Fuzhou World Bank Financed Projects Nanjiang Binlu, Phase-ii project of the Third Ring Road and Kuiqi Bridge environmental impact report
Assessment of Impact on Water Environment during Operation Period
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- 7.3.2 Standard for Assessment
- 7.3.4 Assessment Factors
- 7.3.6 Hydrological characteristics
- 7.3.7 Results of forecast and assessment
7.3 Assessment of Impact on Water Environment during Operation Period7.3.1 Scope of assessmentAccording to Specifications for Environment Impact Assessment of Highway, the evaluated part of the riverbed of Minjiang River is 200m downstream and 200m upstream from the bridge centerline. 7.3.2 Standard for AssessmentThe waters crossed by this bridge adopt the Class III of Environmental Quality Standard for Surface Water (GB3838-2002), so the standard for assessment is Class III (GB3838-2002). 7.3.3 Content of Assessment and Forecast of Pollution Discharge VolumeThe assessment focuses on the pollution of rainwater from the bridge ground during the operation period. For water environment risk assessment, please refer to the chapter dedicated to risk assessment. The bridge itself does not produce wastewater, but most the pollutions from motor vehicles crossing the bridge go into the air or drop to the ground around the road, and are washed by rainwater into water body near the project and may affect the quality of water around the water body. a) Calculation of bridge ground rainwater volume For the method for calculation of the ground water volume of this project, please refer to the method recommended in the article Impact of Road Ground Rainwater Pollutions on Water Environment, Environmental Protection in Transportation (2-3, 1994). The authors of this article is Zhao Jianqiang, etc of the Environmental Engineering Research Institute of Xi’an Road Institute. According to this method, first calculate the average daily rainfall on basis of the average annual rainfall over several years and the average number of rainy days per year in the place where the project is located; then consider the correlation between the heaviness of the rain and its duration. Assume the average daily rainfall is concentrated during the first 2 hours of the shower. Then, the ground water volume is the ground rainflow coefficient BY contaminated ground area BY average heaviness of the rain in the rainflow concentration period. The above calculation can be expressed by the following formula: Qm =C×I×A I＝Q/D Whereinto: Qm —— volume of ground rainwater produced by 2 hours of rain; C —— ground rainflow coefficient of the rainflow concentration area; I —— average heaviness of the rain in the rainflow concentration period; A —— road ground area; Q —— the average annual rainfall over several years in the place where the project is located; D —— the average number of rainy days per year in the place where the project is located; The same method can be used to calculate the volume of ground rainwater of Kuiqi Bridge. According to statistics of the historical climate information on the region of Minjiang River, the average annual rainfall over several years is 1343.8mm and the average annual number of rainy days is 150 (rainfall over 0.1mm). The ground rainflow coefficient is 0.9, which is adopted for concrete/asphalt road ground in the Specifications for Indoor Designs used in China. The ground area of the bridge is about 42, 200 square meters. The calculated ground rainwater volume of Kuiqi Bridge is 340m3/d (0.05m3/s, 170m3/h). b) Concentration of pollutions in the road ground rainwater Studies, either domestic or foreign, show that，the concentration of pollutions in the ground rainwater of roads for motor vehicles is related to such factors as the flow of passing motor vehicle, motor vehicle types, heaviness of rain, cycle of rainfall, road nature, nature of fuels used by motor vehicles, etc. So, generally speaking, it is very difficult to calculate the concentration. The concentration of pollutions in the ground rainwater of Kuiqi Bridge over Minjiang River can use the value obtained from the assessment of impact of expressway on environment in a southern province of China. Please refer to Table 7.3-1 for details. Table 7.3-1 Concentration of Pollutions in Road Ground Rainwater for Adopted for Assessment of An Expressway on Environment (Unit: mg/L)
It can be seen from Table 7.3-1, the concentration of pollutions in road ground rainwater changes from high to low. The concentration reaches the maximum during the first 15 minutes and then gradually decreases and becomes stable after one hour of rain. ② Discharge source intensity of pollutions For this project, the discharge source intensity of pollutions can be calculated on the basis of the average value of concentration of pollutions in the ground rainwater of the first 2 hours BY ground rainwater volume of the bridge over the Minjiang River. For calculation results, please see Table 7.3-2. Table 7.3-2 Discharge Source Intensity of Bridge Ground Pollutions (Unit: Kg/d)
7.3.4 Assessment FactorsAccording to the pollution discharge condition and the characteristics of water in Minjiang River, CODcr, oil and SS are selected as the factors to be evaluated. 7.3.5 Mode of ForecastUse the Bank Discharge Mode of the Stable Mixed Attenuation Accumulative Flow Mode. 
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; π— pi 7.3.6 Hydrological characteristicsFrom Zhuqi Hydrological Station on, the area of the region of Minjiang River is 54, 500km2. According to the hydrological data collected from Zhuqi Hydrological Station, from 1990～1995, the average annual flow rate is 168m3/s and the average annual flow is 53.2 billion m3. The area of Yongtai Hydrological Station of Dazhang River that runs into Nangang is 4,032km2 and from 1956～1986, the average annual flow is 5.46 billion m3. The measured minimum flow of Zhuqi Hydrological Station is 196m3/s (1971). After the construction of Shuikou hydroelectric power station (1994), the minimum let-down flow rate is 308m3/s and reaches 511m3/s at Zhuqi Hydrological Station. Minjiang River splits near Huaian. For the split ratio of Nangang and Beigang and changes of flow, please see Table 7.3-3. Table 7.3-3 Nangang and Beigang Split Ratio
The tide of Minjiang River is the regular half-day tide. During the low-water season, the boundary of the big-tide area is near Houguan, but the tide can reach as far as Wenshanli. So, basically, during the low-water season, Nangang has no flow from the Jiyuanzhou region and only has tide water. Kuiqi Bridge crosses over Beigang. 7.3.7 Results of forecast and assessmentSelect the average flow rate during low-water season for forecast. Please refer to Tables 7.3-4～7.3-6 for the results of forecast. Table 7.3-4 Forecast of Impact of Bridge Deck Rainwater on Water Quality (CODCr) of Minjiang River Beigang Unit: mg/L
Table 7.3-5 Forecast of Impact of Bridge Ground Rainwater on Water Quality (Oil) of Minjiang River Beigang Unit: mg/L
Table 7.3-6 Forecast of Impact of Bridge Ground Rainwater on Water Quality (SS) of Minjiang River Beigang Unit: mg/L
The above forecasts show that, because the concentrations of CODcr, oil, and SS in the bridge deck rainwater are low and the flow rate at Kuiqi section of Minjiang Beigang is high, so the bridge deck rainwater has a limited impact on the water quality of Minjiang River. 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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