Water / Soil / Ground Environment

Water Quality Criteria for Bathing Beaches

1. Bathing beaches are classified based on the criteria indicated below.

(1) Beaches for which any of the four survey items (colon bacillus, presence of oil film, COD, or transparency) are rated as "unsatisfactory" are classified as "unsatisfactory" bathing beaches.

(2) Bathing beaches not rated "unsatisfactory" are classified by measurements of the amount of colon bacillus, presence of oil film, COD, and transparency, with ratings of AA, A, B, or C. Type AA or A are considered "good", while type B or C are considered "satisfactory."

  • Beaches for which all measurement items were rated as water quality AA are classified as AA bathing beaches.
  • Beaches for which all measurement items were rated as water quality A or above are classified as A bathing beaches.
  • Beaches for which all measurement items were rated as water quality B or above are classified as B bathing beaches.
  • Beaches not falling into the above categories were classified as water quality C beaches.
Water quality categoryNumber of colon bacillusPresence of oil filmCODTransparency
Good AA Not found
(detection limit : 2/100ml)
Not found 2mg/1 or less
(3mg/1 or less for lakes)
Clear
(or more than 1m)
A 100/100ml or less Not found 2mg/1 or less
(3mg/1 or less for lakes)
Clear
(or more than 1m)
Satisfactory B 400/100ml or less Found at times 5mg/1or less 50 cm to 1 m
C 1,000/100ml or less Found at times 8mg/1or less 50 cm to 1 m
Unsatisfactory Over 1,000/100ml Found consistently Over 8mg/1 Less than 50 cm*
Notes:
  1. Classification of each bathing beach is based on the average of the values obtained at that beach during the survey.
  2. "Not found" means that the average value is under the detection limit.
  3. As for transparency indicated with an asterisk, clouding caused by stirred-up sand is excluded from assessment.

2. Bathing beaches which need remedial measures are as follows:

(1) Bathing beaches categorized as B or C which have more than one measurement result indicating the amount of colon bacillus as over 400 per 100 ml.

(2) Bathing beaches where oil film was detected.

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