Great East Japan Earthquake Strikes Sewerage System

Takeshi Yamauchi

5. Proposal

The Ministry of Land, Infrastructure, Transport and Tourism cooperating with Japan Sewage Works Association set up a committee, and proposed the proper ways to recover sewerage system from emergency, and to recover fully and prevent recurrence. (25)

5.1 Emergency Measures
  • Pipes

    When the sewerage systems were damaged from earthquake or other disasters, we should make clearance of sewage from cities the first priority. In case sewage overflows, immediately lead sewage to nearby waterway using sandbags and tarpaulins. Don’t let people contact with raw sewage.

  • Treatment plants

    In order to prevent raw sewage to overflow, make reconstruction of pumps the first priority. Set up temporary pumps as substitute to damaged ones. At the very least, chlorinate sewage before discharging into the river.

5.2 Temporary Recovery
  • Pipes

    Remove sand that is piled up in, or set up as bypass for pipes where ability to make sewage flow down deteriorated. Consider a measure to discharge the sewage at the pump station located at upstream than treatment plant.

  • Treatment plants

    For the districts where the recovery would be relative easier, we have to consider the increase of waste water due to recovery of other infrastructures. If it takes much time to recover fully, perform the treatment process.

    For the districts where damage from tsunami is severe, consider setting up temporary treatment plants, or maybe send sewage to nearby district where treatment plants are working by temporary pipes.

5.3 Full Recovery
  • Pipes

    In Kurihara city, Miyagi, pipes that were recovered from earthquake in 2006, were not so damaged, compared to other pipes. This is because those pipes that were broken in the earthquake in 2006 were reconstructed with earthquake-proof structure　following the guideline reported by Japan Sewage Works Association.

    This guideline was created in 1981 after the Miyagi Coast Earthquake in 1978, which damaged infrastructure such as electricity, gas and waterworks badly. Its main purpose is to prevent drain pipes and relating structure from floating or sinking due to soil liquefaction. It shows the counter-measure against soil liquefaction of backfilling soil. It also shows the counter-measure against breakage of junctions which is also the major damage of sewerage system.(26)

    http://www.toho-c.co.jp/pdf/gesuidousisetunotaisintaisakusisin.pdf(Japanese)

    When reconstructing the damaged pipes, apply this technology to prevent recurrence.

  • Treatment plants

    The guideline reported by Japan Sewage Works Association shows the counter-measure for soil liquefaction. It is reported that the damage due to soil liquefaction was small, and rather, breakage of mechanics and electrical connections which were covered with tsunami was the main damage in waste water treatment plants.(27) Thus, following things are said to consider when recovering or reconstructing treatment plants.

    • If necessary, transfer the treatment plants to a location where is safer than contemporary location.
    • Set up emergency channel in case of emergency.
    • Top of the channels and tanks should be covered with concrete.
    • Doors and windows should not face the course of tsunami.
    • If a machine has a risk of submergence, apply water proof parts.
    • Put electronic equipment at second floor or higher.

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