Replies

Gate Side seals susceptible to Debris? Diving Boats (divers) working to "unseal" or "ready" gates 1 day before a new flow - Unusual Stream Shooting as an arc in Gate 3?

According to DWR/FERC documentation, all Gates have been refurbished in their inflatable side seals & other hardware problems found in 2007 (DSOD 2015 report). So why is Gate 3 "streaming" in a leak? The circular "splash" reveals the streaming nature of the flow. The curvature or angle cannot be from a gravity flow (drain) directly above. Clues are revealed in photographs of fine floating debris. Divers were required to "unseal" the gates for a new flow on March 17 (boat/diver pic taken March 16). DSOD Inspection reports and DWR O&E reports detail the difficulty in "tuning" the side seal spacing against the stainless steel sidewall plates (embedded in the concrete gate walls).

Evidence infers that this design of "tuning" is easily knocked out of alignment from gate operation. Heavy bronze slide shoes (3 to each side) - called "guide shoes" - rub on the stainless steel plates as part of the side seal assembly. Yet, the side seal assembly is a weak structure that can be "shifted" with respect to the forces of the approx 33 ton Radial Gate body that they are "eyebolt" compression linked to. Gate 3 is also the gate with the highest number of known cracks in the 50 yr old anchor tendons.

I suspect a piece of debris lodged into a side seal causing an unusual stream opening that may be causing the unusual "arc stream" revealed in the photograph.

This issue also answers why DWR has never been able to seal the gates. Even after documenting all of the eight gate refurbishments to FERC, the gates still cannot properly seal. DWR cannot filter all of the fine debris during flows - even their log boom system is not functioning.

Debris jamming in the side seal assemblies were linked to multiple occasions of gates binding. I suspect this is a weakness that will not be brought to light.

Unusual "arc stream" observed in Gate 3 near the sidewall concrete column of the gate. Picture taken before March 16 "diver" crew work to unseal gates.

Divers "unsealing" debris caught in the side seal assemblies of the gates. Gates will "jam" if too much debris is wedged into the sidewalls. DWR image taken March 16, one day before reopening the flow on March 17. DWR photo metadata notes "unsealing" of the gates.

Massive Gate 3 Leak (2003 DSOD report photo) - DWR readying to troubleshoot the issue by closing gate inlet with stoplog panels.

This image reveals just how serious the gate problems are in the side seal assemblies. Massive pressurized leakage observed from wide gaps in the side seal. DWR found that the side seals were irregular in gap to wall seal spacing, even though the design had "J-bolts" that were intended to allow fine tuning the spacing to the wall to the spec setting of 0.040 inches (all along the 38+ foot arc on each side assembly).

DSOD Inspectors noted that significant leakage from the gates to be a common condition ("extensive leakage" was considered normal). Problem is - these "gaps" allow lodging or wedging of debris. A "frozen" gate (unmovable) is a Category 1 Failure Mode and is extremely serious. The root of the problem goes to the mechanical stability of the side seal assemblies - note the angled connection bolts in Gate 3. These are "bent" bolts (in the pre-fix design). A very weak alignment mechanical design when considering the forces the approx 33 ton main radial gate may apply in dynamic forces (0.017 inch effective axis "vibration" causes complete loss of the 0.040 specified "gap" spacing").

The side assemblies may be outgunned in the mechanical forces from the heavy radial gate - thus "shifting" the gap alignment constantly.

Even after the divers worked to clean out and "unseal" the gates March 16 (see post above), Gate 7 is observed closed in the March 17 flow. (perhaps it was jammed and causing the lift motor circuit breakers to trip from excessive current?). The other possibility is that DWR is having gate issues to where they are sequencing neighboring gates to shift the hydrostatic pressure to allow "lifting" of a sensitive gate (i.e. keeping 7 closed to allow a differential flow reduction on Gate 8 - and thus allowing an easier lift of Gate 8). However, information will likely not be flowing like water on these issues.

Massive leakage gushing from a supposedly "sealed" Gate 3. DWR prepping closing the inlet to Gate 3 to figure out the problem.

DWR keeps Gate 7 closed during startup for some reason (jam on 7 or alleviating issue on 8). Flows start in paired gate openings from the middle and are paired outward until the desired base flow startup is achieved. This photo is an abnormal condition.