April 11

Apopka Blue Sink

View of Apopka Blue Sink from above.

Bob Giguere & Renee Power at Apopka Sink

Cave formation inside Apopka Blue.

Keith Mille after completing his orientation dive.

Team Orientation Dive at Apopka Blue

Friday, April 11, 2003

Sinkholes are depressions that collapse suddenly or subside gradually over time, forming depressions or bowls in the earth. They usually occur when water levels in underground caverns recede. Initially, these caverns are formed when rainfall percolates down through the topsoil from uplands into the porous rock below. The slightly acidic water gradually dissolves the soft rock, and over time creates a very complex system of water-filled conduits, enlarging fissures and cracks to allow the captured water to flow underground. These underground rivers together form our aquifer‚ the major drinking water source for 90 percent of Floridians. A sinkhole often becomes a primary area of recharge, a place where surface water can enter the aquifer and replenish the groundwater supply. For this reason, anything entering the sink‚ either as storm water runoff or as discarded trash‚ also pollutes the aquifer.

Sinkholes are considered “karst windows” because they provide a glimpse into the health of the underlying potable water supply, and into its dynamics. If a sinkhole can be linked to a spring, then hydrologists have a better idea how the water migrates underground. Upland terrain that serves as “recharge” for a spring can then be better identified. Abrupt collapse-type sinkholes have become more common over the past twenty-five years, primarily due to activities of humans such as withdrawal of groundwater, diversion of surface water, or construction of ponds. There are 1,600 sinkholes documented by the Sinkhole Institute of Florida.

This weekend the Cambrian Foundation has organized a clean up of Apopka Blue Sink. Apopka Blue Sink is located on 40 acres of land owned by the City of Apopka in Florida. It is due west of Rock Springs. Local troops of Girl Scouts will be schooled at the site in the geology and hydrology of this underground system. Terrence will use a full-face scuba mask with audio links to the surface to let the children communicate with him and actually “steer” him around the cavern. Additionally, the Girl Scouts will get a chance to earn badges by assisting divers with data collection, identification, and classification of materials recovered from the bottom of the sinkhole.

Today, thanks to the gracious permission by the City of Apopka, the entire team met at Apopka Blue at 9 am for an orientation to the site both topside and underwater. An offset sink would describe the area best. The entire sink is fenced off and only accessible via the City of Apopka. A steep, narrow pathway guided the divers down to the water. Due to wet leaves and debris, the short trek proved to be a bit precarious at times. Fortunately no one entered the water in an untraditional manner! The team was divided into three groups. 1) Terrence, Bob, and Renee 2) Doug and Anna 3) James, Keith, and Jeff. Each group had roughly one hour of bottom time with a maximum depth of around 105 feet. The cavern zone, full of organic debris and trash, sloped quickly down to a depth of 70 feet where the line then went into a 50-foot long restriction. The bottom composition is a silt/sand combination while the ceiling and walls are white limestone. The visibility was reduced to zero as the teams passed through the restriction. Once through, the cave opened up into larger passage that was absolutely beautiful. It seemed slightly reminiscent of Orange Grove at Peacock Springs in Florida. However, there is one major difference – the walls and ceilings of this cave are covered with fossils!! They were literally everywhere. A favorite were the tiny sea biscuits. It was strange to see salt-water fossil life in a fresh water cave. We tried to imagine the area once teeming with sea life. Team members also spotted a blind crayfish and one very large catfish. During the exit, the teams picked up various non-cave articles including a stainless steel bowl, some plastic items and a lovely “pearl” necklace. After very short decompression obligations, the teams surfaced. A safety rope was used to assist divers in exiting the sinkhole. Once out of the water, everyone enjoyed sandwiches and a vegetable tray donated by Publix grocery store.

Team Apopka:

  • Anna Olecka, Project Director
  • Artie Ahr
  • Jeff Bauer
  • Doug Chapman
  • Amy Giannotti
  • Bob Giguere
  • James Hurley
  • Keith Mille
  • Renee Power
  • Reese Rechnitz
  • Leon Sturtz
  • Allison Tysall
  • Terrence Tysall

After leaving Apopka, the tanks were taken to Scuba World in Orlando for filling for Saturday. Friday evening, the team met at the Tysall “manor” for a discussion of Saturday’s activities over a barbeque dinner.

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