Analysis of The Cost and Time Comparison of Diversion Methods and Dewatering of Box Culvert Work

Low geographical conditions and flowed by many rivers and the reduction of retention ponds in Jakarta, then built a reservoir. However, during the implementation period, it was delayed by 9.74%. One of the things that can be done to overcome delays is to choose a method of implementation. The method is diversion and dewatering. The results of the analysis are expected to produce a large comparison of the costs and time of each method. From the analysis results, the cost of implementing the method of soil and rock diversion in the box culvert work is Rp. 363,935,953, while the sandbag diversion method is Rp. 332,805,831. For box culvert work using open pumping dewatering method, the required cost is Rp. 394,637,510. From these data, it was concluded that the difference in the cost of diversion sandbag and rock soil was Rp. 31,130,122. While rock soil and dewatering diversion are Rp. 30,701,557. As well as sandbag diversions with dewatering of Rp. 61,831,679. The results of observations of the implementation time obtained the conclusion that the work of box culvert with sandbag diversion method takes 35 days, and rock soil diversion 49 days while dewatering 63 days. By time comparison the sandbag diversion method is 14 days faster than rock soil diversion, and 28 days compared to the dewatering method. From these data, it can be concluded that in terms of cost and time, the sandbag diversion method is more economical and efficient than the other two methods.


Introduction
Low geographical conditions and flowing by many rivers, as well as environmental problems, and the reduction of retention ponds in Jakarta, built reservoirs, where their function is to overcome problems such as flooding. Based on the schedule the work plan starts on September 13, 2019 and will end on December 12, 2019. But there was a delay until the 7th week the work took place. Job deviations reached 9.74 percent, while jobs that were delayed were Box Culvert jobs. One of the things that can be done in overcoming work delays is to choose the right implementation method, both in cost and time.
The method used in the box culvert work consists of three methods, namely the method of soil and rock diversion, the sand bag diversion method and the open pumping dewatering method. Diversion work is carried out to divert the flow of water contained in the work area during the excavation process until the installation of the box culvert. While dewatering is a process of drying certain areas which aims to control water which impedes the process of carrying out a construction work.
The work methods certainly have differences in their implementation, both in terms of cost and time. Based on the above, the researcher is interested in Analyzing the Cost and Time Comparison of the Diversion Method and Dewatering Of Box Culvert Work On The Cakung Timur Construction Of Reservoirs.
The formulation of the problem is needed so that the research has a direction in the process, then the formulation of the problem is needed that can be drawn from the identification of the problem, namely as follows: 1. How much is the comparison of the costs required to complete the box culvert work with the diversion method using piles of soil and rocks, the diversion method with sand bag, and the open pumping dewatering method? 2. How long does it take to complete the box culvert work with the diversion method using soil and rock deposits, the sand bag diversion method, and the open pumping dewatering method?
The purpose of this research is: 1. To find out the comparison of the costs involved in box culvert work, with soil and rock diversion methods, sand bag diversion methods, and open pumping dewatering methods. 2. To find out how much time is needed to complete the box culvert work, with the method of soil and rock diversion, the method of diversion with sand bags, and the open pumping dewatering method.

Literature Review
In general, reservoirs are places on the face of the land that function to store sufficient rainwater in the rainy season, so that water can be utilized in the dry season. Reservoirs are the output from the construction of dams, and are often called artificial lakes [1]. VOLUME 2 │ NUMBER 2 │ MARCH 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656-1174 (online) The construction of dams or reservoirs is one of the construction project activities. Project activities are temporary work that is limited by planned time and resources. Planned resources or project costs consist of direct costs and indirect costs. Direct costs are obtained by analyzing the unit price of work, namely the calculation of labor, materials and equipment to get the unit price or one particular type of work. Cost analysis consists of materials and wages [2].
Material analysis is to calculate the amount of each ingredient, as well as the costs needed for a job. While the wage analysis is to calculate the amount of energy needed to complete certain jobs [3].
Cost and time analysis in this study is the method of diversion and dewatering in box culvert work. Box Culvert channel is a drainage channel of reinforced concrete in the form of a box, has a connection in each segment so that it is waterproof. Diversion channel is a process to divert the flow of water in a channel not entering the work site. Making channel diversion is part of the drying work [4]. In this open pumping dewatering method what is done is by making a channel (sump pit) that has a lower surface than the surrounding excavation area [5]. The methodology used in this study is by processing primary data from the results of the field survey, as well as gathering some information needed as secondary data. VOLUME 2 │ NUMBER 2 │ MARCH 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656-1174 (online)

Research Methodology
Data processing and analysis is carried out based on the method of excel calculation and unit price analysis based on the Standar Nasional Indonesia (SNI) and PUPR Unit Price Analysis using the price of the DKI region. The final result of the analysis is the comparison of cost and time of the diversion and dewatering method.

Results and Discussion
The object of this study, the authors conducted a comparative study of the method of diversion and dewatering on cost and time. The method of implementation is a systematic description of the implementation in the field in an appropriate manner and in accordance with work procedures. Following are the methods of implementing diversion and dewatering. The diversion method uses piles of soil and rocks, consisting of preparatory work, excavation work, embankment work, and finishing work. The working principle is to make the embankment half a part of the channel width so that a dry land is obtained which allows the construction to be carried out. Preparatory work on the rock soil diversion method includes land clearing and measurement work. In the implementation of this method work, as for the things that need to be done, namely the pile work which includes the work of procurement of rock soil material and the pile work itself. Laying sandbags layer by layer. Afterwards the local soil fill works will be relatively dry between the sand bags and compacted as needed. From the picture above can be seen how to arrange sand bag material. Broadly speaking, it can be explained that the method of sand bag diversion is almost the same as rock soil diversion, but in this method the sand bag material is placed in the excavation area to a minimum as high as the original land surface as a barrier.
Unlike the sand bag diversion and rock soil diversion, this open pumping dewatering method is done by making a channel (sump pit) that has a lower surface than the surrounding excavation area. Making sump pit aims to collect surface water from seepage of ground water and rain water. This method is carried out in conjunction with the excavation process of the area to be excavated.

Cost Comparison Analysis
Comparative analysis between methods is obtained by processing data obtained from the Cakung Timur Reservoir Construction Project, including volume, labor cost analysis, and AHS. The cost calculation is done not only direct costs, but also indirect costs include costs incurred by the company outside of material, equipment and man power. The indirect costs are as follows : Recapitulation of direct and indirect costs of box culvert work as follows: VOLUME 2 │ NUMBER 2 │ MARCH 2020 Available online at http://proceedings.worldconference.id. ISSN: 2656-1174 (online)

Time Comparison Analysis
The method used in determining the duration of box culvert work is field observations. How much time is needed to complete box culvert work. As for the results of field observations, the duration of time needed to carry out the box culvert work is as follows: Based on the above analysis it can be concluded that of the three box culvert work methods, the duration required for the rock soil diversion method requires 35 days of implementation. While the duration of time needed to complete the box culvert work with the sand bag diversion method is 49 days. And for the box culvert dewatering method it takes 63 days to complete the work.

The Results
The results of the cost and time analysis of box culvert work from three methods namely rock soil diversion, sand bag diversion and open pumping dewatering obtained comparative data as follows:

Conclusions
Based on the results of research conducted related to the cost and time comparison of the methods of diversion and dewatering in the work of the box culvert construction project of the Cakung Timur Reservoir, it can be concluded as follows: 1. From the analysis results, the cost of implementing the rock soil diversion method in the box culvert work is Rp. From these data it can be concluded that in terms of cost, the sand bag diversion method is more economical than the other two methods. 2. Based on the analysis, it was found that the implementation time of the sand bag diversion method is 35 days, while the rock soil diversion takes 49 days and the dewatering method is 63 days. From these data it can be concluded that the sandbag diversion method is 14 days faster than rock soil diversion, and 28 days compared to the dewatering method.