The digging is done on Monroe County's $5 million effort to restore five troubled canal systems but the watching goes on.
The installation of a weed-gate curtain in Big Pine Key's Atlantic Estates subdivision marked the end of the construction phase on six prototype projects that test varied techniques in a quest to cure sick canals.
For the next two years, Florida International University experts will compare changes in water quality against water samples taken before construction work began in early 2015.
"The initial post-construction monitoring results are promising," said Rhonda Haag. "They show improved dissolved-oxygen levels and [water] clarity.... We are pleased that the early results show the restored canals are helping to bring back marine life."
Haag, who oversees the pilot program as Monroe County's sustainability director, said, "We already have learned much from each type of project."
The first slate of projects test restoration methods that could be used for future projects if funding is available. Some prototype canal projects have already revealed needed changes in planning and technology.
Poorly planned canal systems dug decades ago can create environmental conditions that degrade water quality. That unhealthy water then flows into nearshore Keys waters.
"The threat is real to our nearshore waters, the same waters that drive our tourist-based economy," County Commissioner George Neugent said in a prepared statement.
Status of the first six canal projects:
- Canal No. 29, in Key Largo's Sexton Cove subdivision. Engineering and construction costs of $1.36 million backfilled a deep canal, about 225 yards long, to depths of 8 feet. The project's four-month construction finished in July 2015. Water clarity has improved, healthy plants sprouted and "a return of abundant sea life was noted by canal residents."
- Canal Nos. 470 and 472 on Geiger Key were connected by a 112-foot culvert, 24 inches by 38 inches, to improve flushing. It worked after its April 2015 opening, but a seaweed buildup in the pipe caused it to be closed in July 2015. After changes were made, the culvert was reopened last month. Cost was $221,000, of which the state funded $100,000.
- Canal No. 266 in Big Pine Key's Doctor's Arm subdivision, described as "one of the very worst in the entire county" due to muck and decayed seaweed. The $1.35 million project finished last month after extensive vacuum dredging and air-curtain installation.
- Canal No. 290 off Avenue I on Big Pine saw similar vacuum dredging to remove muck five feet deep from the bottom at a $798,000 cost. A pre-existing weed gate needs replacing or upgrades since it did not block some seaweed from returning
- Canal No. 277 in Tropical Bay Estates on Big Pine Key got a 200-foot culvert, 60 inches in diameter, to improve tidal flushing at a cost of $424,000.
- Canal 287 on Big Pine Key received a $150,000 air curtain to block seaweed.
Two more canal projects, funded by an additional $2 million, are planned for this year.