• 상하수도학회지
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• 제29권1호
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• pp.97-106
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• 2015

A CCTV inspection method has been widely used to assess sewer condition and performance, but Korea lacks a proper decision support system for prioritizing sewer repair and rehabilitation (R&R). The objective of this paper is to introduce the results that we have developed in the Sewer Condition Assessment and Rehabilitation Decision-making (SCARD) Program using MS-EXCEL. The SCARD-Program is based on a standardized defect score for sewer structural and hydraulic assessment. Priorities are ranked based on risk scores, which are calculated by multiplying the sewer severity scores by the environmental impacts. This program is composed of three parts, which are decision-making for sewer condition and performance assessment, decision-making for sewer R&R priority assessment, and decision-making for optimal budget allocation. The SCARD-Program is useful for decision-makers, as it enables them to assess the sewer condition and to prioritize sewer R&R within the limited annual budget. In the future, this program logic will applied to the GIS-based sewer asset management system in local governments.

• 한국물환경학회지
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• 제33권1호
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• pp.97-106
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• 2017

In this study, the characteristics of nonpoint source pollutant loads from separate sewer overflow (SSO) and combined sewer overflow (CSO) were evaluated during 2016 in Namyangju city, Korea. Five rainfall events were monitored during 2016 with ranging from 14.5 mm to 121.5 mm. The runoff ratio of CSO was higher than that of SSO because only design volume of maximum sanitary sewer ($1Q_h$) was transported and treated and $2Q_h$ was overflowed to waterbody during rainy day although combined sewer system was designed to transport $3Q_h$ to treatment system. The event mean concentrations (EMCs) and pollutant loads from CSO were higher than those from SSO. BOD and COD of CSO, and TOC and TN of SSO represented distinct first flush phenomena. The inadequate management in combined sewer system from which the untreated $2Q_h$ from CSO was overflowed to waterbody during rainy day could influence on high pollutant loads and first flushing. Treating $2Q_h$ from CSO, source control such as low impact development, and treating outflow from SSO were strongly recommended to control non-point source pollution in urban area.

• 상하수도학회지
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• 제19권5호
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• pp.647-654
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• 2005

Recently, the economic losses caused by inundation are increasing due to the urbanization and industrialization, i.e., intensive land utilization and concentration of population and properties. It is regarded that the role of the storm sewer systems in urban areas becomes more important as one of the effective countermeasures for reducing the inundation losses. In this study, the effects of rainfall design frequency enhancement on the construction cost of the storm sewer systems were analyzed by increasing the design frequency from the present design frequency of the sewer systems, which is 5~10 years, to 15 years, 20 years and 30 years. The change rate functions of the design discharge and construction cost based on the various design frequencies were derived by regression analysis. According to the analysis, change the rate of design discharge at 15, 20, 30 years rainfall design frequencies were increased by 10%, 17.1%, and 27.2%, respectively, when compared to that at 10 year frequency. Furthermore, it was found that by increasing the design frequency from 10 years to 15 years, 20 years and 30 years, the construction costs were increased by 5.0%, 8.0% and 12.4%, respectively. Finally, their reliabilities need to be tested by applying the rate functions to the real storm sewer districts.

• 상하수도학회지
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• 제34권3호
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• pp.211-220
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• 2020

When domestic sewage and rainwater runoff are discharged into a single sewer pipe, it is called a "combined sewer system." The sewage design standards in Korea specify the flow velocity based only on the volume of rainfall; therefore, sedimentation occurs on non-rainy days owing to the reduced flow rate and velocity. This sedimentation reduces the discharge capacity, causes unpleasant odors, and exacerbates the problem of combined sewer overflow concentration. To address this problem, the amount of sewage on non-rainy days, not just the volume of rainfall, should also be considered. There are various theories on sedimentation in sewer movement. This study introduces a self-cleansing velocity based on tractive force theory. By applying a self-cleansing velocity equivalent to the critical shear stress of a sand particle, sedimentation can be reduced on non-rainy days. The amount of sewage changes according to the water use pattern of citizens. The design hourly maximum wastewater flow was considered as a representative value, and the velocity of this flow should be more than the self-cleansing velocity. This design method requires a steeper gradient than existing design criteria. Therefore, the existing sewer pipelines need to be improved and repaired accordingly. In this study, five types of improvement and repair methods that can maximize the use of existing pipelines and minimize the depth of excavation are proposed. The key technologies utilized are trenchless sewer rehabilitation and complex cross-section pipes. Trenchless sewer rehabilitation is a popular sewage repair method. However, it is complex because the cross-section pipes do not have a universal design and require continuous research and development. In an old metropolis with a combined sewer system, it is difficult to carry out excavation work; hence, the methods presented in this study may be useful in the future.

• 한국수자원학회논문집
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• 제38권12호
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• pp.1021-1028
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• 2005

본 연구는 도시 우수관망 설계 시 주어진 설계유랑을 효율적이고 경제적인 단면 구성과 관망에 따른 우수배제능력을 극대화시키기 위해 최적화된 설계를 통하여 경제적인 우수시스템을 설계할 수 있는 모형의 개발이 이루어져야 할 필요성이 있다. 이에 본 연구에서는 최적화 기법으로 동적계획법(Dynamic Programming : DP)의 특수한 방법인 이산미분형 동적계획법(Discrete Differential Dynamic Programming : DDDP)를 이용해 최적화된 설계조건을 구할 수 있도록 하였다. 이산미분형 동적계획법의 기법은 설계유랑과 맨홀의 위치가 결정되면 그에 따른 최적 우수시스템이 될 수 있는 관의 용량, 경사, 수위, 수심, 위험도, 회수비용 등을 결정할 수 있는 방법으로 이는 공사비용에 따른 최소비용을 목적함수로 위험도 분석을 통하여 최적화된 조건을 찾는 방법으로 모형개발을 하였다.

• 상하수도학회지
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• 제23권6호
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• pp.711-717
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• 2009

In this study, SWMM model is used to reproduce the main storm sewer system located in the Nae-Hang drainage basin of the Mokpo city and keep track of flood discharge. Given the outlet of the reaches border the coastline, this paper has taken the dual-drainage approach to perform inundation simulation, considering both the overflows and inflows at the manholes of the sewer system, and at the same time, taking the impacts of tidal stage into consideration. The following conclusions are reached in this study: First, when planning lowland sewer system alongside the coastline or the riverside, the tidal stage or flood stage need to be considered in the planning and design processes. Second, an analysis that fails to consider overflow and inundation at the manholes may overestimate inundation depth of the flooded area. In other words, in order to estimate flood discharge and flood stage in a lowland storm sewer system, it is desirable to analyze the conveyance capacity of storm sewer system and simulate overflow and inundation at the manholes at the same time.

• 한국물환경학회지
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• 제32권4호
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• pp.367-374
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• 2016

In this study, the RDII impact on sewer designing in the upstream monitoring area (A site) was considered. Based on the long-term (1/1/2011~12/31/2011) rainfall and flow data consisting of 10-min interval sampling in the nearby design area (B site), the maximum RDII/DWF ratio was selected. The sewer network system at B site was evaluated by the Manning equation. Scenario 1 considering the hourly maximum flow with respect to the flow velocity showed that none of the sewer pipes satisfied the minimum flow velocity condition (0.6 m/s), and 40 pipes did not achieve half of the velocity condition. In scenario 2 considering I/I, 1 the pipes satisfied 0.6 m/s, and 35 pipes showed 0.3 m/s. Scenario 3 reflected the effect of RDII. Velocities in 26 pipes were less than 0.3 m/s, and 4 pipes satisfied the velocity condition. With respect to the allowance rate, 17 pipes were shown to have more than 99%, and none of the pipes satisfied less than 95% of the allowance rate in scenario 1. In scenario 2, 17 Ed: Per the Table pipes showed more than 99% and one pipe showed less than 95%. In scenario 3, 16 pipes showed more than 99% of the allowance rate, and 19 pipes showed less than 95%. Based on these results, it is predicted that deposition would occur due to the slow flow velocity; however, capacity would not be a problem.

• Spatial Information Research
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• 제5권2호
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• pp.185-194
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• 1997

의사결정지원체계의 한 분류인 공간의사결정지원체계(SDSS)는 지리정보체계(GIS)와 의사결정지원체계(DSS)의 결합으로 이루어진다. 계획지원체계(PSS)는 공간의사결정지원체계의 기능에 지리정보체계보다 고차원의 공간분석기능과 시간기능을 추가하여 구성된다. 본 연구는 계획가와 기술자가 적정 하수도 관경대안을 생성할 수 있는 계획지원체계의 개발에 관한 연구이다. 적정 하수도관경 결정을 위한 계획지원체계(PSS/GSS)의 이론적인 근거는 토지이용계획과 개발이 우오수관로의 수요를 유발한다는데 있다. 공급, 수요, 대안생성, 그리고 평가의 4단계를 통하여 PSS/GSS는 하수관거 생성의 기본계획, 기본설계,실시설계단계를 통합한다. GIS와 사용자 인터페이스는 하수도관망 배치, 하수량 산장, 그리고 생성된 대안의 도시에 유용한 수단이다. 모의에 ?나 하수도관경결정모델은 초리관망을 생성하낟. 사용자는 하수도관망의직접조작에 의하거나 하수도관경결정모델의 매개변수 조정에 의하여 대안을 생성할 수 있으며 이러한 대안의 타당성은 하수도관경결정모델에 의하여 점검된다.

• 한국방재학회 논문집
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• 제9권1호
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• pp.1-7
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• 2009

최적의 우수관망 설계를 위한 기존의 연구 모형들은 관경, 관 경사 등을 포함한 관거의 설계에 있어서 설계 강우에 대하여 최소의 비용을 목적으로 하여왔다. 그러나 이러한 모형들은 우수관망 관거 내 흐름의 중첩효과에 대한 고려는 하지 않고 있다. 관거 내 흐름의 특성은 관경, 관 경사 등에 따라서 달라지며 특히 관망의 구성이 달라짐에 따라서 크게 영향을 받는다. 본 연구에서는 우수관망을 구성함에 있어서 관거 내 흐름을 분산시키고 제어함을 목적으로 하고 있다. 이것은 관망 구성에 따른 관거 내 흐름의 중첩효과를 제어함으로써 가능하며, 이러한 흐름의 제어를 통하여 우수관망에서의 내수침수 위험도가 저감될 수 있다. 본 연구에서는 맨홀간 관거의 연결 방향을 조정함으로써 관내 유입량을 분산시키고 그 결과로서 유출구에서의 첨두 유출량은 저감되도록 우수관망을 구성하였다. 이때 관망 내 흐름에 대한 수리학적 분석은 SWMM(Storm Water Management Model)을 본 모형과 연계 구성함으로써 가능하였다. 관망 구성에 따른 내수침수 위험도의 저감을 검증하기 위하여 본 연구에서는 서울시 가락 배수분구의 현재 구성된 관망에 대하여 유출구에서의 첨두 유출량을 최소화하기 위하여 맨홀간 관거의 연결 방향을 변화시켰으며, 그 결과 30분 지속시간의 설계빈도 강우에 대하여 유출구 첨두 유출량은 약 20% 감소하였다. 또한 수정된 관망 구성은 설계빈도를 초과하는 강우에 대해서도 월류량 발생량이 저감되는 결과를 나타내었다.

• 상하수도학회지
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• 제23권1호
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• pp.47-55
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• 2009

Sewers are important national infrastructure and play an essential part by handling both wastewater and stormwater to minimise problems caused to human life and the environment. However, they can cause urban flooding when rainfall exceeds the system capacity. Sewer flooding is an unwelcome and increasingly frequent problem in many urban areas, and its frequency will increase over time with urbanisation and climate change. Under current standards, sewers are designed to drain stormwater generated by up to 10 year return period storms, but data suggests that many in practice have been experienced flooding with exceeding system capacity under increased storm events. A large number of studies has considered upgrading or increasing the design standard but there are still lack of information to propose a suitable return period with the corresponding system quantity to achieve. A methodology is required to suggest a proper level of standard within a suitable sewerage rehabilitation planning that can avoid the exceedance problem. This study aimed to develop a methodology to support effective sewer rehabilitation that could prevent urban flooding mainly resulted from the exceedance of existing storm sewer system capacity. Selected sewerage rehabilitation methods were examined under different storm return periods and compared to achieve the best value for money.