Scientific Investigations Report 2006–5290
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5290
Table 6. Summary of microbiological data, by type of principal-aquifer lithology, collected from wells in 22 study units of the National Water-Quality Assessment program, 1993–2004.
[Type of lithology: residuum, remains from chemical and physical weathering of parent aquifer materials or formation. Abbreviations: CFU/100mL, colony-forming units per 100 milliliters; <, less than; >, greater than; –, no data or not applicable]
Tests | Type of lithology | Number of wells |
Number of wells with detections (percentage) |
Concentration (CFU/100mL) |
||
---|---|---|---|---|---|---|
Median | Range | |||||
Total coliform | Carbonate rocks (limestone, dolomite) | 202 | 121 | (59.9) | 2 | <1 – 1,600 |
Sandstone, shale | 118 | 45 | (38.1) | <1 | <1 – 420 | |
Crystalline rocks | 74 | 38 | (51.4) | 1 | <1 – >80 | |
Semiconsolidated sand, residuum | 112 | 30 | (26.8) | <1 | <1 – >80 | |
Volcanic | 48 | 10 | (20.8) | <1 | <1 – >18 | |
Sand, gravel | 301 | 61 | (20.3) | <1 | <1 – >110 | |
Alluvium | 111 | 12 | (10.8) | <1 | <1 – 60 | |
Escherichia coli | Carbonate rocks (limestone, dolomite) | 253 | 65 | (25.7) | <1 | <1 – 1,200 |
Volcanic | 130 | 2 | (1.5) | <1 | <1 – 90 | |
Crystalline rocks | 63 | 4 | (6.3) | <1 | <1 – 38 | |
Sand, gravel | 280 | 13 | (4.6) | <1 | <1 – 23 | |
Semiconsolidated sand, residuum | 112 | 13 | (11.6) | <1 | <1 – 15 | |
Sandstone, shale | 89 | 7 | (7.9) | <1 | <1 – 33 | |
Alluvium | 51 | 0 | (0) | <1 | – | |
Coliphage | Semiconsolidated sand, residuum | 86 | 3 | (3.5) | – | – |
Volcanic | 40 | 2 | (5.0) | – | – | |
Carbonate rocks (limestone, dolomite) | 78 | 6 | (7.7) | – | – | |
Sand, gravel | 192 | 2 | (1.0) | – | – | |
Crystalline rocks | 12 | 0 | (0) | – | – | |
Sandstone, shale | 0 | – | – | – | – | |
Alluvium | 15 | 1 | (6.7) | – | – |