【Haichuan Building Design Review】--Which enterprises need initial rainwater ponds? How to build an initial rainwater pond?

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The 25th National \"Safety Production Month\" in 2026: Everyone should talk about safety and know how to handle emergencies; identify and address potential risks and hazards. -------------------------------------------------- [HaiChuan Building Design Review] Summary Post – Learn about the requirements for design review and improve design standards: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5721370 (Source: HaiChuan Chemical Industry Forum (HCBBS)). An initial rainwater pond is an infrastructure used to collect and treat rainwater that is highly polluted at the beginning of rainfall. Its main purpose is to prevent pollutants carried by rainwater runoff from entering natural water bodies or municipal drainage systems directly. Currently, laws and standards do not specify which industries are required to have initial rainwater tanks; however, some specific industry regulations include such requirements. The Environmental Protection Design Code for the petrochemical industry specifies that petrochemical enterprises must install rainwater collection tanks. The Environmental Protection Design Code for chemical construction projects (GB50483) also requires that initial rainwater be collected. According to the relevant regulations in the chemical industry, chemical and petrochemical enterprises are obliged to have such rainwater collection tanks. The Technical Guidelines for Hazardous Waste Disposal, the Standards for Pollution Control in the Storage of Hazardous Waste, and the Technical Specifications for Centralized Chemical Disinfection of Medical Waste also contain explicit provisions regarding the installation of initial rainwater tanks; therefore, hazardous waste disposal facilities, medical waste disposal units, as well as those responsible for storing hazardous waste in tank areas should also install such tanks. Furthermore, in the guidelines for feasible pollution control technologies in various industries, such as glass manufacturing, electrolytic manganese production, steel manufacturing, coking, thermal power generation, the automotive industry, non-ferrous metal smelting, and nitrogen fertilizer production, it is explicitly required to collect initial rainwater. Furthermore, if the enterprise’s application for a pollution discharge permit and the relevant technical specifications require control over initial runoff, it is also necessary to consider installing an initial runoff collection system. The General Provisions of the Technical Specifications for the Application and Issuance of Pollution Discharge Permits define initial rainwater as a type of wastewater. Since it is classified as wastewater, it cannot be discharged directly; instead, it must be collected. Therefore, industries covered by these technical specifications also need to install systems for collecting initial rainwater. Therefore, industrial enterprises with a high pollution risk, those whose emission permits specify that initial rainwater must be under control, and those whose environmental impact assessment documents require the installation of initial rainwater tanks must establish initial rainwater collection systems in accordance with the regulations. How large should the initial rainwater tank be? The size of the initial rainwater pond is primarily determined by the catchment area of the polluted area; the larger the catchment area, the greater the volume of the initial rainwater pond required. Currently, there are no specific design codes for the design of initial rainwater ponds; although some industry design standards contain relevant provisions, the definition of initial rainwater varies slightly among them. For example, GB/T50483 specifies that the amount of initial rainfall refers to the precipitation falling during the first 15–30 minutes of a rain event, or an amount equivalent to 20–30 mm of rain over that initial period ； SH/T3015 specifies that the total amount of initial rainwater is equivalent to a rainfall depth of 15–30 mm ； According to Q/SH0729, initial rainwater refers to the rainfall amount during the first 10–20 minutes of a single rainfall event. Based on these definitions, there are two methods for calculating the initial rainfall: one is to calculate it based on the duration of rainfall along with its intensity, and the other is to calculate it using the catchment area and rainfall depth. In terms of methodology, the second algorithm is simpler: the volume of initial rainwater is obtained by multiplying the catchment area by the rainfall depth. For example, if the catchment area of an area affected by industrial pollution is 10,000 square meters and the rainfall depth is 20 mm, then the volume of initial rainwater is V = S × H = 10,000 square meters × 20 × 10^-3 meters = 200 cubic meters. Thus, the volume of initial rainwater is 200 cubic meters, and the effective capacity for storing this initial rainwater should be at least 200 cubic meters. The first method is relatively complex; Q = designed rainfall intensity × catchment area × runoff coefficient. This value needs to be determined by taking into account the formulas for rainfall intensity, the design manuals for water supply and drainage, as well as the type of ground surface. Companies interested in this topic can refer to Section 4.1 of the \"Code for Design of Outdoor Drainage Systems\" (GB 50014-2021). If there are enterprises in Jiangsu, they can follow the local standards. Jiangsu Province has issued the Interim Measures for the Environmental Management of Rainwater Discharge from Industrial Enterprises in Key Industries in Jiangsu Province; according to these measures, the rainfall depth is set at 10mm–30mm, which means that in Jiangsu’s key industries the minimum rainfall depth required is 10mm.