Thursday, December 18, 2008

Know Your H2O

This from our friends in San Diego:

A little comedy goes a long way... More here

Tuesday, December 16, 2008

Matilija Dam - Alternative Slurry Design

Additional Comments on Matilija Dam Final Design – Slurry Disposal

Letter to the Army Corps of Engineers Via e-mail:

During the Design Oversight Group meeting of December 4, 2008, project managers indicated that a decision would be made on slurry disposal (by Feb 2009) based upon the alternatives presented at the meeting. These alternatives are as follows: (Click here for more background on the Slurry Disposal)

We suggest that Alternative 6 be modified to reflect the parameters that we proposed in our comment letter of October 20, 2008.

The following is a description of this alternative:

BRDA 1 would provide temporary storage of 750 AF of fine sediments, intended to be completely transported downstream following a series of flood events. This is accomplished by managing a pilot channel that follows the alignment of the existing river side-channel. This pilot channel will direct high flows from the mainstem channel through the disposal area to initiate and actively erode the sediments. This is controlled with a temporary levee (or containment dyke) that includes a ‘flushing weir’ at the upstream end of the pilot channel.

The footprint outlined in blue in this figure includes expansion of the disposal area onto the floodplain terrace to the east of the active channel. This would provide greater insurance that flows would not enter behind the disposal area and threaten downstream infrastructure. This area will also provide a staging area and additional capacity to account for the pilot channel, which would necessarily be an area of lower fill depth.

Adaptive management of this area would include monitoring the containment dyke and erosion to ensure release of fine sediments downstream occurs during predetermined flow events. The weir entry is designed to direct flows into the pilot channel during such events to facilitate removal of stored sediments. In this manner a large flood event may effectively remove a large portion of the temporary sediments (highlighted in blue.) In the dry season following such an event the remaining sediment could be re-distributed within this erosion zone in preparation for the next flood. Eventually this area would return to natural floodplain with little evidence of the slurry activities.

The BRDA 2 disposal area
may store 600 AF of sediment (BRDA 2 with BRDA 2A superimposed.) BRDA 2A is a 15-acre sub-area in which the total deposition would average 30 ft deep. The erodable area (pink) includes a pilot channel designed in the same manner as BRDA 1. The fill is deepest adjacent to Baldwin Rd, which could be used as a containment dyke. The east edge of the disposal area will taper down to leave a 75 ft buffer/channel from the toe of the bluff to accommodate existing flows and maintain the mature sycamore and oak trees. The disposal area is expanded slightly to the west and south to provide additional capacity to account for the buffer zone and pilot channel.

Adaptive management would be used to optimize the erosion of temporary storage areas as described for BRDA1. The upland terrace would be revegetated, but the pilot channel and erosion zone would require minimal restoration. In the future, the BRDA 2A area may be all that remains as a permanent feature of the landscape, so full restoration efforts need only be focused on this 15-acre area.

Benefits of modified Alternative 6:
  1. Does not interfere with existing public access and recreation
  2. Simplified land acquisition (County and OVLC)
  3. Majority of slurry is placed in temporary storage for natural transport
  4. Minimized restoration costs
  5. Minimized disturbance of side channels and mature trees
  6. Minimized long-term disturbance

Other considerations:
It is unclear how the slurried sediment will compress after drying at the disposal areas. Discussion during the December 4th meeting suggested that the material may reduce from 70lb/sq.ft to 150 lb/sq.ft, perhaps resulting in as much as a 50% reduction in disposal height. How this will affect revegetation/restoration is not clear, so adaptive management of revegetation efforts needs to be considered in the planning process.

We submit this concept to clarify our preferred alternative for slurry disposal. We believe that temporary sediment storage, while having a short-term impact, will provide the greatest opportunity for ecosystem restoration and have the least impact on the affected community.


A. Paul Jenkin, M.S.

Coordinator, Matilija Coalition
Environmental Director, Surfrider Foundation, Ventura County Chapter

Saturday, December 13, 2008

Matilija Hot Springs Resort

The sign at the entrance to the Matilija Hot Springs below the dam tells the history.

From 1887 until the 1980's, the hot springs drew people from afar for the healing properties of the natural springs as well as the scenic natural beauty of the area and renowned fishing.

In 1947 as plans were made to construct a dam in Matilija Canyon, the Ventura County bought the land which held the hot springs. The resort was leased and continued to operate for many years as a health center. Much of the spa, however, was damaged in the floods of 1969. In the 1980's, due to difficulty with insurance, Matilija Hot Springs was finally closed to the public.

Now, with the removal of Matilija Dam planned for 2013, the property will revert back to the county. This is largely due to the potential for increased flooding directly beneath the dam site.

Because of the historical value of the site and its proximity to the dam, potential future uses may include a visitors center and access point to the restoration site upstream.

A more complete history of Matilija Hot Springs may be seen at

Harbor dredging

According to BEACON, average sand bypassing at Ventura County harbors is almost 600,000 cubic yards at Ventura Harbor and over 1 million cubic yards at Channel Island harbor. Their report illustrates how littoral drift transports sand downcoast, where it accumulates in sediment traps designed to keep the harbor entrance open for navigation. Because downcoast beaches depend on a steady supply of sand, these harbor sand traps need to be dredged annually to keep the sand moving down the coast.

Here the dredge is operating at Channel Islands Harbor, depositing sand on Silver Strand Beach in Oxnard. The dredge basically sucks up the sand behind the breakwater and sends it through a pipe along the beach where it spews out 'nourishing' the beach. While this may seem benign, the discharge from the slurry contains fine sediment and potentially hazardous organic debris that accumulates at the harbor entrance over the year. Surfing while the dredge is operating puts you out in smelly black water, where ear infections or worse are to be expected...

More on this blog:

Matilija Dam - slurry design

At the December 4th Design Oversight Group (DOG) meeting, the Corps of Engineers presented further information on the details of the proposed slurry operations.

Standard slurry operations discharge the spoils into a temporary pool formed by sand berms. Dredged sand deposits in the pool, and slurry water flows out. (This can be seen every year when the Ventura and Channel Islands harbors are dredged to bypass sand down the coast.) In this case, the 'turbid' (muddy) water left over flows into the ocean where silt is slowly dissipated.

Because the Matilija Dam slurry operation will be transporting sediments much finer than beach sand, a more complex method of depositing the sediments is being proposed. The "Thickening Method" is similar to that used in mining operations.

This method uses large industrial equipment called a flocculant thickener processor. This processor adds a chemical to the water/sediment mixture, separating out the water so that a sediment 'paste' is discharged. This paste may be pumped through a pipe or trucked to a site and may form up to a 4% slope. (It may be processed for a thicker paste if a steeper slope is required.)

In the Matilija Dam slurry operations, it is desirable to recycle the slurry water, pumping it back up to the reservoir for reuse. Because the sediments are so fine, the engineers propose to use the 'thickening method' which will speed water separation and drying time at the slurry discharge point and optimize water recycling. They propose the use of a 46 ft diameter deep cone paste thickener processor, located at single central location, to process the slurried sediment. Once up and running, it will be able to provide a continuous production rate according to the amount of water in the slurry mixture. (Note that a google search turned up other more compact processes:

It is unclear how the slurried sediment will compress after drying at the disposal areas. Discussion during the December 4th meeting suggested that the material may reduce from 70lb/sq.ft to 150 lb/sq.ft, perhaps resulting in as much as a 50% reduction in disposal height. How this will affect revegetation/restoration is not clear, so adaptive management of revegetation efforts needs to be considered in the planning process.

Friday, December 12, 2008

Rainwater harvesting planned for Ojai home

An Ojai resident, inspired by all the information from the Ojai Green Coalition Watershed Committee events, decided to landscape their property to take advantage of rainwater. (Brad Lancaster's talk was especially motivating.)

· To harvest 100 percent of the water that falls on the land.
· To store a majority of the roof runoff in tanks for domestic use.
· To turn the soil back into a sponge to absorb and hold the moisture throughout the dry season.
· To create an oasis in the arid land of Ojai

Proposed Water Flow Description:
Water that falls on the roof will first fill up cisterns. After they reach capacity, overflow pipes will lead them to the highest point of the landscape – at which a pond will be located. Once the pond fills up, the spillway will overflow to a series of basins that will allow the water to slow down and absorb just where we want it – where we put in plants. After that it will fill up a second pond – with its inlet planted to reeds for filtering out sediment – and head to a final catch basin. If this ever overflows, then it will head to the street.

This design was created by Devin Slaven of Ojai, and the owners are documenting their progress as they make their landscape "water wise" and "ocean friendly."

The Surfrider Ocean Friendly Gardens website has more examples...

Tuesday, December 2, 2008

Silt impacts downstream of quarry

Last year Santa Barbara ChannelKeeper documented the impacts of the Ojai Quarry on the Ventura River. Last week we saw similar runoff, despite attempts by the operator to create silt traps and other "best management practices."

These photos of the creek were taken yesterday at the bridge downstream of the quarry. Although the water is now flowing clear, a thick layer of silt has blanketed the creek bottom.

Smothering the gravel impacts the endangered steelhead trout, as well as the other aquatic species which rely on a healthy river ecosystem.

Monday, December 1, 2008

Cemetery Park plan unveiled

On the evening of Nov 19, 2008, the City of Ventura Parks Commission presented the plans for Cemetery Park. The room at the Presbyterian Church was packed with residents. As with most issues these days, the community is divided almost evenly - in this case between those with relatives buried in the cemetery, and those whose dogs now play in the park. (News stories here and here)

Most troubling was the presentation by the consultant, who in trying to please everyone seemed to please nobody except the Parks Commission.

In keeping with the memorial theme, and in an attempt to include 'stormwater,' the consultant included a garden design. This includes a riparian area, which the presenter said is intended to pay respect to the historic creeks (which have also been buried under urban concrete.) The design includes sycamore trees as a symbol of this lost riparian ecosystem. (These trees grow to over 100 feet in the riverbeds of Ventura County, and if watered as required, they would soon outgrow this small garden on the hillside of Ventura.)

In my comments I reminded the Parks Commission that the city is using drinking water to irrigate grassy lawns (and sycamore trees) while stormwater is flushed away in concrete storm drains. Our Urban Watershed Plan illustrated how Cemetery Park could fit into a stormwater strategy to capture and reuse rain water.

Unfortunately, this $4M plan for Cemetery Park does not provide any functional stormwater improvements. However, with the right designer and a regional plan, much of the improvements desired for this area could come from stormwater grants and Integrated Water Management Planning.

For more on the park plan see the City of Ventura website.