UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 4 

ATLANTA FEDERAL CENTER 

61 FORSYTH STREET 

ATLANTA, GEORGIA 30303-8960 

May 10, 2010 

New Jacksonville ODMDS Designation Dive Report 

Dates: 3/31/10 

Divers: Drew Kendall (Dive Master, EPA Region 4); Chris McArthur (EPA Region 4); 

Nadia Lombardero (ANAMAR Environmental Consulting) 

Water Temp: ~60F 

Purpose: To ground-truth sidescan sonar data to determine bottom type. 

Dive #1 

Date: 3/31/10 

Time: 1308 

Duration: 24min 

Depth: 63’ 

Location: DS2 

Divers: NL, CM 

Buoy Location at end of dive: 30 19.706’N; 81 17.138’W 

Description: Dive may have been off target by 80 to 100 feet based on measurement of 

the buoy at the end of the dive. Visibility was very poor (1-2 feet) with moderate bottom 

current. Was able to see the bottom with use of video camera lights. Bottom consisted of 

waves in a very fine sand intermingled with patches of silt at the bottom. Silt appeared to 

be approximately 3 inches thick over sand. Observed one sea star and numerous worm 

tubes. 

Dive #2 

Date: 3/31/10 

Time: 1404 

Duration: 12min 

Depth: 56’ 

Location: DS4 

Divers: DK, CM 

Buoy Location at end of dive: 30 19.755’N; 81 16.936’W 

Description: Poor visibility. Bottom appeared to be coarse sand bottom with some shells. 

Dive #3 

Date: 3/31/10 

Time: 1458 

Duration: 19min 

Depth: 60’ 

Location: DS7 
Divers: CM, NL 

Description: Very poor visibility, worst visibility of the 3 dives performed today. Anchor 

landed on rock outcrop. Rocks appeared to be fixed in place and ledge like (flat and quite 

large, did not move when pushed, but they also seemed jagged in nature). Could not 

determine if the area was a natural or artificial reef.. Change in elevation (2 feet) at 

rockface with upper surface consisting of a very fine and soft silt (about 2 -3 inches 

covering either more rocks or hard bottom. Photos taken. Very poor visibility (1 foot) 

and moderate current at the bottom, surge-like in nature. Circular pattern search was 

attempted but not conducted due to conditions, instead a short (about 5 meter) transect 

was done. A portion of the transect encountered the rock outcrop described above and 

the next perpendicular 5 meter transect had a 1⁄2 foot layer of very, very soft fine silt 

(pudding like) over loose medium coarse sand. No rocks were observed on the second 5 

meter transect. The fine silt seemed to be agitated by the bottom surge creating an 

“underwater cloud” that affected the visibility even further. 

Figure 1: Growth on Rocks at DS7 Figure 2: Growth on Rocks at DS7 

Dive #4 

Date: 4/1/10 

Time: 1218 

Duration: 22min 

Depth: 63’ 

Location: DS1 

Buoy Start Position: 30 18.542; 81 16.020’W 

Buoy End Position: 30 18.528’N; 81 16.025’W 

Divers: NL, CM 

Description: Decent visibility (4 feet). A semicircle with radius of 25 feet was conducted 

to the west of the buoy. Areas of dense polychaetes were encountered. Bottom was a 

mixture of grey sand, gray sand with shells, gray sand with tube worms, and sandy areas 

with a thin transient layer of brownish silt intermixed with the sand. A limited amount of 

video was obtained in this area. The video shows a transition zone between fine sand 

with some small shell fragments mixed in and a thicker silt area that when disturbed 

dissolved readily in the water column thus creating poor visibility. The consistency of 

the silt was like “pudding”. Some of the silt areas had settled creating small balls and 

some relief which is evident on the video. The area with the “pudding balls” relief was 
about 6 inches deep. Two samples were taken, one of the gray sand material and one of 

the very fine silt. 

Figure 3: Sandy bottom at DS1 Figure 4: Lumpy clay bottom at DS1 

Figure 5: Polychaete covered bottom at DS1 Figure 6: Matted bottom at DS3 

Dive: #5 

Date: 4/1/10 

Time: 1319 

Duration: 20min 

Depth: 59’ 

Location: DS3 

Buoy Start Location: 30 17.700’; 81 81 17.830’W 

Buoy End Location: Not Recorded 

Divers: DK, CM 

Description: Moderate Visibility (3 feet). Sandy bottom was encountered with very thick 

mats of organisms including bivalves. The thick mats occurred as mounds as high as 6 

inches above the surrounding sandy bottom. One sample was taken. One theory is that the 

mats are Caulerpas rhizome holdfasts. 
Dive #6 

Date: 4/1/10 

Time: 1406 

Duration: 25min 

Depth: 62’ 

Location: DS5 

Buoy Start Location: 30 18.795’N; 81 17.055’W 

Buoy End Location: 30 18.787’N; 81 17.052’W 

Divers: NL, CM 

Description: Poor Visibility (2 feet). Three quarters of a 50 foot circle starting from the 

north of the buoy was conducted. The first half of the circle consisted of a sandy bottom 

with limited polychaetes. Starfish and sea stars were also observed. The last quadrant 

consisted of the same very fine silt that was encountered in DS1, it was easily stirred up 

upon contact. Did not see the same type of relieve or depth of the silty material as 

encountered on DS1, but a much finer “veneer” layer up to 3 inches deep. 

Figure 7: Bottom at DS7 
Sidescan Sonar Record 

DS4