Based on two water outflow accidents, i.e. high level radioactive water 
(hereinafter referred as "contaminated water") to the sea around Unit 2 
water intake on April 2, 2011 and contaminated water outflow from the pit 
(the vertical shaft made of concrete) near the water intake of Unit 3 to 
the sea on May 11, 2011, TEPCO reported on countermeasures against 
contaminated water outflow and diffusion to Nuclear and Industrial Safety 
Agency (NISA) of Ministry of Economy, Trade and Industry on May 20 and 
June 1, 2011 and implemented the countermeasures in turn.

As part of the countermeasures, from July 12, we will conduct block up work 
by using steal sheet piles as planned at the southern part of Unit 1 to 4 
open water channel* where damaged by tsunami.

During the work, it will be inevitable to temporary open and close the silt 
fence at the northern part of Unit 1 to 4 intake channel in order that the 
work ships can get in and out. We will make best effort not to influence to 
surrounding environment and enhance the monitoring by increasing sampling 
frequency in the vicinity.

(Attachment)  
 "Implementation of water seal work at the southern part of Unit 1 to 4 open 
 water channel in Fukushima Daiichi Nuclear Power Station" (PDF 49.9KB) 
 
* Open water channel normally means the channel without lids. We define 
here that the open water channel means sea water channel without lids for 
heat exchange, sea side from water intake, while closed water channel 
means sea water channel with lids, building side from water intake. 

Appendix1: Countermeasures to prevent water flowing and to control expansion 
           of water (PDF 55.2KB) 
Appendix2: Total amount of radioactive materials in port (PDF 97.4KB) 
Appendix3: Result of Monitoring  -Result of Density (Bq/ L) 
           of Seawater(Upper Layer)- (PDF 474KB)