Alabama Drainage, Irrigation and Flood Control Contractor Examination

In grading for surface drainage, what is the primary purpose of establishing a positive grade away from structures?

• ATo increase soil compaction density near foundations
• BTo direct stormwater runoff away from buildings and prevent ponding
• CTo reduce the need for underground utilities
• DTo maximize infiltration under the building footprint

What does a 1% grade mean on a drainage channel invert?

• AA 1-foot vertical rise or fall for every 1 foot of horizontal distance
• BA 1-foot vertical rise or fall for every 100 feet of horizontal distance
• CA 1-inch vertical rise or fall for every 1 foot of horizontal distance
• DA 10-foot vertical rise or fall for every 100 feet of horizontal distance

During earthwork, when is a proof roll typically performed?

• AOnly after final landscaping is complete
• BOn subgrade or base to detect soft, yielding, or unstable areas before placing pavement o…
• COnly when the engineer requests a concrete cylinder test
• DAfter asphalt has fully cooled

What is the main purpose of a silt fence on a drainage or flood-control construction site?

• ATo permanently replace a storm sewer system
• BTo intercept and filter sediment-laden sheet flow and keep sediment on site
• CTo provide structural support for trench walls
• DTo mark the permanent right-of-way boundary only

Using the Rational Method, peak runoff Q is calculated as Q = CiA. What does the variable i represent?

• AInfiltration rate of the soil in inches per hour
• BRainfall intensity for the design storm in inches per hour
• CInvert elevation of the outfall structure
• DIrrigation application rate in gallons per minute

A drainage area of 2.0 acres has a runoff coefficient C of 0.70. Design intensity i is 3.0 in/hr. What is the Rational Method peak discharge Q?

• A2.1 cfs
• B4.2 cfs
• C5.7 cfs
• D8.4 cfs

What is cut and fill balance trying to achieve on a sitework project?

• AEqual numbers of trees planted and removed
• BMinimizing imported fill and exported spoil by matching excavation volume to embankment n…
• CUsing only rock fill and no soil fill
• DPlacing all excavated material under building slabs regardless of suitability

When compacting trench backfill over a storm drain, why is material placed and compacted in lifts?

• ATo eliminate the need for bedding under the pipe
• BTo achieve uniform density throughout the depth and reduce settlement
• CTo allow the pipe to float during compaction
• DTo keep moisture content as high as possible at all times

What is the primary function of a detention basin in a stormwater management system?

• ATo permanently store water for irrigation supply only
• BTo temporarily hold peak runoff and release it at a controlled rate
• CTo replace all on-site curbs and gutters
• DTo increase peak discharge leaving the site

On a topographic map or grading plan, what do closely spaced contour lines indicate?

• AA flat area with little slope
• BA steep slope
• CA wetland boundary only
• DThe location of underground utilities

What is the typical purpose of a French drain (subsurface drain) in site drainage?

• ATo convey roof downspouts at surface grade only
• BTo collect and redirect subsurface water using perforated pipe and aggregate
• CTo serve as a primary traffic-bearing pavement section
• DTo replace the need for any outfall or discharge point

When placing fill for an embankment that will support a drainage structure, why must organic topsoil generally be stripped first?

• AOrganic soils provide the highest structural strength available
• BOrganic material compresses and decomposes, causing settlement and instability
• CTopsoil is required under all structural fills by OSHA
• DStripping is only cosmetic and never structural

In open-channel flow, what does Manning’s equation primarily relate?

• AConcrete compressive strength to water-cement ratio
• BChannel discharge or velocity to roughness, hydraulic radius, and slope
• CIrrigation precipitation rate to nozzle arc only
• DUtility ticket validity period to excavation depth

Compared with smooth concrete pipe, corrugated metal pipe (CMP) typically has which effect on flow capacity for the same diameter and slope?

• AHigher capacity because CMP always has a lower Manning’s n
• BLower capacity because CMP generally has a higher Manning’s n (rougher)
• CIdentical capacity because diameter alone controls flow
• DZero capacity unless concrete lined

What is the main reason to stabilize disturbed slopes promptly after grading?

• ATo increase the Rational Method C coefficient as much as possible
• BTo reduce erosion, sediment transport, and rill or gully formation
• CTo eliminate all need for temporary drainage ditches
• DTo raise groundwater for irrigation supply

When excavating for a storm sewer, what does “invert elevation” refer to?

• AThe elevation of the top of the pipe exterior
• BThe elevation of the lowest inside flow line of the pipe
• CThe elevation of finished grade above the trench
• DThe elevation of the manhole rim only

A storm pipe is specified with 0.40% slope. Over a run of 250 feet, how much does the invert drop?

• A0.40 feet
• B1.00 feet
• C2.50 feet
• D10.00 feet

What is a common purpose of a swale in site drainage design?

• ATo act as a pressurized water main
• BTo convey surface runoff in a shallow, vegetated or lined channel
• CTo replace all underground storm sewers on every project
• DTo support heavy truck traffic as a structural pavement

Why is geotextile often specified under riprap at a storm outfall?

• ATo permanently waterproof the soil so no drainage occurs
• BTo prevent underlying soil from washing out through voids in the rock
• CTo eliminate the need for any energy dissipation
• DTo bond the riprap into a single rigid slab

What does “benching” an embankment or cut slope typically accomplish?

• AIt creates level steps that improve stability and reduce continuous slope length for eros…
• BIt converts the slope into a vertical free face without protection
• CIt removes the need for any drainage on the slope
• DIt is only used for decorative landscaping with no engineering purpose

In trench excavation for drainage pipe, what is the purpose of providing adequate bedding under the pipe?

• ATo create point loading on the pipe invert for strength
• BTo provide uniform support along the pipe barrel and control grade
• CTo eliminate all backfill above the springline
• DTo allow the pipe to rest only on rock outcrops

What is the primary difference between detention and retention for stormwater?

• ADetention permanently keeps all runoff; retention always drains completely within minutes
• BDetention temporarily stores and slowly releases runoff; retention holds water longer (of…
• CThey are identical terms with no design difference
• DRetention always increases peak discharge; detention always decreases storage

Why is moisture content controlled during compaction of structural fill?

• ABecause only completely dry soil can ever be compacted
• BBecause soils densify best near an optimum moisture content related to the Proctor test
• CBecause water content has no effect on density
• DBecause OSHA requires fill to be saturated during all compaction

A survey crew sets a temporary benchmark (TBM) for a drainage project. What is its main purpose?

• ATo permanently replace the county geodetic control network
• BTo provide a convenient local elevation reference for construction staking and grade chec…
• CTo mark only the location of gas utilities
• DTo measure horizontal property lines exclusively

What is the primary effect of increasing the water-cement ratio of a concrete mixture, all else equal?

• AHigher strength and lower permeability
• BLower strength and generally higher permeability
• CNo change in strength or durability
• DAutomatic air entrainment to 10%

Why is air entrainment commonly specified for exterior concrete exposed to freezing and thawing?

• ATo eliminate the need for any curing
• BTo provide microscopic air voids that relieve pressure from freezing water in the paste
• CTo increase the water-cement ratio for higher strength
• DTo make concrete waterproof without any thickness

What does a concrete slump test primarily measure?

• A28-day compressive strength
• BWorkability/consistency of fresh concrete
• CAir content percentage
• DAggregate specific gravity only

What is the main purpose of curing concrete after placement?

• ATo remove all cement from the mixture
• BTo maintain adequate moisture and temperature so cement can hydrate and develop strength
• CTo freeze the concrete as quickly as possible
• DTo increase the water-cement ratio after finishing

During hot-weather concreting, which practice helps reduce problems such as rapid stiffening and plastic shrinkage?

• AUsing the hottest water available and delaying placement as long as possible
• BCooling materials, placing promptly, protecting from wind/sun, and starting curing early
• CAdding unmeasured water on site until the mix is soup-like
• DEliminating all vibration so the mix dries faster

What is the primary purpose of consolidating (vibrating) concrete after placement?

• ATo force large air pockets and honeycombing out and fill the forms
• BTo entrain 15% air for freeze-thaw resistance
• CTo replace the need for any formwork
• DTo cool the concrete below freezing

Segregation in fresh concrete most often results from which condition?

• AProper vibration for a few seconds at each insertion point
• BExcessive water, over-vibration, or dropping concrete from excessive height
• CUsing well-graded aggregate and correct slump
• DCuring under wet burlap

What is cold joint in concrete construction?

• AA planned construction joint detailed on the drawings with proper bonding preparation
• BAn unplanned joint formed when fresh concrete is placed against concrete that has already…
• CA joint filled only with asphalt sealer in pavement
• DA type of expansion joint material made of foam

Why is reinforcement cover (clear concrete over rebar) important in drainage structures?

• ACover has no effect on durability
• BAdequate cover protects steel from corrosion and provides bond and fire resistance as des…
• CZero cover is preferred so steel can be inspected daily
• DCover only matters for interior architectural concrete

What is the typical purpose of a waterstop at a construction joint in a concrete flood wall or channel?

• ATo decorate the joint for architectural appearance only
• BTo create a continuous barrier that resists water passage through the joint
• CTo replace all reinforcement across the joint
• DTo allow unlimited joint movement without any restraint

When ordering ready-mixed concrete for curb and gutter, what information is most essential to specify?

• AOnly the truck color preferred by the crew
• BStrength, slump, air content (if exterior), aggregate size, and any special exposure requ…
• COnly the brand of form oil used on site
• DOnly the number of finishers scheduled

What is plastic shrinkage cracking in concrete?

• ACracking that occurs in hardened concrete after years of service only
• BCracking of the surface while concrete is still plastic, often from rapid moisture loss
• CCracks caused solely by freezing of fully cured concrete
• DIntentional score lines cut for jointing after 28 days

In cold-weather concreting, why must concrete be protected from freezing early after placement?

• ABecause freezing of fresh or young concrete can permanently damage strength development
• BBecause concrete only gains strength when frozen
• CBecause OSHA requires all concrete to freeze within 1 hour
• DBecause freezing increases the water-cement ratio beneficially

What is the function of a water-reducing admixture in concrete?

• ATo permanently prevent all hydration
• BTo achieve required workability with less water, helping maintain a lower water-cement ra…
• CTo replace cement entirely in the mixture
• DTo entrain 20% large air voids only

When constructing a cast-in-place concrete headwall, why must formwork be tight and properly braced?

• ALoose forms improve concrete strength by allowing free drainage of cement paste
• BTight, braced forms hold the concrete to line and grade under fluid pressure without bulg…
• CForms only need to resist wind, never concrete pressure
• DBracing is optional if the concrete is air-entrained

What does “28-day compressive strength” typically represent for structural concrete?

• AThe strength of the cement powder alone before mixing
• BThe standard age at which concrete cylinders are tested to verify design strength
• CThe maximum life of a concrete structure
• DThe time when curing must stop permanently

Why should concrete not be placed on frozen subgrade for a slab or structure foundation?

• AFrozen ground always increases concrete strength
• BThawing later can cause settlement and loss of support under the concrete
• CFrozen subgrade is required by cold-weather specifications
• DIt automatically air-entrains the mixture

What is honeycomb in hardened concrete?

• AA desirable textured architectural finish specified for all drainage structures
• BVoids and rock pockets left where mortar failed to fill spaces around aggregate or reinfo…
• CA type of air-entraining admixture
• DIntentional weep holes cast into a wall

For concrete exposed to sulfate soils or aggressive water, which mixture strategy is most appropriate?

• AUse the highest possible water-cement ratio available
• BUse a low water-cementitious materials ratio and sulfate-resistant cementitious materials…
• COmit curing entirely so salts can dry faster
• DUse only non-air-entrained concrete with high permeability

What is the main purpose of control (contraction) joints in concrete slabs and channels?

• ATo completely prevent all concrete shrinkage
• BTo create planned weakened planes so cracking occurs in controlled locations
• CTo increase the water-cement ratio at the joint
• DTo eliminate the need for subgrade preparation

When placing concrete in a deep form or wall, why is free fall of concrete limited?

• ATo encourage segregation of aggregate from mortar
• BTo reduce segregation and impact that can displace reinforcement or forms
• CBecause concrete cannot be moved horizontally after it leaves the chute
• DTo ensure the mixture freezes before consolidation

A concrete mixture requires a maximum water-cement ratio of 0.45 and uses 564 lb of cement per cubic yard. What is the maximum allowable mixing water per cubic yard?

• A127 lb
• B254 lb
• C400 lb
• D564 lb

What is the primary drainage function of a curb and gutter section along a roadway?

• ATo act as a structural bridge beam for traffic loads only
• BTo collect and convey surface runoff along the pavement edge to inlets or outlets
• CTo replace all roadside ditches and storm sewers permanently on every street
• DTo provide the only base course under asphalt pavement