — Model Verification Task 6 — Sensitivity Analysis Task 7 — Predictive Simulations Task 8 — Technical Memorandum Task 8 — Meetings (3 meetings) TOTAL ESTIMATED COSTS $ 5,000 $ 24,000 $ 12,400 $ 5,700 $ 7,200 $ 30,000 $ 15,600 $ 9,500 $109,400 RESOLUTION NO. 200746 Ai RESOLUTION OF THE LODI CITY COUNCIL AU OFVZI*G THE CITY MANAAER TO EXECUTE TASKI&IDER:11VITH TRUDWELL & ROLLO, INC., FOR GR NIA -T NER MODELING WORK FOR THE LODI CENtRAL PLUME PCE REMEDIATION DESIGN, AND FURtHER APPROPRIIATING FUNDS NOW, THIEREFCAE, BE IT RESOLVED that the Lodi City Council hereby authorimes the pity Manager to ex#cute the Task Order with Treadwell & Rollo, Inc., for groundwater modblinlg work for the Lo*i Central Plume PCE remediation design; and BE IT FUIRTHEft RESOLVED that funds in the amount of $125,000 be apptoprl W frors the Central Plumes Trust Fund for this project (proposal amount of $109,400, plus a cor*gercy for additional work and/or meetings as necessary). Dated: March 21, 2007 I hereby oertffy *it Resolution No. 2007-46 was passed and adopted by the City Council of the City of Loci in a regular meeting held Birch 21, 2007, by the fbilowing rem: AYES: CCKJNCIL MEMBERS — Hansen, Hitchcock, Katzaklan, Moiunce, and Mayor Johnson NOES: CCJUNCIL MEMBERS — None SINT: COUNCIL MEMBERS — None ABSTAIN: CC 3NCIL MEMBERS - None K$ CITY COUNCIL B013 JOHNSO% Mayor JOANNE L. MOWICE Mayor Pro' ernpore LA14RY D. HA SEN SUSAN HITCI$COCK PHO- KATIAKI 1 CITY OF LODI PUBLIC WORDS DEPARTMENT CITY HALL, 221 WEST PINE STREET P.O. BOX 3006 LODI, CALIFORNIA 95241-1910 (209)333-6706 FAX (209) 333-6710 EMAIL pwdeptQIod1.9ov http:k\www.lodi.gov March 16, 2007 aOwe# & Raho :Ilrn 5 MonljoMery Stre, Ste. 1 )0 n Ptar*sco,,CA 94111 BLAIR KING City Menoger RANDI JOHL City Clerk D. STEVEN SCHWA"ER City Attoiney RICHARD C. PMMA, ,fit. Public Works I@ir*tor l3 CT: Adopt R lution Authorizing City Manalper to Ex6ct� Task Order with Treadwe� Rollo for Groundwater Modeling Wok for Lodi Centrad Plurrw PCE Remediation Design and Appropriating Funds ($128,000) 4closed is a copy of tackground information on an item on the City Council agenda of J!dy, Mbrch 2 2007. The meeting Will be held at 7 p.m. in the (Wymil Chambero.Camegie Forum, 305 West Pine Stmt. pIs on the co nt Calendar and is usually not discussed unless a ur l Aliilamb r requ s cl cLasiom The public is given an opportunity to address ilns an the consent rear at the appropriate time. Ifyou wish to write to City Council, please address your later to City Council, t' ty of Lodi, P.O. Bo*1006, Lodi, California, 95241-1910. Be sure to allow time for the viii. Or, you may hand -deliver the letter to City Hall, 221 Vilest Pirie Street. lfyod wish to address the Council at the Council Meeting, be sure to fill out a speaker's cord (avalable at the Oarnegie Forum immediately prior to the start of the meeting) and 'e it to the City Clerk. If you have any questions about communicating with the ODundl, please conta* Randi Johl, City Clerk, at (209) 333-6702. :you have any questlpns about the item itself, please call me at (209) 333.6759. chlofd G. Priya, Jr. Y : Foible Works Wrector: 4CTREAD W i iLLROLtp_GROU*WATERMOIDEL.DOC