← JE Departmental
Past Questions
If the axial load including self weight of footing is 750 kN and the bearing capacity of soil is 300 kN/sqm. The area of footing required would be
A)
2.00 sqm
B)
2.50 sqm
C)
3.00 sqm
D)
3.50 sqm
To determine the required area of a footing, we use the fundamental formula for bearing pressure:
Pressure (P) = Load (F) / Area (A)
Given data:
1. Total axial load (including self-weight), F = 750 kN
2. Safe Bearing Capacity (SBC) of soil, P = 300 kN/sqm
Rearranging the formula to solve for Area (A):
Area (A) = Load (F) / Bearing Capacity (P)
Area (A) = 750 kN / 300 kN/sqm
Area (A) = 2.5 sqm
Therefore, the required area of the footing is 2.50 sqm.
Comparing this result with the given options:
- Option (a) 2.00 sqm is insufficient to support the load without exceeding the bearing capacity.
- Option (b) 2.50 sqm is the exact calculated requirement.
- Option (c) 3.00 sqm and (d) 3.50 sqm are larger than required; while they would be safe, the question asks for the 'required' area, which typically refers to the minimum area needed to satisfy the bearing capacity limit.
Methemoglobinemia is caused by consumption of water by infants contaminated with
A)
Lead
B)
Nitrates
C)
Oxides
D)
Fluoride
Methemoglobinemia, commonly known as 'Blue Baby Syndrome,' occurs when nitrates (NO3-) in drinking water are converted to nitrites (NO2-) by bacteria in the digestive tract of infants. These nitrites oxidize the iron in hemoglobin from the ferrous (Fe2+) state to the ferric (Fe3+) state, forming methemoglobin. Unlike normal hemoglobin, methemoglobin cannot bind or transport oxygen effectively, leading to hypoxia (oxygen deprivation) and a characteristic bluish tint to the skin (cyanosis).
Why other options are incorrect:
- a. Lead: Lead poisoning causes neurological damage, kidney failure, and anemia, but not methemoglobinemia.
- c. Oxides: This is a general chemical term and not a specific contaminant associated with this condition.
- d. Fluoride: Excessive fluoride intake leads to dental fluorosis (mottling of teeth) and skeletal fluorosis, not the impairment of oxygen transport in the blood.
The general value of safe bearing capacity of medium clay readily indented with a thumb nail is
A)
100 kN/sqm
B)
150 kN/sqm
C)
250 kN/sqm
D)
450 kN/sqm
In soil mechanics and foundation engineering, the consistency of cohesive soils (clays) is often categorized by their field identification (thumb penetration tests) and their corresponding unconfined compressive strength (qu) and safe bearing capacity (SBC).
1. **Consistency Classification**:
- **Very Soft**: Readily compressed between fingers.
- **Soft**: Readily indented by a thumb nail.
- **Medium/Firm**: Indented by a thumb nail with moderate effort.
- **Stiff**: Indented by a thumb nail with considerable effort.
- **Very Stiff**: Indented by a thumb nail with great effort.
- **Hard**: Cannot be indented by a thumb nail.
2. **Bearing Capacity Correlation**:
For a 'Medium' or 'Firm' clay that is readily indented by a thumb nail, the typical safe bearing capacity (SBC) ranges between 100 kN/m² to 200 kN/m².
3. **Evaluating Options**:
- **Option (a) 100 kN/sqm**: This aligns with the lower to middle range of medium/firm clay consistency.
- **Option (b) 150 kN/sqm**: While possible, 100 kN/sqm is the standard textbook benchmark for the transition into medium consistency in many civil engineering handbooks used for departmental exams.
- **Option (c) 250 kN/sqm** and **Option (d) 450 kN/sqm**: These values are characteristic of 'Stiff' to 'Hard' clays, which cannot be 'readily' indented by a thumb nail.
Therefore, based on standard soil consistency tables, 100 kN/sqm is the most appropriate general value for this description.
The minimum cement concrete grade for all RCC members of water retaining structures in touch with liquid or encasing the liquid shall be
A)
M 25
B)
M 30
C)
M 35
D)
M 40
According to IS 3370 (Part 2): 'Code of Practice for Concrete Structures for Storage of Liquids', specifically for the design of water retaining structures, the durability and permeability of concrete are critical to prevent leakage and corrosion of reinforcement. To ensure low permeability and high durability, the code specifies a minimum grade of concrete for members in contact with liquid. For reinforced concrete (RCC) members of water retaining structures, the minimum grade of concrete required is M 30. This higher grade ensures a denser concrete matrix, reducing the porosity and increasing the resistance to water penetration. Options a (M 25), c (M 35), and d (M 40) are incorrect because M 25 is below the minimum requirement for liquid-retaining RCC, while M 35 and M 40, although acceptable, are not the 'minimum' required grade specified by the standard.
If the average increase in population of a city during the years 1990, 2000 and 2010 is 2,00,000 and the population of the city in 2010 is 5,00,000. What would be the projected population of the city in the year 2020 using Arithmetic incremental method?
A)
5,20,000
B)
7,00,000
C)
7,20,000
D)
8,50,000
The Arithmetic Increase Method is used to project population based on a constant average increase per decade.
1. **Identify Given Data:**
- Population in 2010 ($P_{2010}$) = 5,00,000
- Average increase in population per decade ($ ext{Avg Increase}$) = 2,00,000
- Projection year = 2020
2. **Formula for Arithmetic Increase Method:**
The projected population ($P_n$) is calculated as:
$P_n = P_o + (n \times X)$
Where:
- $P_o$ = Population of the last known census (2010) = 5,00,000
- $n$ = Number of decades between the last census and the projection year (2020 - 2010 = 10 years = 1 decade)
- $X$ = Average increase per decade = 2,00,000
3. **Calculation:**
$P_{2020} = 5,00,000 + (1 \times 2,00,000)$
$P_{2020} = 5,00,000 + 2,00,000$
$P_{2020} = 7,00,000$
Therefore, the projected population for the year 2020 is 7,00,000. Option (b) is correct. Options (a), (c), and (d) are incorrect as they do not follow the arithmetic progression based on the provided average increase.
Which of the following is not among the components of every rainwater catchment systems?
A)
A delivery system
B)
A storage reservoir
C)
A bore well to recharge the ground water
D)
None of these
A rainwater catchment system generally includes a catchment surface, a conveyance/delivery system, and a storage or recharge arrangement. A bore well to recharge groundwater is not a mandatory component of every rainwater catchment system; it is only one possible recharge method in some systems. Option b is incorrect because storage is a common component in many catchment systems. Option a is incorrect because a delivery/conveyance system is part of the basic setup. Option d is incorrect because at least one option (c) is clearly not a universal component.
The size of filter media in water treatment plant is specified by
A)
Standard size
B)
Nominal size
C)
Effective size
D)
None of these
In water treatment plants, specifically for rapid sand filters, the size of the filter media (sand) is specified by the 'Effective Size' (D10). The effective size is defined as the sieve size through which 10% of the filter media is retained (or 90% passes). This parameter is critical because it determines the filtration efficiency and the penetration depth of the particles.
- Option (a) 'Standard size' is a general term and not a technical specification for filter media.
- Option (b) 'Nominal size' refers to a named size for identification but does not account for the distribution of grain sizes necessary for hydraulic performance in a filter bed.
- Option (c) 'Effective size' is the industry-standard technical specification used by engineers to ensure the filter media provides the correct balance between head loss and turbidity removal.
Aeration in connection with water treatment process is used in
A)
Pre-chlorination
B)
Break point chlorination
C)
De-chlorination
D)
Plain chlorination
Aeration is the process of bringing water and air into close contact to remove dissolved gases or add oxygen. In the context of water treatment and chlorination:
1. **De-chlorination**: After the disinfection process, residual chlorine may remain in the water. If the water is being discharged into a natural water body or if the taste/odor is undesirable, this residual chlorine must be removed. Aeration is an effective physical method to remove volatile dissolved gases, including residual chlorine (as it helps in the volatilization of chlorine compounds), thereby acting as a de-chlorination step.
2. **Pre-chlorination (a)**: This is the addition of chlorine at the start of the treatment process to control algae or oxidize metals; it does not involve aeration.
3. **Break point chlorination (b)**: This is a chemical process where chlorine is added until the chlorine demand is met and free available chlorine begins to appear; it is a chemical dosage phenomenon, not an aeration process.
4. **Plain chlorination (d)**: This refers to the simple addition of chlorine for disinfection without preceding complex treatments; it does not inherently involve aeration.
Therefore, among the given options, aeration is used specifically to facilitate the removal of chlorine (De-chlorination).
The pipe which is installed in the house drainage to preserve the water seal of traps is called
A)
Soil pipe
B)
Anti-Siphonage pipe
C)
Waste pipe
D)
Vent pipe
In house drainage systems, traps are used to create a water seal that prevents foul gases from the sewer from entering the building. However, when a large volume of water flows through the main soil or waste pipes, it can create a partial vacuum (negative pressure) behind the flow. This vacuum can 'siphon off' the water seal from the traps, leaving the building open to sewer gases. An Anti-Siphonage pipe is specifically installed to connect the trap to a vent stack, allowing air to enter the system and neutralize the negative pressure, thereby preserving the water seal.
Why other options are incorrect:
- a. Soil pipe: This pipe carries human excreta (soil) from water closets to the main sewer.
- c. Waste pipe: This pipe carries liquid waste (sullage) from sinks, baths, and washbasins.
- d. Vent pipe: While an anti-siphonage pipe is a type of vent, a general 'vent pipe' provides overall ventilation to the system to prevent pressure buildup, whereas the 'anti-siphonage pipe' is the specific term for the pipe designed to protect the water seal of individual traps from siphonic action.
The recommended curing period for Portland Pozzolana Cement concrete (PPC) to attain full strength for concrete exposed to dry and hot weather condition is
A)
7 days
B)
10 days
C)
14 days
D)
28 days
Curing is the process of maintaining moisture and temperature conditions in concrete to allow the hydration of cement to continue, which is essential for the concrete to gain strength and durability. For Portland Pozzolana Cement (PPC), the pozzolanic reaction (the reaction between calcium hydroxide and silica) occurs more slowly than the primary hydration of Ordinary Portland Cement (OPC). Consequently, PPC requires a longer curing period to achieve its full design strength. According to standard engineering practices and IS codes (such as IS 456), while minimum curing periods are specified (e.g., 7 days for OPC in moist conditions), the standard period to attain the characteristic strength (full strength) for concrete is 28 days. In 'dry and hot weather conditions', the rate of evaporation is higher, making strict adherence to the full 28-day curing cycle critical to prevent shrinkage cracks and ensure the pozzolanic reaction is completed. Options a, b, and c are insufficient for the concrete to reach its full 28-day characteristic strength, especially under adverse weather conditions.
The minimum thickness of the footing at the edge shall not be less than
A)
150mm
B)
175mm
C)
180mm
D)
200mm
According to standard engineering practices and building codes (such as IS 456:2000 for plain and reinforced concrete), the minimum thickness of a footing at the edge is specified to ensure adequate cover for reinforcement and to prevent shear failure. For most standard residential and light commercial footings, the minimum thickness at the edge is stipulated as 150 mm. This thickness ensures that the concrete provides sufficient protection to the steel reinforcement against corrosion from soil moisture and chemicals, while maintaining structural integrity at the periphery where the load is distributed to the soil. Options b, c, and d represent thicknesses that may be used in specific heavy-load designs, but they do not represent the general 'minimum' requirement for standard footings.
The type of foundation suitable where bearing capacity of soil is low or other loaded areas are so close in both directions that individual footing would nearly touch each other is
A)
Spread footing or Pad foundation
B)
Strap footing
C)
Raft or Mat foundation
D)
Combined footing
The question describes two specific scenarios: 1) Low bearing capacity of soil, and 2) Closely spaced loaded areas where individual footings would overlap or touch.
1. **Low Bearing Capacity:** When the soil is weak, the load must be distributed over a larger area to reduce the pressure exerted on the soil to a value less than or equal to the allowable bearing capacity. A raft foundation covers the entire area under the structure, effectively spreading the load.
2. **Overlapping Footings:** When columns are so close that individual footings would cover more than 50% of the total building area, it is more economical and structurally sound to provide a single continuous slab (raft) rather than multiple individual or combined footings.
Why other options are incorrect:
- **a. Spread footing/Pad foundation:** These are used for individual columns in soils with good bearing capacity and where columns are spaced far apart.
- **b. Strap footing:** This is used when a column is located on a property line, connecting it to an interior footing via a beam to prevent eccentricity.
- **d. Combined footing:** This is used for two or three columns that are close to each other, but not when the entire building's footprint requires load distribution due to low soil capacity.
Which kind of the following sedimentation tanks minimizes the effect of inlet and outlet disturbances?
A)
Rectangular
B)
Circular
C)
Square
D)
Elliptical
In environmental engineering, sedimentation tanks are designed to remove suspended solids by gravity. Circular sedimentation tanks (also known as clarifiers) are specifically designed to minimize the effects of inlet and outlet disturbances. This is achieved through the use of a central feed well (inlet) that dissipates the energy of the incoming water and a peripheral weir (outlet) that collects the clarified water uniformly around the circumference. This radial flow pattern ensures a more stable hydraulic environment compared to rectangular tanks, where 'short-circuiting' (water bypassing the main volume of the tank) is more common due to inlet/outlet turbulence and dead zones in the corners. Rectangular tanks are more space-efficient for large capacities but are more susceptible to flow disturbances. Square and elliptical tanks are not standard industry designs for primary sedimentation due to hydraulic inefficiency.
The minimum cover for 2.0 hour fire rating in continuous RCC beams is
A)
30 mm
B)
40 mm
C)
50 mm
D)
55 mm
For RCC beams, the minimum concrete cover required to achieve a 2.0 hour fire resistance rating is 50 mm. This is the standard value used in fire design provisions for reinforced concrete members, including continuous beams, to provide adequate insulation to the reinforcement during fire exposure. Hence, option (c) 50 mm is correct.
Why the others are incorrect:
- 30 mm: too small for a 2-hour fire rating; generally used for much lower fire resistance or ordinary durability cover, not fire protection.
- 40 mm: still insufficient for 2 hours; may be associated with lower fire ratings or general structural cover requirements.
- 55 mm: exceeds the standard minimum for 2 hours, so it is not the prescribed minimum value.
Which of the following population forecasting methods assumes a constant rate of growth?
A)
Uniform percentage method
B)
Curvilinear method
C)
Logistic method
D)
Arithmetic method
In Environmental Engineering, population forecasting is crucial for designing water supply and sewage systems.
1. **Arithmetic Increase Method (Option d):** This method assumes that the population increases by a constant absolute amount each decade. The rate of growth is constant in terms of the number of people added, making it a linear growth model. It is typically used for old, established cities where growth has stabilized.
2. **Geometric/Uniform Percentage Increase Method (Option a):** This method assumes that the percentage growth rate remains constant. This means the population increases exponentially, as the growth is proportional to the current population. This is used for rapidly growing young cities.
3. **Logistic Method (Option c):** This method assumes that the growth rate changes over time and eventually levels off as the city reaches a saturation limit (carrying capacity). It follows an S-shaped curve.
4. **Curvilinear Method (Option b):** This is a general term for non-linear growth models, which do not assume a constant rate of growth in the same way the arithmetic method does.
Therefore, the method that assumes a constant rate of growth (in terms of absolute increase per unit time) is the Arithmetic method.
As a general guide to gutter dimensions in relation to roof area, a useful thumb rule is to make sure, for every sqm of roof area, provision of
A)
5 sqcm gutter cross section
B)
10 sqcm gutter cross section
C)
15 sqcm gutter cross section
D)
20 sqcm gutter cross section
In building services and plumbing design, specifically for rainwater drainage systems, thumb rules are often used for preliminary sizing of gutters before detailed hydraulic calculations (based on rainfall intensity and roof slope) are performed. A widely accepted general guide/thumb rule in civil engineering and plumbing practice is to provide a gutter cross-sectional area of approximately 10 square centimeters for every 1 square meter of roof area. This ensures that the gutter has sufficient capacity to handle typical peak rainfall intensities without overflowing. Therefore, if a roof is 100 sqm, the gutter cross-section should be approximately 1000 sqcm. Options a, c, and d provide values that are either too small to prevent overflow or unnecessarily oversized for a general thumb rule.
Discoloration of clothes and plumbing fixures and incrustations in water mains is caused by
A)
Chlorides
B)
Algae
C)
Dissolved oxygen
D)
Iron
Step-by-step reasoning: 1. Iron is a common mineral found in groundwater. When iron is present in water, it typically exists in the soluble ferrous state (Fe2+). 2. Upon exposure to air (oxygen) or chlorine, it oxidizes to the insoluble ferric state (Fe3+), forming ferric hydroxide precipitates. 3. These precipitates are reddish-brown in color. When this water is used for laundry, it leaves yellowish-brown stains (discoloration) on clothes. 4. Similarly, it causes reddish-brown staining on plumbing fixtures (sinks, tubs) and leads to the formation of 'incrustations' (deposits/scaling) inside water mains, which can reduce the effective diameter of the pipes.
Why other options are incorrect:
- a. Chlorides: Primarily cause corrosion of metal pipes (pitting) and impart a salty taste, but do not cause reddish-brown discoloration or incrustations.
- b. Algae: Cause taste, odor, and green discoloration in open reservoirs, but do not cause mineral incrustations in closed water mains.
- c. Dissolved oxygen: While it facilitates the oxidation of iron, oxygen itself is a colorless gas and does not cause staining or physical incrustations.
The RCC slab will behave as two-way slab if the ratio of longer to shorter span is
A)
>1
B)
<1
C)
>2
D)
<2
In Reinforced Concrete Cement (RCC) design, slabs are classified based on the ratio of their longer span (Ly) to their shorter span (Lx).
1. One-Way Slab: A slab is considered a one-way slab if the ratio of the longer span to the shorter span (Ly/Lx) is greater than or equal to 2. In this case, the slab bends primarily in one direction (along the shorter span), and the load is transferred mainly to the supports on the shorter sides.
2. Two-Way Slab: A slab is considered a two-way slab if the ratio of the longer span to the shorter span (Ly/Lx) is less than 2. In this case, the slab bends in both directions, and the load is distributed to all four supporting edges.
Therefore, for a slab to behave as a two-way slab, the ratio Ly/Lx must be < 2.
Smith’s test is performed in a stone sample to find out
A)
Presence of soluble matter
B)
Crushing strength
C)
Hardness
D)
Rate of wearing
Smith's test is a specific chemical test used in civil engineering to determine the presence of soluble matter (such as soluble salts) in a stone sample. The test involves placing a piece of stone in a glass of distilled water and observing if the water becomes tinted or if any soluble substances leach out. If soluble matter is present, it can lead to the deterioration of the stone (efflorescence) and weaken the bond with mortar, making the stone unsuitable for certain construction purposes.
Why other options are incorrect:
- b. Crushing strength: This is determined using a Universal Testing Machine (UTM) or a Compression Testing Machine (CTM) by applying a compressive load until failure.
- c. Hardness: This is typically measured using the Mohs scale or a Sclerometer.
- d. Rate of wearing: This is determined by the Attrition Test or the Los Angeles Abrasion Test to check the resistance of the stone to wear and tear.
A Rock forming mineral which is also known as Black mica is
A)
Olivine
B)
Muscovite
C)
Dolomite
D)
Biotite
The question asks for the rock-forming mineral known as 'Black mica'.
1. **Biotite (Option d):** Biotite is a common phyllosilicate mineral. Due to its high iron and magnesium content, it typically appears dark brown to black. It is widely known in geology as 'Black Mica'.
2. **Muscovite (Option b):** Muscovite is also a mica mineral, but it is colorless or silvery-white. It is known as 'White Mica'.
3. **Olivine (Option a):** Olivine is a magnesium iron silicate usually found in ultramafic rocks. It typically appears olive-green and does not have the sheet-like structure of mica.
4. **Dolomite (Option c):** Dolomite is a carbonate mineral (calcium magnesium carbonate) and is not a member of the mica group.
Therefore, Biotite is the correct answer.
The soffit formwork to Ring beam of RCC Overhead water tank can be removed after
A)
3 days
B)
10 days
C)
21 days
D)
28 days
In reinforced concrete construction, the removal of formwork (stripping time) depends on the type of structural member and the support it provides. According to standard engineering practices (such as IS 456:2000), formwork for structural members supporting slabs or beams (soffits) must remain in place until the concrete has gained sufficient strength to support its own weight and any superimposed loads. For beams and slabs spanning more than 4.5 meters, the minimum period for removal of props to soffits is typically 21 days. In the case of an RCC Overhead Water Tank, the ring beam is a critical structural element that supports the weight of the tank walls and the water load. To ensure structural integrity and prevent deflection or cracking, a conservative stripping period of 21 days is standard for these heavy-duty structural soffits. Options (a) and (b) are too short for structural soffits (usually reserved for vertical sides), and (d) 28 days is the full curing period for design strength but is generally longer than the minimum required for formwork removal if the concrete has gained adequate strength by day 21.
‘Un-accounted for’ water in water distribution system is due to
A)
Public buildings
B)
Jails
C)
Meter and pump slippage
D)
All of these
‘Un-accounted for’ water (UFW), also known as Non-Revenue Water (NRW), refers to the difference between the volume of water produced at the source and the volume of water billed to customers. It is categorized into two main types: Physical (Real) losses and Commercial (Apparent) losses.
1. Physical Losses: These include leakages in the distribution mains, service pipe leaks, and overflows from reservoirs.
2. Commercial/Apparent Losses: These include water used for public purposes that is not billed, theft, and measurement errors.
Analyzing the options:
- Public buildings and Jails (Options a and b): Water supplied to government institutions, public parks, and jails is often provided free of charge or is not metered/billed. Since this water is produced but not billed, it falls under 'un-accounted for' water.
- Meter and pump slippage (Option c): This refers to inaccuracies in measurement. If a meter under-registers the actual flow of water (slippage), the water is consumed but not recorded or billed, contributing to the un-accounted for total.
Since all three options contribute to the gap between produced water and billed water, the correct answer is 'All of these'.
Which of the following processes may be omitted in treating water of low turbidity and industrial processed water in a rapid filtration?
A)
Coagulation
B)
Flocculation
C)
Disinfection
D)
Clarification
Flocculation may be omitted for water of low turbidity and for many industrial processed waters in rapid filtration because these waters contain little suspended matter, so the formation of large flocs is not necessary before filtration. In such cases, direct filtration or simple coagulation may be sufficient.
Why the others are incorrect:
- Coagulation (a): Usually still needed to destabilize fine colloids and improve removal efficiency, even in low-turbidity water.
- Clarification (d): This is a broader settling/solid-removal step and is not the specific process typically omitted in rapid filtration; it may be bypassed in direct filtration, but the standard answer here is flocculation.
- Disinfection (c): Cannot be omitted, because it is essential to kill pathogenic microorganisms and ensure safe drinking water.
In a plain sedimentation for treatment of water, particles entirely removed will be
A)
which settle at velocities equal to surface overflow rate
B)
which settle at velocities equal to or less than surface overflow rate
C)
which settle at velocities equal to or greater than surface overflow rate
D)
None of these
In a plain sedimentation tank (ideal settling basin), the removal of particles is governed by the Surface Overflow Rate (SOR), also known as the surface loading rate. The SOR is defined as the flow rate (Q) divided by the surface area (A) of the tank (SOR = Q/A). This value represents the critical settling velocity (v_s).
1. Particles with a settling velocity (v_s) equal to the SOR will travel from the very top of the tank to the bottom exactly as the water reaches the end of the tank, resulting in 100% removal.
2. Particles with a settling velocity greater than the SOR will reach the bottom of the tank even faster, meaning they are also 100% removed.
3. Particles with a settling velocity less than the SOR will not reach the bottom before the water exits the tank, meaning they are only partially removed (the fraction removed is v_s / SOR).
Therefore, for a particle to be entirely (100%) removed, its settling velocity must be equal to or greater than the surface overflow rate.
Which of the following water use would demand a high rate for short period?
A)
Very large fire
B)
Schools
C)
Commercial and Industrial
D)
Flushing streets
In Environmental Engineering and Water Supply Design, water demand is categorized into different types based on duration and intensity.
1. **Fire Demand (Option a):** Firefighting requires an extremely high volume of water delivered at a very high flow rate (discharge) to extinguish a blaze. However, this demand is temporary and lasts only for a short period (the duration of the fire). This is the classic example of a 'high rate for a short period' demand.
2. **Schools (Option b):** These have predictable, periodic demands (peaks during breaks or morning/afternoon), but the flow rate is relatively low compared to fire demand.
3. **Commercial and Industrial (Option c):** These typically have a steady or cyclical demand throughout the working day, not a sudden, extreme spike for a very short duration.
4. **Flushing Streets (Option d):** This is a maintenance activity that is usually scheduled and does not require the extreme instantaneous flow rates associated with emergency fire fighting.
Therefore, a 'Very large fire' is the only option that necessitates a massive surge in water flow for a limited window of time.