Two big design decisions had to be made early.
Decision 1: Powered or static? We picked static. No motor, no propulsion, no batteries. The river current does the work.
Why? Reliability, cost, maintenance, theft. A motor is one more thing that breaks, requires fuel, drains a battery, gets stolen, or floods. The Ocean Cleanup proved you can do this passively. So we're going passive.
Decision 2: One barrier or several? Several. Three, specifically. Because trash is a spectrum, not a category.
Here's the staging:
Stage 1 — The Big Stuff. Two or three columns, anchored across the creek. Wood or recycled metal. These catch tree trunks, large furniture pieces (yes, people throw furniture in the river), and any debris big enough to break the lighter stages downstream of them. Frequent monitoring required — these will need to be cleared often, especially after storms.
Stage 2 — The Floaters. A line of buoyant elements with a barrier hanging beneath. This is the classic surface-skimming approach the Ocean Cleanup pioneered. It catches plastic bottles, bags, styrofoam — everything that rides the surface. Float material is still being decided. Repurposed drums or buoys are the leading candidates.
Stage 3 — The Submerged Net. This is the one we added because of what we found in the manual cleanup (Post 3). A net that hangs below the surface, catching the heavy textiles and waterlogged debris that would otherwise pass under the floaters and end up in the bay.
Three stages, escalating from coarse to fine. Like a kitchen sieve, but for a creek.
What we don't know yet:
- Exact float material
- Exactly how the submerged net attaches and tensions across the columns
- Whether the column anchoring will survive flood season
- How often each stage needs to be cleared in practice
That's what the pilot is for.
Next post: the pilot site itself. Why we picked a creek 2 meters wide.