Xxxxxx Firs Pond, Kitsap County. The basic data that were used to estimate infiltration rates at the Xxxxxx Firs pond are shown in Table 4.1 and in Figure 4.15. The information in Table 4.1 describes the flow rates, the duration of the test, and the pond geometry. Figure 4.15 shows the depth of water as a function of time. These depths were measured at 10-minute intervals. The flow rate into the pond was approximately 1850 ft3/hr (230 gpm or 52 m3). The pond was filled for approximately 2 hours, and the water reached a maximum depth of approximately 26 inches (66 cm). The total volume of water discharged into the pond was approximately 4190 ft3 (119 m3). The draining phase of the test, which lasted for approximately 70 hours, can be divided into two parts. During the first part, from hour 3 to hour 30, the water level decreased exponentially. The water level declined linearly for the next 40 hours. However, there were two jumps in the curve: one after approximately 30 hours and one after approximately 55 hours. These times correspond to October 29 and October 30 2000. There was very little precipitation on October 29th (0.05 inches or 0.1 cm) and no precipitation on October 30th (National Oceanic and Atmospheric Administration, 2000). However, 0.30 inches (0.76 cm) and 0.13 inches (0.33 cm) of precipitation fell on October 27th and 28th, respectively. The jumps could be explained by this precipitation if the response time between precipitation and water levels was on the order of 2 days, but such a long response time is improbable.
Xxxxxx Firs Pond, Kitsap County. In October 2000 a flood test was performed at Xxxxxx Firs storm water infiltration pond in Kitsap County. This pond, which is shown in Figure 4.4, is located in a residential area less than 3 miles (4.8 km) southwest of the Balsam 7-11 facility. The basin area draining into the pond is approximately 10.6 acres (0.04 km2) (Xxxxxxx, 1998). A chain-link fence encloses the pond. The pond was designed in 1978. The pond bottom is rectangular with dimensions of 26 feet (7.9 meters) by 39 feet (11.9 meter). The pond side slopes were estimated to be 0.4V:1H and the depth of the pond is approximately 6 feet (1.8 meter). The water inlet is located in the north west corner of the pond. There is no pre-treatment for the stormwater that discharges into the pond. The pond bottom has dense patches of xxxx and grass. Shrubs and large gravel (ranging from 10 to 100 mm in size) are scattered throughout the bottom of the pond. The side slopes have patches of dry grass and xxxx. This pattern indicates moist conditions in the pond bottom, but not for the side slopes.
