The Building Blocks of the Replacement Calaveras Dam

If you are new to the world of dam construction, you might wonder what types of materials are used in building one.  Today’s blog will focus on what types of materials we are using to construct the new Calaveras Dam. Calaveras Dam is an earth embankment dam.  Earth embankment dams tend to be constructed of all types of geologic materials.

Calaveras Dam, July 2017

The picture above was taken recently; from it you can visually see the different materials. Let’s start with the middle and the most important material used in our dam, the core. 

The Core of Calaveras Dam

Zone 1 & 1A—aka…the Core

The core is made up of clay.  Clay is very dense and less permeable than most materials.  Our new dam will have a large core, which will help ensure that the dam withstands a 7.2 magnitude earthquake.  The clay used in our dam has been ‘borrowed’ from the south end of Calaveras Reservoir.

The core is taking shape.

Zone 1A- Core’s foundation

At the bottom of the core, you will find Zone 1A material. This clay is plastic, pliable clay, or another words, clay that has a Play-dohtm like consistency.   Zone 1A material is placed on the foundation’s bedrock and acts as a seal against water flow beneath the dam.

The core is the most important element of the dam and therefore must be protected.  We protect our core by using filters in both the upstream (reservoir side) and the downstream (dry side) of the dam to control the seepage of water and remove it safely from the Dam.

Zone 2 and 2A- Sand

Upstream zones are made of sand  (Zone 2A) and large gravel (Zone 5A)The downstream filters or chimneys are made of sand (Zone 2) and pea gravel (Zone 3).

Zone 5-Rock Fill

Further protection for both the core and filters is provided by rockfill shells. The upstream shell consists of hard durable rock because it will be submerged in the reservoir, Zone 5 material.  This material consists of metamorphic rock known as blue schist.

The downstream shell (Zone 4) consists of onsite material from a geologic formation known as Temblor Sandstone.  While this is a sedimentary rock, it tends to degrade into a gravelly, sandy soil and is best suited for drier conditions than the upstream shell.

Zone 6- Rip Rap

Wave action in the reservoir due to wind can erode most earthen materials.  Large durable rocks are placed on the slopes of the dam at the waterline to prevent this erosion. This is Zone 6 also known as rip rap.

Image courtesy of www.fhwa.dot.gov

See you around the valley!

Sunol Valley Fire Safety #1

It’s always fire season in California, although it officially begins in May. Our warm and dry climate coupled with climate change has made California more susceptible to frequent wildfires.  According to CAL FIRE, between January 1, 2017 and May 20, 2017 there have been a total of 921 fires in California.

Here at Calaveras dam want to prevent wildfires by our watersheds. During the summer months we will be dedicating a series of fire prevention blogs with tips on how you can help prevent forest fires.


Today we will focus on equipment safety.  Operating equipment like lawn mowers, chainsaws and tractors improperly could ignite a wildfire.  However, according to CALFIRE there are simple steps that you can take to prevent these types of fires.

(Image courtesy of http://pacificsun.com/home-garden-lawn-be-gone/)

Equipment Safety Tips:

·       Mow during the cool time of day before 10 a.m. while there is still dew on the ground, not during the day and especially not when the wind is blowing.

·      Remove rocks and metal from the year that could be hit by the mower and cause sparks. 

·       Use a weed eater with a plastic line when cutting dry grass not a lawn mower (use lawn mower on green grass only).

·       Don’t top off fuel tanks.

·       Make sure spark arrestors are in proper working order and there is no carbon build up.

·       When transporting tractors, mowers, and recreational vehicles make sure that chains on the trailers are not hitting the pavement as you are driving.

·       Take special care when using tractors in dry grass that can easily ignite. 

·       Last but not least, always have a least one of the following items with you: fire extinguisher, water supple or a shovel.

Wildfires have an effect on watersheds, reservoirs, and the quality of our drinking water. 

By protecting our watersheds we are protecting our environment. Remember metal

blades hitting rocks can spark a fire!

For more information on wildfires go to: http://www.preventwildfireca.org/Equipment-Use/