Colin: I was contracted by the board to determine a design plan for the Martinez crossing that could be permitted by Fish and Wildlife.

There are actually two properties overlapping the area. Besides Martinez there is Lineck on the downstream end. It’s somewhat of a complicated site.

There are two main risks at the crossing as constituted now.

(1) The crossing was installed prior to the 1950’s. I’ve seen aerial old photos. The crossing contains a lot of organic debris –including logs and material from road construction. This is apparently decomposing and is destabilizing the fill.

(2) The other main issue is the culvert itself. The culvert is somewhat squashed so its hydraulic capacity is less than that of a circular culvert of that radius. Its hydraulic capacity is far less than what you would provide these days. In a big storm the water could potentially back up and form a big pressure head, flowing over the road eroding the road. If a really big storm you lose a portion of the crossing and hence a portion of the stream-stored fill materials.

The culvert is installed high up in the fill. Nowadays the design standard is to install culverts at the base of the fill. When you install a culvert high up it allows aggregation in the channel, kind of like a pond. That’s what’s happening there. Over 60 odd years you’ve had deposition of channel-mobilized deadload that has built up behind the crossing. Now it’s a large wide flood-plain-looking deposit of channel sediment. It’s like a filled-in pond.

It could be looked at as a groundwater recharge site, and Bill Seekins has been adamant about pointing that out. There is water stored in those channel sediments that releases over time in the summer. That being said, the channel is almost a perennial creek. Water flows nearly year round. It’s known as “Wallace Creek.”

The creekbed is next to Miriam Martinez’s home, with all the willows in it.

The approach supported by the agencies – State Water Resources Control Board, Fish and Wildlife – is a channel restoration approach. Normally when they permit projects to replace culverts in streams, that includes the removal of the foreign material because it is a risk in the event of culvert failure. That material stored in the channel can potentially be released. Downstream from that crossing is Mill Creek which is a valued salmon stream.

Miriam: Will the flow be restored to its original position?

Colin: That would be the design goal. The sections I have distributed to you show that. By looking at older aerial photos you can easily tell that was the native alignment. 59:40

As contracted we evaluated what designs are viable. Do we need to follow these protocols which are widely accepted by Fish and Wildlife, or could we go with an engineered approach in order to save some of that floodplain area? We also looked at the cost of installing a bridge. The cost was much greater. That was dismissed because the cost was much greater than even the cost of the larger culvert.

I engaged Fish and Wildlife in the discussion to determine which way. We had Rich Macedo from Fish and Wildlife review the site. He has never seen an “engineering” project of that large magnitude go through the permitting. They were all dismissed. I’m talking about some large engineered rock structure which could retain the stored material in even a large storm context [i.e. turning the crossing into an engineered dam.] He said that’s not likely something that would be permitted. So I’ve gone with the classic methodology of excavating the foreign material and placing the culvert at the bottom of the fill.

Miriam: That means taking all my soil from the creek?

Colin: Along the profile of the channel, yeah.

Roger: This costs less than a couple of bridges?

Colin: Yes. You would probably want a double-lane bridge. We have engineers on staff. We do a couple of bridges a year. [1:02:09] That being said, there’s a seven foot knickpoint in a bedrock step below this crossing so we don’t need to provide for fish passage. In a fish channel – which this isn’t – F&W wants a natural stream channel which pretty much necessitates a bridge or an arch culvert. Since this isn’t a fish channel we’ve specified an 8’ diameter culvert 140’ long.

The current 48” culvert is functioning like a 42” culvert.

Based on our 100 year flow calc, a 7’ culvert is just barely enough. I’ve recommended an 8’ because the cost difference is negligible. For a few more dollars, an 8’ is more tolerant of blockage by debris.

Colin: Here are the risks of not going ahead. The culvert fill is compromised. Even when you don’t see surface flow you can see water seeping beneath the pipe. There have been past attempts by local landowners to apply plastic to limit infiltration. In the culvert itself, the fill slumped and sheared the culvert incredibly. In Francois’s picture you can see some of that. There was an attempt to install uncured concrete in the culvert separation.

Bill: The patch was cured concrete and it was applied 25 years go. It’s held for 25 years and not shifted.

Fred: Looking into your crystal ball, considering that this is supposed to be an El Nino year, how fragile do you think it is?

Colin: There’s no formulaic way to determine risk. I’ve seen these things over the years. The fill being compromised in my mind is the primary driver for replacement. The culvert capacity could probably pass the 10 year storm. But it would not necessarily require the magnitude of the 100 year storm to cause failure. Over time the organic material degrades. This allows “preferential flow paths” – macropores and soil-piping – through these fills. That’s happening at our crossing right now. There’s erosion occurring with the fill over time. I’ve seen these types of crossing undergo massive settling from erosion within the crossing. Then everything collapses inward. It’s hard to predict how rapidly that would occur. But it’s obvious that has occurred in the past. Those are the primary issues with that crossing. 1:08:03

Bruce: To cast some doubt about the odds – on 1/1//2006 we had what was calculated to be the “75 year storm”. This determination was by Fish and Wildlife’s people – a colleague of Linda Macawee. I own a quarter mile of Mill Creek. That flood knocked down every [alder] tree in the Mill Creek ravine and completely changed the cross section of the creek at several points. No other event in 15 years has begun to touch the effect of that one day. But I understand the Martinez culvert held. It didn’t even settle.

Miriam: It did just fine. I keep that channel clear of all trees and debris. I spend a lot of money on that. I also have the fence posts [.i.e., “trash racks”] that prevent any logs from floating down to block the culvert. So I’m always cleared.

Not to mention – the road is in the position it’s always been, and has never flooded out.

Colin: The volume of material I compute we’d be excavating we’ll locally store, on Nash Mill Road by building up Nash Mill and out-sloping it.

Colin: We would remove the channel-source sediments that provide Miriam’s in-channel aquifer.

Colin: I’ve included costs for the re-establishment of domestic water infrastructure. We plan to capture water upstream.

Miriam: Roederer pumps that; they have water rights. You won’t be able to get that. I have secondary rights to them. It’s in my deed.

Fred: How “fragile” is it? If the crossing fails the entire ranch would be cut off.

Colin: Using the established methodology for estimating sediment risk we estimate the quantity of material that would fall into the creek. (explains the technical methodology.) We compute that in that event, 8,800 cubic yards of material would fall into the creek.

I’ll go into the details of the design.

Fred: The cost?

Colin: $436,000.

Don: Before everybody dies of a heart attack, remember that it’s something for which we would get grants. We’re not going to do special assessments or something like that. [1:16:10]

Colin: The two major risks are: (1) what if it fails? In that event the Road Association would have to pay for repairs. A preemptive approach will allow you to reduce the risk, to get grant funding.

Fred: Does your organization offer counsel on funding?

Colin: Generally these grants need to be pursued by non-profits. We work on 50 or more projects a year.

Roger: How many years will we get out of this new culvert?

Colin: We propose an aluminized galvanized steel culvert. The design life is 30-50 years.

Roger: Did you consider and price a concrete culvert?

Colin: No.

Colin: (walks through the costs, listed on a handout we all received.) Major costs are excavation, removal, placement of sediment as close as possible; out sloping of the road. Replacement of the culvert entails digging all the way down to base; placing the culvert.

Colin: Incidentals include moving two PG&E power poles. We contacted PG&E for a figure for this. We used a figure of $50,000.

Colin: The permitting process I outlined is through a coordinated grant/permitting process. If the various permits were sought separately I estimate costs of $40,000. By this combined approach the permitting cost is much less.

Bill: How would you mitigate the loss of the water? The water that goes underground and percolates out is a good source of cold water to Mill Creek. Last summer Mill Creek dried up a quarter mile upstream. Blue Meadow Farm had to buy water and have it trucked in. The Martinez floodplain leakage was the only source.

Colin: I don’t have designs for mitigating for that, but the view of F&W is that the channel-stored sediment should be removed. 1:21:33

Zach: How to preserve vehicular access during the work?

Colin: Awkward. As we begin to excavate we could lower the crossing a lot, allowing continued access along the alignment of Nash Mill. But once we work with the crossing fill itself to put in the culvert, we’d have to place ramps that enable a wild turn, upstream and then back out again onto the shoulder.

Nancy Mayer: On Miriam’s property?

Colin: Yes.

Colin: This is a summer job; it would not be allowed in winter. Clear water diversion is always a significant cost to these jobs. You need a clear water diversion above the site that conveys clear water from Wallace Creek all the way past the worksite and back into the channel below. You would have extremely turbid waters coming out of the construction site as you excavate. This would need to be pumped to flat areas so the sediment would be dropped into the ground without reaching downstream channels.

Miriam: That’s probably my front yard – that flat area.

Colin: We would have to utilize many different areas of your and the other properties.

Colin: There are a lot of alternatives. The engineered alternative I mentioned earlier I brought up to F&W. They said it probably never would be permitted. If there were a continued risk of failure they would want to know what it is. Design plan $45,000 – $50,000 just for a plan for that type of treatment. So I did not pursue that.

Colin: Continuing with the costs… the PG&E component I mentioned. Water infrastructure needs to be changed; costs are in there. Another undersize culvert is on Boondoggle creek. It has to be addressed. Otherwise you would have a shotgun culvert feeding into this stream.

Fred: A bridge is not viable? It’s more than $400,000?

Colin: The materials alone – a bridge perhaps 19’ wide, 40’ long – is about $75,000.

Doug: The Mill Creek bridge was $60,000. But that’s an old cost – around 2001.

Colin: What I have designed is based on tape and clinometer surveys, laser rangefinder surveys. Though I provided my design plan with profiles and cross sections it assumes a shape morphology of channel beneath the sediment – guesses. This is a natural channel restoration attempt. So an expert knowledgeable in exhumation of channels would have to be engaged by permitting agencies to confirm the channel location. If a slight meader or change in the alignment in the channel were uncovered, that would have to be followed.

Nancy Mayer: So there are a lot of unknowns.

Colin: There’s not a lot. It’s typical. But there’s on-the-ground evaluation that will be required. 1:28:07

Colin: There’s a really significant re-vegetation component. We called for riparian vegetation, conifers, redwoods. We allowed for labor.

Miriam: One of my main concerns with the alignment is my main cistern. It’s right there. That’s vital to my survival on my property. If you reroute the stream, what will you do about my cistern?

Colin: Replace it , with a water source that would be upstream, some spring box type of channel that feeds to – I budgeted for – 5000 gallon water storage capacity.

Miriam: It’s currently much bigger than that.

Colin: There’s ample costs in the design plan for domestic water infrastructure.

Colin: We also budgeted for re-rocking Nash Mill Road and drainage, all the effects there. Some soil will be stored on the Lineck property, most on Martinez. And there’s a Ruffler property that’s a bit east that would have minor impact.

Steve: Is there a compromise opportunity other than complete excavation, leaving some sort of dam so that her water is not impacted so much – some opportunity to solve both things?

Colin: Two things: (1) The culvert needs to be totally excavated and replaced. Existing fill needs to be totally excavated. It’s compromised. (2) You’d have to retain that wall somehow, to build like a dam face. I was told, F&W (Fish and Wildlife) will not permit that and you’d have to pay design costs for something that is unlikely to be allowed.

Fred: Can you tell how long it’s taken for all this to accumulate?

Colin: It looked really aggraded in 1952. That’s when timber harvest ended. There was a lot of debris.

(Colin concludes; audience applause.)