Contractor: AL Jaber Transport & General Contracting, LLC.
Abstract.
The installation of water table control in any soils is a key tool in the efforts to improve the soil environment for better and effective growth of vegetation. In addition to this, water table control installations also regulate or manage the irrigation water and drainage. This systems help in storage of water for future use as well as ensuring the rainfall is effectively used. This study looks forward to exploring the effects of a poorly controlled water table and how the damages involved can be done away with.
Introduction
Drainage is a very important component of land development and has so far been a very important subject of concern by many. This is because, the drainage subject directly and greatly affect the environment and its ongoing activities. Poorly drained soils directly hinder even transport and communication as well as growth of crops and trees. On flat and at times poorly drained soils, it is important and at the same time necessary to ensure that intensive drainage is done so as to facilitate seedbed preparation as well as planting so as to minimize plant stress and also yield reduction that results from poor soil aeration which normally accompanies waterlogging. It is important to note that the drainage intensity required for agricultural production normally changes periodically over the year with periods of wetness emerging coupled with drought that causes crop stress. Intensive drainage systems are therefore required in order to provide trafficability during extreme wet periods of time as well as to remove more water than necessary during drier periods thus leading to temporary overdrainage. The problems of drought on drained soils have so far resulted in a great transition from conventional drainage methods to water table management systems as will be discussed in details in the report below.
Purpose
The main purpose of water table management is to provide drainage during wet periods. This level of control is only achieved through the use of control structures in order to manage the water level in the drainage outlet hence making it possible to reduce overdrainage. The systems can still be used in some places to provide sub irrigation during the dry periods. All this practices are still classified as water table management practices and greatly involve a combination of management practices which include surface drainage, controlled drainage or subsurface drainage and at times sub irrigation. This study however aims at offering a solution to the discovered challenge of a raised water table level at the soft and hard landscape works at the park adjacent to Bawabat Al Sharq Mall which after approximately 7 months from the completion of the hard and soft landscape works in the subject project was found to have some plants, trees and grass dead with some areas with paving tiles full of salt. These highlighted defects made the appearance of the landscape works unsatisfactory and did not at any point allow for the handing over of the project to the client. To curb this problem, this research has therefore taken action to create a sub soil drainage system that will control the water table level and give a permanent solution to avoid future damages.
Background
Water control is a very important aspect of the landscape that is normally considered before any form of construction is made. Although providing a good internal moisture control is the first step in ensuring an adequate surface drainage, a properly and well designed as well as properly installed subsoil drainage system is equally very essential. The natural soil is made up of solid particles and various sizes of pores whose drainage level varies from one pore size to another. Water retention and movement on the other hand constitutes the two important phases in soil moisture relationship. Water movement occurs through the capillarity action or through gravity. Therefore subsoil drainage can only work to improve the soil moisture relationship by keeping the ground water table well beneath the paved surface. The major principle of any drainage system is to effectively facilitate the production of a given subgrade of uniform bearing strength and value. In the midst of looking for a solution to the death of the plants, grass and trees as well as the fully salty paving tiles of the soft and hard landscape project, samples of the irrigation water and existing soil together with the soil from the damaged areas of the tiles were taken to the laboratory for testing. The results obtained showed that the salinity rate of the soil was very high in the samples and that the water table level had increased or raised due to the construction of new buildings and villas at the project area. The salty water had beenmixed with irrigation water which had caused damages to the plants and trees as well as the tiles. This observation serves as a clear consequence of poor drainage and its adverse effects on the environment. The only solution to this problem is a construction of a subsoil drainage system that will give a permanent solution to this challenge. The construction of a subsoil drainage installation entails four key aspects. First, the installation should be specific in addressing the particular problem and should be specifically designed to meet the problem. The designed drain must be able to pass water without clogging over long period of time which calls for proper material selection with the right type of filters in use. Lastly, the drain must be able to support any loading that is superimposed which means that the quality of the pipes must be thoroughly checked before their use is accepted.
Scope
The designed approach of this project problem entails a deep investigation of the problem which has been noted as the increased or raised water table. The cost impact in relation torectifying the problem shall also be covered in length. The required materials for use in the design shall also be selected with right equipment in place. Manpower to take care of the whole construction process shall also be solicited and the procedure for the rectification of the damages and defects identified in details. This will be then be followed by the last step of inspection and client approval.
Solution Approach
In order to effectively establish a proper subsoil drainage system, a series of steps were undertaken to reach a final and effective installation of the permanent solution. The first stage involved the complete removal of the defects. This entailed the uprooting of all the defective and salt infected grass, plants and trees. All this unhealthy pasture was removed from the area. In addition to this, the salty paving tiles were also removed and the surface was left without any material except the original salt infested soil.
Step2
After removing all the vegetation and tiles from the ground, the installation process took a second turn of providing a slope for the embankment formation under sweet soil and tiles. This was done in order to allow the ground water to flow to the proposed location of the perforated sub surface drainage system. The establishment of the right slope was done using the following standard for determining the site feasibility for water table control using soil redoximorphic features below.
Normally, the depth to redoximorphic features is as follows; 0 to 24’’ contains natural seasonal high water table that is not a limiting factor. For a 24’’ to 30’’ depth, landscape position and depth to impermeable layer becomes a key factor in determining site feasibility while in a 30’’ or more depth, most soils that fall in this category present a problem because of their landscape position and slope although there are exceptions still.
Step 3
This step entailed the construction of the subsoil drainage system by laying perforated pipes with proper aggregate surround and direction manholes at the approximate levels of 60 to 80 cm from finished ground level for landscape and tiles areas. This was done in order to guide the underground water to the nearest main storm water system for each landscape area in the project. The sub surface drainage was established as shown below as stated in the drainage guideline standard handbook.
In cases where a controlled drainage was require, the following figure shows the approach used.
The laying of the uPVC perforated pipes with proper aggregate surround and direction manholes at the stated level of approximately 60 to 80 cm was done according to the section detail for pipe and gravel surround shown in the layout below.
Step 4
After a successful mission of installing the subsoil drain system, there followed another step of reinstatement of the soft landscape area. This was then proceeded by a complete dumping of new sweet soil to the established final dumping station. The height of the plantation was then raised in many areas of the park. This step was then crowned by planting of different plants that were proven to comfortably adapt to the underground soil condition and the high salinity.
Step 5
This marked the last step or procedure in the complete subsoil drainage system installation. It entailed the reinstatement of the tiles area which was tackled by laying of new tiles in the damaged areas. Considering the large budget that accompanied the whole installation process, care was taken not to waste the resources used. Actually, in the reinstatement of tiles, the same existing tiles were reused once more so as to reduce on the total cost.
Results
The whole subsoil drainage system installation for the soft and hard Landscape Works at the Park adjacent to Bawabat AL Sharq Mall was completely and successfully installed with the whole installation project running for a continuous period of 12 weeks as can be shown in the schedule or plan section below. The major secret to thesuccessful laying out and installation of the system can be attributed to the right choice of the materials used as well as a clear reference to the standard sub- surface drainage book constantly used in every step of the construction process. A careful analysis shows a positive usage of the allocated budget due to the reuse of the removed tiles in the laying of the new installation.
Plan of action
After a careful and close supervision of the installation process to its ultimate completion. The damaged areas were again checked to ensure that the whole set up was completely clear of any flaws. This led to the last stage of inspection by the client. The client’s engineer was called to have the final approval of the work done. The method of rectification for the damaged areas and the installation drain system approach was approved. The snags were completed and the project was finally handed over.
4. Schedule
The following table shows the schedule of activities done to ensure a complete and successful installation of the subsurface drainage system.
5. Budget.
The whole subsurface drainage installation took an approximated budget of 79550$. The quantity of each equipment used and its respective price was as shown in the table below. It is important to note that despite the seemingly high cost of the project, a lot of care was taken to ensure that a small amount of finances were used throughout the project. This was achieved through the various measures undertaken such as the reuse of the already affected pavement tiles which cut down on the cost of purchasing new set of tiles. The entire budget of the whole drainage system together with the individual materials used is as shown below.
6. Qualifications.
The sub surface drainage installation system for the park was finally approved and accepted as the right procedure for rectification of the damaged areas of the soft and hard landscape works of the park adjacent to Bawabat AL Sharq Mall and the best ,standard installed drain system.
7. Conclusion
Soil drainage is a very important aspect never to be ignored at any point of decision making concerning land development ranging from building construction to plant growth. The extent of wetness of the soil is a key determinant of the kind of activities to be carried out on such a piece of land. Heavily soaked soils are less aerated and require effective drainage. Stagnated soaky soils have also been realized to be holding a lot of soils and carbon dioxide leading to death of grass and plants growing in that area. Therefore from the above project, it’s clear that water level table management is necessary for effective and successful constructions and developments to be done on any given piece of land.
Works Cited
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Chamen, Tim, et al. "Prevention strategies for field traffic-induced subsoil compaction: a review: Part 2. Equipment and field practices." Soil and tillage research 73.1 (2003): 161-174.
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Harr, R. Dennis. "Water flux in soil and subsoil on a steep forested slope."Journal of hydrology 33.1-2 (1977): 37-58. Patent No. 4,880,333. 14 Nov. 1989.
Skaggs, Richard W., and J. W. Gilliam. "Effect of drainage system design and operation on nitrate transport." Transactions of the ASAE 24.4 (1981): 929-0934.
