Oral History
Narrator: Dave Hendricks
Interviewer: Donna Sinclair
Date: February 4, 2,000
Place: Multnomah Drainage District #1, Portland, Oregon
Transcribed by Donna Sinclair
Edited by Bob Groncznack, Manager, Multnomah County Drainage District #1
Dave Hendricks is the Operations Manager for MCDD#1. MCDD#1 also manages Peninsula Drainage District #1 and #2, and Sandy Drainage Improvement Company. The four drainage districts abut the Upper Columbia Slough, the Lower Columbia Slough, and the Columbia River. Peninsula Drainage District #1 starts on the west end of the districts, from Smith and Bybee Lakes east to I-5. The north border is the north harbor and the south border is the lower Columbia Slough. Peninsula Drainage District #2 starts at I-5 and goes east to Peninsula Drainage Canal. The north border is the Marine Drive levy and the south is the lower Columbia Slough. Multnomah County Drainage District is the largest district. It starts at Peninsula Drainage Canal, and goes east to NE 223rd. The southern border is Columbia Boulevard at Sandy Boulevard. The district manages 25 miles of levee throughout the four districts; the levee is adjacent to the Columbia River and the Lower Columbia Slough. The district manages the levees for external flood events, and the waterways for internal flood events with pump stations. In the following interview, Mr. Hendricks describes the maintenance and operations of the drainage districts, which control the flow of water. He explains how water is pumped from the Columbia Slough, a “big bathtub,” into the Columbia River, and the role-played by environmental regulations in reformulating the district’s goals and everyday operations. In addition, he provides descriptions of the construction, role, management, and significance of levees; wildlife on the Slough; the Flood of 1996. The District is a public utility serving its landowners and governed by a three-person elected Board. The District may be contacted for further information at 503-281-5675.
DH: [describes the operation of the drainage district]
We have six cross-levees in the districts, so if we have a breach in one section we protect the remaining portions of the districts, these are at (west to east): the main Burlington-Northern Rail Line, the I-5/Denver Ave. embankment, the bank of the Peninsula Drainage Canal, a single-purpose cross-levee located at about NE 142nd, the embankment at or near NE 223rd which is the border of the Sandy Drainage Improvement Company, and the eastern boundary of Sandy Drainage Improvement Company, a levee adjacent to the Sandy River from I-84 to the confluence with the Columbia River. The levies are basically at elevation 44, on the top of the levee; that’s mean sea level. The floodplain for Peninsula Drainage District #1 has just been converted. It’s at elevation 11. The Flood Plain for Peninsula Drainage District #2 is elevation 5. The floodplain for MCDD is at 14, and Sandy Drainage Improvement Company is at 14. Those floodplains have been designated by FEMA [Federal Emergency Management Agency], and the cities of Portland, Gresham, Fairview, Wood Village and Troutdale have to make sure all new structures have a finished floor elevation at least one foot above the managed flood plain elevation. The difference in elevation between the managed flood plain and the 100-year flood event on the river defines the level of protection the district provides.
With the internal floodplain set that means you have to have internal drainage, also. And, that’s where the Columbia Slough comes into play for Multnomah County Drainage District because the Columbia Slough runs through the center of the district, it doesn’t border the district. So we use the Columbia Slough as it served the area before development, a stormwater conveyance system. And we have pump stations located at NE 172nd, which pumps about 600,000 gallons per minute and we have one on NE 174ththat pumps 650,000 gallons a minute. That’s a lot of water when you think about it . . . pump station #1 pumps into the Lower Columbia Slough, through conduits in the levee. NE 172nd pumps into the Columbia River . . . the Columbia Slough is a main channel that goes east west through the center of MDD#1. We have secondary pump stations that pump into the Columbia Slough. Then, at the eastern and western ends of the Upper and Middle Columbia Slough, we have large pump stations that pump it out of the Columbia Slough and into the Columbia River or the Lower Columbia Slough. There’s no gravity flow – we have to pump it. (Note: Pumping occurs when the Columbia River is above elevation 7′, which is most of the time in a normal water year, considering seasonal variations.) So, these districts are a great big bathtub when it comes to collecting the stormwater that falls on the property inside the Districts. They’re surrounded by levies, so all the water that comes in has to be pumped out. Not only stormwater, but also ground water. We receive about 100 cfs or about 54,000 gallons a minute of groundwater flow into the Upper and Middle Columbia Slough, which has to be pumped out. Now most of the ground water comes from south of Columbia Boulevard and Sandy Boulevard, which everybody refers to as mid-county.
[talks about district management: Pen. 1 has 2 pump stations – the primary station pumps about 28,000 gallons a minute. The secondary station pumps about 6,000 gallons a minute; Pen. 2 has 2 primary pump stations, no secondary pump stations, which means they pump directly to the Lower Columbia Slough. Their total capacity is 80,000 gallons a minute. MDD#1 has two primary stations and six sub-stations. The secondary stations pump between 5,000 and 8,000 gallons a minute, each. Sandy has one pump station that pumps into the Columbia River. Its capacity is about 46,000 gallons a minute.]If you add all those up, we’re pumping a lot of water during the winter rainy period. Actually, we’re pumping over a billion gallons per day. Our pumps run 9-10 months a year, continuous, twenty-four hours every day . . .
We’ve also developed new techniques to provide flood protection, stormwater conveyance environmental protection of our waterways and levee areas. We used to manage the waterways by what we referred to as land-based operations. .
. . .We used to do all of our maintenance from top of bank, and to do that, that means you have to remove all the trees. You know, the old dragline excavator would work from top of the bank to remove debris and silt that blocked the flow of water. To do this, they had to reach down the bank, and that would damage the vegetation. And that’s a direct conflict of what we’re trying to accomplish now with all the water quality issues and the habitat restoration that we’re trying to do along our waterways. Along with the City of Portland’s environmental goals, and also Metro’s, (for riparian restoration and water quality), the district is working to provide shading for the water and sediment removal from the waterway. So, we’ve converted our operation to what we refer to as ‘water-based’. We designed a scaled down operation from those that you see in the Columbia River all the time. We designed and built barges that handle a small excavator, just the size to fit our smaller waterways. Now, we do all of our maintenance from within the water-without touching the banks. That allows the banks to be replanted, and so we have programs to restore the native vegetation.
When we look at our whole network of waterways, we can use these new techniques to restore wildlife corridors. One of the biggest things we’re doing now is changing very straight, linear ditches into meandering channels with shallow side slopes that are replanted with native vegetation. We have about sixty miles of old ditches that will be restored to this original habitat condition.
We also have a new water level management program. We developed this in partnership with the City of Portland. The Upper and Middle Columbia Slough has had a problem with high water temperature in the summer. Using the district’s pumps, we keep the water level lower and confined in our new and deeper meandering channels. This strategy brings in greater quantities of cold groundwater and confines it in a channel that is narrower and does not absorb as much solar heating as the previous wide and flat channels. We’ve had great results, and our new meander reaches have new emergent wetland and shrub-scrub planted areas on their banks.
And what we’re doing is we’re trying to connect all these waterways with these corridors. Instead of having a lot of culverts connecting them, we’re taking the culverts out, we’re re-opening the waterways so we can have a corridor, or connectivity between the corridors so the wildlife can go from one point to the other without having to go over the concrete buildings or through parking lots and everything else. That’s a different mission than the districts ever had before. Our mission before was flood control. Pump water. I spend probably ten percent of my time working on the ‘pumping water’ mission, anymore. I spend probably sixty percent of my time on the environment. Trying to figure out: “How can we change the drainage basin to balance the flood control and the environmental concerns?”
DS: So what steps are being taken to take those culverts out and is your involvement in the watershed council, does it stem from that?
DH: [The District is a member of the watershed council. The District also deals with city of Portland BES (Bureau of Environmental Services) which has been mandated by DEQ, which is mandated by EPA, to clean up the water]
. . . the only way you can clean up the water, to the standards, and the standards that are set are referred to as TMDL’s, Total Maximum Daily Loads, that can be discharged into the Columbia Slough. The Columbia Slough water is discharged to the Willamette or the Columbia River at the end. There is the concern about the fish (salmon) in the river and the Lower Slough (outside the District). And so, we have two primary things to be concerned about for the water that is pumped from the Upper Slough to the river and Lower Slough, and one is what they refer to as TSS, Total Suspended Solids, that’s sediment load. The other one is temperature. The only way we’re going to control temperature in the Upper Slough and the other District waterways is by movement of water, so that means we take out the culverts because culverts are usually a restriction, either because of size limitation or elevation. Pipes were put in too high, because, in the past, people really didn’t worry about flow too much because the entire District area was managed by pumping. So, today we use the pumping ability to also control the water levels for water quality. If we want to leave the water at elevation eight, we just don’t turn the pumps on as often. But, if we want to bring it down to elevation four and draw in greater quantities of cool groundwater, then we have to pump more often. And, in order to do that, you have to either remove the culverts, or put in a larger culvert at a lower elevation, so we can pull water through the entire District system and manage for the lower overall water elevation . . .
The primary agency the MDD#1 works with is BES, but it also works with DEQ, the Port of Portland, the watershed council, the governor’s watershed council, the neighborhood associations, the environmental activist groups, and with the Corps of Engineers.]
The Corps has a special role with the District-they inspect and certify the District flood protection system, and have done so for decades. They are also becoming more ‘green’, if you will. In the past, they’ve had a great impact on our waterways because of the construction of levees and dams and everything else. And so, today, they have a responsibility to restore our environment as close as you can to what it used to be. They are supporting projects to do just that . . .
DS: Let me just ask you what you think is the most critical issue on the slough?
DH: . . .us now that we’re addressing is the contamination of the sediment. Basically, we can pass all the regulations we want to, to mandate people to clean up the water, and to restore the habitat for the wildlife. But if we don’t do something with the sediments from past practices, we’re not solving the whole problem. They’re contaminated with DDT and DDE, and Also, I don’t know how much is coming through ground water. You know, because this region’s been sumped for a long time, and so you have contaminants from old sumps coming through the groundwater today.
As for the sediments in the slough, we’re doing testing now, and we found DDT, DDE. They are at a level in certain areas that we have to use as upland disposal if we remove the sediments. We can’t put them back in the water. In some case it’s okay to place them back in the water by moving them to the adjacent bank or forming an island and then planting it. But, in cases where really costly disposal would be required, we need to look at options that might be affordable, for example, do we cap those? Or, do we dredge them and place them somewhere else? If we don’t deal with it, it’s only going to be there in the future. As we try to improve everything else, it’s still going to have an impact if we don’t do something with it. That’s probably the biggest thing.
And, then the next thing is start looking at our discharges into the Columbia Slough. There aren’t any CSOs in the upper or middle Columbia Slough; they’re all in the Lower Columbia Slough and the Willamette. But we still have industrial leases out here that are discharging pollutants into the Columbia Slough. DEQ is now implementing the new NPDS permits called the 1200 CLOS, which identifies industrial discharges to the Columbia Slough. So, a lot of industries are going to have to take out that permit and be in compliance with the new TMDL standards. However enforcement will be a problem. Both DEQ and the City of Portland are understaffed when you look at the geographic area to be covered. And, when there are budget constraints coming down, the first thing cut is enforcement and inspection. . .
Another real challenge is this: we can restore all the habitat we want to, but without the proper maintenance, without people overseeing and managing newly planted areas, it’s going to deteriorate just as fast as we restore it. And, this is especially true for wetland creation-something we do a lot of in the Columbia Slough Watershed. Coupled with this, another big thing we’re doing wrong is we allow people to fill wetlands, then we allow them to create a new wetland or enhance another smaller wetland. We have pockets of little wetlands all over the place, and they are not maintained after the five-year maintenance requirement from DSL and the Corp. They get silted in, the reed canary grass takes them over, and they’re non-functional wetlands. They still have some value. You know, water quality filtration. They still provide some habitat to the wildlife. But really, they’re not a full or high-value wetland. And that’s where we’re falling down on the Columbia Slough, in this whole watershed basically, is the enforcement inspection of the whole thing . . .
. . . In eleven years I’ve seen acres and acres being filled in through development. You just heard me say I really oppose small creation or enhancement of tiny pockets of wetlands. We have a waterway that is a natural resource to us right now. It has old-growth cottonwoods (most of them are hollow) and reed canary grass along the banks and blackberries-a lot of blackberries. We should take that and enhance those areas. Excavate those out; create large wetland benches on both sides of these waterways. Forty, fifty, sixty feet wide-within the regulatory buffers we place on top of the waterways. And, have these improved areas as the wetlands, and the waterway inside of it will also serve as your stormwater conveyance. We would want to have a 5 to 1 slope or a buffer zone on both sides of this new habitat, so the wildlife can have a true corridor and can survive in urban settings. To me that makes the most sense to this whole thing. It would be good for recreation, it would be good for water quality, it would be good for wildlife, it would be good for flood control. And we could achieve a lot of uses out of this if they would just look at all the waterways and don’t allow any more filling or culverting in the waterways themselves. . .
DS: Maybe you could talk a little bit about the design of a levee.
DH: There’s two differences between a levee and a river embankment. They both hold back water, but a river embankment has the same elevation at ground behind the river that goes out continuously. So natural ground behind that is the same elevation. So if a river wants to change path, all it does is erode the river embankment. And it doesn’t do any more than change the path of the river. Now does it have an affect on water quality and habitat and everything else, but it doesn’t have an impact to the possibilities of flooding adjacent to that river. Now a levee is a man-made structure, and most of these levies are made out of sand. And the face of a levee is at a 3 to 1 slope, with a 14-foot wide crown top, with a 5 to 1 slope on the back. And they are designed typically three foot higher than the hundred-year flood event. That’s called the free board.
Now some levies are built higher and wider, depending on the drainage district and what kind of development’s behind the levee. If that water decides to change path and erodes into that levee, then the levee becomes structurally unsound, and eventually will breach. And behind the levee the grounds are lower than the water elevation for an average high water event, and that will turn, all those properties behind the levee into a great big lake. Seasonal lake, of course, just like it was historically. In the Columbia Slough Watershed, this whole area was nothing but lakes and it would flood all the way up to the Columbia River near Columbia Boulevard, it would be under water. The Sandy Drainage Improvement Company would also flood from the Sandy River. It would all be part of the river for three to four months, maybe even up to six months, depending on the flows in the Columbia that year. So the levies keep that water out.
Now, for today’s conditions, a hundred year event is at 29’6 or 30 foot NGVD, mean sea level. The reason they build levies out of sand is so that the water can seep through the levee. Unless you build a concrete wall or sea wall or something else, you just can’t hold back all the water. They design them so they seep, and we have toe drains on the backside of the levee that gets the water away from them so it doesn’t pond on the backside, and so the water is removed from the backside. This is critical to the levee standing up to the floodwaters. And we watch the levee saturation level based on the height of the seepage that’s coming through. Once it seeps to that level it means that the ground is totally saturated. As the water seepage moves up the levee face, which means your structure is becoming weaker. And so we have to guard against that level of seepage by reinforcing the backside or making sure that the levee has a substantial dimension to it. You can also get too much erosion going on at the front side of the levee-the riverside. You can have beaver and nutria and carp that burrow into the levees. Beaver are one of our worst enemies out there. We have many, many beaver around here. And they will penetrate the levee about ten, twelve feet and build their den. And their dens are anywhere between twelve to twenty feet diameter size hole. And that’s just a conduit for the water to go through. It can be very dangerous.
DS: Is there anything being done about the beaver?
DH: Years ago, we used to just trap the beaver, but we found out there’s just too many beaver, you just can’t trap them. So we’re trying to live with the beaver. We will try to relocate them. We build diversion points for the beaver. Sometimes when they build dams in the waterways, and we’ll place an overflow pipe in the dam, and so the water will stay that level, won’t create flooding. Then the beaver becomes happy with that level, and so do we, so we live with them. We do have a permit from Fish & Wildlife to trap the beaver if we have a really dangerous situation. Once the beaver are gone, we collapse the dens, we fill them back in, on the levies. During August and September, when the water drops down in the Columbia River and the Willamette, we can see those dens. We do boat trips back and forth and we see them. We’ll collapse them and fill them back in with rock, because they’ll come back otherwise . . .
[talks about finding a way to work around the beavers. Also, the levies are regulated by the federal govt., by the Corps of Engineers, but are owned by private landowners. However, there’s an easement. They have to be maintained to federal standards. That’s why there are no trees on the levies. Trees like cottonwood that we have around here, have a shallow root system.] [high wind events, 40-60 miles per hour blows trees over, takes root wad out, creating a point of erosion, making it a high potential area for a breach.]. . . that root wad is as deep as twelve to fourteen feet, eight to ten feet wide. And that’s a point of erosion. And so it will continue to erode in that place. And it’s a high potential area for a breach. And if we had hundreds and hundreds of these trees on the levee, there’s no way that we could ever control the erosion that goes on. The old saying is, the strongest portion of your levee is the weakest link, and the weakest link is a conduit going through the levee, which is a root wad that has been blown over and exposed. So that’s why we keep it all in grass . . .
[levees inspected on a monthly basis; walking, not driving. Talks about vegetation – ivy is ineffective because you can’t see erosion. Experimentation with different types of grasses and shrubs is occurring with private landowners.]. . . It’s going to take probably three to five years of experimenting with these different types of shrubs, and we’re going to have to experience at least one high water. Because most shrubs shade out the grasses in the understory and so you don’t have any erosion control underneath there, and it’s a good place for erosion to start. They wanted to plant wildflowers on the levee. A wildflower is not a perennial, it’s an annual, and so during the winter months, when you need erosion control protection the most, they’re dead. There’s no protection then . . .
DS: Could you talk a little bit about the ’96 flood?
DH: . . . Well, the ’96 flood was not a surprise to anybody. We’re in touch with NOAA, the weather service. We have our own weatherman that we get reports from everyday. We knew that we were getting a high, low-level snow pack. We knew that we had an arctic front coming in, and then behind that we knew we had pineapple express, a warm rain coming in. So, we knew that we were going to have a melt down from the Snake River to the low level snow, so we knew we were going to have high water. We just didn’t know how high and what the duration of that water was going to be. And so we expected the water, the forecast was to get up to elevation 24 mean sea level. That’s what was expected.
Most of our riprap along the levies is at 18, and then our benches go all the way up to 22, 24, so it was going to be right there. We were not too concerned about it. But then what happened is the arctic front that came in stalled over the top of us and it froze everything. We had snow and everything froze up, and then the pineapple express came and it stalled over the top of us also. And so we had intense rainfall on top of ice and [if] you don’t have any percolation in the ground, then everything sheet flows right off, and that’s what was happening to the first part of the snow melt is the water just came all into the Columbia River and brought the Columbia River up to about 17, 18, but then it warmed up, then all the snow melt came down on top of it. And the water reached 29.4. Twenty-nine point six is the hundred-year event, externally.
Now, internally it was only a 25-year rain event. So we really didn’t have too much internal flooding. We had a lot of fast run-off because of the ice and everything else, and the melt of the ice, but that was managed by our stormwater pumping system. The great concern was the external event. Because of the pineapple express stalling over the top of us, the snowmelt was much greater than had been expected. And when it happened, we usually have a spring freshet in March anyway . . . but with that stalling in February, then we went right into the spring freshet. And so that left the water up high. The river did recede from the 29.4 down to 24, but it fluctuated between 24 and 25. For almost four months. When we had that high water, we had the east winds and they caused a lot of wave action on the levies. And that started eroding levies. And we were losing three to four foot chunks of the levee because of the wave wash and also the traffic from barge traffic in the Columbia River. And from the deep generated waves from that barge. So we shut down the traffic for three days on the Columbia River, and then that gave us the time to get out erosion control or plastic and geo-cloth and protect these eroded spots. We took out inmates from CRCI and from a lot of help from private industries around here we covered all those sections that were eroded so the wave wash wouldn’t take out anymore levee.
By the time we finished we had about 6,000 lineal feet, that’s over a mile, of the levee, that had lost thirty-five feet of the face of the levee, thirty-five foot in depth. But still, we had enough levee in those sections that I was not concerned, because those levies have a base of 300 feet wide . . . We shut down Marine Drive for almost two weeks because the levee was becoming saturated. The Marine Drive levee wasn’t saturated that high, so I wasn’t too concerned about it, but we didn’t want to pump the base and make it soft. So we shut down all the traffic on Marine Drive.
During that time, though, what we experienced in the Pen 1 and Pen 2 area, a lot of boils. A boil is a conduit that comes either through the levee or under the levee, as a natural ‘pipe’ through the soil, and it exposes itself on the backside of the levee or in the property on the backside, and it moves material with it. The velocity is so great that it moves material and as it moves material the conduit gets bigger and bigger and bigger. So what you have to do is you have to ring these with sandbags to equalize the pressure with the water elevation in the river. You don’t stop the flow, but equalizing the pressure slows the flow enough to stop the movement of material. And we had twelve boils in that area that potentially could have created problems for us, but we had them all under control. . . [these were all in Pen 1 and Pen 2. There was one boil at the airport. They continued seeping water, but it wasn’t a big problem]
. . . The biggest problem we had in the February ’96, though, was the communication problem. We all learned a lot. In ’63 we had the high water, but most of the time from ’63, most of those people are retired, they’re not around anymore. On the west coast here, we don’t really have severe flooding or anything else, so you don’t have a lot of people that are experienced in dealing with floods. . . there was a few people that went back to Mississippi during that flood, but it was a different situation completely than here. So we had to learn everything from scratch, basically. And what we found was that we didn’t have good emergency plans, we did not know how to coordinate. We didn’t have communications. We didn’t have the training on the proper terminology. What it meant. And so one agency communicating to another agency was using the wrong terminology; they didn’t understand what we meant. We didn’t have coordination between services needed. For example, if we wanted dump trucks to bring sand in or rock in, I’d call one agency and somebody else would hear that, so they would send over ten trucks, then the other agency sent over ten trucks. Pretty soon we had thirty trucks here; we only needed ten. We had all that labor force out there we didn’t know what to do with. It wasn’t managed properly. And so it was really confusing.
So we learned a lot about the training and organizing we need to handle another flood. And that’s what we’ve been concentrating on, with all the agencies. Multnomah County Emergency Management, City of Portland, the Drainage District. I put on training classes now, even with the Corps of Engineers, I train the Corps people, on the proper way to sandbag, the proper terminology. I’ve trained the Army National Guard, the Port of Portland, the City of Portland Water Bureau, a lot private industry, I do training of the proper techniques of sandbagging, what to look for in a levee, what a levee is designed to do. We’ve set up radio communications. The radio communications cost us over thirty thousand dollars in case we lose the phone lines. But we’re connected with fire, police, emergency management, and all the other agencies. We all have the same radios, which is an 800-megahertz radio.
DS: And that’s only been set up since the ’96 flood?
DH: Most of it has been set up in the last year and a half. Because after the ’96 flood we were all scrambling through FEMA and everything else to get all the repairs done. In the ’96 flood, through the three districts, Pen.1, Pen. 2, and MCDD, with the Corps of Engineers we spent over six million dollars on repairs. Six million dollars sounds like a lot, but it really isn’t when you start repairing levies. We only had a total of about three and a half miles of damages throughout the whole District area.
DS: Who provides the labor force for the repairs? You said that you had prison inmates who assisted during the flood . . .
DH: Right. During that kind of emergency, we look at outside resources; the private sector. We use city agency resources. We use the Corps resources. However, the district and the Corps had to finance that whole thing. The levies are inspected annually by the Corps of Engineers and you’re on a rating basis. It’s an A, B, or C. All of our levees get an A+ and they have for years. If you don’t maintain at least a B rating- now a B rating is not very good -if you have any damage, the Corps will not help finance your repairs. They pay 75% of the repairs if the levee had an A rating in the past inspection. Now, the district has to pay 25%. So, then we also got money from FEMA.
We also had 117 slides in the Columbia Slough during the February ’96, and primarily that was because of the ice build up on the slopes. Once we lost electricity for a long period of time and the water in the slough built up. So, once we got electricity back on, we started pumping again and we drew the water down. Another thing we learned, if we drew the water down real fast�� Well, you don’t do that. Banks are saturated, and you draw the water down fast, your banks fail and now you have more damages. If you draw down slowly, the stability of those banks will more likely stay there.
DS: What area were most of those slides in?
DH: Well it was throughout the whole upper, middle Columbia Slough. Anywhere from Fairview Lake, actually between 138th to about 62nd were the majority of them. And most of those were because of trees that came down. Again the ground was saturated. The wind came in, blew the trees down and left a big void, and then the top of the bank slid back in.
Out of those slides I’d say probably sixty or sixty-five percent were what we refer to as a rotational slide. A rotational slide isn’t the same as a debris slide in which material is liquefied and slides down the hill Ours were rotational, where the banks are so steep that the top is heavier than the bottom and it’s saturated so the top would actually push the whole bottom down, the whole thing would just rotate. And so the bottom would heave up and the top would go down. Also, it’s caused by the trees on steep banks-the loading up on top. That’s why what I said earlier about environmental improvement-what we can do to improve the ditches and banks–we can create the benches with shallow slopes, then plant those. That would stop the rotational failure because you’d have ballast at the bottom.
The other issue that we found that we would not expect was cause of the flooding that we experienced in Pen. 1 over by Expo, and over by James River and that area west of I-5.Remember the levees were built years ago, and, in that area we have a lot of old pipes that go through the levee. And those pipes had been abandoned or not maintained. The tide gates that stops the water from coming back through the pipes were broke and deteriorated because people hadn’t experienced high water like this in the past. So the water was finding those culverts and flowing backwards and flooding the properties. The problem had nothing to do with the levee; it was the pipes themselves. So we’ve identified all those pipes. There’s seventeen over in just that one area there, and we’ve replaced the pipes, the tide gates and everything else to prevent that from happening in the future. . .
DS: You said that the private landowners are responsible for maintaining their own culverts.
DH: [Maintaining the culverts was the responsibility of private landowners in the past. The drainage district is taking it over because the District has to be able to protect the lands behind the levee. They are entering into agreements with the landowners. If they own the pipe, they have to pay to update the pipe to today’s standards, and then MCDD takes the pipe over. Still a lot of unidentified pipes]
DS: You said that there were two weak links in the levee.
DH: Basically the Marine Drive levee along the Columbia River, it’s a large wide levee, it’s high, and it’s probably considered up to a five hundred year event.
Some of the other levees, though, are built to the minimum specifications of the Corps and they were built years ago. . . .The top of these levees is at elevation thirty-five. The flood in that area is 29.6 or say 30, and they have three foot of freeboard, typically for the Corps standards. So they only have two feet extra on top of them. They are 14 feet wide at the top. And those levees were built in the era when people used natural soils, whatever they had around them. PIR has a section between Heron Lakes Golf Course and PIR racetrack that has-we suspect-old theater foundation still left in the levee. They cut down trees when they rebuilt the levee and they just dropped the trees and they were left in the fill, so those trees will decompose over a period of time and act as conduits coming through. And that creates a weak link. And that whole section needs to be re-evaluated on its integrity and we need to do core drilling and sampling in there to find out how bad it really is. I don’t know how bad it is, but I can tell you that we have high seepage in that levee. Every high water we have a lot of boils. That tells you something right there.
DS: And that’s the same place where Vanport was.
DH: That’s next to the place where Vanport breached. Exactly. Then Bridgeton levee is the second weak link, along Bridgeton Road where the houseboats are located. It hasn’t been maintained well in the past. There’s blackberries covering the whole thing. We did an investigation last year, we removed a lot of the blackberries, looked at the face of the levee, and we found some vertical erosion points at fifteen, twenty feet high, straight. That’s not a good sign for a levee. We saw a lot of boils in that area, a lot of seepage, and a lot of sinkholes during the February ’96 event. Also in ’96, we saw a number of stress cracks on top of the levee.
The history here is a little different. When people put in houseboats they saw the levee was so narrow but they needed a place to park. So they just dumped whatever they had over the side of the levee on the waterward side to create parking. It wasn’t put in structurally sound. What kind of material did they use? Concrete, bricks, whatever they had. You know the landowner’s not going to go out and buy good material. They’re going to use what they had. Wasn’t compacted, no toe was put in to hold that material up, so as it becomes saturated it is loaded on top and then that stuff’s all rotating again, rotating out because there’s nothing to adhere to.
The biggest mistake a lot of developers, landowners, contractors do is they don’t remove the sod away from the levee or away from any embankment. When they fill against it, that creates a slip plane. And when it gets saturated that whole stuff will break loose, separate and break loose and it will fail. Now we don’t know whether the levee’s giving way or whether that illegal fill is actually moving. So it makes my job very difficult in determining whether we have a safe levee section or not. This year we’re going through with the Corps and reevaluating that whole Bridgeton section and finding out if we have to tear all of it out and rebuild it or not.
DS: So you’re still recovering from the ’96 flood.
DH: A lot of work has been done, and we’re still recovering in some places, yeah. Especially those two districts. (Peninsula Drainage Districts No. 1 and 2) The Peninsula Drainage District No. 2 still has some areas that we need to further investigate, identify whether there are any more weak points. But, we’ll find out. We have miles of levee that has withstood the ’96 high water event, but we don’t know if another weak point will show up until we have another high water. That’s the bad thing about it. You just don’t know. There’s no way really to do any test on the deep conditions inside the levee. You just have to do a good job with the problems you see and with maintenance, and wait and see what’s going to happen with the next event. By what we did these last few years we’re prepared the best we can be, but we’ll see whether we’ve corrected all the problems that could be out there, or not. . .
[Interview ends]