A Ten-meter "Wall of Water"
− Mr. Sasaki, can you tell our readers what happened on that fateful day of March 11 , 2011?
Mr. Sasaki: Well I was inside the prefectural building that day. Sendai, as a city located right on the coast of Miyagi, had been struck by a tidal wave about 10 meters high, as generated by a massive earthquake. A ten-meter "Wall of Water" washed ashore from the Pacific, entering about 4 km inland to inundate a dozen square kilometers. After destroying many buildings, the retreating water carried away people as well as about two-fifths of the resulting debris amounting to 15 million tons. Still, it left in its wake an estimated 9 million tons of debris to be dealt with. The debris waste strewn across the Sendai coastline totaled at nearly double the amount of garbage produced by Tokyo in a year.
The earthquake had also led to the ground level falling by 40 to 80 cm, so we needed to fill in the lost ground with something sturdy. We had to find a way to turn an incredible amount of debris into usable items as building materials, to work together to find a viable solution. The waste materials from the Great Kanto earthquake in 1923 were used to produce a waterfront park in Yokohama while those from the Great Hanshin-Awaji earthquake in 1995 were used as Osaka Bay landfill, but we did not have such major landfill option available to us so we had to think of other methods.
− Can you tell us about how you came to be involved in the current efforts?
Mr. Sasaki: As a public servant we spent the first month after 3-11 searching for survivors, then the next two removing the debris, in line with Japanese government policy. The national policy of recycling as much as possible of the waste and debris from three months later was implemented by the prefectural government. This was because some small municipalities were unable to cope with management due to loss of personnel, including top people for certain locations.
Prof. Hisada: In my case, I had been involved closely with the Japan Society of Civil Engineers (JSCE) so I wanted to make sure the network of experts could bring their knowhow to good use. Since I was in Tokyo on a business trip when I felt the seismic shock, I returned to Sendai to find that the city’s infrastructural damage was extensive indeed. Since concrete is my selected field of research, I wanted to find out if the remaining structures were still strong enough to enable the city to be rebuilt based upon them.
Mr. Sasaki: We had to clear things up as soon as we could because of potential hazards like spontaneous combustion as well as the gas and odor being produced by the organic materials contained in the debris – we looked to process most of recyclable items within 3 years… thus we hit upon the idea of creating a consortium to bring together all available technical resources from public and private sectors.
Prof. Hisada: In response, we at Tohoku University helped form the "Consortium on the Utilization Management of Disaster Waste and Unused By-product Resources"; I was certain that Tohoku University could fill the role of principal organizer because not only were we "neutral" but many of the SoE alumni could be found in both private and public sectors, including academia.
At the onset, we brought together general constructors like Kajima and companies with local presence such as Mitsubishi Materials to become members of the consortium. We asked for a membership fee of 1,000 USD (we now have some 80 members) so we could coordinate the research activities within the disparate group. This coordination not only enabled researchers at SoE but those from other Tohoku University faculties as well as those from the private sector to work together closely upon trying to "coagulate" solutions.
