The E.P.A currently uses the “River Pollution Index” as the comprehensive index for assessing river water quality, calling it “RPI” for short. RPI consists of four water quality parameters, Dissolved Oxygen(DO), Biochemical Oxygen Demand(BOD5), Suspended Solids(SS) and Ammonia Nitrogen(NH3-N), which are calculated to index integral value, and which indicate the pollution level of river-water. The calculation and comparison baselines of RPI are shown below: Si: The points of the “i” item water parameter, water parameters including DO(mg/L), BOD5(mg/L), NH3-N(mg/L), SS(mg/L) River Pollution Index(RPI)=(1/4) ΣSi River Pollution Index standards for single parameter Water Quality / Item Non/mildly-polluted Lightly-polluted Moderately-polluted Severely-polluted Dissolved Oxygen (DO) mg/L DO ≧ 6.5 6.5 ＞ DO ≧ 4.6 4.5 ≧ DO ≧ 2.0 DO ＜ 2.0 Biochemical Oxygen Demand (BOD5) mg/L BOD5 ≦ 3.0 3.0 ＜ BOD5 ≦ 4.9 5.0 ≦ BOD5 ≦ 15.0 BOD5 ＞ 15.0 Suspended Solids (SS) mg/L SS ≦ 20.0 20.0 ＜ SS ≦ 49.9 50.0 ≦ SS ≦ 100 SS ＞ 100 Ammonia Nitrogen (NH3-N) mg/L NH3-N ≦ 0.50 0.50 ＜ NH3-N ≦ 0.99 1.00 ≦ NH3-N ≦ 3.00 NH3-N ＞ 3.00 Point Scores 1 3 6 10 Pollution Index Integral Value (S) S ≦ 2.0 2.0 ＜ S ≦ 3.0 3.1 ≦ S ≦ 6.0 S ＞ 6.0 Remark: According to the resolution of “River pollution index (RPI) standard and calculation revision” meeting on May 30, 2013, RPI classification standard is adjusted with reference to monitoring report decimal rules published by Environmental Analysis Laboratory, starting from 2013.