Water Journal : Water Journal December 2012
operations water DECEMBER 2012 75 Destruction of the Water Supply System The city’s water infrastructure system suffered extreme damage from the tsunami. Three DWTPs, providing about 98% of the city’s total production volume, were completely destroyed. A large portion of water distribution pipelines were either destroyed or disappeared, and the quality of the groundwater resources deteriorated to such a level that more sophisticated and expensive treatment was required. Figure 2 is a Google Earth aerial photo of the Shizugawa area, previously the most populated area in the city, showing the areas of tsunami inundation and the locations of important water infrastructure. Due to the high elevation of the distribution reservoirs, they were saved from the tsunami. However, almost all the water distribution network and the DWTPs were situated in areas that were inundated by the tsunami. Destruction of the DWTPs Figure 3 shows Sukezukuri, the city’s biggest DWTP representing about 58% of total water production capacity, immediately after the tsunami. Only the concrete structure on top of the groundwater well remained. Everything else disappeared, including all the equipment inside. Figure 4 shows the remainder of Isatomae DWTP, the second biggest DWTP representing about 27% of the city’s total water production capacity. Similar to the Sukezukuri DWTP, only the concrete structure remained after the tsunami. Damages to the Distribution Network As a country with frequent seismic events, Japan’s water industry has for some time been promoting earthquake-resilient pipes such as earthquake-resistance ductile iron pipes with earthquake-proof joints. Table 2. Raw water quality analysis results (selected parameters one month after tsunami). Sukezukuri DWTP raw water (11 April sample) Japanese drinking water standard Odour No odour No odour Colour Less than 0.5 degrees Less than 5 Turbidity Less than 0.1 degrees (1) Less than 2 Standard bacteria (plate count) 24/ml Less than 100 E. coli Not detected Not detected Anaerobic spore-forming bacteria 0 CFU/100ml Not detected Sodium 330 mg/L Less than 200 Manganese Less than 0.005 mg/L Less than 0.05 Chloride ion (Cl-) 1330 mg/L Less than 200 Hardness 1270 mg/L Less than 300 Total solids 2720 mg/L Less than 500 Note: (1) Japanese water quality standard does not use NTU. Figure 4. Isatomae DWTP after the tsunami. Legends Water distribution network Area inundated by tsunami Facility inundated by tsunami Facility not damaged by tsunami Figure 2. Aerial photo of the Shizugawa area and water infrastructure. Figure 3. Sukezukuri DWTP after the tsunami.
Water Journal February 2013
Water Journal November 2012-1