Publication Summary

Burnt Bridge Creek, a small urban stream near Vancouver, was listed on Washington State′s 2008 303(d) summary of impaired waters for temperature, dissolved oxygen, and fecal coliform violations of Washington′s surface water quality standards. To support development of a comprehensive water cleanup plan for the creek, the Department of Ecology conducted targeted field studies, in 2008, to assess current stream temperatures, water quality, and other environmental factors affecting the creek. This study and resulting report were part of that effort. This report describes the study area hydrogeologic setting, characterizes local surface water / groundwater interactions, and evaluates near-stream groundwater quality along gaining reaches of the creek.

Burnt Bridge Creek is a small urban stream that flows through the City of Vancouver, in Clark County, Washington. Portions of the creek were listed on the Washington State 2008 303(d) summary of impaired waters for temperature, dissolved oxygen, and fecal coliform violations of state surface water quality standards.

To support development of a comprehensive water cleanup plan (or Total Maximum Daily Load) for the creek, the Washington State Department of Ecology conducted targeted assessments of the environmental and water-quality issues affecting the creek. This study was part of that effort and was undertaken to evaluate how groundwater influences in-stream temperatures and water quality.

A variety of common field techniques were used for this assessment to derive both point and reach based estimates of the volume and quality of groundwater entering the creek. These included: stream seepage evaluations, installation and monitoring of instream piezometers, collection and evaluation of groundwater quality samples, and monitoring of streambed thermal profiles.

Baseflow seepage evaluations conducted in July and September 2008 showed net overall streamflow gains from groundwater of +2.14 and +3.08 ft3/s respectively between the creek headwaters at river mile 12.8 and its terminus at Vancouver Lake. The evaluated sub-reaches between these end points showed considerable local variation in both the pattern and volume of streamflow gains from or losses to groundwater. Groundwater samples collected from 5 instream piezometers and 2 off-stream wells had measurable concentrations of dissolved orthophosphate (range 0.038 to 0.163 mg/L), dissolved total phosphorus (range 0.033 to 0.595 mg/L), and dissolved nitrate+nitrite-N (range 0.011 to 3.52 mg/L). Measurable concentrations of dissolved ammonia were found at roughly half of the sampled sites (range 0.194 to 1.44 mg/L).

Link to EIM data for User Study ID STEB0002