Fuzhou World Bank Financed Projects Nanjiang Binlu, Phase-ii project of the Third Ring Road and Kuiqi Bridge environmental impact report
Analysis of Impact on Water Environment during the Construction Period
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- 7.2.1 Wastewater from Construction of Kuiqi Bridge and the Impact
- 7.2.2 Impact on Water Environment by Construction of Piers of Kuiqi Bridge
- 7.2.3 Analysis of water environment of inland rivers during the construction period
7.2 Analysis of Impact on Water Environment during the Construction PeriodThe main impact on the water environment during the construction period is that of the construction of Kuiqi Bridge on Minjiang Beigang. So, quantitative calculation and analysis must be done on Kuiqi. For inland rivers crossed by Nanjiang Binlu and the Phase-II Project of the Third Ring Road , only qualitative analysis is needed. 7.2.1 Wastewater from Construction of Kuiqi Bridge and the ImpactThe wastewater during the period of construction mainly includes the living wastewater and the production wastewater. (1) Living wastewater Living wastewater from the construction area comes mainly from the Employer, contractor, subcontractors and offices. Unless processed, the living wastewater from the construction area shall not be directly discharged into water bodies. Living wastewater includes washing/bathing water from construction personnel, wastewater from the dining hall and lavatory, etc. In addition to living wastewater, there is also living garbage. The living wastewater and garbage are directly discharged into nearby rivers without being treated. The living wastewater produced by the construction personnel (300) is usually low-concentration wastewater. It comes to about 24 cubic meters per day. Among the main pollutions discharged, BOD5 is bout 3.6kg/d, CODcr 6.0kg/d and SS 5.4kg/d. These pollutions shall be properly treated. The specific measures for treatment are given in the chapter dedicated to the measures for environmental pollution treatment. (2) Production wastewater of the construction area The production wastewater of the construction area comes mainly from the foundation pit wastewater, washing water from gravel, machinery, vehicles, concrete mixing and flushing, tank car washing, etc. First, pollution by foundation pit wastewater. Foundation pit wastewater consists of rainwater, construction-used water, etc. The concentration of suspended matter in the water is high. Foundation pit wastewater is collected from foundation digging, concrete pouring, concrete maintenance, washing wastewater and rainwater. If discharged directly without sedimentation, it will affect the downstream sections of the construction area. Second, pollution from wastewater produced by the gravel, sand and aggregate processing system. Wastewater of the gravel, sand and aggregate processing system comes mainly from the washing of aggregate. Aggregate must be washed to eliminate the sticky soil and other residues. The wastewater mainly contains suspended matter. The wastewater produced from gravel and sand production has a high SS concentration. So, the wastewater produced from processing of gravel and sand must be treated before discharge. The third is the pollution by wastewater from the concrete processing system. Below is the analysis of the impact of the production wastewater from the construction area on the water environment of Beigang. The production wastewater contains not only suspended matter (sand, etc), but also a lot of oil. This kind of production wastewater is usually treated in sedimentation tanks and the oil/water separation system. The oil content in treated production wastewater is usually below 5mg/L and the content of SS is about 120mg/L. The daily washing water for construction machinery is about 20m3. It takes 3 hours to discharge the washing wastewater after sedimentation and oil/water separation. The method used to forecast in an analog manner the impact of discharged wastewater on the water environment of Beigang is the Bank Discharge Mode of the Stable Mixed Attenuation Accumulative Mode. The formula is as follows:
Whereinto: x— the distance between the point of forecast and the point of discharge, m; y— the horizontal distance between the point of forecast and the point of discharge, m; K1— the degradation coefficient of pollutions in the river, 1/d; c— the concentration of pollutions at the point (x,y) of forecast, mg/L; cp— concentration of pollutions in wastewater, mg/L; Qp— wastewater flow, m3/s; ch— concentration of pollutions in the upstream of the river, mg/L; H—average depth of water in the river, m; My—horizontal mixture (diffusion) coefficient of the river, m2/s; u— flow rate of the river, m/s; Qh—flow of the river, m3/s; π-- pi The construction period of Kuiqi Bridge falls between January 2006 and December 2006. Select the most unfavorable period – the low water season. Qh=600m3/s, water depth H=3.0m, river width B=600, degradation coefficient for SS and oil = 0. This assessment forecasts the value-added impact of SS and oil, so ch=0. Use the Bowden method to get the value of My, namely My=0.295uH=0.292 m2/s. Table 7.2-1 Impact of SS in Wastewater from Construction of Kuiqi Bridge on Water Environment of Beigang Unit: mg/L
Table 7.2-2 Impact of Oil in Wastewater from Construction of Kuiqi Bridge on Water Environment of Beigang Unit: mg/L
It can be concluded from Table 7.2-1 and Table 7.2-2 that, after sedimentation and oil/water separation, the production wastewater discharged from the construction area has a low degree of impact on the water environment of Beigang. SS have little impact on the water environment of Beigang; however, oil has some impact on the quality of water near the point of discharge. 130m down from the point of production wastewater discharge, the water quality can meet the Water Quality Standard for Fisheries. 7.2.2 Impact on Water Environment by Construction of Piers of Kuiqi Bridge(1) Pollution source intensity and selection of forecast equipment Comparative analysis of similar projects shows that the amount of suspended matter produced during the construction of one pile foundation is about 0.108t/h. A steel cofferdam is built around the foundation during the process of construction. At the same time, where the cofferdam is extended to the water body, measures (protection net, etc) are taken to prevent debris and oil from falling into the water body, so the impact of construction of pier foundation on the water environment mainly happens after the cofferdam is removed. The impact is calculated on the basis of 3000 mg/L for SS within the cofferdam. Let’s take as example the construction of pier No.19. The method used to forecast in an analog manner the impact of discharged wastewater on the water environment is the Non-bank Discharge Mode of the Stable Mixed Attenuation Accumulative Mode. The formula is as follows: 
Whereinto: x— the distance from the point of forecast to the point of discharge, m; y— the horizontal distance from the point of forecast to the point of discharge, m; K1—the degradation coefficient of pollutions in the river, 1/d; c— the concentration of pollutions at the point of forecast, mg/L; a— the distance from the point of wastewater discharge to the river bank (0≤a≤B), m; cp— concentration of pollutions in wastewater, mg/L; Qp— wastewater flow, m3/s; ch— concentration of pollutions in the upstream of the river, mg/L; H— average depth of water in the river, m; My— horizontal mixture (diffusion) coefficient of the river, m2/s; u— flow rate of the river, m/s; Qh— flow of the river, m3/s; π— pi The forecast pier is 190 meters away from the riverbank. Other parameters are the same as above. (2) Calculation results and analysis For the results of calculation of the suspended matter (SS) produced from construction of Kuiqi Bridge on the water environment, please see Table 7.2-3. Table 7.2-3 Impact of SS on Water Environment (foundation for pier No.19) Unit: mg/L
It can be drawn from Table 7.2-3 that wastewater from construction of bridge pier foundations has a high degree of impact on the water environment. However, cofferdams are used in construction of pier foundations, so the impact of wastewater is transient. 7.2.3 Analysis of water environment of inland rivers during the construction periodFor Nanjiang Binlu and the Phase-II Project of the Third Ring Road , most of the wastewater during the construction period comes mainly from construction wastewater and living wastewater. Construction wastewater includes slurry from digging and drilling activities, cooling and washing water from machinery and equipment, and oil-bearing wastewater from construction equipment operation or maintenance/service. Unless treated before discharge, these kinds of wastewater will have impact on receiving waters. Because Nanjiang Binlu is going to be constructed within the flood-preventing dam, the living wastewater from local residents, as that from the construction personnel, enters the urban drainage system instead of being directly discharged into Minjiang River. And the living garbage is collected by the environmental protection station for treatment. So the living wastewater and living garbage during the construction period will not produce obvious pollution. The 3rd Ring (Phase II) is also going to be constructed within the flood-preventing dam, but there are no urban underground drainage systems along the route, so measures shall be taken to prevent pollution by living wastewater and living garbage. Ground water washes the loose soil, construction-used gravel and sand, garbage, abandoned soil, etc, and carries a lot of soil and sand into the Minjiang River and may block the riverbed and water pipes. Directory: curated curated -> Concept stage curated -> Concept stage curated -> Republic of Côte d'Ivoire Urbanization Review curated -> Report No: aus11011 Central America curated -> Report No. 94474-pk fiscal Disaster Risk Assessment Options for Consideration curated -> Environmental and Social Management Framework for the Costa Rica Telecommunications Sector Modernization Project curated -> Environment Impact Assessment For Jiangxi Shangrao Sanqingshan Airport Beijing Guohuantiandi Environmental Technology Development Center. Ltd. Oct. 2012 Content curated -> Growth through Innovation An Industrial Strategy for Shanghai By Shahid Yusuf Kaoru Nabeshima April 22nd, 2009 curated -> Report No: 70178. People's Republic of China Download 3.93 Mb. Share with your friends:
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