14 replies to this topic

[UncleVinny]

What is going on with all the construction around Folsom Lake and the Dam?

1. At the intersection of Folsom Lake Crossing and E. Natoma there are piles of rock up on the ridge by the top of the dam. What is going on there?

2. If you go to Folsom Point, where the boat launch is, you can see construction
and heavy equipment moving massive amounts of dirt, rocks, and gravel.

3. Across from Mormon Island Wetlands, construction has been underway for a few
years now? What is that all about?

I know the answers are floating around out there, but I feel like there are at
least three different projects going on simultaneously.
Are they all related?

[john]

1. They are building a new spillway
2. Raising the dam 8 feet
3. Strengthening the Mormon Island earthen dam.

[ducky]

I'm not sure, but I think it's for the new spillway.

I saw them moving that dirt finally at Natoma and Folsom Lake Crossing that's had the plastic covering over it. That's for the new bike crossing.

I don't know about the rest of it.

[tony]

OK, so you made me do some research, which you can verify and dig deeper into yourselves at: Folsom Dam Joint Federal Project

1. As Ducky said, moving the pile of dirt is for the embankment for the Johnny Cash Bike Path Bridge over the Folsom Lake Crossing Road (can't we come up with a better name for the road?). This is not part of the Folsom Dam work. Unfortunately, the actual bridge is still a year or two from construction. I think the city got tired of hearing complaints about the white tarps and decided to move on the embankment construction.

2. This is the new auxiliary spillway project, which will be going on for the next 5 or 6 years. They are also doing work on the various wing dams and dikes (in addition to Mormon Island Dam) to address seepage problems, but this work should be done already. Material from the excavation for the spillway was used to repair the various dikes, which is why they had those long haul roads.

3. This is the repair work on Mormon Island Auxiliary Dam (MIAD, the giant earth embankment along Green Valley Road across from the wetlands, which are wetlands because the MIAD leaks). Work is to reduce the risk of failure due to seepage and liquefiable soils (during earthquakes) upstream and downstream of the MIAD.

They are also doing seismic work on the main concrete dam and the spillway gates.

They are not, however, currently raising the dam. Apparently, a 3.5' raise is still a possibility, but it is not part of the current work.

[Chad Vander Veen]

OK, so you made me do some research, which you can verify and dig deeper into yourselves at: Folsom Dam Joint Federal Project

1. As Ducky said, moving the pile of dirt is for the embankment for the Johnny Cash Bike Path Bridge over the Folsom Lake Crossing Road (can't we come up with a better name for the road?).

Just be glad it's not Bridge Street. I'm sure that was #2 on the list. Or maybe River Road was #2.

[rpo]

They are not, however, currently raising the dam. Apparently, a 3.5' raise is still a possibility, but it is not part of the current work.

They have begun work on raising the main dam by 3.5', but that does not include the earthen dam by Green Valley Road. I believe I read years ago that the earthen dam is actually higher than the concrete structure already, so it does not need to be raised (only strengthened since it is most likely to fail). Does anyone remember the pumps at the base of the dam during the 2007/2008 winter that was pumping water back up into the lake? That was not a good sign!

[Walnut]

Thank you for this question/answer. I'd been wondering this myself, and never made it to Google.

Why does the dam need an auxiliary spillway? Water seems to come out of the existing concrete dam gates just fine when needed

[tony]

Thank you for this question/answer. I'd been wondering this myself, and never made it to Google.

Why does the dam need an auxiliary spillway? Water seems to come out of the existing concrete dam gates just fine when needed

Short answer: The gates are too high up on the dam, so they can't release large volumes of water unless the lake level is on the gates. In the design storm event, the gates (in combination with the existing low level outlets) do not have enough capacity to release water fast enough to prevent overtopping (which almost occurred in 1955, the year the reservoir was originally filled). The new spillway will allow much more water to be released much more quickly, allowing the operators to keep lake levels higher in the spring.

[Harold]

Short answer: The gates are too high up on the dam, so they can't release large volumes of water unless the lake level is on the gates. In the design storm event, the gates (in combination with the existing low level outlets) do not have enough capacity to release water fast enough to prevent overtopping (which almost occurred in 1955, the year the reservoir was originally filled). The new spillway will allow much more water to be released much more quickly, allowing the operators to keep lake levels higher in the spring.

You're right, the new spillway is to prevent the actual dam from being topped which would cause catastrophic failure. This spillway I believe is completely passive, if the water gets that high, it just flows, it can't be controlled, but it spills it safely so as not to erode the dam which would absolutely be disastrous. I think it is a part of the general attempt to improve flood protection for the valley from 100 year floods to a theoretical 200 year flood level.

[4thgenFolsomite]

my only hope is that when its all done, they return the staging area on the southeast side of the dam back to a state park operated dam overlook with a vendor running a little concession stand out there! that was always the best place to relax and gaze out over the this beautiful lake that is really the crowing jewel of Folsom.

[ducky]

my only hope is that when its all done, they return the staging area on the southeast side of the dam back to a state park operated dam overlook with a vendor running a little concession stand out there! that was always the best place to relax and gaze out over the this beautiful lake that is really the crowing jewel of Folsom.

Excellent idea! Shaved ice in the summer and hot cocoa in the winter.

You're right, the new spillway is to prevent the actual dam from being topped which would cause catastrophic failure. This spillway I believe is completely passive, if the water gets that high, it just flows, it can't be controlled, but it spills it safely so as not to erode the dam which would absolutely be disastrous. I think it is a part of the general attempt to improve flood protection for the valley from 100 year floods to a theoretical 200 year flood level.

So is that why they feel confident enough to spend a bunch of money building the BOR/State/National Weather Service operations center in a floodplain down river?

[UncleVinny]

1. As Ducky said, moving the pile of dirt is for the embankment for the Johnny Cash Bike Path Bridge over the Folsom Lake Crossing Road (can't we come up with a better name for the road?). This is not part of the Folsom Dam work. Unfortunately, the actual bridge is still a year or two from construction. I think the city got tired of hearing complaints about the white tarps and decided to move on the embankment construction.

Now it looks as if that whole area is going flat (level). Thought they might even be
making a tunnel UNDER the road. I'll check out your link and see what's going on.
Does that mean they will have to build up another hill to eventually make
a bridge there for bicycles?

[momof1]

my only hope is that when its all done, they return the staging area on the southeast side of the dam back to a state park operated dam overlook with a vendor running a little concession stand out there! that was always the best place to relax and gaze out over the this beautiful lake that is really the crowing jewel of Folsom.

I remember when it was nothing but a free parking lot, my friends and I used to drive out to hang out and swim. Too bad it will never return to that.

[tony]

Now it looks as if that whole area is going flat (level). Thought they might even be
making a tunnel UNDER the road. I'll check out your link and see what's going on.
Does that mean they will have to build up another hill to eventually make
a bridge there for bicycles?

The bike path bridge will be several hundred feet up the hill from the intersection of the Folsom Lake Crossing Rd and E Natoma. The pile of dirt being moved will make up most, if not all, of the west approach embankment for that bridge.

[vinnyhung]

Does anyone know what that big pile of dirt they moved next to the Mormon Islands Wetlands is for? They just made a huge flat dirt pile across from the MIAD damn improvemnts. Are they dumping dirt they dig up there?