LARE 4 Flashcards
Stormwater wet pond design
Use organic geometries
include topographic variation
Maintain a depth of 4-8’
Increasing flow length (distance water travels downstream)
Lawn or grass area maximum slope
25%
Burrow Pit Method
Used for calculating cut/fill in complex grading projects;
Involves a grid across the site, assigning an elevation to each point; spacing of grid contributes to accuracy
Standard sections in a technical specification
General - basic scope of work
Product - specific materials and manufacturing or fabrication processes
Execution - actual means of preparing, installing or constructing, and quality or performance requirements
AASHTO
American Association of State Highway and transportation Officials - creates standards for public roadway construction
NFPA
National Fire Protection Association
ACI
American Concrete institution
CSI
Construction Specifications Institute (creates master format)
Master Format
01 - Gen Requirements 02- Existing Conditions 03- Concrete 04- Masonry 05- Metals 06- Wood, plastics, composites 07- Moisture/thermal protection 08- Openings 09- Finishes 10- Specialties 11 - Equipment 12 -Furnishings 31 - Earthwork
Strategies for improving site safety
Improve visibility Design for natural surveillance promote positive image of site multiple access points perceived ownership of site
Observation well
Slotted or screened tube or pipe in an infiltration trench to allow operator to check conditions
Recharge trench
placed downhill of a vegetated filter strip; linear trench filled with gravel, lined with filter fabric, including sand filter or filter fabric
Snap ties
used to hold formwork together while concrete is being poured; designed to break away after formwork is removed; can remain inside concrete to provide reinforcement
Level spreader
distributes stormwater over a wide area
Filter strips
filter sediments from stormwater, improve water quality, treat sheet flows
How to rehabilitate compacted soils
determine if compaction is located in surface or subsoil; amend soils with organic matter
Asphalt treated base
used in construction in wet or freezing conditions; prevents infiltration into fines of subgrade; 3x as strong as untreated base (crushed rock) so base layer can be 1/3 the depth
Invert elevation of a pipe
the distance between the bottom of the interior of the pipe and the surface of the ground.
Bioengineering
using plant material (such as live stakes) to restore eroded stream banks and stabilize soils, reducing sediment deposition and erosion in waterways
countersinking
having a conical hole so a bolt or screw top is flush with the material surface
Ledger
component of a deck - a board that supports joists and transfers loads from deck to structure to which it is attached
Site protection plan
protects natural resources on a site, sensitive areas on or adjacent and downstream or site, and complies with local laws and codes; includes tree protection, materials salvage, site access, erosion control and noise control
Connected imperviousness
Runoff drains directly from impervious surfaces to drainageways
Disconnected imperviousness
Runoff drains from impervious surfaces to previous like grass, resulting in more infiltration and better water quality
Ideal buffer around urban streams
25 ft undisturbed forest, plus 50-100 feet of managed vegetated area
Schematic design for stormwater key points
Slow runoff velocities to pre development conditions
Try to remove impervious surfaces from drainage pathways
Place development away from drainage ways, step slopes, complex plant communities and porous soils
Factors that effect stormwater velocity
Surface friction, surface shape, slope
Best place for impervious surfaces and pavement in stormwater design
High points, like along ridges
Type of storm that major anf minor flood protection systems are designed for
100 year, 24 hour design storm - major system
2, 5 or 10 year 1 hour design storm - minor system
ADA hand rail height
34-38”
Guard rail heigh
42” minimum
Surface albedo
measure of the diffuse reflection of solar radiation off a surface; black surfaces have albedo of 0; a surface that reflects all radiation would have an albedo of 1
Cribbing
walls placed in a series perpendicular to water flow to intercept stormwater running down a slope and trap sediment.
Benefits of compost blankets
Reduces soil erosion on slopes (usually up to 2:1), slows flow of stormwater, reduces peak flow, traps moisture and protects seeds to stimulate plant growth, reduces sediment and nutrients in stormwater, stimulates microbial activity which increases organic matter in soil and improved soil structure
Hydrograph
a graph showing the rate of flow versus time past a specific point in a river or stormwater system, usually expressed in cubic feet per second
Discharge
Rate if runoff flow, volume traveling at a particular velocity, expressed in cubic feet or cubic meters per second. Equal to velocity times area of flow
Volume of flow
Discharge times length of time, expressed in cubic feet or acre feet
Hydrograph
Summary of stormwater flows, record of flow rates at a particular location over a given time. Can be a tabular form or a graph plot (discharge vs. Time). The area under the plotted curve is the total volume of flow for the plot period.
Peak rate of flow
Top of the hydrograph, occurs when flow consists of one drop of water from every point in the watershed
Minor stormwater system
Designed to reduce inconvenience of 2, 5 or 10 year storms. Includes storm sewers and roadside swales. Maybe designed using rational method (storm sewrs) or SCS runoff method (overland systems)
Major stormwayer system
Pay that runoff takes when minor system is overwhelmed. May be designed or natural. Examples are emergency spillways, and floodwaters. Designed for 100 year storm, typically using SCS runoff method.
