$name - King County

Matthews Beach 0818SB

For algal toxin data please visit the State Toxic Algae web page and follow the “Find Lake” menu.

Please select a site and a year

Sample Date	Temperature (°C)	Temperature (°F)	Included in Bacteria Geomean Calculation?	Daily Average Bacteria	Bacteria Geometric Mean – using the three most recent samples
09/23/2019	19.0	66.2	No	not sampled
09/16/2019	21.0	69.8	Yes	596	145
09/09/2019	22.0	71.6	Yes	433	31
09/03/2019	22.0	71.6	Yes	12	31
08/26/2019	23.0	73.4	Yes	6	59
08/19/2019	23.0	73.4	Yes	440	166
08/12/2019	24.0	75.2	Yes	79	123
08/05/2019	25.0	77.0	Yes	132	101
07/29/2019	24.0	75.2	Yes	181	124
07/25/2019	21.0	69.8	Yes	44	134
07/22/2019	23.0	73.4	Yes	244	174
07/18/2019			Yes	226	263
07/15/2019	23.0	73.4	Yes	97	220
07/08/2019	21.0	69.8	Yes	833	141
07/01/2019	23.0	73.4	Yes	132	96
06/24/2019	21.0	69.8	Yes	26	152
06/17/2019	22.0	71.6	Yes	263	141
06/10/2019	20.0	68.0	Yes	516	97
06/03/2019	20.0	68.0	Yes	21	93
05/28/2019	17.0	62.6	Yes	86	101
05/20/2019	17.0	62.6	Yes	453
05/13/2019	17.0	62.6	Yes	27

Table Legend

Cell Color	Bacteria Value	Concern Level
	Individual day <= 200 CFU/100 ml	Low Concern - safe for swimming
	Individual day > 200 & <= 1000 CFU/100 ml	Moderate Concern – still safe for swimming
	Individual day > 1000 CFU/100 ml or geometric mean > 200 CFU/100 ml	High Concern – probable closure. For more information see Beach Closure Protocol

NOTE: Beach closure and reopening decisions are made by Public Health – Seattle & King County. Decisions are based on these results plus additional information about beach conditions, and may not always match the concern levels shown here.

Redirecting to NWToxicAlgae site...

Seattle Parks and Recreation

Due to high bacteria counts, do not wade in Thornton Creek
Learn more about the pump station