Specialty Plans

Question 1

Erosion Control - Biotechnical Measures

Answer 1

Live staking, Live fascines, Brush layering, Branch packing, Live cribwall, fiber rolls, and log terraces are all ways to create natural barriers to slow or redirect the flow of water down a steep slope. They all involve planting roots that will grow into shrubs, or in the case of log terraces, placing logs in a manor to divert or even retain pockets of water. All of this is done to reduce erosion on a site.

Question 2

Emergency Access Plan

Answer 2

An Emergency Access Plan would typically show EVA (Emergency Vehicle Access) routes. Or potentially paths out of a building or to a safe spot on or adjacent to the site.

Question 3

Emergency Access Plan - Knox Box

Answer 3

A Knox Box - also known as a Fire Access Box - is a type of metal box that allows police, fire fighters and other emergency personnel access via a PIN or common key. Keys or other entry devices are kept inside the box and allow emergency personnel access to private properties, locked gates, etc. A Knox Box does not require electrical power, data/phone lines or any other infrastructure and is thus well-suited for use in a remote, rural location. NOTE: This would be used for Emergency Vehicle Access (EVA) and shown on an Emergency Access Plan.

Question 4

Irrigation - 2 wire vs Conventional Wire

Answer 4

Two-wire systems have lots of advantages, the main one being technology. Two-wire technology allows for features not available with a system that just sends a signal down a wire. The most obvious benefit of 2-wire technology is the ability to operate hundreds of sprinklers at the same time anywhere you want. Most conventional systems are limited to a maximum of 16 solenoids at the same time per controller. Two-wire systems also have the ability to do a great deal of self-troubleshooting that is extremely accurate, pinpointing very closely the location of a problem. This is accomplished by monitoring voltage and, in the case of some manufacturers, amperage at each sprinkler/module. However, the 2-wire technology’s biggest advantage is that it continues to evolve allowing the manufacturer to add additional features to your system in the future. This is not possible with a conventional signal type control system. Of course, there are also disadvantages to the 2-wire system. For example, if you damage the communication cable, then the system is not operational downstream of the damage. Also, if you lose the computer, then you cannot operate. And 2-wire systems are very sensitive to lightning and power issues. Conventional systems have much more redundancy as there are field controllers/satellites which you can operate from if you lose the computer or communication signal.

Question 5

Irrigation - Flow Sensor

Answer 5

Installed at the beginning of an irrigation system, after the backflow and master valve. It is used to detect the movement of water in the irrigation mainline when the system is off (i.e. to detect leaks in the mainline).

Question 6

Landscape Lighting

Answer 6

Landscape lighting should always facilitate safety and this is best accomplished by improving the legibility of a space and through establishing a uniform layout of lighting fixtures. Consistent and thoughtful placement of lighting fixtures provides users with a safe means to negotiate a space in the evening and early morning hours. While attractive, uplighting should be minimized whenever possible given that it results in light pollution.

Question 7

landscape Lighting - Transformers

Answer 7

The purpose of a transformer is to convert 120V standard “line voltage” to 12V low-voltage electricity. Generally speaking, landscape contractors are legally allowed to install 12V electrical systems, but require additional training to work with 120V electrical systems.

Question 8

“Live Staking” (Part of Bioengineering)

Answer 8

Through techniques such as live staking, plant material can be used to restore eroded stream banks and stabilize soils. This process is often referred to as bioengineering, and is a cost-effective and low-impact way of reducing sediment deposition and erosion in waterways.

Question 9

Pumping Water Uphill

Answer 9

elevation change = PSI * 2.31 (which is a constant number… just use it). So if we want to see what an elevation change is between a lake and top of hill, we can fill a hose with water and put a PSI gauge at the bottom of the hill. Say it reads 40 PSI, then 40 * 2.31 = 92.4 feet of elevation change. That is NOT the length of the pipe, just the elevation of the top of lake and elevation of top of hill. Note that if we want to instead find the PSI, you could arrange the equation to read PSI = elevation/2.31.

Question 10

Phasing Strategy for Landscape Design

Answer 10

Phasing in this case is talking about preparing for the project by taking into consideration factors like large amount of plants needed, use of special equipment that will need to be rented, installing sleeving long before a Landscape Contractor is needed on the site, etc. Example of factors that would be considered in a Phasing Strategy: Staging areas would ideally be placed in an area that is accessible throughout all phases of construction or, if the staging area needs to move according to project phases, additional locations would need to be identified prior to construction. Plant species and quantities should be taken into consideration, as specifying unusually large amounts of a single species of plant or selecting rare or uncommon plants may require advance preparation and coordination with the contractor and/or nursery. The presence (or lack thereof) of a two-wire irrigation system should be taken into account, as it is generally easier to add additional valves to a two-wire system than it is to a conventionally wired irrigation system. Crane access would also need to be taken into account if any proposed site elements (ex. large trees or sculptures) would need to be placed in areas that might become inaccessible to construction equipment or the crane itself during later phases of construction. Finally, sleeving for both electrical and irrigation lines would need to be considered, as proposed site elements from future phases of construction may require the installation of sleeving in earlier phases (ex. installing electrical sleeving under concrete in phase I to provide power to a future lighting fixture in phase II).

Question 11

Roads - Vertical Roadway Alignment (Vertical Curves)

Answer 11

Vertical curves are used to ease the transition whenever there is a vertical change in direction (slope). Such transitions eliminate awkward bumps along the vehicular path, allow for proper sight distances, and prevent scraping of cars and trucks on the pavement at steep service drives and driveway entrances. In the graphic to the right, the basic points for the Vertical Curve Formula are shown. Point “A” is the Point of Vertical Curve (PVC) and can also be known as Beginning of Vertical Curve (BVC). The Point of Vertical Intersection (PVI) is the point in the middle. And the Point of Vertical Tangency (PVT) is at the end, and this point can also be the “End of Vertical Curve” (EVC). In the other example image (above right) the point B would be referred to the “Center of Curve”. Think of it like the center point of the circle in CAD, or center of an Arc.

Question 12

Roads - Cross Section

Answer 12

A typical cross section through a road will be a graph with the elevation on the left side, and the station points along the bottom. The elevation will go from low to high (bottom to top) as you would expect, and the Station Points will typically be low to high from left to right. Then there will be a center line shown on the graph to show how the road slopes along the lengh. If the line is going down, then the slope will be shown as a negative, if the line is going up then the slope will be shown as a positive. Example to right.

Question 13

Roads - Crown

Answer 13

The slope from the center of a street to the outside edge of the roadway is referred to as a “crown”.

Question 14

Storm Drainage System (3 Basic Functions)

Answer 14

A storm drainage system is designed to 1. collect, 2. conduct, and 3. dispose of storm runoff.

Question 15

Storm Runoff Rates and Volumes (Rational Method)

Answer 15

A frequently used formula for computing the peak rate of runoff from small drainage areas (less than 200 acres) is the equation q = CiA where q: peak runoff rate in cubic feet per second (answer is in the form of cubic ft/sec); C: dimensionless coefficient (between 0 (completely pervious surface with 0 runoff) and 1 (completely impervious and wetted surface with total runoff) and usually based on a given chart); i: rainfall intensity, inches per hour (iph) for the design storm frequency and for the time of concentration of the drainage area; A: area of drainage area, usually in acres (SEE CHAP 12 in Site Eng for LAs for examples)

Question 16

Storm Runoff - Time of Concentration

Answer 16

Time of concentration is defined as the time it takes water to flow from the most distant point in a watershed to its outlet.

Question 17

Stormwater Best Management Practices (BMP)

Answer 17

Measures that have been developed to control, store, and/or treat stormwater runoff from developed areas for the purpose of reducing flooding and removing pollutants while maintaining or enhancing environmental quality. The GOAL is to control non-point-source pollution while providing effective storm water management. They include methods such as infiltrating stormwater, thereby mimicking the natural hydrological regimen and recharging groundwater. They will also aim to reduce stormwater velocity and volume (surface roughening, temporary sod, ‘logs’ of straw staked at the perimeter of a work area, etc.), as doing so improves water quality and reduces the potential for erosion during storm events. While they may use cistern structures and other rainwater harvesting devices to store water, BMPs generally do not deal with the long-term storage of stormwater, and they certainly would NOT channelize stormwater flows, as channelization results in high water velocities that lead to erosion (the exact opposite of BMPs). This is a concept that advocates for sustainable design and the implementation of “green” infrastructure. BMP’s also address issues of irrigation, plant selection and maintenance, among other things, with the goal of reducing resource use and protecting overall ecosystem health.

Question 18

Stormwater - BMPs General Thoughts

Answer 18

BMPs are sustainable design initiatives aimed at reducing resource use and protecting overall ecosystem health. They address the design of stormwater management systems, planting design and selection, irrigation and site maintenance, etc. So things like “Amending nutrient-poor soils with composted organic material” would be a part of BMP’s, while “Incorporating a backflow in an irrigation system” would not be since it is a health and safety device and not something that protects ecosystem health.

Question 19

Stormwater - Forebay for a constructed stormwater wetland (aka sediment basin)

Answer 19

A forebay is often located upstream of a constructed stormwater wetland or other infiltration device to intercept and reduce the velocity of flows entering the wetland and to settle sediments and other solids that may be present in the water. Doing so helps the water quality within the wetland structure and improves its efficiency and operational lifespan. Technically a retention basin can also function as a sediment basin, though a sediment basin is not normally a retention basin. Due to the build up of sediment, they require periodic cleaning to remove sediment.

Question 20

Stormwater - Wet Ponds

Answer 20

Wet Ponds (or Retention Basins) are basins that contain a permanent pool of water. This control measure can serve multiple purposes including storm water management, pollutant removal, habitat improvement, and aesthetic enhancement. Potential benefits derived from wet ponds may include increased property values, recreational opportunities, and the creation of wildlife habitat. The configuration and edge treatment of retention ponds may be designed to appear refined, naturalized, or wild. Treatment and habitat value can be improved in stormwater wet ponds through the use of topographical variations and organic geometries. Both of these design gestures create variations in the wet pond’s conditions that promote greater biodiversity and increase the treatment time of stormwater. Note that wet ponds generally benefit from increasing flow length and should be designed to be anywhere from 4-8’ deep. Possible disadvantages include safety problems, algae bloom, offensive odors, mosquitoes, or the need for maintenance and sediment removal.

Question 21

Stormwater - Reducing Peak Flows

Answer 21

The reduction of peak stormwater flows during storm events carries with it numerous benefits, including – but not limited to – limiting soil erosion, minimizing channel widening and the frequency of severe floods, and protecting against downstream scouring and stream siltation that reduce the health of riparian ecosystems. Reducing peak flows does not directly mitigate against land subsidence (gradual settling or sudden sinking of the earth’s surface due to below grade issues); this is usually achieved through groundwater recharge and stormwater infiltration.

Question 22

Stormwater - Level Spreader

Answer 22

A level spreader is an erosion control device designed to reduce water pollution by mitigating the impact of high-velocity stormwater surface runoff. It is used both on construction sites and for permanent applications such as drainage for roads and highways. The device reduces the energy level in high-velocity flow by converting it into sheet flow, and disperses the discharged water so that it may be infiltrated into soil. It can help minimize erosion and maximize filtration by adjacent vegetated surfaces (since the flow is wide spread and slowed down).

Question 23

Stormwater - Swale

Answer 23

A swale is a constructed or natural drainage channel that has a vegetated surface (usually grass). A gutter is a paved swale. The depth of swales (but not necessarily of gutters) is usually measured as the difference in elevation between the centerline and a point at the edge of the swale on a line taken perpendicular to the centerline. Since swales are depressions similar in form to valleys, the contour signatures are also similar. Swales are commonly used to intercept, direct, and control storm runoff.

Question 24

Stormwater - Sediment Traps

Answer 24

To be most effective, sediment traps should always be located at the point of discharge, as doing so allows this water quality device to treat runoff before it disperses over a greater area and potentially gains greater flow velocity.

Question 25

Stormwater - Design Standards for Drainage Channels and Swales

Answer 25

Drainage channels and swales should generally be designed to accommodate a 10-year design storm. Note that they will often be designed to handle 2-year design storms without experiencing erosion.

Question 26

Stormwater - Invert Elevation

Answer 26

Invert elevation is the elevation of the bottom of the pipe opening in a drainage structure. The invert elevation of the outlet pipe must be equal to or lower than the invert elevation of the inlet pipe. One technique used to ensure this relationship is to match top of pipe elevations. The invert elevation of a pipe is measured at the bottom of the inside/interior of the pipe and is measured from the surface (finished grade) of the ground. For example, the top of a 0’-6” diameter pipe with an invert elevation of 3’-0” would be located 2’-6” below the landscape finished grade.

Question 27

Stormwater - Silt Fence

Answer 27

Silt fences are typically laid out along the contour of a slope to maintain water quality during construction activities. Silt fences are generally composed of a fine plastic mesh that retains and filters sediments from stormwater while also allowing water to pass through the plastic membrane. They are best suited to treat sheet flow.

Question 28

Stormwater - Water Quality

Answer 28

Infiltration basins, silt fences and water quality basins are all commonly employed means to improve or maintain water quality during or after construction activities.

Question 29

Stormwater - Detention Facilities

Answer 29

Detention facilities are used to hold runoff during storm events and release the storm water after a period of time - usually once the peak storm flow has passed. In this sense then, detention facilities are best used to reduce downstream flooding and erosion. They are either structured or landform impoundments made for the purpose of reducing peak flow and controlling the rate of flow. Surface techniques use ponds, basins, and paved areas, while subsurface techniques use dry wells, porous fill, oversized drainage structures, and cisterns or tanks. Subsurface techniques may be costly, but they reduce land consumption and may be appropriate on very tight sites where space for surface techniques is not available. Detention systems can be designed to add a retention function, where water is stored for various purposes.

Question 30

Stormwater - Detention Basin (aka dry basin)

Answer 30

They are used as a means of controlling peak discharge rates through the temporary storage of storm runoff. Outflow rates are set at or below predevelopment rates, and flow is metered out of the basin until no water remains. Detention basins may work effectively in reducing downstream flooding and stream bank erosion, depending on the quantity of storm water detained and release rates, but they may not be very effective in enhancing storm water quality. Note: 1. The length-to-width ratio is not as critical for a detention basin as for a wet pond, but an elongated form is still preferred. Flow length between inlet and outlet should be maximized, and short-circuiting of flow should be prevented. 2. The side slopes of the basin should not be steeper than 3:1 (H:V). Less-steep side slopes are preferred, although more area will be required for the basin. The floor of the basin should have a 2 percent minimum slope toward the outlet to ensure positive drainage. An access way at least 10 ft. wide with a slope of 5:1 or less should be provided for maintenance equipment. 3. A low-flow channel should be provided to reduce drying time and improve usability.

Question 31

Stormwater - Detention Basin Combos

Answer 31

Uses can be combined in some cases to work as both 1 use plus as a Detention Basin. For example, parking lot detention areas may be an inexpensive way to control runoff, reduce storm sewer pipe sizes, and reduce erosion. Collecting runoff in a parking lot may cause inconvenience to traffic and pedestrians, but if the collection area is properly located, such conflicts can be minimized. These type of combinations are best used on small sites with little area available for detention or retention basins.

Question 32

Stormwater - Water Quality Basin

Answer 32

Detention ponds that extend temporary storage time, referred to as water quality basins, allow for more effective removal of particulate pollutants and provide a technique for improving water quality. In retention (wet) basins, additional volume is provided for the settling out of sediments. Detention (dry) basins may have a small orifice at the bottom of the outlet structure so that runoff from frequent storms, which tends to flush contaminants into the pond, is retained for a prolonged period. The extended detention period resulting from the small orifice allows the contaminants to settle out and the pond to drain gradually.

Question 33

Stormwater - Vegetated Detention Basin

Answer 33

A vegetated detention basin used vegetation to slow flow through the basin. This enhances infiltration and removes water through plant uptake and transpiration.

Question 34

Stormwater - Filter Strip

Answer 34

A device that is typically placed on slopes adjacent to impervious surfaces to intercept overland sheet flow. They can lower runoff velocities, increase the time of concentration, improve infiltration, and contribute to groundwater recharge.

Question 35

Stormwater - Infiltration Systems

Answer 35

Infiltration techniques can significantly reduce or eliminate surface runoff while at the same time replenishing groundwater, which supplies wetlands, streams, and wells. Other benefits include reduced downstream peak flows, reduced soil settlement caused by depletion of groundwater, preservation of existing vegetation, and lower development costs based on a reduced size of the storm sewer system. However, infiltration practices should not be used to remove sediment or other particulates, since sedimentation will eventually clog the infiltration device and render it useless. Sediment should be removed by the use of filter strips or sediment traps before it enters an infiltration device. Limitations to the use of infiltration facilities include soil permeability rates, potential reduction in permeability rates over time, and the potential for groundwater contamination. Conditions that must be examined to determine the appropriateness of infiltration facilities include depth to groundwater, seasonal variation in groundwater levels, slope and direction of groundwater flow, soil permeability, vegetative cover, and quality of storm water runoff. Infiltration facilities may be classified as either surface systems, such as basins; subsurface systems, such as trenches; or porous pavement systems.

Question 36

Stormwater - Infiltration Basins

Answer 36

An infiltration basin is a surface impoundment created by damming or excavating. The purpose of the basin is to store runoff for a selected design storm or specific volume temporarily so that the water will enter the soil over a given time period. These basins, in terms of performance and appearance, are very similar to detention basins, and, in fact, basins are often designed to combine infiltration and detention functions. In addition to the limitations of Infiltration Systems, infiltration basins may require large areas, are not adaptable to multiple uses, and have high rates of failure due to improper maintenance and installation. In recent years, infiltration basins that have been designed as a depression in the landscape, as opposed to requiring an embankment for containment, have become more commonly known by the name rain gardens.

Question 37

Stormwater - Infiltration Trench ( aka Recharge Trench)

Answer 37

A space for water to infiltrate the soil and replenish the groundwater. These can be used in tandem with filter strips. Generally speaking, water would sheet flow off of an adjacent surface, flow through the filter strip for treatment and then enter the recharge trench for infiltration. More specifically, an infiltration trench is an excavation backfilled with coarse aggregate stone. The voids between the aggregate materials provide the volume for temporary storage of storm runoff. Runoff stored in the trench gradually infiltrates the surrounding soil. The surface of the trench may be covered with grass having a surface inlet, or with porous material, such as sand, gravel, or stone. Infiltration trenches are appropriate for relatively small drainage areas. They are flexible systems that can easily be fit into underutilized or marginal areas of a site, and where soil and groundwater conditions allow, they can be easily adapted to retrofitting an existing developed site. An observation well, such as a perforated polyvinyl chloride (PVC) pipe placed vertically in the trench, should be installed to monitor any change in infiltration rate on a periodic basis.

Question 38

Stormwater - Dry Well

Answer 38

Dry wells are similar to infiltration trenches with the main difference is that the volume of aggregate and water storage is oriented vertically, projecting more deeply underground. Prefabricated storage systems are beginning to replace both infiltration trenches and dry wells in use. These prefabricated systems function similarly in that they are buried underground and used for infiltration. The main benefit is that a larger volume of water can be stored in a smaller footprint, because the storage chamber is designed to support a loading of earth or other materials above without being filled with aggregate.

Question 39

Stormwater - Porous Pavement

Answer 39

The objective of porous pavements is to increase perviousness while still providing a stable, protective surface. There are several types of porous pavement, including porous asphalt, open-gridded modular pavement, reinforced sand and gravel paving, and pervious concrete. Porous pavements are appropriate for such uses as low-volume roads, driveways, parking lots, bikeways, and emergency lanes. They can even be combined with subsurface storage facilities for use on densely developed sites. Porous pavements should be used only where the subgrade soil conditions provide the proper permeability, depth to groundwater does not pose a problem, or contamination will not occur from degraded storm water quality. Advantages include generally higher recharge rates than natural conditions due to less vegetative uptake, control of both the rate and volume of runoff, reduced potential for swale and channel erosion, preservation of existing vegetation by maintaining proper soil moisture levels, reduced surface puddling, enhanced pollutant removal, and reduced construction costs through decreased infrastructure, such as curbs, drains, and pipes. A major concern is limited experience installers as a high level of workmanship is required in preparing the subgrade, placing the base course, and installing the paving material if the system is to perform at the desired level. Also there is the potential for clogging if the pavement is improperly maintained or installed. Other disadvantages include the potential for groundwater contamination (oil from cars, etc.), weakening of the subgrade in saturated conditions, and the development of anaerobic conditions in areas where there are frequent storms. Also, in cold climates, sand and deicing salts cannot be used on porous pavements.

Question 40

Stormwater - Blue Roof (Rooftop Detention)

Answer 40

Low-slope roof surfaces can be utilized for detention of storm water. A flow control device (a vertical pipe or weir) that fits over the roof drain with sized openings cut into the sides to provide the rate of release of storm water. It may also have a 2nd drain for redundancy should one get clogged, and will involve a waterproof membrane on the roof, and scuppers or overflow drains to set the maximum depth of water detention. Water is typically ponded to a depth of no greater than 4 inches.

Question 41

Stormwater - Safety

Answer 41

Measures should be taken to reduce safety hazards that may be created by retention and detention ponds located in populated areas. Safety issues are related to access, large volumes of flowing water, constrictions created by pipes and culverts, and the intermittent nature of stormwater storage. Safety measures may include installing fencing, avoiding steep side slopes or sudden drops, minimizing constriction points, and covering outlets with properly designed grates. Of course they must meet all federal, state, and local regulations, including state dam safety regulations where appropriate.

Question 42

Stormwater - Hydrologic Soil Groups (HSG)

Answer 42

Soils are classified by the Natural Resource Conservation Service into four Hydrologic Soil Groups based on the soil’s runoff potential. The four Hydrologic Soils Groups are A, B, C and D. Where A’s generally have the smallest runoff potential and D’s the greatest. A is a sandy soil with high infiltration so low runoff, while D is a clay soil with almost no infiltration so very high runoff.

Question 43

Stormwater - wetted perimeter of a pipe

Answer 43

Wetted perimeter of a circular pipe is equal to the Circumference or 2πr for a pipe flowing full.

Question 44

Stormwater - Sustainable Management

Answer 44

One of the keys to successful and sustainable stormwater management is increasing the amount of time that stormwater is within the so-called “treatment train”. Doing so reduces peak flows and can aid in the reduction of downstream flooding and improve public safety during storm events. Well-designed stormwater facilities and treatment devices can enhance recreational opportunities for a community, while also providing wildlife habitat. Given that sustainable stormwater management practices mimic natural hydrological flows, these techniques result in a more consistent and ecologically beneficial level of soil moisture. The naturalistic aesthetic and function of these resources also results in lower site maintenance costs (ex. less mowing, reduced “hard” infrastructure to maintain, etc).

Question 45

Stormwater - Sediment

Answer 45

Of all the factors that affect water quality in numerous ways and have the potential to introduce contaminants into aquatic ecosystems, sediments are considered the single greatest source of pollution to waterways in the US. Though agricultural activity produces large quantity of sediment pollution and nutrient runoff, it is considered less of a factor compared to the general term ‘sediment’ since construction and other such activities add to sediment runoff, making it a bigger problem.

Question 46

Stormwater - Hooded Riser

Answer 46

Hooded risers are used in wet ponds to control the discharge of water from the treatment facility. The riser itself is protected by wire mesh and a hood, which prevents floatable debris from clogging the outlet. Note that the height of the riser typically corresponds to the maximum storage depth of the wet pond or retention basin.

Question 47

Traffic Control Plan

Answer 47

There are numerous criteria for locating signage properly on a Temporary Traffic Control Plan and much of this guidance will vary by locality. As a general rule, however, signage location should take into account the location of parking vehicles and vegetation so that it is not obscured. Signage should also be located within the normal field of vision of both motorists and pedestrians to ensure the safety of all users. Roadway signage standards are developed to meet strict safety standards and should not be altered to match zoning overlays, such as those of a historic district.

Question 48

Wayfinding Plan

Answer 48

When developing a Wayfinding plan, the primary actions taken should include; 1. Emphasize site entrances, 2. Establish a path hierarchy, 3. Create a small number of discernible regions. Note that discernible regions act as distinct areas that are memorable to the average site user and can be used to help orient users.

Question 49

Wayfinding Plan - Factors to Take into Account

Answer 49

Maintenance budget and the proposed plant palette would have long-term effects on the visibility and upkeep of wayfinding tools, and the size of the site would directly impact the organization strategy for wayfinding (ex. larger sites may require site maps for users). User demographics are important given that different user groups have varying levels of physical ability, visual acuity and literacy (among other factors). Proposed circulation is arguably the most important factor in determining a wayfinding system given that circulation and wayfinding are codependent. Something like “Anticipated parking demand” would have the least impact on the design of a site wayfinding system.