The URL can be used to link to this page

Home My WebLink About03.c. Authorize General Manager to execute a construction contract change order $800,000 with C. Overaa & Co. for Sludge Blending Tank under the Solids Handling Facility Improvements, Phase 1A, DP 7348Page 1 of 7 Item 3.c. DCENTRALSAN MEETING DATE: OCTOBER 2, 2024 BOARD OF DIRECTORS POSITION PAPER DRAFT SUBJECT: REVIEW DRAFT POSITION PAPER TO AUTHORIZE THE GENERAL MANAGER TO EXECUTE A CONSTRUCTION CONTRACT CHANGE ORDER IN THE AMOUNT NOT TO EXCEED $800,000 WITH C. OVERAA & CO. FOR ADDITIONAL WORK FOR THE SLUDGE BLENDING TANK UNDER THE SOLIDS HANDLING FACILITY IMPROVEMENTS, PHASE 1A, DISTRICT PROJECT 7348 SUBMITTED BY: INITIATING DEPARTMENT: CRAIG MIZUTANI, SENIOR ENGINEER EDGAR J. LOPEZ, CAPITAL PROJECTS DIVISION MANAGER ENGINEERING AND TECHNICAL SERVICES - CAPITAL PROJECTS REVIEWED BY: GREG NORBY, DEPUTY GM - ENGINEERING & OPERATIONS ROGER S. BAILEY, GENERAL MANAGER ISSUE Authorization from the Board of Directors (Board) is required to execute a construction contract change order in an amount greater than $200,000. BACKGROUND The sludge blending tank (SBT), located at the Martinez wastewater treatment plant, is crucial for the sludge dewatering process. On January 16, 2020, JDH Corrosion Consultants, Inc., performed an internal condition assessment of the SBT at Central San's main treatment plant. The composite steel/concrete cover was found to be in poor condition with severe corrosion of the steel structural members. Replacement of the cover was included in the Solids Handling Facility Improvements, Phase 1 A Project and work is currently underway. The existing cover was demolished, and a new cover is being fabricated. The SBT was constructed in the 1960s as a sludge digester and was converted into a blending tank in 1980s. The tank was originally constructed as a post -tensioned tank with steel post -tensioning cables which allows for thinner concrete walls. Once installed, post -tensioning cables cannot be cut without affecting the tank's structural properties. When it was converted, all of the side manways were utilized for pipe penetrations, and the only access for inspection and maintenance is from maintenance hatches in the cover, which makes it extremely difficult to inspect and maintain the tank interior. October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 24 of 42 Page 2 of 7 The demolition of the existing cover allowed full access to the tank interior for visual inspection. On August 12, 2024, the SBT was inspected by Central San, the construction management team (MW H Constructors, Inc.), the contractor (C. Overaa & Co.) and Redwood Painting (coating subcontractor). The interior of the tank is in very good condition given its age. There was minimal corrosion of the concrete with no significant cracks or delamination observed. However, most of the original coal tar epoxy coating is missing. With the tank fully accessible and the coating subcontractor onsite to coat the tank cover, now is an opportune time to sandblast the tank walls to remove the remaining existing coal tar, prepare the tank walls, and coat the walls. The most practical and cost-effective solution would be to use the same coating being applied to the steel cover. The coating will be a glass flake containing epoxy, Sherwin Williams Sher - Glass, which provides excellent resistance to hydrogen sulfide. Coating the tank walls with the cover off will allow full access to all portions of the wall and will be much easier than coating the tank walls after the new cover is in place. In addition, the Maintenance Division has requested that the sludge blending piping inside and outside the tank be cleaned. Central San adds carbide lime to the tanks to adjust the sludge pH for polymer activation, and help the furnace process to produce consistent and acceptable ash to deliver off site (clinker control). I n time, the lime builds up against the interior piping and reduces the internal diameter for flow causing burden to the sludge blending pumps and potential failures related to over pressuring the system. Staff recommends including this work as a change order so the tank can be cleaned while it is out of service. The buildup of lime in the piping is in a state that requires immediate cleaning. The scope of work includes disassembling the piping, transporting the piping out of the SBT, blasting the interior of the piping, cleaning, and re -installing the piping back in the tank. The piping also extends into the basement and nearby tunnels. Both the coatings and cleaning of the piping are not included in the contract; however, they are within the scope of the project work and can be included to the contract upon Board authorization as additional work due to unforeseen conditions. California Environmental Quality Act (CEQA) Staff has concluded that this project is exempt from CEQA under Central San's CEQA Guidelines Section because it involves minor alterations to existing public facilities involving no expansion of use. Approval of this project will establish the Board's independent finding that this project is exempt from CEQA. ALTERNATIVES/CONSIDERATIONS The proposed work is in the best interest of Central San to be implemented now under a change order to the project. Any alternative to postpone the work will result in a significant cost increase and impact the Operations Division by performing additional shutdowns and coordination. FINANCIAL IMPACTS The construction contract change order is estimated not to exceed $800,000. The coatings work is approximately $380,000 and the piping work is $420,000. These costs have been reviewed by the construction management team and are in line with the coatings work in the project, and past spending for the pipe cleaning. The Solids Handling Facility Improvements, Phase 1 A Project has adequate contingency approved by the Board at $13,000,000. Change orders total approximately $402,328 as of September 2024. October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 25 of 42 Page 3 of 7 COMMITTEE RECOMMENDATION The Engineering and Operations Committee reviewed this matter at its meeting on October 2, 2024 and recommended RECOMMENDED BOARD ACTION Authorize the General Manager to execute a construction contract change order in the amount not to exceed $800,000 with C. Overaa & Co. for additional work for the sludge blending tank under the Solids Handling Facility Improvements, Phase 1A, District Project 7348. Strategic Plan Tie -In GOAL ONE: Customer and Community Strategy 1— Deliver high -quality customer service GOAL TWO: Environmental Stewardship Strategy 1 - Achieve compliance in all regulations GOAL FOUR: Governance and Fiscal Responsibility Strategy 3 - Maintain financial stability and sustainability GOAL FIVE: Safety and Security Strategy 1 - Reduce and eliminate risks of injury or illness, Strategy 2 - Protect Personnel and assets from threats and emergencies GOAL SIX: Infrastructure Reliability Strategy 1 - Manage assets optimally, Strategy 2 - Execute long-term capital renewal and replacement program ATTACHMENTS: 1. Presentation October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 26 of 42 Page 4 of 7 October 2, 2024 Construction Contract Change Order Request - Sludge Blending Tank Additional Work Engineering and Operations Committee Meeting Edgar J. Lopez, P.E. Capital Projects Division Manager Sludge Blending Tank (SBA Old digester repurposed to a storage tank for blending solids/sludge prior to the furnace handling process Tank cover is being replaced under the Solids Handling Facility Improvements, Phase 1A with C. Overaa & Co. Tank exterior was retrofitted several years ago with a fiber wrap, including seismic considerations Future plans to be an emergency storage tank Attachment 1 'IV, October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 27 of 42 1 Page 5 of 7 SBT Interior Wall Condition Very little coal tar epoxy coating remaining Operations has determined that the operating level of the tank should be lower than the previous decade, and this is a likely cause of why the tank interior is deteriorating faster than anticipated Coating now is the ideal time and more cost effective than performing the work later Before Cleaning t 0 I] After Cleaning s October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 28 of 42 2 Page 6 of 7 Current Nozzle Buildup Current condition: Restricted nozzle reduces pump mixing efficiency Lime buildup in the piping Maintenance has requested the work be completed prior to returning the tank back into service to avoid another shut down and overall tank cleaning Change Order Costs Total estimate for the work is $800,000: $380,000 for specialty coatings $420,000 for pipe cleaning Costs are in line with bid pricing and previous cleaning efforts conducted by Central San r Q� 0ICENTRALSAN October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 29 of 42 3 Page 7 of 7 Recommended Board Action 0- Authorize the General Manager to execute a construction contract change order in the ` amount not to exceed $800,000 with C. Overaa & Co. for additional work for the sludge blending tank under the Solids Handling Facility Improvements, Phase 1A, District Project 7348 October 2, 2024 EOPS Regular Committee Meeting Agenda Packet - Page 30 of 42 4