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LARE Section 4 > Site Engineering > Flashcards

Site Engineering Flashcards

1
Q

Four Categories of Grading

A

Geomorphic
Architectonic
Sculptural
Naturalistic

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2
Q

Perception of Slope

A

Influenced by texture of the surface material and relationship to surrounding grades

Coarser texture - less noticeable the slope
Slopes of 2% or greater on pavements can be easily perceived
Horizontal reference lines increase awareness of slopes

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3
Q

Being at a higher elevation

A

Provide a feeling of expansiveness by extending views and overall field of vision
Provide sense of superiority, feeling of control of dominance of place
Provide opportunity to contrast or exaggerate steepness or flatness of surrounding landscape

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4
Q

Concave

A

Appears more graceful from the downhill side, exhibits uplifting quality

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5
Q

Convex

A

From uphill side, sense of height is accentuated
Sense of distance appears compressed since middle ground is foreshortened

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6
Q

Grading enclosure

A

Containment, protection, privacy, screening, seclusion, intimacy, terminates site lines, eliminates undesirable views

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7
Q

Caution with enclosure

A

Inadvertently promote careless recreational uses
Reduces visibility into the area, creating a potentially unsafe condition

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8
Q

Properly designed and placed landforms excellent outlet for creative play

A
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9
Q

Berms

A

Vegetated or paved embankments, somewhat dike-like in appearance, commonly used for enclosure and separation purposes

Must be carefully evaluated since many cases the scale and proportion have been insignificant or inappropriate with regard to surrounding context

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10
Q

Channeling

A

Landform may be used to direct, funnel, or channel auto and pedestrian circulation

May be used to direct and control viewing angles and vistas as well as wind and cold air drainage

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11
Q

Functions of landform and grade changes are reinforced and strengthened by

A

The use of plantings and structural elements

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12
Q

Properly placed landforms can control drifting snow and significantly reduce the impact of wind on structures and even over large areas such as playfields and parking lots

A
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13
Q

Microclimate Modification

A

Topography can be used to channel or deflect winds, capture solar radiation, and create coke or warm pockets

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14
Q

Recommended minimum distance between wood frame and exterior grade to reduce moisture problems

A

8 in.

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15
Q

Minimum stair width

A

3 ft

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16
Q

Minimum stair width to allow two people to pass comfortably

A

4 ft

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17
Q

Two risers plus one tread

A

24-26 inches

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18
Q

Common stair ratios

A

6 in riser with 12 in tread
5 in riser with 15 in tread

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19
Q

Min and Max risers

A

Minimum 3 risers
Maximum 10-12 risers

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20
Q

Stair treads pitch downhill %

A

1%

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21
Q

Handrails required at slopes

A

20:1 or 5%

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22
Q

Total ramp length before landing

A

30 ft

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23
Q

Maximum rise for ramps

A

12:1 and 16:1 must not exceed 30in and landing 30 ft
16:1 to 20:1 cannot exceed 30 in and landing 40 ft

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24
Q

Maximum rank cross pitch

A

Not exceed 50:1

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25
Q

Percentage of slope between risers important because

A

In uphilll direction the slope shortens a persons stride

In downhill the slope lengthens the stride

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26
Q

Erosion and Sedimentation Process

A

Detachment, transportation, and deposition of soil particles by the action of water, ice, wind, and gravity. Rainfall impact, flowing water, freezing and thawing, and wind dislodge soil particles, and the movement of water and wind transports them to a new location.

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27
Q

Rate of Erosion at Construction Sites

A

5x agricultural land
10x pastureland
250x forestland

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28
Q

Largest non-point water pollutant

A

Sediment, by volume

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29
Q

Examples of problems created by excessive erosion

A

Filling of lakes, ponds, and wetlands
Decreased channel capacity in streams and rivers
Degraded animal and plant habitats
Increase potable water treatment costs

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30
Q

Passage of Clean Water Act

A

all states are responsible for implementing a storm water permitting program that regulates the discharge of runoff from most construction sites

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31
Q

Who is responsible for developing an erosion and sediment control plan that complies with all regulatory requirements

A

site planner

32
Q

Four primary factors that determine the potential for erosion

A

Soil Type
Vegetative cover
Topography
Climate

33
Q

Erodibility of a soil is determined by:

A

particle size and gradation
soil structure
permeability
organic content

34
Q

Soils with high erodibility potential

A

Soils with a high content of silt and fine sand

35
Q

Soils with low erodibility potential

A

Soils with increased clay and organic content
Once in suspension clay does not settle otu easily

36
Q

Lowest erosion potential

A

Well-drained, well-sorted gravels and gravel-sand mixtures that are highly permeable and easily infiltrated
Organic content enhances the permeability and water absorption characteristics of a soil, thus decreasing erodibility

37
Q

Most Widely Known Models for estimating erosion rates and evaluating various erosion and sedimentation management practices

A

Universal Soil Loss Equation (USLE)
Revised Universal Soil Loss Equation (RUSLE)

38
Q

Ways vegetation prevents soil erosion

A
  1. Shields soil from raindrop impact. This dissipates energy that would otherwise dislodge soil particles.
  2. Slows runoff velocity through increased surface friction.
  3. Plant root systems hold soil in place while increasing its water absorption capacity.
39
Q

Vegetation Goals of Site Development Projects

A

Retain as much existing vegetation as possible, particularly in vulnerable areas such as steep slopes, stream banks, drainageways, and areas with poor soils.

40
Q

Topography Impact on erosion

A

Length and steepness of slopes influence the amount and rate of storm water runoff.
As extent and gradient of slope increase, amount, rate, and velocity of runoff increase, thereby increasing potential for erosion

41
Q

To reduce erosion caused by topographic conditions:

A
  1. avoid developing steep slopes
  2. Limit the length and gradient of proposed slopes
  3. protect disturbed slopes as quickly as possible
    Slope orientation may influence the ability to reestablish a protective vegetative cover.
42
Q

Climate Impact on Erosion

A

The frequency, intensity, and duration of rainstorms will directly influence the amount of runoff generated on a particular site

43
Q

Ways to alleviate climate impact

A

Site construction should be scheduled during months in which low precipitation and low runoff are anticipated
Scheduling construction to coincide with optimum seeding periods for a particular region can also promote the establishment of a cover crop for soil stabilization.

44
Q

Goal of erosion and sediment control plan

A

to reduce the detachment and transport of soil

45
Q

Principles of erosion and sediment control

A
  • minimizing disturbance
  • controlling runoff
  • collecting sediment
  • monitoring construction
46
Q

Minimum disturbance can be achieved through five basic principles:

A
  1. Work with existing topography
  2. Restrict the areas of disturbance
  3. Develop compactly
  4. Manage site construction
  5. Preserve existing vegetation
47
Q

Ways to reduce runoff velocities

A

Low gradients, short slopes, and the preservation of existing vegetation, coupled with stabilization techniques such as sodding, seeding, or mulching.
Runoff must be directed and routed to sediment control devices (such as traps, interceptors, and silt fences) if these measures are to be effective.
Where long stretches of steep slopes do exist, they should be altered at regular intervals when possible to intercept runoff and divert the runoff longitudinally along the face of the slope.

48
Q

Where erosion is unavoidable, sediment should be …

A

collected on-site through sediment traps and basins, inlet protections, silt fences, and similar devices.
Stabilized construction site access points should be located to reduce the tracking of soil from construction equipment tires onto adjacent streets or other paved surfaces.

49
Q

If control measures are to function at optimum levels, …

A

a routine maintenance schedule is essential during construction to avoid silt fence or hay bale blowouts and sediment traps that have become filled.
Poor monitoring and maintenance are often the cause of the failure of these measures.

50
Q

Developing an erosion and sediment control plan

A
  • identify critical or sensitive areas like highly erodible soils, steeply sloped topography, steam corridors, and wetlands. Avoid disturbance by siting structures or improvement in less critical locations.
51
Q

Two basic strategies for development of erosion and sediment control plan.

A
  1. Focus primarily on erosion control to keep the soil in place.
  2. Seeks to minimize the off-site transport of sediment.
    Both are effective at reducing non-point-source pollution, but most effective is to incorporate both erosion control and sediment control features.
52
Q

Control of erosion during land development is achieved by

A

controlling or managing runoff

53
Q

To develop an effective plan to control runoff, a site designer should

A
  1. review the existing runoff patterns on the undeveloped site.
  2. Determine what the runoff patterns will be once development is completed
  3. Determine how to manage runoff as the site changes from the existing to the developed condition.
54
Q

Construction sequencing is critical to a comprehensive soil erosion and sediment control plan

A

that outlines the timing and order of construction operations

55
Q

Erosion control measures

A
  • Runoff control measures
  • Soil stabilization practices
    measures may be temporary or permanent.
    Various practices can be used alone or in combination.
    Biotechnical measures may incorporate both structural and vegetative elements, typically using woody vegetation.
56
Q

Soil Stabilization Control Measure

A
  • Vegetative Soil Cover
  • Non-vegetative soil cover
  • Diversions
57
Q

Runoff Control
Control Measure

A
  • Diversions
  • Waterways
  • Outlet stabilization
  • Slope Protection
58
Q

Sediment Control
Control Measure

A
  • Sediment basins
  • Sediment filters and barriers
  • Mud and dust control
59
Q

Intention of Runoff Control Measures

A

To intercept or control storm water runoff before it can concentrate or before it has reached sufficient volume or velocity to cause damage

60
Q

Specific Runoff Control Measures

A
  • Diversion
  • Waterway Stabilization
  • Slope protection structures
  • Grade control structures
  • Outlet protection
61
Q

Diversions

A

Channels that intercept and redirect the flow of surface runoff.
- Typically sited above disturbed locations to divert clean water or within disturbed areas to break up sheet flow concentration before gullies can form.
- Runoff is direct to suitable outlets such as existing well-vegetated areas for low discharges or to stable channels for larger flows.

62
Q

Waterways

A

Natural or constructed channels that provide for the safe disposal of excess water.
- They may be stabilized vegetatively or with an erosion-resistant lining such as riprap, modular concrete paving units, or other suitable material. Biotechnical techniques may also be used.

63
Q

Slope Protection Structures

A

Convey concentrated runoff down steep slopes.
- Typically consist of pipes or chutes.
- Because of high velocities, chutes are usually lined with riprap or concrete.

64
Q

Grade Control Structures

A

Consist of chutes, weirs, or pipe drop spillways installed to prevent the advance of gullies or to reduce the grade in a natural or artificial channel.
- The slope of a steep channel may be reduced, and thus flow velocity reduced, by a series of low drop structures.

65
Q

Outlet Protection

A

Provided at the end of a pipe or paved channel to allow for energy dissipation and to create a stable transition to a receiving channel.
- Aprons, roughened surfaces, or shallow pools line with riprap or precast concrete modular units are commonly used.

66
Q

Stabilization measures protect the soil surface against

A

particle detachment caused by raindrop impact and from sheet or rill erosion associated with dispersed flow.
(Concentrated flow must be diverted and managed by other means)

67
Q

Vegetative Measures that provide soil stabilization

A
  • Maintaining and protecting as much of the existing vegetation as possible
  • Retaining existing topsoil for reuse
  • Establishing new vegetative cover, such as seeding on disturbed areas as quickly as possible
  • selecting plants and a planting design scheme that are appropriate for the site and will promote long-term stability
68
Q

Nonvegetative stabilization measures

A
  • employ materials such as organic and inorganic mulches, gravel, crushed stone, and geotextiles (meshes, nets, and mats)
  • Synthetic or organic binders or adhesives may be applied to the soil surface to enhance resistance to erosion by sheet flow or wind.
69
Q

Soil Bioengineering

A

The use of live, woody, and herbaceous plants to stabilize or protect steam banks, shorelines, drainageways, and upland slopes.
It combines biological and ecological concepts with engineering principles to prevent or minimize slope failure or erosion.

70
Q

Soil bioengineering
materials and techniques

A

Vegetation may be used alone or in combination with structural elements, such as rock, wood, concrete, or geotextiles.
Techniques include the use of live woody plant cuttings to provide soil reinforcement, as well as conventional plantings of grasses, forbs, and shrubs to prevent surface erosion.
Stems or branch parts of living plants can be used as the initial and primary materials for reinforcing and stabilizing soil.
As roots and foliage develop, the vegetation becomes a major structural component of the bioengineering system.
Techniques include planting, burying, staking, or driving vegetation into the ground. Live staking and the use of live fascines and brushlayers are examples of such techniques.

71
Q

Live Staking

A

An appropriate technique for the repair of small earth slumps that are frequently wet
- involves the insertion and tamping of live, rootable cuttings into the ground
- as the stakes root, they create a stabilizing mat that reinforces the soil. Excess soil moisture is extracted through water uptake and transpiration.

72
Q

Live Fascines

A
  • long bundles of branch cuttings bound together into sausage-like structures with the branches and bud ends oriented in the same direction.
  • bundles are capable of propagation.
  • use of live fascines is an effective technique for stabilizing slopes by reducing erosion and face sliding.
  • are placed in shallow trenches parallel to contours for wet slopes, and are anchored with live and dead stakes.
73
Q

Brushlayering

A
  • similar to the live fascine system, except that the brushlayers are oriented primarily perpendicular to the slope.
  • this orientation is more effective in terms of earth reinforcement and mass stability.
  • consists of placing live branch cuttings, usually in a crisscross fashion, on small benches excavated into the slope and then covering them with soil .
74
Q

Branch Packing

A
  • constructed and function similar to brushlayering, except with the addition of vertical live staking to improve initial structural stability.
  • used specifically for repairing small localized slumps or holes
75
Q

Live Cribwall

A
  • box-like structures fabricated with untreated timbers and filled with layers of live branch cuttings and soil or other appropriate backfill material.
  • this type of structure is employed in place of low walls at the bottom of cut or fill slopes to stabilize the toe of the slope and reduce its overall steepness, providing immediate protection from erosion and sliding.
  • branch cutting should be installed to extend into the slope.
  • Rooting and establishment of the vegetation will take over the structural functions of the timbers over time.
  • this technique can also be used with rock gabion and rock walls
76
Q

Fiber Rolls

A
  • prefabricated tubes consisting of biodegradable materials such as rice straw, wheat straw, coconut fiber, and wood excelsior bound together by netting.
  • tubes are typically 8 to 12 in. in dia.
  • used at the toe, top, and face of slope to intercept and slow runoff, remove sediment, and release runoff as sheet flow.
  • should be trenched and staked to operate effectively
  • can also be used to control erosion along streams, pond, and lakes.
  • can be planted with vegetation that will take over the role of the fiber roll as it degrades

LARE Section 4 (6 decks)

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