Welcome! This is our monthly Water Operations capital project newsletter for Commission employees. Each newsletter will provide construction project updates and information about the upcoming work at our drinking water assets and facilities.
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WPF Clearwell & Backwash Pump Station Site |
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What’s on the Horizon for Water Operations? |
The Commission is embarking on large-scale upgrades to its drinking water infrastructure. Commission water infrastructure ranges from 50 to over 100 years old, and much of it is in need of rehabilitation or replacement due to its age or inability meet regulatory requirements. The Commission has also been periodically out of compliance with the regulatory limits for disinfection by-products. We have identified several cornerstone projects to complete in the next 5-7 years to address these needs, including a new clearwell and backwash pumping station (construction underway), a new conventional water treatment plant with dissolved air flotation as a clarification process, and rehabilitation of the 42-inch raw water pipe and new hydropower infrastructure.
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The following projects have progressed over the last month:
- The Clearwell & Backwash Pump Station project is underway with Nickerson continuing demolition of Slow Sand Filters #1-3 and submitting their 60% Design Documents.
- Emergency repairs of Rapid Sand Filters #3 and #6 are underway, after the Filter #6 underdrain system failed this month. AECOM is developing a new underdrain design for Filter #6, and Commission Staff are repairing grout and replacing the nozzles in Filter #3.
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Clearwell & Backwash Pump Station Project Highlights
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The Clearwell & Backwash PS project is in full swing with the demolition of Slow Sand Filters (SSFs) #1-3. Nickerson completed demolition of SSF#3 this month and is currently demolishing SSF#2. |
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Demolition of SSF #3 (SWSC Drone Footage) |
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Slow Sand Filter Demolition |
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C.H. Nickerson began actively demolishing SSFs #1-3 in early January, starting at the northeast corner of the structures. The structural concrete will be crushed, mixed with the filtration sand and other backfill material, and reused for site grading, reducing the overall project cost. |
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CH Nickerson making the first break into SSF #3 (photo by SWSC) |
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Before demolishing each section, the contractor removes topsoil and backfill from the top of the structures and stockpiles it onsite for reuse later in the project. |
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Stripping topsoil and overburden from SSF #3 (photo by AECOM) |
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Stockpiling topsoil and overburden
(photo by AECOM)
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Work is continuing through January's snowstorms and frigid weather. Our GIS department is capturing regular drone footage of the work. |
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Demolition of SSF #3 complete, and continuing into SSF #2 (SWSC Drone Footage) |
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Demolition work in the snow (photo by SWSC) |
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Stockpiling material (photo by SWSC) |
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Demolition of SSF #3 (SWSC Drone Footage) |
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Demolition in SSF #2 (photo by AECOM) |
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Nickerson is segregating the concrete material from the sand, and will use a rock crusher next to pulverize the concrete blocks into smaller stone acceptable for backfill. The contractor will place the backfill, overburden, and topsoil at the design elevation, creating the space and establishing the elevation needed for the construction of the Clearwell & Backwash Pump Station. |
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Rapid Sand Filters - Emergency Repairs |
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On January 16, WPF Operators observed that Rapid Sand Filter #6 effluent turbidities were unusually high after running a routine backwash. The operators visually inspected the filter and identified underdrain nozzles and a piece of underdrain tile that had broken through the media. The operators immediately shut the filter down for inspection.
WPF Staff removed the filter media and identified that a large section of tile underdrain had failed during the backwash.
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Underdrain nozzles could be seen from up above. These nozzles are covered with over 3' of filter media and are not visible during normal operation. (photo by Pete Thayer) |
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WPF staff removed media and uncovered the failed underdrain tiles. (photo by Pete Thayer) |
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Commission staff responded over the three-day weekend to quickly remove all of the filter media in the failed half of Filter 6. Borden Brook and Provin Mountain staff worked around the clock on the 17th to clear the media in time for an AECOM inspection of the underdrain system. Media was placed into the other half of the filter, because storing it outside would cause it to freeze.
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AECOM inspected the Filter 6 underdrain on January 18 and determined that the underdrain system could not be repaired in place, recommending full replacement with a new underdrain system. |
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AECOM inspection (photo by SWSC) |
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Closeup of failed underdrain (photo by SWSC) |
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Filter backwash data was evaluated to help determine the cause for the Filter 6 failure. Backwash pressure appears to be the highest in Filter 6, indicating that filter media that has migrated into the underdrain is creating a blockage in the filter nozzles. Filter 3 was showing similarly high pressures. The Commission decided to inspect the underdrain under Filter 3 to look for signs of a similar problem that could lead to another underdrain failure. The remaining filters will also be inspected.
WPF staff removed the media from half of Filter 3 and removed all of the filter nozzles. A close look at the underdrain showed that grout repairs are needed in Filter 3, but it appears that the filter is repairable. After the filter is cleaned, grout repairs will be made, the underdrain and flume will be flushed to remove media, new vents will be installed, nozzles will be replaced, and the filter will be put back into service within the next month.
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Commission staff finish up removing media from Filter 3 (photo by SWSC) |
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WPF staff cleaned each of approximately 5,000 filter nozzles using a pressure washer and bottle brushes. |
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Madroy Mabry pressure washes nozzles
(photo by SWSC)
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Clean nozzles waiting to be re-installed!
(photo by SWSC)
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All hands on-deck for nozzle cleaning assembly-line work (photo by SWSC).
Pictured (left to right): Rich Lafreniere, Kevin Zeneski, Beth Gillespie, and John Godard.
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Over the next two weeks, WPF staff will repair damaged areas of grout, clean sand and grit out of the underdrain system, reinstall 3,000 nozzles, and re-install the filter media. The filter will then be disinfected per AWWA standards and put back online.
Thank you to all of the Water Operations staff who came together and worked around the clock in cold, wet, and uncomfortable conditions, to keep our water flowing!
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The following projects are in construction or are in the design pipeline: |
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In Progress:
Clearwell/Backwash Pump Project -
Tighe & Bond and C.H. Nickerson (the Design-Build team for the project) is currently demolishing Slow Sand Filters #1-3. This project will replace our existing clearwell and the rapid sand filter backwash pumps, which are old and need regular maintenance to continue to run.
ACH Bulk Storage/Chlorine Building -
RH White was awarded the contract for a project and they will construct a new bulk storage tank and related equipment for ACH (water treatment chemical). The project also includes important upgrades to the chlorine building, including new scales and chlorine piping. The contractor is preparing to mobilize in March.
Phase 1 Dam Inspections - Dam inspections of our high-hazard dams were completed. Six of the Commission's dams are considered high hazard and must be inspected every two years to determine their condition and if there are any deficiencies.
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Coming Up:
WTP Design - In February we will select a consulting firm to complete an alternatives analysis and begin design of the new water treatment plant. The alternatives analysis will include plant layout and residuals handling options.
Hydropower Plan - The Commission is taking a step back from the 42-inch repair and inline hydropower design to evaluate our long-term raw water supply and hydropower options. We are currently working to select a hydropower consultant to help identify the right solution for the Commission.
Upper Lagoon Dam #2 - Tighe & Bond is evaluating options for repairing or removing Dam #2, as a result of the slope failures that occurred in August.
Rapid Sand Filter #6 Underdrain - AECOM is developing an emergency design for a new underdrain system for Rapid Sand Filter #6.
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The Old Lab and Aerator (photo not dated, circa 1914-1926). |
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