Frequently Asked Questions
What is an acre?
An acre is 43,560 square feet, or an area approximately
208 feet long by 208 feet wide.
Top
What is an ordinance?
A municipally adopted law or regulation.
Top
What is runoff?
The portion of a rainfall event that is seen traveling over the ground surface or within conveyance facilities.
Top
What is stormwater management?
Stormwater management is the mechanism for controlling stormwater runoff for the purposes of reducing downstream erosion, water quality degradation, and flooding and mitigating the adverse effects of changes in land use on the aquatic environment. Stormwater management facilities are those facilities, including but not limited to, stormwater retention and detention ponds and BMPs, which retain water for a period of time to control runoff and/or improve the quality (i.e., by reducing the concentration of nutrients, sediments, hazardous substances and other pollutants of stormwater runoff.
Top
What is infiltration?
The downward movement of water from the surface of the land to subsoil.
Top
What is a BMP?
BMP's, also known as Best Management Practices, are common-sense actions required, by law, to keep soil and other pollutants
out of streams and lakes. BMPs are designed to protect water quality
and to prevent new pollution.
Top
What is an impervious surface?
Those surfaces in the landscape that can not infiltrate rainfall, such as rooftops, pavement, sidewalks, driveways, etc....
Top
What is pervious pavement?
A pavement material that looks very similar to standard impervious pavement, except that the design contains less "fine" material and subsequently more void space that allows runoff to pass through instead of traveling accross. Pervious pavement is typically set upon a stone bet that has a depth of at least 18-inches, which collects the infiltrated runoff and either holds it until it recharges into the soil substrate or exists the stone bed via some type of constructed outlet facility.
Top
What is an Easement?
A grant of one or more of the property rights by the property owner to and/or for the use by the public, a corporation or another person or entity.
Top
What is a watershed?
A watershed is the area of land that drains to a particular point of interest. For example, the Chesapeke Bay Watershed includes all land area that contributes runoff to the Chesapeke Bay. Likewise, the watershed to a single roof downspout includes all of the land (roof) area that contributes runoff to that downspout.
Top
What is ground water?
When rainwater soaks into the ground, it becomes ground water. Ground water moves into water-filled layers of porous geologic formations called aquifers. If the aquifer is close to the surface, its ground water can flow into nearby waterways or wetlands, providing a base flow. Depending on your location, aquifers containing ground water can range from a few feet below the surface to several hundred feet underground. Aquifer recharge areas are locations where rainwater and other precipitation seeps into the earth's surface to enter an aquifer. Contrary to popular belief, aquifers are not flowing underground streams or lakes.
Top
What is a seepage pit or dry well?
A seepage pit or dry well is a subsurface storage facility that received and temporarily stores stormwater runoff from roofs of structures. Discharge of this stored runoff from a seepage pit occurs through infiltration into the surrounding soils. A seepage pit may be either a structural chamber and/or an excavated pit filled with stone. Due to its storage capacity, a seepage pit may be used to reduce the total stormwater quality design storm runoff volume that a roof would ordinarily discharge to downstream stormwater management facilities.
Top
What is a detention basin?
A detention basin is a facility constructed through filling and/or excavation that provides temporary storage of stormwater runoff. It has an outlet structure that detains and attenuates runoff inflows and promotes the settlement of pollutants.
Top
What is a retention basin?
A retention pond or wet pond is a stormwater facility constructed through filling and/or excavation that provides both permanent and temporary storage of stormwater runoff. It has an outlet structure that creates a permanent pool and detains and attenuates runoff inflows and promotes the settlement of pollutants. Retention basins can be designed as a multi-stage facility that also provides extended detention for enhancing stormwater quality design storm treatment and runoff storage and attenuation for stormwater quantity management.
Top
What is recharge volume?
The portion of the water quality volume used to maintain groundwater recharge rates at a development site. This helps to preserve existing water table elevations thereby maintaining the hydrology of streams and wetlands during dry weather.
Top
What is water quality?
Water quality is associated with several different topics; water quality design storm, storage, velocity and volume.
A water quality design storm is: a benchmark rainfall event, used to develop criteria for the design of water quality BMPs. Water quality design storms are used to size BMPs that are intended to achieve specific quality treatment objectives. Criteria based on water quality storms generally require that the design treatment efficiency be achieved during the water quality design storm and all smaller events. Complete specification of the storm includes total rainfall quantity, storm duration, and distribution of rainfall.
Water quality storage is: the volume set aside within a BMP to detain storm runoff. The detained water is released over an extended period of time. The water quality storage is frequently expressed as a multiple of the water quality volume.
Water quality velocity is: The maximum flow velocity encountered in a water quality BMP during the course of the water quality design storm.
Water quality volume is: The total volume of runoff which is delivered to the inlet of a water quality BMP during the course of the water quality design storm.
Top
What is perc testing?
The purpose of a percolation test is to determine the suitability of soils for the installation of a septic system and treatment of sewage effluent. The actual perc test measures the rate clear water seeps into the soil from a standard test hole. The test hole is dug at the depth a septic system would be installed.
Top
What is well sampling and why is it done?
Well sampling is the testing of home well water for nitrogen levels. Nitrate (NO3) is a naturally occurring form of nitrogen found in soil. Nitrogen is essential to all life. Most crop plants require large quantities to sustain high yields. Common sources of nitrate include fertilizers and manure, municipal wastewater and sludge and septic systems. The sampling is done to see if subdivision is a feasible option for a land owner/developer and also to see how large septic recharge easements would have to be for septic systems to be installed . Normally any number above 10mg/liter is considered high and will most likely not allow for lot subdivision.
Top
What is a speed study and why it is sometimes needed?
A speed study is a study of the overall speed along a specific length of road. The study is often needed to find the safe sight/stopping distance for proposed streets or driveways intersecting an existing road. These distances are set as requirements by the county or municipalities. Often times, roads without posted speed limits need a speed study if a reasonable sight distance is not available. Municipalities may conduct a speed study for any number of reasons. Design and physical factors place a limitation on safe operating speeds such as horizontal and vertical curves, hidden driveways and other roadside developments, high driveway density, rural residential or developed areas and lack of striped or improved shoulders.
Unless roadway geometry parameters dictate otherwise, speed limits on roadways are set based on spot speed studies and the 85th percentile operating speed. The 85th percentile is the speed at which 85% of the motorists traveling a given road are driving at or below. Posting a roadway's speed limit based on its 85th percentile speed is considered safe, appropriate, and typical engineering practice. This is the accepted engineering practice across the nation.
Top
|
