Dredge (and Rainey) Report Cell 4 December 2, 2011

Dredge (and Rainey) Report
Cell 4

December 2, 2011

 

Summary of accomplishments:

One year since dredging started.
Turned dredge around to dredge toward main canal
Fluid mud to low water level in deepest part of Cell 4
Total time pumped directly into Cell 4: 29 hours
Total time pumped into Cell 5 (with spillover to Cell 4 & 3): 72.75 hours
Total dredging time at study cells: 102 hours
Impediments: extreme low water in the pond; spud cable broke; submerged discharge hose disconnected; overhead tractor drive binding; traveling winch controls stick.

Tuesday, November 29

Karen started out the week by passing through Abbeville to pick up more cable and other supplies, and met Timmy at the dock for 9:30. She had planned to bring the Avocet down, but with the early morning temperature in the 30s and 40s, she opted for the nice warm cabin of the Goose over the open deck of the 17’ skiff Avocet.

We got to the dredge site around 11:00 with plans to remove the bad part of the cable on the left rear spud since it had become dangerously frayed the last time we used it. Unfortunately, pulling it out of the mud was too much strain on the remaining two strands, and the cable broke. We would have to use the come-along anyway.

Figure 1. Setting up the come-along to pull  the spud out of the mud and onto the deck to repair the cable.

Figure 1. Setting up the come-along to pull the spud out of the mud and onto the deck to repair the cable.

Timmy went back to the camp for the come-along and other tools. Karen took the time to clean the bird poop off the chairs and get other things ready at the dredge. A pelican startled her at one point by plunging into the water right behind the dredge for its dinner.

When Timmy returned, Karen used the ladder to get on top of the engine cover to secure the upper end of the come-along to the overhead beam. Timmy pulled the spud up out of the mud by increments, using another piece of webbing to keep it from sliding back in the mud while the come-along was repositioned for another pull. The NW wind had pushed the water out of the bay and canals, and we had very little water under the dredge to work with. So the other spud had to be pulled up as well, to allow the dredge to move forward as we rotated the bad spud out of the mud and onto the deck. By 1:30, Timmy had it fixed and back into its upright position.

Since it is hunting season, the dredge, hoses and cables in the narrow canal are a hazard for hunters moving about in low light conditions to access the neighbor’s property, so we needed to move it to the side for overnight. We are also at the limit of the discharge length of the hose in the canal and plan to move it to the east side of the landing. With only a few hours left in the day, it wasn’t worth setting everything up to dredge for an hour and then taking it all apart again. And, with the water so extremely low, we could not access the shore to check the pond. So, we were done for this day at the dredge.

Timmy wanted to burn some areas of marsh today since there were prime wind conditions. We went up to the first location canal, but he said the vegetation was too green here to burn yet. The water level across the weir showed how low the water was in the bay and canal with the pelican sitting at our eye level. The pelicans were more tolerant of our approach than earlier in the year, but finally flew off, and two raccoons spotted us late as they were foraging for lunch along the mudflat.

Figure 2. Water level in the canal and bay was very low, highlighted by the more normal water level in the blocked off canal with a pelican floating at our eye-level.

Figure 2. Water level in the canal and bay was very low, highlighted by the more normal water level in the blocked off canal with a pelican floating at our eye-level.

Figure 3. Brown pelican and foraging raccoons.

Figure 3. Brown pelican and foraging raccoons.

We headed back toward the camp and down to the Goose Pond. The Dugas Square on the south side of the canal from the Goose Pond had not been burned in 3 years, so Timmy said it was time. The snow geese have not come down in numbers yet, and Timmy said it was because the marsh had not been “opened up” yet. He explained that they didn’t like to feed in an area with too much high grass because they couldn’t see predators approach. We stopped in two corners for him to get the fires started, and the steady NW winds did the rest. As soon as the fires started running and the smoke swirled up, raptors came from every direction to feed on the insects and rodents the fire flushed.

Figure 4. Fires are an important method of marsh and wildlife management.

Figure 4. Fires are an important method of marsh and wildlife management.

Figure 5. Immature redtail with smoke background. Raptors came from all over as soon as the smoke rose, to feed on flushed insects and rodents.

Figure 5. Immature redtail with smoke background. Raptors came from all over as soon as the smoke rose, to feed on flushed insects and rodents.

Figure 6. You never go hungry at Rainey as long as you have a few fishhooks...

Figure 6. You never go hungry at Rainey as long as you have a few fishhooks...

Timmy had dropped a few baited jugs in a waterway on our way down to the Goose Pond area. On our way back to the camp, we collected a few catfish and rebaited for tomorrow.

 

 

 

 

Wednesday, November 30

The temperature was 34° when I got up this morning. Outside before dawn as usual, the breeze was light, and the day was quiet except for two great horned owls hooting in the live oaks on the point and the mallards just starting their morning conversations out in the pond behind the camp. The cool air called for more clothes, which was welcome against the ever present mosquitoes.

 

The sun comes up so far to the south now, it no longer reflects in the lake but peeks through the tall marsh cane.

 

 

 


We bundled up and took the flat boat down to collect the catfish jugs. We could still see smoke in the distance coming up from yesterday’s marsh burn. As we picked up the last jug, Timmy shut the motor off for a moment, and we could hear the sound of geese. Timmy broke into a big grin.

Figure 7. Smoke from yesterday's marsh burn still hung in the morning air.

Figure 7. Smoke from yesterday's marsh burn still hung in the morning air.

We headed back to Dugas Square, stopping several times to listen for geese. Several Vs passed over as we pulled in at the last area burned yesterday. As we climbed up on the levee, we could see what looked like a swirling cloud of smoke in the distance. It was snow geese coming in from all directions to the area that was burned just yesterday! If I didn’t believe Timmy yesterday, I did today! Lines of geese were coming in, and big swirls would condense into a vortex and settle on the cleared marsh prairie. Then the next swirl would build and condense. It was noisy, and beautiful, and exciting!

Figure 8. Clouds of snow geese congregated on the marsh that was burned yesterday.

Figure 8. Clouds of snow geese congregated on the marsh that was burned yesterday.

I’ve begun to understand how important fire is to these marshes after following Timmy around this year and seeing the results. He rotates the areas burned so that different areas are burned roughly every 3 years. He waits until the conditions are right: enough wind to move the fire along quickly in a calculated direction, the wind direction such that the smoke does not inconvenience any neighbors, enough water in the marsh to keep the roots cool, and known barriers – either canals, lakes or previous burns – to contain the fire. The marsh grass takes advantage of the ash fertilizer and puts up new, healthy green shoots within a few weeks without the thick tangle of overgrowth cutting down on light. The fire flushes destructive hogs and invasive coy-dogs, and opens up feed areas for the geese. Muskrat and rabbits feed on the new grass, and within a year there is thick healthy marsh for nesting birds. It seems like the burned areas have a higher stem density, which could only be a good thing for storm resistance (I’ll have to see if there has been any research results on this…).

We took our fish back to camp, and then loaded up to head to the dredge site. The water in the canal was up, so we went to shore first to look over the pond. It was full of ducks and wading birds. With hunting going on in other parts of the region, our little pond full of wigeon grass was ideal for ducks looking for a quiet corner and a snack – until we got there.

With the low, low water in the canals and bay for the last few days, the pond level was down as well, to roughly 8 inches below marsh level. This exposed a good bit of the fill in Cell 4.

Figure 9. A flock of gadwall and wigeon crossing our dredge site.

Figure 9. A flock of gadwall and wigeon crossing our dredge site.

The test area was next. It has been a good month since I’ve seen it, so it was nice to see it in good condition with the mud exposed. The spikerush and Bacopa had spread well and looked like a carpet in many places.

Figure 10. The test site had the substrate exposed. This view was to the south.

Figure 10. The test site had the substrate exposed. This view was to the south.

Back to the dredge, we replaced the starboard traveling cable, and then turned the dredge around and moved it to the east side of the landing. We started pumping at 11:00 overlapping with the first place we started dredging in June.

The nice thing about the new arrangement was that you could see the discharge in the pond from the dredge with a pair of binoculars.

Figure 11. The outfall could be seen from the dredge now that it is in Cell 4 and the dredge is back near the landing. The arrow indicates the outfall (end of the hose) up on the pontoon.

Figure 11. The outfall could be seen from the dredge now that it is in Cell 4 and the dredge is back near the landing. The arrow indicates the outfall (end of the hose) up on the pontoon.

Unfortunately, this day didn’t go well. In the five hours we attempted to dredge, we barely totaled 2 hours successfully. We had multiple pump clearouts necessary where apparently a dead tree had tangled with a crabtrap and parts kept getting in the impellers. The overhead tractor drive kept jamming so that we had trouble moving the dredge forward and back. The dredge hose laying along the bottom of the canal blew open and we had to replace the camlock levers that had rusted out. This was the most time consuming as it involved hanging over the bow of the flat boat to slip a rope over the end of each hose, sliding the rope to pull ourselves along the muddy, barnacle covered hose until we found the end, tying each end so we didn’t lose them, Timmy knocking out what was left of the old pins and putting in the new levers, pulling the ends together in the flat, then wrestling the two hoses together until we could get them locked again. I did most of the wrestling, so got wet and covered in mud and squashed barnacles. Timmy did most of the pulling and knocking, so he got covered in mud and squashed barnacles too. The good thing was, that for everything that went wrong, we had a solution.

Figure 12. Mud covered, stopped up pump.	Figure 13. Karen wrestling the hose and covered in mud and barnacles.

Figure 12. Mud covered, stopped up pump. Figure 13. Karen wrestling the hose and covered in mud and barnacles.

 Thursday, December 1

The morning dawned again cool, quiet and clear (37°). With no fear of being drained dry by mosquitoes while wearing my insulated clothes, I made my way out to the pond behind the camp to see what the mallards were talking so loudly about. Apparently, the conversations centered around the best tasting banana lily roots or wigeon grass.

Figure 14. Mallards in the pond behind the camp.

Figure 14. Mallards in the pond behind the camp.

The water level was up in the canal this morning, so we knew we would be able to access the pond. The airboat has been sitting by the boardwalk and Timmy wanted to retrieve it to do some maintenance work back at the camp. So, we began our work day at 8:30 with a tour of the dredge area by airboat to see how the work was progressing and to attempt to discern where the sediment plume might be going. We also wanted to make sure the containment was performing adequately.

Even though the water level in the canal was up, the pond level was still very low, at roughly 7 inches below marsh level. As we walked over the levee, a small flock of ducks left for parts south (you’re welcome, Christian Marsh hunters!), and a great egret and black-necked stilt continued working the far shoreline.

We circled the study cells and parked the airboat next to the south side of Cell 4 where the discharge is currently tied. With only 6 hours of pumping at the current location, we had built a new delta at the outfall and filled the western end of Cell 4 with fluid mud up to the waterlevel. The deepest part of Cell 4 was roughly 18 inches deep (relative to marsh level) at the former escape route through the reed containment 4c, which we had blocked with a plywood wall prior to this round of pumping. At the present waterlevel, we estimated that it was filled with roughly 11 inches of sediment. The western part of the cell was coated with a good 2-4 inches of sediment, and the old reed containment was thoroughly packed with mud. There was also fluid mud to the waterlevel just outside of the gap in containment 4b, in Cell 2, and a visible plume into Cell 1.

Figure 15. The outfall was placed facing containment 4d to the southwest end of Cell 4, and in 6 hours of pumping had filled the area to the west of the hose to the waterlevel. Notice the gap in the plywood containment 4b toward the top (north) of the photo.

Figure 15. The outfall was placed facing containment 4d to the southwest end of Cell 4, and in 6 hours of pumping had filled the area to the west of the hose to the waterlevel. Notice the gap in the plywood containment 4b toward the top (north) of the photo.

Figure 16. Containment 4c with reeds full of mud and plywood holding the water level higher inside (toward the top) of the cell.

Figure 16. Containment 4c with reeds full of mud and plywood holding the water level higher inside (toward the top) of the cell.

As we had hoped, the delta of shell and coarser material formed at the outfall made a ridge that effectively cut off containment 4d and the site where we think the effluent previously had been escaping through the marsh. This also forced the flow to wrap around the outfall, but there was very little new fill east of the dredge hose.

It is apparent that in order for sediment to build up, there has to be an exit flow for the movement of the slurry. With the low water level in the pond, the 4 inch hose essentially made an unintended containment, and to the east there was no place for the water to escape, and therefore there was no flow to carry sediment. We had the same problem in Cell 5 where the sediment would not move into the small finger embayments. We plan to leave gaps in any interior plywood containment, or use reeds to allow some flowage between cells to attempt to train the sediment build-up where we want it to go.

Timmy drove the airboat around the outside of the experimental cells so that we could check for evidence of sediment plume through the outer containment. We found what was obviously fill that had escaped through containment 4c before we added the plywood wall, but none that we could decide was new. The fluid mud was at an even level against the containment without any discernible drainage channel, so we assume that the plywood worked to contain the flow.

Figure 17. View to the east of Cell 4 from the outer containment 4c. The airboat made a trail through fluid mud outside the cell.

Figure 17. View to the east of Cell 4 from the outer containment 4c. The airboat made a trail through fluid mud outside the cell.

From the outside of containment 1, we could see a plume curling around from the gap in containment 4b. A little further over to the north, a second plume curled from the same gap around a marsh island in Cell 2 and back to Cell 1. It was apparent that the flow was exiting through the tiny gap at the north end of the outer containment of Cell 1, taking with it the lightest components of the sediment outfall. The water needs to go somewhere, and at this stage, this is perfect. If we stopped this gap, the flow would find somewhere else to go that may not be as advantageous. However, we will have to watch this gap to make sure the flow is not eroding into the marsh platform.

Figure 18. View to the east from outside containemtn 1. Two plumes were observed flowing from the gap in the containment 4b to the right of the photo, into Cell 1.

Figure 18. View to the east from outside containemtn 1. Two plumes were observed flowing from the gap in the containment 4b to the right of the photo, into Cell 1.

Figure 19. The flow from the study cells was exiting through a 4 inch gap between the north end of containment 1 and the marsh edge.

Figure 19. The flow from the study cells was exiting through a 4 inch gap between the north end of containment 1 and the marsh edge.

Back on the dredge at 9:30, Timmy shortened the left traveling cable so that it wouldn’t keep binding in the winch, while I started setting up to dredge. We also brought some 6×6” wooden blocks to use when clearing the pump, and tested the concept. Both of us had been uneasy when trying to clear the pump. The idea of lying beneath a 600 lb piece of equipment suspended by a ¼” cable has always been unnerving. With the new cable suspension, we can raise the pump up a few inches higher, allowing easier access and the blocks to be used as firm support – a much better arrangement.

Pumping started at 10:15, Timmy made sure everything was working, and then departed to go into town for some necessary errands. I settled in for a hopefully easy day, and it was relatively uneventful. I only had to unclog the pump of sticks and shells twice, and the overhead tractor drive hung up once, but there was nothing that stopped pumping for long. Handling everything by myself ensured that I would not get bored, and I could see the outfall in the pond with binoculars for added interest. I managed a full 5 hours of pumping and was just finishing up when Timmy got back. He helped me shut down and move the dredge to the side, and we went ashore to view the pond from the boardwalk, and still made it back to camp by 5:00.

Figure 20. View of the new delta in Cell 4 and the outfall at the end of the day from the boardwalk. The smoke on the horizon was from the neighbors burning marsh.

Figure 20. View of the new delta in Cell 4 and the outfall at the end of the day from the boardwalk. The smoke on the horizon was from the neighbors burning marsh.

Figure 21. Sunset across from the camp.

Figure 21. Sunset across from the camp.

Friday, December 2

It was a rosy dawn. Unfortunately, Timmy had to get to town early today, so there was no time to do a last site visit with better light. The ride back was the start of another beautiful day. Too bad I would have to spend the rest of it back at the office!!

Figure 22. Estimated status of the study cells for December 2, 2011.

Figure 22. Estimated status of the study cells for December 2, 2011.

Karen A Westphal and Timmy J Vincent, National Audubon Society
Louisiana Coastal Initiative and the Paul J Rainey Wildlife Refuge
6160 Perkins Road, Suite 215, Baton Rouge, LA 70808
225-768-0921 office, kwestphal@audubon.org

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