Journal of Global Resources
Volume 4 (02)
July 2018
ISSN: 2395-3160 (Print), 2455-2445 (Online)

Page 146-155

19
SHADOW RUNOFF THEORY, AN ENGINEERING DESIGN APPROACH TO IMPACTCONTROL OF MINE RUNOFF ON TSS CONCENTRATION AND SEDIMENTATION
Hernadi Untung Surapati
Mentor-Understanding Research Methods Course by University of London at Coursera
untung.gv@gmail.com
Abstract: An open mining system that uses a selective method is a system commonly used forthe retrieval of mineral materials as is commonly done in nickel mining. This mining system
resulted in extensive land clearing. If not accompanied by reclamation and revegetation actions,
it will cause problems to the environment, especially for the physical environmental componentsof the chemical erosion and sedimentation, one of which is the increase of TSS
concentration.Shadow runoff is "environmental friendly", no chemical, low cost and easy
maintenance, but must pay close attention to potential safety risks when the work activity isdone. This research tested shadow runoff hypothesis, with approach of hydrological science,oceanography, and fluid mechanics can decrease TSS concentration in pond at mining industry
using open pit method. shadow runoff theory using a simple method that is by understanding thecharacteristics of water flow energy, be it surface flow or turbulent flow in water or commonlyreferred to as water flow patterns. This method applies the natural process of mixing flow in thefjord-type estuary zone combined with the fluid flow mechanism.This theory is then tested withfield experiment and statistics using the autocorrelation test. Where there is a positive
autocorrelation between rainfall and TSS concentration after shadow runoff applied. There are
two benefits that can be obtained by using shadow runoff on erosion and sedimentation
problems, as a dilution pond and a sediment pond. Significantly shadow runoff shows whenrainfall is high then TSS concentration will decrease. This condition applies when the pond
serves as a diluent pond. The function as a sedimentary pond is able to reduce the sedimentload out of the maximum outlet by 8 percent.
Key words: Total Suspended Solid (TSS), Shadow Runoff Theory, Sediment Pond.
Introduction
In mining activities carried out, techniques used to take ore reserves using selective mining
techniques. In the AMDAL (EIA) study and other research on study mining areas, the majority ofland types are dominated by laterite soil types.Although previous studies have recommended
environmental management and management techniques for important impacts, there is no
possibility for additional research studies to be applied directly in the field.The results of theevaluation of the significant impacts occurring and looking directly at the conditions occurring in
the field, in particular the environmental components of physical-chemical properties, on the
management of erosion and sedimentation and the rate of surface flow, an additional theoreticalengineering approach to address the problem.
Key Questions• How to approach the best engineering design, so the problem of increasing TSS
concentration can be reduced.
• How much the maximum sediment volume that can be accommodated using theengineering design approach.
Literature Review
The working area of this study shows that the geomorphological conditions have a low to
medium wavy hill type. Rolling hills with a slope of 5° - 30° with southeast orientation. This unit iscomposed of laterite soil, gravel and saprolite blocks and located at elevations of 50-100 meters
above sea level. Lateritization on this morphology based on the slope of the slope indicatesmedium-high weathering process. The result of this erosion process is covering soil and thick146

and wide laterite deposit.(PT.Reka Bumi, 2017). The TSS concentration was determined using afiltration method. Porcelain crucible was oven dried at 103º C to remove all the water vapours.
The mass of the porcelain crucible plus a glass fibre filter with pore size of 0.6 µm were weighedusing 4 digits analytical balance. The TSS concentration was calculated by taking the difference
between the total mass of dried porcelain crucible, a fibre filter and its filtrate and the empty
dried porcelain crucible and its fibre filter over the volume of river water samples of 25 mL.
(Daphne, Low Hui Xiang, Handojo Djati Utomo, and Lim Zhi Hao Kenneth, 2011). Clay andsludge particles have electro-magnetic properties that bind hybrid grains together to give massor mass cohesion (CIRIA 1996). This process is called "Flocculation" which occurs when thedispersed colloidal phase (ie sludge) forms discrete particles that can precipitate from thedispersion medium (ie water). (Mohamed A. Abdelrhman. 2016). Settle rate for erosion anddeposit of cohesive and non cohesive particles, the treatment is different. Particles of cohesive
aggregates to form larger particles with higher precipitation speeds will pull particles out of thewater column, reduce turbidity, and increase the clarity of water. This process is the result ofelectrical charges on the surface of cohesive particles (clay and sludge). (Mohamed A.
Abdelrhman. 2016). Short rain may not cause runoff, but rain with the same intensity and longer
will cause surface runoff. Thus the total surface flow for a rain event is related to the duration of
the rain with a certain intensity. (Irwan Sukri Banuwa, 2013). The runoff is responsible forcausing erosion, as this runoff will transport the soil and parts of the soil from the higher to thelower area.(Irwan Sukri Banuwa, 2013). Sediment yield is the total number of particles(suspended or bedload) that reach outlets from the drainage of the river over a period of time.
The amount of transport flow/sediment delivery is usually expressed as kilograms per square
kilometer per year. The process of sediment delivery is influenced by many factors such as thesize of the drainage area, the slope of the basin, the climate, the type of sediment (lithology), thevegetation cover, and the practice of human land use/management. The theoretical concept of'Sediment Delivery Ratio' (ratio between yield and total amount of eroded sediments) illustrates
the fact that not all deposits are eroded in a particular catch area that reaches the sewer(because, for example, deposition in the floodplain). Such storage opportunities usually increasein larger size catches, resulting in a lower sediment delivery ratio. (Marangu PK, Mwenda E and
Theuri DM. 2016).
In addition, also a problem is the presence of sedimentation in the downstream area.
Where the total sediment transported from upstream to downstream is expressed in units ofvolume over a period of time. The total amount of this sediment (sediment yield) refers to the
inorganic fraction in the sediment regardless of the organic material transported. (MacGregor K.
2011). The problem of transition to turbulence has now been studied formally for over 100 years.
Despite this, one of the very few things upon which all research workers agree is that the issue
is a complex and difficult one. At the present time, there is no general theory of transition - nor
are we even close to developing one. Consequently, an important philosophical gap exists
between those who perform theoretical work and those who have to produce estimates fortransition to be used in engineering design. This has resulted in a dual and largely unrelated
approach to the problem. As a rather general statement, the theoreticians (and the experimental
scientists) have concentrated on trying to understand transition in certain types of very simple
flows where the number of variables is reduced to the absolute minimum. Examples of thosewhich have been studied are flat-plate flow, pipe and channel flow and flow over simple shapes
such as cones. Extensive work has revealed that, even though the shapes may be simple, thephysics of the transition process is always complex. The consequence of this has been that all
attempts to predict the details of transition - usually through stability theory (not transition theory)or, occasionally, turbulence modeling (not strictly a theoretical approach) have required adetailed and accurate description of the basic flow upon which a very large number ofcomputations need to be performed. This approach is of little use in an industrial design process
where candidate configurations may be changed repeatedly in an attempt to find a solution
which satisfies a very large number of absolute constraints. The implications of shape changemust be assessed rapidly and, particularly in the early stages, an extensive knowledge of detailand a high level of accuracy are not always needed. Consequently, the "industrial" approach has
been to produce simple estimation techniques based upon correlations of data from wind-tunnel
tests and, whenever possible, from flight using overall characteristics such as length Reynolds
147

number, freestream Mach number, incidence configuration-specific correlations. (Poll, D. I.
"Laminar-turbulent transition." AGARD Advisory Report 319, 1996). Fjord-shaped estuary, theprofile of the valley U-shaped. Like the Drowned river valley, this estuary fjord is also found intemperate regions and formed by melting of icebergs (glaciers) during the Pleistocene. At themouth of the estuary there is usually a sill (valley plateau sticking out), so the waters in that
section are quite shallow. While the depth of the valley (water basin) under a very deep sill, canreach about 300-400 m, some even reach 800 m. the freshwater input from the river is relatively
large compared to the volume of sea water when the tide, while the outflow of the rivercompared with the total volume of the fjord is relatively small (Dedy Kurniawan. 2010).
Methodology
This research uses quantitative methods (postpositivist claims) and uses the method of sampling
purposive random sampling.
Framework
Unlike the case with maintenance which has been done. The maintenance activities performed
regular routine dredging is known volume of sludge issued. While in the normalization ofactivities include the making/design changes that exist to achieve maximum results of anproblem object.There are 3 (three) ponds at the study location, where all three ponds arecovered in thick sludge that has not been maintained for several years.So that the runoff waterfrom upstream to study location as its downstream becomes the main problem, either from thequality factor or the quantity of runoff. The engineering design for ponds normalization is scaled
up or focused on decreasing TSS concentration in ponds capacity with a certain capacity.
Shadow Runoff Theory – State of Art"The surface flow rate will be inhibited by its flow rate by breaking the water energy when
passing through the drop structure (sr1), then divided into two streams flow. Where, there is astraight stream (sr2) and also there is a deflected (sr3).This deflected flow, then backflows dueto the depth contours at the ends is made higher. In addition there is also a narrow angle factor
at the end of the drainage channel (slope), so that when the flow end the slope, there was atransition of laminar water flow into turbulent flow. The faster the speed of the surface flow, it willencourage the flow turbulence process under the surface flow. Before the process of turbulencein water, then first the flowing water undergoes a process of precipitation by gravity."
Figure 01: The Principle Engineering Design (Shadow runoff) Drainage Channel Ponds
AL1

Runoff

SR1

SR2
Drainage base profileSR

148

Figure 02: Longitudinal Slope Shadow Runoff Technical Design

Simple Calculation of Ponds Water Capacity
A simple calculation is done by calculation approach in the work area image map (google map).
While this is less accurate, it can provide the basic information needed for the research.

149

Figure 03: Simple Calculation Approach Ponds Water Capacity

Total wide pond
± 21.763 m2
Thickness of sludge ± 5 m
Water capacity estimation± 109.000 m3

Ponds
s was originally designed to accommodate runoff or sediment yield from upstream
sources. Large ponds have been created to anticipate the impact. But the construction of thepond does not pay attention to routine maintenance on a regular basis that will be done. The
extent of the pond makes it difficult for long arm PC 200 excavator to reach the thick sludge
surface. This condition is particularly noticeable in pond 3. When the rain falls, the upstream
water carrying the sediment will continue to flow unhind
unhindered to the pond outlet. This is because
the sludge level was almost close to the outlet of pond.. In pond 2, some of the surface is rather
hard allowing long arm excavators to descend into the pond and sludge dredging. Neverthelessit remains to be considered
red the water flow plan that will be made. This is intended to anticipate
when the rainfall in high intensity with water discharge is also high. While in pond 1, has a layerof sediment that is not thick. So the ground base is easily found at a depth of ± 0,5 meters.
Trend of Rainfall Evaluation and TSS Concentration
Based on the graph of Fig. 3, there is a significant improvement pattern between rainfall and
TSS concentration. Rainfall is directly proportional to the concentration of TSS, whereas whenlarge
ge rainfall will be followed also the TSS concentration is also increased. This indicates ponds
is not working properly. In other words, ponds is merely a place through which runoff water flows
from upstream to downstream.
Figure 03: Trend Evaluation of Rainfall and TSS Concentration December 2017150

Table 01: Rainfall and Concentration Data of Ponds, December 2017
Date
01-Des-17
02-Des-17
03-Des-17
04-Des-17
05-Des-17
06-Des-17
07-Des-17
08-Des-17
09-Des-17
10-Des-17
11-Des-17
12-Des-17

Rainfall (mm)
6,4
0,0
20,2
0,0
0,0
0,0
0,0
0,2
18,8
8,6
0,6
0,0

Rainfall Volume (m3)
1.580
4.990
0,05
4.640
2.120
0,15
-

TSS (mg/l)
0,0
48
236
0,0
4,4
0,0
17,8
22,4
65,6
328
10,8
8,8

Source: Primary Data, Swapantau Enviro Section Laboratory, December 2017

The experimental steps are:First Phase
Pond 3 construction
Calculation estimation :1. 74.51 m x 7 m = 521,27 (Drainage Channel 1)2.
3.

102.,84 m x 5 m = 514,2 (Drainage Channel 2)73.38 m x 7 m = 513,66 (Drainage Channel 3)
Figure 4. Construction Design of Shadow

Shadow Runoff Theory is applied in drainage channel 3.
While drainage 1 and drainage 2 drainage only done regular dredging as thick as 5 meter. So it
can be calculated the maximum capacity or capacity of drainage channels to accommodate
water in pond 3 is as follows:(1+2+3)*5 = 1.549,13*5 = 7.745,65 m3
Second Phase
Pond 2 construction
Calculation estimation :1. 73.25 m x 7 m = 521,27 (Drainage Channel4)
2. 42.,14 m x 5 m = 294,98 (Drainage Channel5)
3. 67.23 m x 7 m = 470,61 (Drainage Channel6)
Shadow Runoff application is applied in drainage channel
6. While drainage channel 4 and 5 only done regulardredging as thick as 5 meter.So it can be calculated
maximum capacity or drainage capacity to accommodate
water in pond 2 is as follows: (1+2+3)*5 = 1.278,34*5 =6.392 m3

Shadow Runoff

Figure 5. Skecth of Shadow Runoff Design

RESULTS AND DISCUSSION
Experiment Pond 3
Pond 3 have water reserve is 7,745.65 m3, after 1 x 24 hours this water reserve will be stable orgravity precipitation has occurred and become "diluent" when the runoff of upstream water isintroduced. The steady pace of the settling process is due to the cohesive enegery of clay or
mud that accelerates the flocculation process in water. Visually, the water condition changes
color from brown (turbid) to become greenish. Of course, the capacity of dilution power by using
the runoff shadow theory has a certain limit so that it can work effectively in accordance with the
maximum capacity of the pond. This experiment begins on December 14, 2017 (See Figure 4).
On December 18, 2017, there was heavy rain with 15.2 mm rainfall causing an increase in TSS
concentration of 174 mg/l (still below the water quality standard). Until December 23, 2017 there
is no rainfall. Nevertheless the flow remains out at pond outlet with low discharge.Below is therainfall data and TSS concentration during the first phase of the experiment.
151

Table 02: Rainfall Data and Concentration Pond 3 December 2017 (Construction(Construction Phase)
Date
Rainfall (mm)Rainfall Volume (m3)
TSS (mg/l)
0,017-Des-17
3,0
0,741
174
18-Des-17
15,2
3.754
8,8
19-Des-170,000,020-Des-17
10,2
2.519
0,0
21-Des-17
0,4
0,099
5,6
22-Des-17
5,8
1.432
2,8
23-Des-170,00
Source: Primary Data, Swapantau Enviro Section Laboratory, December 2017.

The concentration of TSS in pond is 2.8 mg/l, which is the lowest TSS concentration during
the last month. This shows, there is a significant process of gravity and the constructions ofdrainage channel shadow runoff optimally.
Figure 06: Rainfall correlation and TSS concentration after
after the shadow runoff experiment

From Figure 6 above, after the shadow runoff experiment has been completed, thecorrelation pattern is directly proportional to rainfall and TSS concentration. If there is anincrease in rainfall, it will be followed by a decrease in TSS concentration.
concentration.January
January 1, 2018, theoutlet does not necessarily become turbid, thus increasing the concentration of TSS. It is seenon the morning of January 2, 2018, the condition of outlet pond 3 still looks clear, although it
looks a little bit colorful. In pond 2 itself, the water bebecomescomes turbid due to sediment yield fromupstream.The concentration of TSS can not be known because sampling is done in theafternoon, and pond 3 outlet is not flowing water (No Discharge). This occurred again on
January 3, 2018, again the rain fell rapidly and long enough where the date of January 4, 2018,is known from the analysis of TSS concentration of 6.80 mg / l.
The concentration of TSS in ponds is 2.8 mg/l, which is the lowest TSS concentration
during the last month. This shows, there is a significa
significant
nt process of gravity and the constructionsof drainage channel shadow runoff optimally. It can be seen the function of shadow runoff has apositive autocorrelation of rainfall and TSS concentration.
Experiment Pond 2
The work continued for the second phase,
phase, the experimental pond 2. During the 40% construction
period there have been two rains with significant rain intensity.Likewise,
intensity.Likewise, on Saturday afternoon
the rainy season is quite heavy and the TSS concentration value is 1.20 mg/l (See Figure 7.).
This TSS value is the lowest during the shadow runoff design development experiment on ponds
2 and 3.
Two days later, the concentration of TSS continues to increase, while the rainfall is decreased,
as shown in Figure 7.

152Figure 07: TSS Concentration at Pond 3 First Week 2018

6

7

The correlation pattern of precipitation with TSS concentration is inversely proportional.
Where, there is an increase in TSS concentration when there is decreased rainfall.This isbecause the design of shadow runoff construction is not suitable that done in the field. Technicalmisinformation occurs, where drainage channeling is done by making sediment trap that leaddirectly from the drainage channel source. In the event of high rainfall with high intensity, thedrainage channel will potentially function as a "By Pass" from upstream. While the drainage
channel corresponding to the initial design on its inlet is closed, so it can not enter the waterfrom upstream, from 7 to 10 January 2018.This theory takes from the actual error conditions in
the field, drainage channels that do not fit this initial design as a real shadow runoff drainage.
Thus, the initial design theory used is called Shadow Runoff.To control the error that occurred,then on January 11, 2018 opened the drainage channel that leads back shadow runoff. Whiledrainage channels leading into sediment trap are intentionally not closed back for use as controlof theoretical argument "By Pass".There has been rainfall with long intensity for threeconsecutive, ie, from January 13 to 15, 2018. This rainfall causes runoff from upstream overflow
and inundate pond 2 and pond 3 with a large enough capacity, which impacts TSS drastic
increase and extreme. Pond 3 capacity in the second phase of the shadow runoff construction
design can not accommodate such a large runoff flow. The following rainfall data and TSS
concentration for three days.
Table 03: Rainfall Data and TSS Concentration January 2018
Date
12-Jan-18
13-Jan-18
14-Jan-18
15-Jan-18
16-Jan-18
17-Jan-18
18-Jan-18

Rainfall (mm)
0,4
67,6
57,4
2,8
0,0
0,0
0,0

Rainfall Volume (m3)0,099
16.697
14.1780,691

TSS (mg/l)
2,0
1.720
14.552
1.672
16.8083.520
7.092

Source: Primary Data, Swapantau Enviro Section Laboratory, January 2018.

Based on the data in Table 3, the maximum runoff volume that occurred was on 13
January at 16,697 m3.Theoretically, the sediment trap serve as a settling pond, where when thefirst pond is filled with water, it will flow into the next sediment trap without any turbulencemechanism inside. So the mixing process for dilution does not occur. Besides, it is also the time
factor of the run-off for running the process too close.The prediction for sediment traps made as"By Pass" of runoff water from upstream proved after a sufficient intensive rainfall for 4 days
resulting in the function of ponds 2 and 3 as a diluent material switching function into
sedimentary sediment ponds. Where from a safety point of view this is a potential risk that canunsafe the maintenance activity of the pond. Rainfall is directly proportional to the concentrationof TSS, whereas when large rainfall will be followed also the TSS concentration is also
increased. This indicates ponds is not working properly. In other words, ponds is merely a place153through which runoff water flows from upstream to downstream.An autocorrelation test was
conducted between rainfall and concentration in September, October, and early December
2017, which for November was not due to only 4 days of rainy days and no outflow at pond
outlet. Followed by autocorrelation graph display during shadow runoff experiment on ponds.
(Figure 8).

1,6

1,6

1,2

1,2

1,2

0,8

0,8

0,8

0,4
0,0
-0,4

Correlation

1,6

Correlation

Correlation

Figure 08: Autocorrelation test of precipitation and TSS concentration before and after shadow runoff

0,4
0,0
-0,4

Before

8

0,4
0,0
-0,4

-0,8

-0,8

-0,8

-1,2

-1,2

-1,2

-1,6

-1,6

-1,6

-2,0
0,0 1,6 3,2 4,8 6,4 8,0 9,6 11,2 12,8-2,00,0 1,6 3,2 4,8 6,4 8,0 9,6 11,2 12,8-2,00,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5

Lag

Lag

Lag

October 2017

September 2017

December 2017 (a)1,6Correlation

1,2
0,8
0,4

After

0,0
-0,4
-0,8
-1,2
-1,6
-2,0
0,0

1,6

3,2

4,8

6,4

8,0

9,6

11,2 12,8

Lag

Desember (b) 2017 – Januari 2018
Shadow Runoff

Calculation of Analysis of Diluent and Settling Ponds
Based on data from Tables 2 and 3 can be calculated as follows:
Total maximum water capacity of pond 2 and pond 3 are:Pond 2 (1+2+3)*5 = 1.278,34*5 = 6.391,7 m3 ...................... (1)Pond 3 (1+2+3)*5 = 1.549,13*5 = 7.745,65 m3 ..........(2)(1+2) = 14.137,35 m3 ............................................(3)The total maximum sediment capacity of pond 2 and pond 3 is:Pond 2 (1+2+3)*5 = 1.278,34*4= 5.113,36m3 ................ (4)Pond 3 (1+2+3)*5 = 1.549,13*4= 6.971,09m3 ..................(5)(4+5) =11.309,88m3 .........................................................(6)Maximum rainfall volume = 16.697 m3 .............................(7)The maximum capacity of the two ponds mentioned above (calculation number 3), it can beunderstood that this capacity can not accommodate runoff from upstream on January 13, 2018
which is equal to 16,697 m3.
The volume of runoff and sediment discharged from outlet pond 3 can be calculated:
MaximumWater capacity
14.137 m3 ................. (3)Maximum sediment capacity
11.309,88m3 ............. (6)Maximum Rainfall volume
16.697 m3 ................ (7)The maximum runoff water coming out of the outlet of pond 3 is:(7)-(3) = 2.560 m3 ....................................... (8)And for the maximum sediment load coming out of outlet pond 3 is equal to(6)/(3) = 0,8 ..................................... (9)(8)*(9) = 2.048 m3 ....................................... (10)154Conclusions and Suggestions
The shadow runoff theory approach to ponds sediment shows a significant decrease in TSS
concentration, in which the water reservoir in the pond serves as a "diluent". In case of runoff
exceeding pond capacity and water reserves unable to process dilution, shadowrunoff switches
into a sediment storage pond. This proves the principle of work done, namely by using shadow
runoff theory to work effectively and optimally on pond sediment.Shadow runoff is"environmental friendly", no chemical used, low cost and easy maintenance, but must pay close
attention to potential safety risks when the work activity is done. Shadow runoff is effective whenapplied to flat topography type and laterite soil type. Routine maintenance is required to maintainthe proper functioning of the shadow runoff theory. This engineering design approach can be aconsideration for the handling of runoff having TSS high concentrations.Nevertheless, there is aneed for further research taking into consideration the important variables other than the above
which have been done to support and constructively correlate the shadow runoff theory.
References
1. Daphne, Low Hui Xiang, Handojo Djati Utomo, and Lim Zhi Hao Kenneth. (2011):"Correlation between turbidity and total suspended solids in Singapore rivers." Journal of
Water Sustainability 1.3 313-322.
2. Dedy Kurniawan. (2010): Sumberdaya Perairan Estuaria. KMP-MSP Universitas Hasanudin.
https://mspuh.wordpress.com/2010/02/08/sumberdaya-perairan-estuaria-editor-dedykurniawan/. Feb 4, 2018
3. Irwan Sukri Banuwa. (2013): Erosi. Kencana-Prenada Media Group Jakarta.
4. MacGregor K. 2011. Sediment Yield. In: Singh V.P., Singh P., Haritashya U.K. (eds)
Encyclopedia of Snow, Ice and Glaciers. Encyclopedia of Earth Sciences Series. Springer,
Dordrecht.
5. Marangu PK, Mwenda E, Theuri DM, (2016). Modeling Open Channel Fluid Flow with
Trapezoidal Cross Section and a Segment Base. J Appl Computat Math 5:292.
doi:10.4172/2168-9679.1000292
6. Mohamed A. Abdelrhman. (2016): Modeling Total Suspended Solids (TSS) Concentrations
in Narragansett Bay. U.S. Environmental Protection Agency Atlantic Ecology Division. USA.
7. Poll, D. I. (1996): "Laminar-turbulent transition." AGARD Advisory Report 319
8. PT. Reka Bumi-Bandung (2017): Laporan Akhir Hidrogeologi PT. TBP, Kawasi. North
Maluku.

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