Different Method Used in Final Round of Toyosu Water Survey

March 6, 2017

Tokyo- The contractor for the final round of the Tokyo metropolitan government's groundwater survey at the new Toyosu wholesale food market said Saturday it was told to use a survey method different from the past rounds.

The ninth round of the two-year-long survey, conducted between late November and early December 2016, showed surges in levels of toxic substances, including benzene, from the readings in the past rounds.

The Environment Ministry's guidelines and other rules require water samples in such surveys be collected from monitoring wells after old water is drained.

Until the eighth round, contractors in many cases took samples the day after old water was drained, while in the ninth round, the contractor collected samples on the day when old water was removed.

Water was collected early at the instruction of metropolitan government staff, a representative of the contactor said during a hearing session of a special committee of the Tokyo metropolitan assembly.

At a news conference, the metropolitan government said it gave the instruction in view of the survey schedule.

In the ninth round, the contractor also submitted for analysis samples taken from old water at a monitoring well, also at the instruction of the metropolitan government.

No harmful substance was detected from the samples. The metropolitan government said it requested the contractor to take the unusual step because the well did not have enough water after the presurvey discharge.

The results of the ninth round have led the metropolitan government to order an additional survey. Its outcome will be announced later this month.

The ninth round found benzene levels in groundwater up to 79 times the national environment standard. In addition, above-standard cyanide and arsenic were detected.

During the survey from November 2014, harmful substances above the standards were not detected until the eighth round, which found above-standard benzene and arsenic.

Asked about the unusual practices in the ninth round, Tokyo Governor Yuriko Koike said she has not obtained detailed information on the matter yet.

"It is necessary to confirm readings" of the additional survey, she also said.

Koike last year decided to postpone the planned relocation of the landmark Tsukiji fish market to the Toyosu site, citing safety concerns. Jiji Press