Got a lot done on Thursday and Friday! This job requires major earth moving (DIRT Moving) and we got major resources allocated. There was a bit of reluctance to put lots of "diggers" (excavators) and dumps trucks on until there was a good understanding and confidence in strategy.
The North Shore Council and Auckland Regional Council (planners, regulators, etc) have been "in the loop" and have approved the methodology to do the work yet protect the resources. For instance, the idea of damming the creek and diverting water around the work area, then pumping out immediate work area, then trapping eels and craw fish, etc, WAS FRAUGHT with Problems.
While it sounds reasonable, the overall effect was much more turbidity than wanted, for a longer period of time, and a badly degraded bottom (from walking on the soft substrate). Also the dams leak causing turbidity. Took us a day to seal the dam as best we could. Secondly, laying the diversion pipes in an "incised stream" was also turbidity producing. Thirdly, when you pump water around site it ended up causing erosion or extremely turbid water downstream - an option would be to require a huge sediment pond (here they use flocculant and decanters (lot like Skimmers - see our episode on Sediment Ponds)). And finally, walking thru the stream to rescue eels and crawfish causes EXTREME damage to bottom and even more turbidity.
So, our new protocol and methodology is to "stay out of active stream, period". When we build structures in banks or bottom, we will use "clean" rock and wood. We will minimize touching the active bottom with equipment. Using clean, "self-launching rock" was, in fact, almost the entire reason for success of our projects in Alberta. (See Hinton I and II, and Willow Creek). We are monitoring the water quality and if a problem occurs we will stop, find out what happened, and re-evaluate.
The agency representatives are very pleased with the way things are working. Please notice that we have left a vegetated berm (called a bund here) between the disturbed banks and the stream. Also not that the "back slope" of the bund is steep so any clods or soil fall away from the water. We are also limiting the actual work in the stream, e.g., when we remove the bund, to 50 meters.
Do you mean that it is even conceivable to to work near a stream without building a silt fence?? I say this so mockingly because silt fence near streams are most often an utter failure - more on that stuff later.
On Monday we are all ready to build some more structures - Living Walls with Compost Socks, Rock Toes (looking natural), Large Woody debris - Keep Coming Back !