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Question 1Erosion Control Principles and Practices

In the Revised Universal Soil Loss Equation, which factor represents the erosive energy of rainfall and runoff at a given location?

  1. Soil erodibility (K)
  2. Support practice (P)
  3. Cover-management (C)
  4. Rainfall erosivity (R) Correct answer.

Explanation

The R factor quantifies the erosive energy of rainfall and its associated runoff at a site, and it is derived from local rainfall records. The other factors describe soil properties, cover, and conservation practices rather than climate.

Question 2Erosion Control Principles and Practices

Which erosion process forms shallow channels that can be smoothed out by ordinary tillage operations?

  1. Sheet erosion
  2. Gully erosion
  3. Rill erosion Correct answer.
  4. Splash erosion

Explanation

Rill erosion occurs where runoff concentrates into small channels that are shallow enough to be obliterated by normal tillage. Once a channel becomes too deep to cross with equipment, it is classified as a gully.

Question 3Erosion Control Principles and Practices

When all other factors are equal, which soil material generally has the highest water erodibility?

  1. Coarse gravel
  2. Heavy clay
  3. Silt loam Correct answer.
  4. Uniform coarse sand

Explanation

Soils dominated by silt and very fine sand have relatively low cohesion and moderate infiltration, producing the highest erodibility values. Clays resist detachment through cohesion, and coarse materials allow rapid infiltration.

Question 4Erosion Control Principles and Practices

What is the primary function of a silt fence on a construction site?

  1. To pond and filter sheet flow before release Correct answer.
  2. To replace other perimeter controls
  3. To permanently store stormwater runoff
  4. To remove dissolved pollutants from runoff

Explanation

A silt fence is a temporary perimeter barrier that ponds runoff and lets it seep through the fabric so sediment drops out. It is not designed for concentrated flow, dissolved pollutants, or permanent storage.

Question 5Erosion Control Principles and Practices

Which installation detail is essential for a silt fence to perform as intended?

  1. Laying the bottom edge on the surface and relying on the posts
  2. Leaving gaps between fabric panels to let water pass
  3. Installing the fence along the centerline of a concentrated flow channel
  4. Burying the bottom edge of the fabric in a compacted trench Correct answer.

Explanation

Flow will scour beneath fabric that is not anchored, so the bottom edge must be set in a trench and backfilled with compacted soil. The fence must also follow the contour and receive sheet flow rather than concentrated flow.

Question 6Erosion Control Principles and Practices

Which settling relationship is used to estimate the velocity at which a soil particle of a given size falls through still water in a sediment basin?

  1. Manning's equation
  2. The Rational method
  3. Darcy's law
  4. Stokes' law Correct answer.

Explanation

Stokes' law gives the settling velocity of a particle as a function of its diameter and density and the water's viscosity. Basin surface area is then sized so the target particle's settling velocity exceeds the basin's overflow rate.

Question 7Erosion Control Principles and Practices

What is the primary function of a diversion berm constructed upslope of a disturbed area?

  1. To divert upslope runoff around the disturbed area Correct answer.
  2. To increase infiltration within the disturbed area
  3. To filter sediment from runoff leaving the site
  4. To reduce wind velocity over exposed stockpiles

Explanation

A diversion collects runoff from undisturbed ground above the site and routes it around the work area, reducing the volume of clean water that becomes sediment-laden. Sediment removal and wind control are handled by other practices.

Question 8Erosion Control Principles and Practices

Two sites share the same soil, cover, and rainfall. Site A has a 10 percent slope over 50 feet; Site B has a 20 percent slope over 50 feet. What does RUSLE predict?

  1. Site B will have a larger LS factor and higher predicted soil loss Correct answer.
  2. Site A will have greater soil loss because its slope is flatter
  3. Both sites will have identical LS factors because the slope lengths are the same
  4. LS cannot be compared unless the C factors are known

Explanation

The LS factor accounts for both slope length and steepness, so doubling steepness at constant length increases LS and raises predicted soil loss. LS is computed from slope geometry independently of the cover factor.

Question 9Erosion Control Principles and Practices

Which practice is most effective for reducing wind erosion on a bare, flat field?

  1. Increasing the number of tillage passes to break up clods
  2. Removing vegetation to expose the soil surface
  3. Irrigating once at the beginning of the season
  4. Maintaining residue or vegetative cover on the surface Correct answer.

Explanation

Wind erosion is controlled by keeping the surface protected and rough, so standing residue or cover lowers wind velocity at the soil surface and traps moving particles. Tillage that pulverizes soil tends to increase wind erodibility.

Question 10Erosion Control Principles and Practices

A series of check dams is placed in a temporary swale. What do they accomplish?

  1. They prevent any water from entering the swale
  2. They reduce flow velocity and promote sediment deposition Correct answer.
  3. They provide permanent grade control in the swale
  4. They increase channel capacity to carry larger floods

Explanation

Check dams are small temporary structures that pond water briefly, lowering velocity so sediment can settle out. They are not designed to increase conveyance or to serve as permanent grade control.

Question 11Erosion Control Principles and Practices

How does required riprap stone size change as flow velocity and channel shear stress increase?

  1. It is independent of channel shear stress
  2. It increases as flow velocity and shear stress increase Correct answer.
  3. It decreases as flow velocity increases
  4. It depends only on the total length of the channel

Explanation

Riprap must resist the shear stress imposed by flowing water, so the required median stone size grows as velocity and shear stress grow. Shear stress is the principal design parameter for riprap sizing.

Question 12Erosion Control Principles and Practices

How is the Revised Universal Soil Loss Equation best described?

  1. A design method for sizing sediment basins
  2. An empirical model predicting average annual sheet and rill erosion Correct answer.
  3. A water-quality model that predicts instream turbidity
  4. A physically based simulation model of channel and gully erosion processes

Explanation

RUSLE is an empirically derived model that estimates long-term average annual sheet and rill erosion from field-scale factors. It does not simulate gully, streambank, or channel erosion and does not predict water-quality parameters.

Question 13Erosion Control Principles and Practices

How does a straw mulch application control erosion on a steep slope?

  1. By drawing water out of the slope through capillary action
  2. By absorbing raindrop energy and slowing surface runoff Correct answer.
  3. By increasing the clay content of the soil
  4. By permanently replacing the need for vegetation

Explanation

Mulch forms a protective layer that intercepts raindrop impact, reduces runoff velocity, and holds soil particles in place until vegetation is established. It is a temporary measure that supports rather than replaces seeding.

Question 14Erosion Control Principles and Practices

A rolled erosion control blanket is specified for a channel. Which information is most important to compare against site conditions?

  1. The color of the blanket
  2. Rated shear stress and velocity limits versus site conditions Correct answer.
  3. Whether the blanket is biodegradable
  4. The weight of the packaging

Explanation

Blankets are selected by comparing the manufacturer's rated shear stress and velocity limits to the hydraulic conditions expected in the channel. Color, packaging, and degradability do not establish hydraulic capacity.

Question 15Erosion Control Principles and Practices

Which of these particles will settle most rapidly in still water?

  1. Fine gravel Correct answer.
  2. Silt
  3. Clay
  4. Fine sand

Explanation

Settling velocity increases with particle size and density, so gravel settles much faster than sand, silt, or clay. Clay particles are small enough to remain in suspension for a very long time.

Question 16Erosion Control Principles and Practices

What is the intended function of a turbidity curtain installed around in-water work?

  1. To neutralize acidity in the water column
  2. To provide structural support for the shoreline
  3. To remove dissolved nutrients from the water column through filtration
  4. To confine turbid water and limit mixing with surrounding water Correct answer.

Explanation

A turbidity curtain is a physical barrier that encloses the work area and reduces mixing of sediment-laden water with the surrounding water body. It does not filter water or alter water chemistry.

Question 17Erosion Control Principles and Practices

What is the purpose of a stabilized construction entrance built of coarse aggregate?

  1. To eliminate any need for street sweeping
  2. To provide a parking area for construction workers
  3. To reduce the tracking of sediment onto public roads Correct answer.
  4. To serve as a sediment basin for wash water

Explanation

A coarse aggregate entrance shakes soil from tires and reduces trackout onto public roads. It is typically paired with street sweeping or a wash rack because it reduces, but does not eliminate, sediment leaving on vehicles.

Question 18Erosion Control Principles and Practices

The sediment removal performance of a vegetative filter strip depends most strongly on which conditions?

  1. The presence of riprap along the edge of the buffer strip
  2. The grass species used, regardless of flow conditions
  3. The depth of the groundwater table beneath the strip
  4. Sheet flow and the ratio of contributing to buffer area Correct answer.

Explanation

Filter strips rely on shallow, uniform sheet flow; effectiveness falls sharply when flow concentrates. The ratio of contributing drainage area to buffer area largely determines how much sediment the strip can remove.

Question 19Erosion Control Principles and Practices

Why is hydroseeding often chosen over dry broadcast seeding on steep slopes?

  1. It eliminates the need for surface preparation
  2. It guarantees immediate full vegetative cover
  3. It requires no water during application
  4. The slurry sticks to the soil and can carry mulch and tackifier Correct answer.

Explanation

Hydroseeding applies seed, mulch, and often a tackifier as a slurry that adheres to the soil surface, improving coverage and reducing seed loss on steep or irregular ground. Seed-soil contact and germination time are still required.

Question 20Erosion Control Principles and Practices

Which statement correctly distinguishes erosion control from sediment control?

  1. Erosion control prevents detachment; sediment control captures detached soil Correct answer.
  2. Sediment control is used only on agricultural land
  3. Erosion control captures sediment after it detaches; sediment control prevents detachment
  4. The two terms are interchangeable in practice

Explanation

Erosion control works at the source by keeping soil particles in place through cover, mulch, or blankets, while sediment control captures soil that has already detached, as with silt fence or basins. The two functions are complementary but distinct.

Question 21Erosion Control Principles and Practices

Water must be pumped from an excavation and discharged off site. Which approach is most appropriate?

  1. Discharging onto the steepest nearby slope
  2. Discharging directly to a storm drain to avoid ponding
  3. Routing discharge through a sediment trap or filter bag Correct answer.
  4. Discharging over the top of a silt fence to save space

Explanation

Dewatering discharge must pass through a sediment-removing device such as a trap, basin, filter bag, or weir before release. Direct discharge to a storm drain bypasses treatment and typically violates permit requirements.

Question 22Erosion Control Principles and Practices

In RUSLE, what does the P factor represent?

  1. The ratio of soil loss with cover to that with bare soil
  2. The effect of supporting practices such as contouring and terracing Correct answer.
  3. The erosive power of rainfall
  4. The inherent erodibility of the soil

Explanation

The P factor reflects the reduction in erosion achieved by supporting practices such as contouring, terracing, and strip cropping relative to straight-row farming. Rainfall erosivity, soil erodibility, and cover effects are captured by other factors.

Question 23Erosion Control Principles and Practices

A topsoil stockpile will remain inactive for several months. How should it be managed?

  1. Covered with a single layer of silt fence fabric
  2. Left bare so wind and sun can dry it
  3. Stabilized with vegetation or mulch, with perimeter controls Correct answer.
  4. Removed within 24 hours in all cases

Explanation

Inactive stockpiles should be stabilized with vegetation, mulch, or a temporary cover and protected by perimeter controls such as silt fence or a berm. Leaving soil bare invites both wind and water erosion.

Question 24Erosion Control Principles and Practices

What is the purpose of adding a flocculant to construction stormwater?

  1. To bind fine particles into larger flocs that settle more quickly Correct answer.
  2. To raise the pH and precipitate dissolved metals
  3. To add coarse aggregate that weighs particles down
  4. To kill algae that cause turbidity

Explanation

Flocculants cause fine suspended particles to clump into larger flocs with faster settling velocities, improving sediment removal in basins or treatment units. They do not adjust pH, control algae, or act by adding aggregate.

Question 25Erosion Control Principles and Practices

A culvert discharges at high velocity onto an unstabilized slope. Which practice is most appropriate at the outlet?

  1. Remove vegetation around the outlet to improve access
  2. Install a riprap apron or other energy dissipator at the outlet Correct answer.
  3. Place a silt fence directly across the outlet
  4. Increase the culvert discharge velocity to spread the flow

Explanation

High-velocity flow must be slowed before it reaches erodible soil, so a riprap apron or comparable energy dissipator is placed at the outlet. Increasing velocity worsens scour, and a silt fence would be destroyed by concentrated flow.

Question 26Erosion Control Principles and Practices

On a bare, freshly graded slope, which process detaches the greatest quantity of soil during a high-intensity rainstorm?

  1. Chemical dispersion of clay particles in standing water
  2. Abrasion of the surface by wind-blown sand
  3. Shrinkage cracking of the soil surface during drying
  4. Raindrop impact breaking soil aggregates apart Correct answer.

Explanation

On bare ground, raindrop impact is the dominant detachment mechanism: splash energy breaks aggregates apart and throws particles into shallow sheet flow that carries them downslope. Impact also seals surface pores, which reduces infiltration and increases the volume and velocity of runoff.

Question 27Erosion Control Principles and Practices

A silt fence is installed downslope of a disturbed area. How should it be positioned so it works as intended?

  1. In a shallow V pointing downslope toward the outlet
  2. Flat against the toe of the slope beside the channel
  3. Along the contour, level, so sheet flow ponds Correct answer.
  4. Across the nearest swale to intercept concentrated flow

Explanation

A silt fence must be laid out on the contour with a level trench so that sheet flow backs up and ponds evenly along its length, allowing sediment to settle. It is a sheet-flow practice and will be overtopped, bypassed, or flattened if it is used to block concentrated flow.

Question 28Erosion Control Principles and Practices

What is the principal function of a temporary pipe slope drain on a steep embankment?

  1. To raise the water table behind the embankment
  2. To filter suspended sediment out of the runoff before discharge
  3. To carry concentrated flow downslope without erosion Correct answer.
  4. To spread runoff uniformly over the slope face

Explanation

A pipe slope drain collects concentrated runoff at the top of a steep slope and conveys it downslope in a closed conduit, so the flow never touches and rills the bare face. It is an erosion prevention measure, not a treatment device.

Question 29Erosion Control Principles and Practices

What is the main erosion-control benefit of roughening or track-walking a bare, compacted slope before seeding?

  1. It raises the pH of the surface soil
  2. It slows runoff and creates niches for seed Correct answer.
  3. It increases the clay content of the surface soil
  4. It removes the need for any surface cover

Explanation

Roughness breaks the surface seal, increases infiltration and surface storage, and slows runoff velocity, all of which reduce detachment and transport. The ridges and depressions also trap seed and hold moisture, improving establishment.

Question 30Erosion Control Principles and Practices

A level spreader is installed at the outlet of a concentrated flow. What does it accomplish?

  1. Converts concentrated flow into sheet flow Correct answer.
  2. Measures the peak discharge leaving the site
  3. Removes fine sediment by settling it before release
  4. Drops flow energy through a rock-lined stilling basin

Explanation

A level spreader is a level lip or trench that redistributes concentrated discharge across a wide front so it leaves as non-erosive sheet flow over undisturbed vegetated ground. It only works if the lip is truly level and the downslope area is not disturbed.

Question 31Erosion Control Principles and Practices

For a sediment basin, why is a length-to-width ratio of at least 2:1 with baffles recommended?

  1. It increases the peak discharge the basin is able to pass
  2. It reduces the total storage volume the basin requires
  3. It allows the basin to be cleaned without dewatering
  4. It lengthens flow paths and reduces short-circuiting Correct answer.

Explanation

A long, baffled basin forces water to travel farther before reaching the outlet, reducing short-circuiting and increasing detention time so particles can settle. Geometry affects treatment performance but does not change the storage volume needed for a given design storm.

Question 32Erosion Control Principles and Practices

A compost filter sock is best suited to which application?

  1. Replacing riprap on a wave-exposed shoreline
  2. Treating sheet flow along a perimeter or around a drop inlet Correct answer.
  3. Providing structural reinforcement beneath a heavy haul road
  4. Intercepting high-velocity flow in a concrete-lined channel

Explanation

Compost socks and berms are designed to slow and filter sheet and low-velocity flow, commonly along site perimeters and around inlets. They are not structural elements and will be displaced or washed out where flow is concentrated or fast.

Question 33Erosion Control Principles and Practices

Which technique uses live, dormant woody cuttings driven into a streambank to provide both immediate and long-term reinforcement?

  1. Gabion basket wall
  2. Riprap with filter fabric
  3. Live staking Correct answer.
  4. Cellular confinement system

Explanation

Live stakes are dormant cuttings installed into the bank, where they root and sprout. They give immediate mechanical reinforcement through the inserted stem and develop a root network over time that binds the soil.

Question 34Erosion Control Principles and Practices

How does an anionic polyacrylamide (PAM) application reduce sediment loss from a disturbed area?

  1. It dissolves clay minerals in the runoff
  2. It makes the surface hydrophobic and sheds rainfall
  3. It kills vegetation so the surface stays uniform
  4. It binds soil particles so they resist detachment Correct answer.

Explanation

PAM flocculates fine soil particles into larger, heavier aggregates that resist detachment and settle faster, lowering turbidity in runoff. It is a supplement to, not a substitute for, cover and proper sediment controls.

Question 35Erosion Control Principles and Practices

What is the primary purpose of a system of gradient terraces on a long cultivated slope?

  1. To raise the water table for crop use
  2. To shorten slope length and intercept runoff Correct answer.
  3. To increase the slope steepness for better drainage
  4. To carry sediment off site more efficiently

Explanation

Terraces divide a long slope into shorter segments and intercept runoff before it can concentrate, reducing rill and gully development and allowing sediment to deposit. Each terrace channel then conveys water to a stable outlet.

Question 36Erosion Control Principles and Practices

Which practice is specifically designed to convey concentrated runoff at a non-erosive velocity?

  1. Sediment trap
  2. Silt fence
  3. Grassed waterway Correct answer.
  4. Vegetative filter strip

Explanation

A grassed waterway is a shaped, vegetated channel sized to carry the design discharge; the dense grass lining resists shear stress and protects the channel from erosion. Filter strips treat sheet flow, while silt fences and sediment traps are sediment controls rather than conveyances.

Question 37Erosion Control Principles and Practices

Why is a geotextile filter typically placed beneath riprap on an erodible bank?

  1. To prevent soil from washing out through the stone Correct answer.
  2. To promote drainage of the embankment into the channel
  3. To anchor the riprap to the slope
  4. To increase the structural strength of the stone

Explanation

The filter passes water but retains soil, preventing fines from piping through the riprap voids, which would otherwise cause the stone layer to settle and fail. It does not add strength to the stone or hold it in place.

Question 38Erosion Control Principles and Practices

A sediment basin is fitted with a perforated riser. What do the size and number of the perforations primarily control?

  1. Drawdown time and fine-sediment settling Correct answer.
  2. The peak inflow rate the basin can accept
  3. The maximum depth of the permanent pool
  4. The rate at which coarse bedload is deposited

Explanation

Perforation area sets the release rate, which in turn sets how long water remains in the basin; a slow, controlled drawdown gives fine particles time to settle. Designers target a drawdown period long enough for settling but short enough to restore storage before the next storm.

Question 39Erosion Control Principles and Practices

Construction traffic compacts the soil across a site that will later be revegetated. Which effect most increases erosion risk?

  1. It increases the roughness of the soil surface
  2. It increases the organic matter content of the soil
  3. It reduces infiltration, so runoff increases Correct answer.
  4. It raises the infiltration capacity of the soil

Explanation

Compaction collapses soil structure and destroys macropores, so infiltration drops and a larger share of rainfall becomes surface runoff at higher velocity. The same dense layer also restricts root growth, making revegetation slower and leaving the surface exposed longer.

Question 40Erosion Control Principles and Practices

Fluvial erosion at the toe of a streambank typically leads to which subsequent failure mechanism?

  1. Accelerated growth of woody vegetation on the bank face
  2. Deposition of a stable point bar along that bank
  3. Undercutting and then mass failure of the upper bank Correct answer.
  4. Uniform lowering of the floodplain surface

Explanation

Toe scour removes the lateral support that holds the upper bank in place, so the bank eventually fails by sliding, slumping, or cantilever collapse even where the upper face is vegetated. Effective stabilization must protect the toe rather than treating only the visible upper bank.

Question 41Sediment Control Practices

What is the minimum depth that silt fence fabric must be embedded below the ground surface?

  1. 6 inches Correct answer.
  2. 12 inches
  3. 2 inches
  4. 18 inches

Explanation

Standard specifications require the fabric to be set in a trench at least 6 inches deep so that runoff cannot scour beneath the fence and undercut it. Deeper embedment is permitted in loose or rocky soils but is not the stated minimum.

Question 42Sediment Control Practices

Which temporary practice is a small impoundment with a controlled outlet, typically sized for drainage areas of about 5 acres or less?

  1. A silt fence
  2. A sediment trap Correct answer.
  3. A sediment basin
  4. A level spreader

Explanation

A sediment trap is a small temporary impoundment with a controlled outlet used where the contributing area is roughly 5 acres or less. Sediment basins serve larger drainage areas and have more elaborate outlet and dewatering structures.

Question 43Sediment Control Practices

Under most specifications, what is the minimum length of a stabilized construction entrance?

  1. 100 feet
  2. 25 feet
  3. 50 feet Correct answer.
  4. 12 feet

Explanation

A stabilized entrance is typically at least 50 feet long and 12 to 20 feet wide, filled with coarse aggregate over a geotextile so tires are cleaned before vehicles reach the public road.

Question 44Sediment Control Practices

Rock check dams in a drainage swale should be spaced so that:

  1. each dam is spaced at least 100 feet from the next one downstream
  2. every dam in the swale is built to exactly the same crest elevation above the channel bottom
  3. the toe of the upstream dam is level with the crest of the downstream dam Correct answer.
  4. dams are placed only on straight, uniform reaches of the swale

Explanation

Spacing is set so the crest of the downstream dam is at the same elevation as the toe of the upstream dam, which keeps the swale between structures wetted and prevents scour at the downstream toe. Dams are also kept low, generally 2 feet or less, with a low point at the center for the overflow.

Question 45Sediment Control Practices

When straw bale barriers are used as a temporary sediment control, the bales should be entrenched at least:

  1. 18 inches
  2. 1 inch
  3. 10 inches
  4. 4 inches Correct answer.

Explanation

Bales are keyed about 4 inches into the soil and staked so runoff cannot pass beneath or between them. Straw bales are a marginal practice that many programs discourage or prohibit because of frequent failure.

Question 46Sediment Control Practices

What is a key limitation of block-and-gravel protection at a drop inlet?

  1. It requires a permanent concrete riser to function.
  2. It works effectively only in heavy clay soils.
  3. It cannot be installed where the inlet is surrounded by pavement.
  4. It stores little sediment and can clog and cause flooding. Correct answer.

Explanation

Fabric-and-gravel or block-and-gravel inlet protection provides limited sediment storage, and once the fabric blinds off it ponds water and can flood the roadway. Frequent inspection and cleanout are therefore essential.

Question 47Sediment Control Practices

Silt fence installed to treat sheet flow should be placed:

  1. on the contour, roughly perpendicular to sheet flow Correct answer.
  2. parallel to the direction of the slope
  3. at the toe of the slope only
  4. along the property line no matter what the local grade is

Explanation

Silt fence works by ponding water behind a continuous barrier, so it is laid on the contour perpendicular to sheet flow and water is dropped out along its length. Running it up and down the slope channels flow along the fabric and concentrates it at low points.

Question 48Sediment Control Practices

A Type I floating turbidity curtain is intended for use in:

  1. fast-moving rivers
  2. calm, protected water bodies Correct answer.
  3. tidal inlets with reversing currents
  4. exposed open-water sites

Explanation

Floating turbidity curtains are classified by the water conditions they can withstand: Type I for calm, protected water, Type II for moderate currents, and Type III for moving water. They are not designed to act as a sediment barrier in flowing water.

Question 49Sediment Control Practices

What is the primary purpose of leaving an undisturbed vegetated buffer along a watercourse during construction?

  1. To filter runoff and stabilize the streambank Correct answer.
  2. To reduce the number of construction entrances needed
  3. To provide a haul route for construction equipment
  4. To increase the velocity of runoff leaving the site

Explanation

An undisturbed vegetated strip filters sheet flow, slows runoff and holds the bank in place, reducing the sediment that reaches the water. It supplements but does not replace structural sediment controls.

Question 50Sediment Control Practices

When polyacrylamide is used to flocculate sediment in a construction basin, the product selected should be:

  1. anionic, because cationic polymers are toxic to aquatic life Correct answer.
  2. of any charge, provided it is applied directly to the receiving stream
  3. nonionic, because molecular charge has no effect on settling
  4. cationic, because positively charged molecules bind clay most strongly

Explanation

Anionic polyacrylamide flocculates suspended clay at low dose and is far less harmful to fish than cationic polymers, which can be acutely toxic at low concentrations. Dose must be controlled to avoid residual polymer leaving the site.