ML063320127

7/22/1993 - Stripe Bass Kill at North Anna

ML063320127
Person / Time
Site:	North Anna
Issue date:	07/22/1993
From:	Virginia Power Co
To:	NRC/EDO
References
DNNA 032769
Download: ML063320127 (6)

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308 the boundary between the anoxic hypolmnion and the oxygenated epilimnion (12m - 13m) during July and August.

Similar behavior has been reported for other southern reservoirs containing striped bass (Mathews et al. 1985) and (Lewis 1973).

. The boundary layer usually has a temperature range of less than 1-2*C but can have a D.O. range of 0.0-4.0 ppm.

Striped bass congregated in the Mid-Lake area of Lake Anna (Rt. 208 bridge to the Lower Lake end of Dike 2) and the area at the mouth of Millpond Creek in WHTF-2 (Appendix B-Figs. 15-38). This congregating reflects refuge seeking behavior. As striped bass follow schools of shad during the spring and early summer they eventually encounter the aforementioned temperature/D.O. "squeeze". To escape this "squeeze" they continually move to the best available refuge. The fish in the WHTF Millpond Creek area best exemplify this. These striped bass moved into Millpond Creek during the spring. As the shallower head waters warmed they were moved gradually down toward WHTF-2. By the time they reached WHTF-2 the morphometrics and temperature regimen of the canal between WHTF-2 and WHTF-3 had sealed off any migration route to WHTF-3 and the lower lake. The canal is stepped in such a way that it effectively pools the deeper, cooler water in WHTF-2 and skims the warmer surface waters off into WHTF-3.

The tracking data confirms the importance of cool summer rains and the opportunity they provide for increased movement out of the best available refuges and through the DNNA 032773

J t 307 Table 4.4-9 Comparison of temperature -dissolved oxygen profiles before and after a period of precipitation (13.6cm from 8/18-8/19)

W H T F -2 - Millpond Creek Ar~a 8/14/1985 8/19/1985 Depth Temp. D.O. Temp.

0 D.o.

(in) (0C) (ppm) ( c)

Surface 33.4 7.0 30.0 6.1 1.0 32.6 7.1 30.0 6.1 2.0 32.0 7.2 29.9 6.6 3.0 31.9 7.1 29.9 6.5 4.0 31.5 7.0 29.7 6.5 5.0 31.4 6.8 29.4 6.5 6.0 30.6 6.8 29.3 6.5 7.0 29.2 5.9 29.2 6.1 8.0 29.0 5.5 29.1 6.1 9.0 28.7 4.5 29.0 5.7 10.0 28.5 4.3 28.7 5.0 11.0 28.3 4.1 28.5 4.9 D.o.

Limit Before Rain-- 11.5 28.1 3.4 12.0 27.6 1.2 28.3 4.7 12.5 27.3 0.2 13.0 26.3 0.2 27.6 4.0 D.O.,

Limit After Rain -__ 13.5 25.6 0.2 26.6 3.7 14.0 24.2 0.2 26.4 0.3 15.0 22.6 0.2 22.2 0.0 16.0 21.8 0.2 22.2 0.0 8/18/1985 8/19/1985 Average Air Temperature 70. 1°F 75.1 0 F Minimum Air Temperature 68.2 0 F 67.0°F DNNA 032773.01