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Gallery Tunnels in Oroville Dam - & DWR's "natural spring" theory - Where's the water?

Carved in the rock in the canyon walls of Oroville dam are access tunnels referred to as "Galleries". They are encased in reinforced concrete and backset into grooves along the abutment rock wall. The Gallery tunnels along the left and right abutments of the dam are called "Grout Galleries" as they follow the grout sealed rock boundaries of the canyon.

Since DWR believes that "a natural spring" may be the cause of the green wet area dam face leakage, even though there are difficulties with the "uphill flow" physics :-) , DWR could investigate for any small moisture spots within the tunnels. A "natural spring" in the hillside could possibly create minor "wet spots" or "seepage" in the concrete, in the location of a purported "spring". The Grout Gallery Tunnel routes downward along the full hillside from 820ft in elevation to the bottom of the dam at the concrete core block. Any "seam" in the weathered rock of the hillside that is producing waterflow in a "natural spring" could elevate the water density surrounding the tunnel.

Dam Safety Inspection reports have documented areas of seepage within these tunnels, but not in the mid to upper elevations. The greatest "seepage" flow is deep in the core block at a seam of section joints 12-13 in the "bypass Gallery" (another connecting tunnel in the core block). This flow is significant, but normal under the high water pressures in the concrete block at the bottom of the reservoir lake level (but within the center of the dam). Sump pumps drain all of the "seepage" inside the concrete core block into a drain pipe that dumps it into one of the two outlet "diversion" tunnels the Hyatt power plant uses in exhausting turbine flow(s).

Yet the Safety Inspection reports do not mention any "seepage" of note in the upper elevations of the Grout Gallery Tunnel in the Left Hillside. Perhaps there is a "clue" if there were a "natural spring". Where's the water? AND- this has to be special water in that it may need an ability to "flow uphill" :-) .

Strong Seepage Water Flow deep inside the dam (normal) within the large concrete "core block" the main earthen clay core is built upon. Sump pumps drain this water into Diversion Tunnel 2 in the Hyatt outlet tunnels.

Original Archive document describing the Left and Right Grout Gallery Tunnels - re-inforced concrete tunnels along the rock abutment canyon walls of the dam. Entrance to the Left gallery tunnel is at/near 820ft.

Entrance to Left Grout Gallery Tunnel - goes 780ft down to the concrete core block at the base of the center of the dam - Fans at this entrance circulate fresh air to the lower tunnels below

Fascinating info, regarding the tunnels.

Incidentally, I’ve been through the “bowels” of the nearby Chickamauga dam, and there are areas way down below that are always wet. There’s a pumping system and a trough that runs through at least one of the galleries beneath the powerhouse at the south end of the dam. I’d be curious as to how that’s possibly changed over the years, but the guy that was taking us through was a former plant operator and said that it was like that 30 years ago when he worked there.

Incidentally, Chickamauga dam was built by TVA in the late 1930s. It is nowhere near as tall as Oroville, but it can spill about 470,000 gps (presently, 3 or 4 of the 18 spill gates are closed off because of a stalled lock improvement project that the federal government started a decade ago).

The tallest earthen dam in California before Oroville was finished was Trinity. Also in Norther CA.

Above are NASA JPL photos showing this dam and lake now at 97% capacity. The Sacramento Bee has an article of concern about this dam just because it is similar and subjected to the huge snow balance while at capacity. It has an internal spillway entry much different from Oroville.

Look up Trinity on the web and it has a lot of information.

Those of us that have been on FreeRepublic for a long time know our sites history of following geophysical events as well as geopolitical events all as they unfold. "Two-Thirds Vote Aye" and I did an armchair analysis of the volume of the twin tower debris needed to be removed the week that the towers came down. I was at a seminar give by the head of the Forensic team sixteen months later and found out we were within 5% as I recall.

JanetJanet may want to start a Reservoir/Dam/SnowMelt thread in general, as I think we are in for an interesting ride this next few months as Oroville serves as a public pointer to the weak points the public should watch for in the unfolding summer.

Oroville 1964 - Sharp Slope of Rock - Left Abutment - Green Area - Trench to Anchor Core in Hillside Rock

An insightful early construction image reveals a wide trench cut in bedrock on the abutment hillside. This trench is designed to anchor the Zone 2 - Core (clay-clayey Zone 1) - Zone 2 sandwich design into the hillside bedrock. The orange colored core material is compacted upon the 300,000 cubic yard concrete "coreblock". The darker Zone 2 "transition zones" are observed adjacent to the center Zone 1 Core. The original Coffer Dam is observed to the left of the core region and meets at the parapet of the subsurface concrete "coreblock". Due to the construction sequencing, the downstream Zone 3 "Shell layer" was being emplaced in the center. To keep the access roads open on the hillsides, for construction of the hillside bedrock trenching formation (blasting, excavation, grout sealing), the downstream Zone 3 fill was built up in a form of a "hump shape".

This image also reveals the consistent sharp steepness of the "future" left abutment of the downstream Zone 3 fill. This sharp elevation drop goes to the "trench" boundary. Above the consistent "sharp elevation drop" is a "shallow slope", or semi-flat bench just above 600ft elevation. Thus, the future "Leaking" & "Green" wet area water flow is consistent with this "transition from a shallow bench area to a sharp hillside slope". This forms a classic differential settlement abutment zone potential. Especially since the shallow-to-sharp slope transition continues back directly to the junction of the "trench" boundary (to the Core region).

p.s. "Greetings to Boilermaker @ metabunk"

Early construction image - wide trench cut in bedrock to anchor core - Green Wet area at transition zone of shallow-steep slope that reaches back to the core zone. Classic "differential settlement" potential.