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Matilija Dam - Alternative Slurry Design

Additional Comments on Matilija Dam Final Design – Slurry Disposal

Letter to the Army Corps of Engineers Via e-mail: Douglas.E.Chitwood@usace.army.mil

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.


Sincerely,


A. Paul Jenkin, M.S.

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

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 http://www.matilijasanctuary.com/history.htm

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: http://www.venturariver.org/2013/12/beach-erosion-and-federal-funding.html

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: http://www.psirotary.com/)



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.

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.)

GOALS
· 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...

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.

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.

runoff and sewage

tried looking for surf yesterday. I normally don't even consider it after the rains, but wanted to show an out of town visitor around...

headed up the coast, hoping for cleaner water...

the oilfields were flowing hard, large brown plumes entering the ocean.

Hobson looked cleaner, surf was rideable...

the work crew on the road said "I wouldn't go out there if I were you"

sewage pipe had broken...

no signs posted on the beach. I thought this was legally required if there was a sewage spill...

I'll stick to the bike for a while...

BEACON Regional Sediment Management Plan

November 21, 2008 - public Hearing on Regional Sediment Management Plan

BEACON has just released the most comprehensive overview of the Santa Barbara/Ventura County coast to date. The Beach Erosion Authority for Clean Oceans and Nourishment (BEACON) is a California Joint Powers agency established in 1992 to address coastal erosion, beach nourishment and clean oceans within the Central California Coast from Point Conception to Point Mugu.

The study includes some interesting graphics describing the state of our coast. This image illustrates the extent of coastal armoring (seawalls, revetments, etc)


This graphic illustrates shoreline trends.
The study defines a sediment budget for the region, outlines sources and sinks of beach sand, and proposes management strategies.



Some of the proposed projects are:

• Investigate the feasibility of beach preservation and enhancement projects at Arroyo Burro County Beach, Butterfly Beach, Summerland Beach, Santa Claus Beach, and La Conchita Beach using multi-purpose offshore reef sand retention solutions.
• Designate the Ventura River Delta as a gravel, boulders, and cobble (GBC) sediment and nourishment maintenance zone.
• Designate the Matilija Dam as a regional sediment source site and support removal of the dam.
• Implement the Surfers Point Managed Retreat Project.
• Implement the Pierpont Beach wind blown sand management project.
• Investigate the feasibility of capturing sand for beneficial reuse just before it falls into the Mugu Submarine Canyon

The study also includes an economic analysis which makes the case for widening beaches. The study is available on the BEACON website, and comments are being accepted.

Matilija Dam - more slurry disposal

In preparation for the next Matilija Dam Design Oversight Group (DOG) meeting on December 4th, we have been out looking at the slurry disposal sites. The issue is summarized in notes from the last DOG meeting on October 2nd.

In our comment letter, we pointed out that one of the proposed disposal areas (MODA) is a very popular public access point, of which there are few within the watershed. We are also concerned that disposal in this area would be permanent, rather than located in an area where the river would be allowed to wash the fine sediments downstream during future floods.




An analysis of erosion potential is available at matilijadam.org: Bureau of Reclamation Hydraulic Analyses of Sediment Disposal Sites Presentation

MODA (Meiners Oaks Disposal Area) is shown in this image. The blue shading is the area which the river could potentially erode in the future during a 100-yr flood. Note that the planned levee upstream of the site would effectively prevent the river from accessing this portion of the floodplain.

This photo is taken from the bluff near the trailhead, and shows the 70 acre floodplain area. The entire 2.1 million cubic yards of sediment could be deposited here at an average height of 35 feet.






The upstream Baldwin Rd site (BRDA1) is within the floodplain. Because these are active river channels there is less old growth vegetation (oaks and sycamores) and more riparian floodplain vegetation. The analysis shows that this site would erode in the future (blue shading).

This photo shows the view looking upstream from the levee that protects a historic 'burn dump' landfill in the floodplain.














The second Baldwin Rd site (BRDA2) is County property that used to be the jail honor farm. The site includes active channel and floodplain terrace, much of which was used for grazing. The river would also erode much of this site in the future.


This is the view from the highway looking south:
This view is looking upstream from the westernmost corner of BRDA2, with the active channel visible to the right.



Discussion of slurry disposal will be continued at the December 4th DOG meeting.

'Salmon Run'

Last Sunday was the 15th Annual Salmon Run. This event has become a tradition in Ventura...


Over a dozen organizations had information tables for the over 400 runners and walkers.

Event proceeds went to the Friends of the Santa Clara River.

Algae: problem or symptom?

The EPA has listed the Ventura River as an "impaired water body" for a variety of problems, including trash, bacteria, water diversion and pumping, and pesticides (DDT/PCBs). The Clean Water Act requires that government take action to solve the problems to ensure the river is fishable and swimable. The regulatory mechanism for this is "Total Maximum Daily Load," or TMDL.

For the past year, the State Water Quality Control Board has been working to develop a TMDL for Algae in the Ventura River. See also the County of Ventura website.

The primary concern is that algae growth may be fueled by excess nutrients (nitrate and phosphate), which in turn creates large daily swings in dissolved oxygen (DO.) If DO drops below 4 mg/l, aquatic life can become stressed and fish kills may occur. (This is also called 'eutrophication') The presence of endangered species makes this issue even more critical.

Stream Team volunteer data has been used along with scientific analysis at UCSB to monitor and study algae over the past year. This graph is actual data from 24 hours of sampling on the Ventura River. It illustrates how photosynthesizing algae releases O2 during daylight hours, generating peak DO measurements in the early afternoon. However, overnight DO levels drop dramatically, with a minimum in the pre-dawn hours.


Traditionally, nutrients are seen as the driver for excess algae growth. Nutrients may originate from broad land uses such as agriculture, livestock, septic tanks, treated wastewater, as well as atmospheric deposition. It turns out that algae is widespread throughout the Ventura River watershed, and is highly variable with season and annual climate (wet or dry year.) Algae is also dependent on river flows, water temperature, sedimentation, and a host of other variables.

Because of these complex relationships, algae may be seen as a symptom of ecological stress, rather than a problem in itself. This raises a complex question when it comes to regulating algae as a pollutant: the TMDL process was originally developed to control point-source pollution.

Recent literature points to the need for an ecosystem level approach to solving such problems. A useful reference is Water Quality: Management of a Natural Resource

It is clear that in this watershed with shallow, over-drafted aquifers and strong surface water/groundwater interactions, a meaningful algae TMDL will require a watershed approach that takes into account ecosystem processes. Integrated watershed management will be necessary to address excess algae in the Ventura River.

Here's one solution: convert all those algae forming nutrients to biodiesel

Pierpont Beach erosion in 1936

Pierpont Beach Flood 1936

Los Angeles developer Frank Meline subdivided the Pierpont Bay area into small lots during the late 1920s, putting in roads, building a pleasure pier and paving Shore Drive along the beach. The lots came with design guidelines for English-style homes, on lanes with English sounding names. The Stock Market Crash of 1929 changed the fate of Pierpont beach forever; lots that had been offered for $2900 per lot suddenly were worth $10. Then, eight years later, two storms – eleven months apart – in January and December 1936 wiped out the pier, bathhouse, boardwalk and Shore Drive. These storms effectively stopped all development in Pierpont until the mid-50s. Between 1925 and 1936, few houses had been built, and after the storm some were moved to higher ground. Only a handful of pre-1936 houses remain in Pierpont. Today, the area is a eclectic mix of mid-century beach shacks and recent 2.5-story custom homes of every style imaginable, and Shore Drive is a memory beneath the dunes at the end of the lanes.

Quoted from the 2009 Ventura Architectural Calendar "Then and Now" available in local shops or by contacting schafphoto@mac.com for prices: http://www.schafphoto.com/

San Clemente Dam removal

On Nov 5, 2008, the California Coastal Conservancy hosted a tour of the San Clemente Dam on the Carmel River near Monterey, CA. Planning is underway for the removal of this obsolete dam. Constructed in 1921, the structure has become a liability to its owner, CalAm Water, mainly due to sedimentation and structural instability.


San Clemente dam is located just downstream of the confluence of the Carmel River and San Clemente Creek, and the majority of the accumulated sediment is located along the Carmel River. This is the view looking upstream: the sediment 'wedge' is clearly visible on the left, and San Clemente Creek is to the right.


The Coastal Conservancy has taken the lead working with CalAm to investigate the potential for removing the dam. As with all dam removal projects, sediment management is the primary technical hurdle. In the case of San Clemente Dam, the geography provides an interesting opportunity to stabilize the 2.5 million cubic yards of sediment in place, and divert the river around the current reservoir. The proposed project would blast a new channel through the ridge separating the river from the creek, and divert the Carmel River into the creek approximately one-half mile upstream from the dam.

The rock blasted from the bypass channel would be used to create a structure (the “diversion dike”) which would force the river into the diversion. The bypassed portion of the Carmel River would be used as a sediment disposal site for the accumulated sediment. Sediment would be removed from behind the dam to the bypassed portion of the reservoir over one season by excavation with heavy earthmoving equipment. Approximately 380,000 cubic yards of sediment in the San Clemente Creek arm of the reservoir would be relocated to the Carmel River arm, where the bulk of accumulated sediment already has been deposited. The sediments at the downstream end of the bypassed reservoir arm would be stabilized and protected from erosion. The San Clemente Creek channel would be reconstructed through its historic inundation zone from the exit of the diversion channel to the dam site.

Project Benefits:

• 25 miles of spawning and rearing habitat for steelhead trout
• restoring the natural sediment supply to the downstream beaches
• providing new recreation opportunities for the public

Cost estimate: $83 million

CAW would pay an amount equivalent to the cost of buttressing the dam in place, which was estimated in 2005 as $49 million. The State and Federal government, through the leadership of the Conservancy and NOAA Fisheries, would secure the additional funds needed from State, Federal and private foundation sources.

Sediment Management: Stabilize on-site

More Information: http://www.scc.ca.gov/disp_gen.file?san_clemente

Project Manager Trish Chapman: tchapman@scc.ca.gov or (510) 286-0749

The EIR is here: http://www.sjd.water.ca.gov/environmentalservices/sanclemente/index.cfm