ML20082H973

Interim Rept on Water Seepage at Station 58 of Wolf Creek Generating Station Main Dam. W/One Oversize Figure. Aperture Card Is Available in PDR

ML20082H973
Person / Time
Site:	Wolf Creek
Issue date:	11/28/1983
From:	KANSAS GAS & ELECTRIC CO.
To:
Shared Package
ML20082H952	List: ML20082H950 ML20082H973
References
RTR-NUREG-0881, RTR-NUREG-881 NUDOCS 8312010338
Download: ML20082H973 (4)

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INTERIM REPORT ON THE WATER SEEPAGE AT STATION 58+50 0F THE WOLF CREEK GENERATING STATION MAIN DAM November 28, 1983 8312010338 831128 PDR ADOCK 05000482 E PDR

SNUPPS-WC This report provides the current status of the program to monitor the rate of water seepage through the Main Dam at Station 58+50.

The previous water seepage eval uation , (as reported in the response to Question 241.15-k'C of the FSAR Site Addendum, and subsequently, in Section 2.5.6.6 of the FSAR Site Addendum) concluded that the observed rate of seepage at Station 58+50 is well below the calculated maximum rate of seepage, except for occasional peak flow rates which are attributed to water infiltration into the drainage blanket from site precipitation. Since the time of this previous evaluation, a weir has been constructed in the vicinity of the observed water seepage at Station 58+50, so that the eval uation of the rate of seepage may be based upon the measured rate of seepage, rather than the estimated rate of seepage.

The observed area of water seepage is located on the land side of the Main Dam at Station 58+50, along the base of the granular toe drain at the toe of the dam, as shown in the plan, elevation and section views of Figure 241.15-

4. A weir has been constructed to collect and measure the rate of water flow through the drainage ditch downstream of the observed seepage. The location of the weir with respect to the area of observed seepage is also shown in Figure 241.15-4.

The drainage swale downstream of the seep was lined with a reinforced concrete slab for a length of 60 feet and a width of 23 feet. Water is retained in the lined swale by a reinforced concrete weir which is 17 feet wide and 2 feet high. The spillway in the weir is constructed of a steel plate with a "V" notch,14 inches high and 14 inches wide at the top.

To detennine the discharge flow rate through the weir spillway, the height of water above the crest of the spillway is measured. The discharge rate is then calculated from the following theoretical expression, where Q equals discharge rate cubic feet per second; O equals the central angle in the V notch; and H equals height of water above crest, feet.:

0 0 = 2.5 tan Y H2.5 (Reference no.1)

Q = 2,5 tan 26.565 H2 .5 0 = '.25 H2.5 Water flow through the weir represents the water seepage through the Main Dam, as well as occasional surface and subsurface drainage of precipitation from the landside surfaces of the Main Dam, for all portions of the Main Dam which are upstream of the weir. Main Dam Station 58+50 is a low point in both the finish grade and the drainage blanket at the toe of the Main Dam. . Water seepage through the Main Dam from approximately Stations 40+00 through.87+00 migrates toward, and exits the granular drainage blanket and rip-rap base at, Station 58+50 The maximum anticipated rate of seepage through the Main Dam is 0.6 x 10-b cubic feet per second per foot of Main Dam (reference Section 2.5.6.6.1, FSAR Site Addendum). As stated in the previous eval uation , the area of water seepage at Station 58+50 conservatively represents the water seepage through 3000 linear feet of Main i 1

SNUPPS - WC Dam; therefore, the maximum anticipated rate of water flow at Station 58+50 and the weir due to seepage through the dam, should be no more than 3000=

linear feet x (0.6 X 10-5 cubic feet per second per linear foot of dam) 0.018 cubic feet per second.

Construction of the weir was completed in mid-August and stabilizion of the grade adjacent to the weir, was completed in mid-September.

Since September 16, 1983, water flow through the weir has been measured periodically. The rate of . flow thrjugh the weir has also been measured during the latter portions of and following, periods of precipitation so that the relationship between precipitation and water flow through the weir could be monitored.

From September 16, 1983 through November 4,1983, a wide range of flow rates through the weir have been measured, ranging from 0.007 cubic feet per second to 0.35 cubic feet per second. All flow rate measurements which are above 0.018 cubic feet per second appear to be related to precipitaiton The which occured prior to the time of the flow rate measurements.

relationship between precipitation and fluctuations in the rate of flow Peak flow rates through the through the weir is shown in Figure 241.15-5.

weir occur innediately following a period of precipatation; and, within less than one week following the period of precipitation, the rate of flow through the weir returns to a rate well below the maximum anticipated seepage rate of 0.018 cubic feet per second.

The recent measurements of the rate of flow through the weir near Station 58+50 of the Main Dam appears to support the earlier conclusions that the normal rate of seepage through the Main Dam is below the maximum anticipated rate of seepage. Those measured flow rates through the weir which are above the maximum anticipated seepage rate of 0.018 cubic feet per second are attributed to periods of precipitation which occured prior to the time of flow rate measurement.

The rate of flow through the weir near Station 58+50 will continue to be measured and evaluated on a weekly basis, until it is established that the rate of seepage through the Main Dan has stabilized, and that the occasional peak flow rates above the maximum anticipated seepage rate are related to periods of precipitation.

REFERENCES

1. Brater, Ernest F and King, Horace Williams (1976)

Handbook of Hydraulics, For the Solution of Hydraulic Engineering Problems, Sixth Edition, Calculation Number (5-45) 4 2

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