SPDSS_Task34-3_Phase 3_StreambedConductanceTesting

Home Browse Search

2.4 Streambed Hydraulic Conductivity Testing and Analysis At each of tlne 30 field test sites, a K test was performed on tlne streambed sediment. The tests were conducted using either afalling-head test or a constant-head injection test using the methods described by Bouwer and Rice (1976) or Cardenas and Zlotnik (2003), respectively. The falling-head tests were performed at sites where there was a very low >lnjection rate observed which would render aconstant-head injection test impractical. The constant-head injection tests were performed using a temporary piezometer equipped with a reservoir and overflow port. The rate at which water was injected into the sediment material was calculated by determining the volume of water injected and the tune over which this occurred. The volume was deternnined by subtracting the overflow amount and the amount of water it took to reach tlne constant-head level in the reservoir from the amount poured alto the piezometer. That amount was divided by the length of time during which water was injected to obtain an >lnjection rate. Falling-Head tests were performed by quickly filling a piezometer with water and collecting multiple water level measurements as the water level in the piezometer fell. Falling-Head tests were performed using a piezometer as shown iln Figure 3. A schematic diagram of the streannbed constant-head injection testing procedure is provided iln Figure 4. Falling-head tests were performed at locations SC-02, SC-09, SC- 11, SC-18, SC-20 and SC-22; all other tests were performed by the constant-Head injection testing method of Cardenas and Zlotnik (2003), as described in the Phase 3 Field Work Plan (CDM 2005). The piezometer's screened interval was driven to a depth corresponding to that from which a gra>ln-size sample was collected at each site, iln order to evaluate an empirical relationship between tlne grain-size characteristics and permeability measured in tlne field. 2.5 Surveying Following the field testing at each site, the temporary benchmarks and stream gage benchmarks were surveyed by Kelly Surveying and Design Group Ltd., a licensed Colorado surveyor, using precision differential Global Positioning System (GPS) methods. The temporary benchmarks were then removed from all sites with the exception of the recently installed Atwood Gage, at wlnicln a survey control po>lnt was unstalled for the DWR. 3.0 Results This section presents tlne results of the field data collection activities presented in Section 2. Stream channel cross section profiles are presented in Appendix A. Descriptions of the streambed sediment samples are presented in Appendix B. Geotechnical grails-size data are presented in Appendix C. Site survey results are presented lln Appendix D. Fnlal T~zsl: 3~TM 06-28-07.doc