3/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 1 

## Glossary 1

activated sludge

. Highly concentrated mass of live bacteria that feed on organic wastes, which 2 are aerated to increase the rate of decomposition

. 3 active/rest cycles (alternating drainfields) . Final treatment and soil-based dispersal componen t 4 of a decentralized treatment system that is compose d of multiple soil treatment areas, which are 5 independently dosed under the control of a flow div ersion valve according to a pre-set schedule. 6 advanced treatment systems . Any treatment of sewage that goes beyond the seco ndary or 7 biological water treatment stage and includes the r emoval of nutrients such as phosphorus and 8 nitrogen and a high percentage of suspended solids. 9
aerobic . Having molecular oxygen (O 2 ) as a part of the environment, or a biological pro cess that 10 occurs only in the presence of molecular oxygen. 11
aerobic treatment . Process by which microbes decompose complex organ ic compounds in the 12 presence of oxygen and use the liberated energy for reproduction and growth. (Such processes 13 include extended aeration, trickling filtration, an d rotating biological contactors.) 14 aggregate. A collective term for sand, gravel, and crushed sto ne mineral materials in their 15 natural or processed state. 16
allochthonos . Derived from outside a system, such as leaves of terrestrial plants that fall into a 17 stream. 18
alluvium . Deposits of clay, silt, sand, gravel, or other pa rticulate material that has been 19 deposited by a stream or other body of running wate r in a streambed, on a flood plain, on a delta, 20 or at the base of a mountain. 21
alum . A double sulphate formed of aluminum and some oth er element (esp. an alkali metal) or 22 of aluminum. It has twenty-four molecules of water of crystallization. Common alum is the 23 double sulphate of aluminum and potassium. It is wh ite, transparent, very astringent, and 24 crystallizes easily in octahedrons. The term is ext ended so as to include other double sulphates 25 similar to alum in formula. 26 alum (aluminum sulfate) treatment . Alum or aluminum sulfate is an acid that is commo nly 27 used as a poultry litter treatment. Available in ei ther a dry or liquid form, alum’s acidic 28 properties are used to reduce ammonia levels in the poultry house, while its binding properties 29 are used to reduce P in runoff (Moore, et al Undate d ). Alum is also used to reduce P losses from 30 manure and wastewater, to increasing the efficiency of mechanical separation of manure, and to 31 reduce P losses from grazing land. 32
ammonia volatilization . The process of ammonia volatilization commonly ta kes place when 33 nitrogen is in an organic form known as urea. Urea may originate from animal manure, urea 34 fertilizers and, to a lesser degree, the decay of p lant materials. Ammonia volatilization is most 35 likely to take place when soils are moist and warm and the source of urea is on or near the soil 36 surface. Ammonia volatilization will also take plac e on alkaline soils (pH greater than 8). 373/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 2 anabranching channel . A distributary channel that departs from the main channel, sometimes 1 running parallel to it for several kilometres befor e rejoining it. 2
anaerobic . Absence of molecular oxygen (O 2 ) as a part of the environment, or a biological 3 process that occurs in the absence of molecular oxy gen; bound oxygen is present in other 4 molecules, such as nitrate (NO 3 -) sulfate (SO 4 +) and carbon dioxide CO 2 . 5 anaerobic decomposition . Reduction of the net energy level and change in c hemical 6 composition of organic matter caused by microorgani sms in an oxygen-free environment. 7 analyte . A substance that is undergoing analysis or is bei ng measured. 8 antidegradation . Provisions in the federal Clean Water Act, codifi ed at 40 CFR 131.12, which 9 provide (1) a minimum level of protection for all s urface waters; (2) requirements for alternatives 10 analyses, intergovernmental coordination, and socia l or economic justification before allowing 11 lowered water quality in high-quality waters; and ( 3) the highest level of protection for 12 outstanding national resource waters. State water q uality standards must include both an 13 antidegradation policy and methods for implementati on. 14 applied organic loads

. The quantity of organic material (e.g., manure) app lied to lands or 15 introduced to a receiving waterbody or treatment pr actice, typically measured as chemical 16 oxygen demand (COD) or biological oxygen demand (BO D). 17 aquifer . Geologic formation, group of formations, or part of a formation that is saturated and 18 sufficiently permeable to transmit water. 19
attenuation . For water velocity: the slowing, modification, or diversion of the flow of water as 20 with detention and retention ponds. For water quali ty: the process of diminishing contaminant 21 concentrations in water because of filtration, biod egradation, dilution, sorption, volatilization, 22 and other processes. 23 autoventing turbine . A hydroturbine with pressure-relieving ports that are open to the 24 atmosphere. 25 bank shaping . Re-grading streambanks to a stable slope, placing topsoil and other materials 26 needed for sustaining plant growth, and selecting i nstalling, and establishing appropriate plant 27 species. 28
bankfull elevation . The water surface elevation within a channel corr esponding to bankfull 29 discharge 30 bankfull discharge . 1. For a natural channel that is not adapting to hydrologic change in its 31 watershed, it is the discharge that occurs when the water just fills the channel to the top of its 32 banks and begins to overflow onto a floodplain. 2. The discharge at which channel maintenance 33 is most effective, that is, the discharge at which moving sediment, forming or removing bars, 34 forming or changing bends and meanders, and general ly doing work that results in the average 35 morphologic characteristics of channels. 36
baseflow . Sustained flow of a stream in the absence of dire ct runoff. It includes natural and 37 human-induced streamflows. Natural base flow is sus tained largely by ground-water discharges. 383/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 3 bathymetry . The measurement of depths of water in oceans, sea s, and lakes; also information 1 derived from such measurements. 2
bed-load . Instream sediment transport mode in which individ ual particles either roll or slide 3 along the stream bed as a shallow, mobile layer a f ew particle diameters deep (the particle size 4 depends on the energy level of the flowing water). 5
benthic/benthos . An organism that feeds on the sediment at the bot tom of a water body such as 6 an ocean, lake, or river. 7
berm . A low earth fill constructed in the path of flowi ng water to divert its direction, or 8 constructed to act as a counterweight beside the ro ad fill to reduce the risk of foundation failure. 9
bioinfiltration . A stormwater management practice where runoff is routed through a soil media 10 that is vegetated. This practice functions in a man ner analogous to bioretention systems but has a 11 higher infiltration capacity, and thus would be cat egorized as an infiltration process. 12 biological treatment . A treatment technology that uses bacteria to cons ume organic waste. 13
bioretention . A stormwater management practice that is designed to provide both temporary 14 surficial water storage and runoff retention subsur face in soil media. Runoff is directed to shall 15 depressions where it is infiltrated, filtered or ev apotranspirated. These systems are typically 16 designed with a soil media selected to promote infi ltration and runoff retention and are vegetated 17 with plants picked to withstand both inundation and drought. Bioretention systems also be used 18 to filter runoff to trap and in some cases degrade pollutants such as oils and greases. This 19 practice is often categorized under “filtration” al though it has additional functions. Some systems 20 are build with underdrain or overdrain systems to c onvey excess runoff offsite. 21
bioswale . A relatively wide, shallow, open channel, typical ly vegetated with turf grasses, with a 22 slight gradient. These systems are designed to let water flow slowly through the turf grasses. The 23 roughness of the turf slows the runoff velocity and provides some filtration and settling of 24 suspended solids. Runoff volumes can also be reduce d through infiltration depending on the 25 porosity of the underlying soils. Swales can be des igned with underdrains to convey excess 26 runoff from saturated soils. 27
blue roofs . A practice that is designed to provide temporary storage of stormwater and slowly 28 release stormwater runoff using the roof surface of a structure. Also referred to as “rooftop 29 detention.” 30 branch packing . A form of soil bioengineering that uses alternati ng tiers of live branch cuttings 31 and compacted backfill to repair small localized sl umps and holes in slopes and a means of 32 reducing the erosive potential of incoming flows at their source. 33
breakwater . A wave energy barrier designed to protect the lan d or nearshore area behind them 34 from the direct assault of waves. 35
brownfields . Abandoned, idled, or under used industrial and co mmercial facilities/sites where 36 expansion or redevelopment is complicated by real o r perceived environmental contamination. 373/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 4 They can be in urban, suburban, or rural areas. EPA 's Brownfields initiative helps communities 1 mitigate potential health risks and restore the eco nomic viability of such areas or properties. 2 brush layering . A form of soil bioengineering that uses live bran ch cuttings laid flat into small 3 benches excavated in the slope face perpendicular t o the slope contour. 4 buffer strip . 1. Area between a stream and construction activit ies that achieves sediment control 5 by using the natural filtering capabilities of the forest floor and litter. 2. Strips of grass or othe r 6 erosion-resisting vegetation between or below culti vated strips or fields. 7
bulkhead . A structure or partition to retain or prevent sli ding of the land. A secondary purpose is 8 to protect the upland against damage from wave acti on. 9
catch basins . A catch basin is a device that receives storm wat er drainage from an outside 10 surface area. They are usually located in parking l ots or in areas where the removal of storm 11 water buildup is desirable. 12 channel incision and widening . A process of channel degradation that results in a lower 13 elevation channel surrounded by one or more elevate d terrace(s) that once were floodplains. The 14 interplay of channel incising (deepening) and widen ing is caused by changes in streamflow or 15 sediment delivery. 16 channel reconfiguration . River and stream channel engineering for the purp ose of flood control, 17 navigation, drainage improvement, and reduction of channel migration potential; activities 18 include the straightening, widening, deepening, or relocation of existing stream channels, 19 clearing or snagging operations, the excavation of borrow pits, underwater mining, and other 20 practices that change the depth, width, or location of waterways or embayments in coastal areas. 21
channelization . River and stream channel engineering undertaken f or the purpose of flood 22 control, navigation, drainage improvement, and redu ction of channel migration potential. 23 Activities such as straightening, widening, deepeni ng, or relocating existing stream channels and 24 clearing or snagging operations fall into this cate gory. 25 chisel plowing . Preparing croplands by using a special implement that avoids complete inversion 26 of the soil as in conventional plowing. Chisel plow ing can leave a protective cover or crops 27 residues on the soil surface to help prevent erosio n and improve filtration. 28
cistern . Tank or storage facility used to store water for a home or farm; often used to store rain 29 water. 30
Clasts . Individual sedimentary particles such as a grain of sand, pebble, or boulder that make up 31 a sedimentary rock or deposit. 32
Clear cut . A silvicultural system in which all merchantable trees are harvested within a specified 33 area in one operation to create an even-aged stand. 34 Cluster treatment systems . Wastewater treatment systems designed to serve tw o or more 35 sewage-generating dwellings or facilities with mult iple owners that are not part of a centralized 36 collection system that discharges to any point sour ces and that treats and disperses effluent to 37 soil-based dispersal systems similar to onsite syst ems. 383/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 5 coarse woody debris (CWD) . A large tree part, conventionally a piece greater than 10 cm in 1 diameter and 1 m in length. 2
coconut fiber roll . Cylindrical structures composed of coconut husk f ibers bound together with 3 twine woven from coconut material to protect slopes from erosion while trapping sediment, 4 which encourages plant growth within the fiber roll

. 5
colloids . Very small, finely divided solids (that do not di ssolve) that remain dispersed in a liquid 6 for a long time due to their small size and electri cal charge. 7 combined sewer overflows (CSOs) . Discharge of a mixture of storm water and domesti c waste 8 when the flow capacity of a sewer system is exceede d during rainstorms. 9 compost amendments . Organic matter that is added to soil to improve i nfiltration. 10 composting . The controlled biological decomposition of organi c material in the presence of air 11 to form a humus-like material. Controlled methods o f composting include mechanical mixing 12 and aerating, ventilating the materials by dropping them through a vertical series of aerated 13 chambers, or placing the compost in piles out in th e open air and mixing it or turning it 14 periodically. 15
concentrated flow . Rills, ephemeral gullies, gullies, channels, stre ams and rivers are examples 16 on the landscape of areas where concentrated flow e rosion occurs. Concentrated flow erosion is 17 also a culprit in embankment breaching and auxiliar y spillway failure on earthen dams. 18 construction runoff intercepts . A temporary berm or channel constructed across a slope to 19 collect and divert runoff. 20
controlled-release or slow-release fertilizers . Inorganic or organic fertilizers that are 21 characterized by a slow rate of release, long resid ual, low burn potential, and low water 22 solubility. Several categories of slow-release nitr ogen fertilizers are commercially available, 23 including urea-formaldehyde, isobutylidene diurea, sulfur coated urea, plastic coated fertilizers, 24 and natural organics. 25 conventional tilling . Tillage operations considered standard for a spec ific location and crop and 26 that tend to bury the crop residues. 27
core aeration . Increasing air penetration of the soil by removin g plugs of soil. A heavy machine 28 with hollow prongs is moved across a lawn pushing t he prongs into the soil and pulling out plugs 29 of soil. 30

cover crop . A crop that provides temporary protection for del icate seedlings and/or provides a 31 cover canopy for seasonal soil protection and impro vement between normal crop production 32 periods. 33
crown fire . The movement of fire through the crowns of trees or shrubs more or less 34 independently of the surface fire. 353/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 6 cross-sectional area . The cross-sectional area of a stream or tributary stream channel is 1 determined by multiplying the stream or tributary s tream channel width by the average stream or 2 tributary stream channel depth. 3 cosspipe or sluice pipe (also called culvert). A conduit used to enclose a flowing body of water 4 to allow it to pass underneath a road, railway, or embankment. 5
culvert . A metal, wooden, plastic, or concrete conduit thr ough which surface water can flow 6 under or across roads. 7
curb extension . A section of sidewalk designed to contain soils a nd vegetation to filter runoff, 8 reduce runoff velocities and in some cases infiltra te runoff. Curb cuts or gaps in the curbs are 9 used to route runoff from street surfaces into this cells. 10
cut-and-fill . Earth-moving process that entails excavating part of an area and using the 11 excavated material for adjacent embankments or fill areas. 12 demand-dosing . Configuration in which a specific volume of efflu ent is delivered to a 13 component (e.g., a drainfield) based upon patterns of wastewater generation from the source. 14
denitrification . The biological reduction of nitrate to nitrogen g as by bacteria in soil. 15 denitrification enzyme assays . An assay used to quantify the initial rate, or Ph ase I, of 16 denitrification using the acetylene block technique to prevent the reduction of N 2 O to N 2 . 17 design flow . Projected flow through a watercourse that will re cur with a stated frequency. The 18 projected flow for a given frequency is calculated using statistical analysis of peak flow data or 19 using hydrologic analysis techniques. (See storm re turn period). 20
dewater . Removing or draining the water from a site, strea m or trench. 21 digestion . The biochemical decomposition of organic matter, resulting in partial gasification, 22 liquefaction, and mineralization of pollutants. 23 dispersal . Spreading of effluent through the final receiving environment, typically soil. 24
distribution box . Level, watertight structure that receives septic tank effluent and distributes it 25 via gravity in approximately equal portions to two or more trenches or two or more laterals in a 26 bed. 27 dormant post plantings . Plantings of dormant cottonwood, willow, poplar, or other species 28 embedded vertically into streambanks to increase ch annel roughness, reduce flow velocities near 29 the slope face, and trap sediment as they grow. 30 dosing and resting . Configuration in which a specific volume of efflu ent is delivered to a 31 component based upon a prescribed interval, regardl ess of facility water use. 32 drainage . Improving the productivity of agricultural land b y removing excess water from the 33 soil by such means as ditches or subsurface drainag e tile lines. 343/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 7 drainage density . In hydrologic terms, the relative density of natu ral drainage channels in a 1 given area. It is usually expressed in terms of mil es of natural drainage or stream channel per 2 square mile of area, and obtained by dividing the t otal length of stream channels in the area in 3 miles by the area in square miles. 4 drainage intensity (DI) . The drainage rate that occurs when the water tabl e is at the soil surface; 5 it increases with drain depth and decreases with dr ain spacing. 6 Drainage Water Management . A practice in which the outlet from a conventiona l drainage 7 system is intercepted by a water control structure that effectively functions as an in-line dam, 8 allowing the drainage outlet to be artificially set at levels ranging from the soil surface to the 9 bottom of the drains. 10 drainfield (soil treatment area) . Physical location where final treatment and dispe rsal of 11 effluent occurs; includes drainfields, drip fields and spray fields. 12
duff . The accumulation of needles, leaves, and decaying matter on the forest floor. 13
effluent . Partially or fully processed liquid flowing out o f a sewage treatment component or 14 device. 15 energy signature . The characteristics of a stream system to allow i t to transport the flows of 16 water and sediment provided by its watershed in an efficient and stable manner. 17 entrapped mixed microbial cells (EMMC) process . A process in which dilute wastewater is 18 passed through a cellulose triacetate matrix contai ning microbial cells for the purpose of 19 removing carbon and nitrogen. 20 ephemeral drainage . A channel that carries water only during and imme diately following 21 rainstorms. Sometimes referred to as a dry wash. 22 epilimnion . Upper waters of a thermally stratified lake subje ct to wind action. 23
erosion control blankets . A manufactured sheet, typically rolled on a spool consisting of a 24 matrix of straw, coconut fiber, aspen fiber, jute, or polypropylene (plastic) woven , stitched glued 25 or bound together, which is placed on disturbed are as to provide temporary erosion control and 26 encourage establishment of vegetation. 27
essential turf . Turf required for the identified needs of the fac ility or jurisdiction, e.g., security, 28 historic preservation, access, other designated use s such as recreation, mental health restoration 29 or rehabilitation. 30 eutrophication . The slow aging process during which a lake, estua ry, or bay evolves into a bog 31 or marsh and eventually disappears. During the late r stages of eutrophication the water body is 32 choked by abundant plant life due to higher levels of nutritive compounds such as nitrogen and 33 phosphorus. Human activities can accelerate the pro cess. 34 evapotranspiration . The loss of water from the soil both by evaporati on and by transpiration 35 from the plants growing in the soil. 363/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 8 fast-release fertilizer . A synthetic fertilizer that releases its nutrient s (especially N) rapidly (e.g., 1 urea, ammonium nitrate). 2 feed pump . Mechanical device for driving fluid flow or for r aising or lifting a fluid by either 3 suction or pressure or both. 4
filter strips . Area of vegetation used for removing sediment, or ganic matter, and other pollutants 5 from runoff or wastewater. 6
filtration . A treatment process, under the control of qualifi ed operators, for removing solid 7 (particulate) matter from water by means of porous media such as sand or a man-made filter; 8 often used to remove particles that contain pathoge ns. 9
first flush . The condition, often occurring in storm-sewer dis charges and CSOs, in which a 10 disproportionately high pollutant load is carried i n the first portion of the discharge or overflow. 11
fish ladder or lift . A series of ascending pools, similar to a stairca se, that enables fish to migrate 12 up the river past dams. Also called a fishway. 13
fish runs . The place where fish, such as native steelhead tr out and salmon, return from the ocean 14 each spring to spawn in the rivers or streams where they were born. Can also refer to the group 15 of fish that is migrating up the stream. 16 fish tagging . The placement of identifying tags or markers, typ ically permanent, on individual 17 captured fish specimens for the purposes of later r etrieval and analysis for species migration, 18 growth, and overall health. 19
floc . A clump of solids formed in sewage by biological or chemical action. 20 floodplain . The flat or nearly flat land along a river or str eam or in a tidal area that is covered by 21 water during a flood. 22 flow regime . Combinations of river discharge and corresponding water levels and their 23 respective (yearly or seasonally) averaged values a nd characteristic fluctuations around these 24 values. 25
flow velocities . The speed, expressed in units of length per unit of time, at which a fluid flows 26 through a culvert, channel or other conveyance. 27 flue gas desulfurization . A technology that employs a sorbent, usually lime or limestone, to 28 remove sulfur dioxide from the gases produced by bu rning fossil fuels. Flue gas desulfurization 29 is current state-of-the art technology for major SO 2 emitters, like power plants. 30
flume . A natural or man-made channel that diverts water. 31
fluvial . Of or relating to flowing waters, especially rive rs. 32 fluvial aggradation . General and progressive raising of a stream bed b y deposition of sediment 33 carried by the stream. 343/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 9 footer . Stone, concrete or other rigid structural materia l placed underneath other materials to 1 provide a foundation or bearing surface. 2 gabion . A rectangular basket or mattress made of galvaniz ed, and sometimes PVC-coated, steel 3 wire in a hexagonal mesh. Gabions are generally sub divided into equal-sized cells that are wired 4 together and filled with 4- to 8-inch-diameter ston e, forming a large, heavy mass that can be used 5 as a shore-protection device. 6 geomorphology . That branch of both physiography and geology that deals with the form of the 7 Earth, the general configuration of its surface, an d the changes that take place in the evolution of 8 landform. 9 geotextile filtration . The use of geotextiles (permeable fabrics) to sep arate solids and liquids in 10 such materials as lagoon sludge and liquid manure. 11 grade breaks . An intentional increase in road elevation on a do wnhill grade that causes water to 12 flow off of the road surface. 13 grade stabilization structure . A structure used to control the grade and head cu tting in natural 14 or artificial channels. 15 grassed swales . A term used to describe a vegetated open runoff c hannel planted with grasses or 16 turf. Similar terms include: grassed channel, dry s wale, wet swale, biofilter, or bioswale. These 17 systems are designed to treat and attenuate stormwa ter runoff. As runoff flows along these 18 channels, the vegetation in the channel promotes fi ltration, settling and infiltration of runoff into 19 the underlying soils. The specific design features and methods of treatment differ in each of these 20 designs, but are improvements on the traditional dr ainage ditch. These designs incorporate 21 modified geometry and other features for use of the swale as a treatment and conveyance 22 practice. 23 Gray water . Any washwater that has been used in a home or bus iness, except water from toilets. 24 This water is considered to be more re-useable, esp ecially for landscape irrigation purposes. 25 grazing . Feeding on standing vegetation, as by livestock o r wild animals. 26 greenfields. Previously undeveloped land such as forests, meadow s or other “natural lands.” 27 green infrastructure . A term that has two commonly used meanings. The m ore common usage 28 refers to vegetated landscapes that are conserved o r restored for ecological or anthropological 29 reasons, e.g., wildlife habitat, flood protection, drinking water source protection and air quality 30 and urban heat island concerns. 31 This term is also used to connote practices and str ategies used to reduce the impact of wet 32 weather events (rainfall and snow melt) on receivin g waters. In this usage, green infrastructure is 33 often also called low impact development or LID and is used to describe an array of strategies, 34 products, technologies, and practices that are desi gned to mimic the behavior of natural systems 35 as they relate to runoff, watershed and site hydrol ogy and pollutant reduction. These systems are 36 typically designed using an integrated design appro ach that relies on engineering, hydrological, 37 biological, architectural, and planning concepts an d practices to plan, design and manage runoff 383/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 10 through plant and soil uptake, filtration, infiltra tion, evapotransipiration and the harvest and use 1 of runoff. 2 green roof . Also known as eco-roofs or rooftop gardens, green roofs are engineered soil media 3 systems that are planted on rooftops and designed t o reduce runoff, combined sewer overflows, 4 urban heat island impacts and provide other ecologi cal and human benefits such as aesthetics, 5 wildlife habitat and aesthetics. The soil media mix and vegetation are planted over existing roof 6 structures, and consist of a waterproof, root-safe membrane that is covered by a drainage system, 7 lightweight growing medium, and plants. Green roofs reduce rooftop and building temperatures, 8 filter pollution, lessen pressure on sewer systems, and reduce the heat island effect. 9 grid point data . Data that is collected at the intersections of im aginary or real lines laid over a 10 surface in a grid pattern. 11 grinder pump system. A pump that shreds solids in a waste stream and con veys the resulting 12 mixture under pressure to a subsequent system compo nent. 13 groin . A shore protection structure built (usually perpe ndicular to the shoreline) to trap littoral 14 drift or retard erosion of the shore. 15 ground fuels . All combustible materials below the surface litte r, including duff, roots, peat and 16 saw dust dumps that normally support a glowing comb ustion without flame. 17 gully . A channel or miniature valley cut by concentrated , non-continuous runoff such as during 18 snowmelt or following heavy rains. 19 gully erosion . Severe erosion in which trenches are cut to a dep th greater than 30 centimeters (a 20 foot). Generally, ditches deep enough to cross with farm equipment are considered gullies. 21 highly erodible lands (HELs) . Land that is very susceptible to erosion, includi ng fields that 22 have at least 1/3 or 50 acres of soils with a natur al erosion potential of at least 8 times their T 23 value. More than 140 million acres are classified a s HEL. Farms cropping highly erodible land 24 and under production flexibility contracts must be in compliance with a conservation plan that 25 protects this cropland. 26 hi-input turf . Turf that requires irrigation, frequent mowing, f ertilization and/or pesticide 27 treatment. 28 hillslope . A part of a hill between its crest and the draina ge line at the foot of the hill. 29 hydraulic connectivity . The ability of the soil to transmit water. Also c ommonly known as the 30 permeability. Darcy found that to relate the flow r ate to the hydraulic head and area of flow 31 required a constant of proportionality (termed k) a s the hydraulic connectivity. It has units of 32 velocity. Note that the value is a function of both the porous media and the fluid. 33 hydraulic residence time . The average time an element spends in a given env ironment between 34 the time it arrived and the time it is removed by s ome process. In the ocean, residence time is 35 defined as the concentration in sea water relative to the amount delivered to the ocean per year; 36 in groundwater, it is the time elapsed between wate r being recharged to the aquifer; in lakes and 37 reservoirs, it is the time elapsed between a parcel of water entering the waterbody and leaving it. 383/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 11 hydraulic resistance . In hydraulics, resistance is the condition engend ered by an obstruction or 1 restriction in the flow path. Hydraulic resistance in a forest setting is the obstruction of the flow 2 of water. Woody debris, forest litter, and surface irregularities and structures that slow the flow 3 of water increase hydraulic resistance. 4 hydric soil . A soil that is saturated, flooded, or ponded long enough during the growing season 5 to develop anaerobic (oxygen-lacking) conditions th at favor the growth and regeneration of 6 hydrophytic vegetation. 7 hydrodynamic simulations . Computer simulations of the motion or movement of water in a 8 stream, lake or estuary. 9 hydrologic cycle . Movement or exchange of water between the atmosph ere and earth. 10 hydrologic extremes . Hydrologic events that change stream flow conditi ons, such as droughts 11 and floods, of significant magnitude compared to no rmal baseline conditions. 12 hydrology . The science dealing with the properties, distribu tion, and circulation of water. 13 hydromodification . Alteration of the hydrologic characteristics of l andscapes, drainage ways 14 and waters of the US that result in changes in wate r balance, stream morphology, habitat, 15 groundwater recharge, evapotranspiration rates and surface runoff. 16
immobilization and mineralization . In mineralization, the N in plant tissue is conve rted by soil 17 microbes into a form (nitrate) that subsequent plan ts can use. Immobilization is the process by 18 which plant usable forms of nitrogen in the soil be come unavailable for subsequent crop growth. 19 Because microbial populations increase with the gro wth of a cover crop, N contained in the 20 cover crop and the soil may be immobilized or "tied up" as part of the physical structure of the 21 microbes. As a result, the cover crop N may not be available for uptake by the following crop. 22 When the microbes die, the N is "mineralized" and b ecomes available for subsequent crop use. 23 impervious surfaces . A hard surface area that either prevents or retar ds the entry of water into 24 the soil mantle or causes water to run off the surf ace in greater quantities or at an increased rate 25 of flow. Common impervious surfaces include rooftop s, walkways, patios, driveways, parking 26 lots, storage areas, concrete or asphalt paving, an d gravel roads. 27 impoundment . A body of water or sludge confined by a dam, dike , floodgate, or other barrier. 28
incised . A channel that has been cut relatively deep into underlying formation by natural or 29 human induced processes. 30 indoor ozone systems . A controversial indoor technique that uses ozone for broiler house 31 cleaning and in-house air contaminant (ammonia) con trol. 32
infiltration . The movement of water from the land surface into the soil. 33
infiltration basin or trench . A drainage facility designed to use the hydrologi c process of runoff 34 soaking into the ground, commonly referred to as pe rcolation, to dispose of stormwater. Note: 35 Infiltration trenches are typically not vegetated a nd designed to significantly filter pollutants 36 from runoff. 373/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 12 inorganic nitrogen . The element nitrogen in combination with other mi neral elements and not 1 derived from plant or animal sources. 2 integrated pest management . The use of pest and environmental information in conjunction 3 with available pest control technologies to prevent unacceptable levels of pest damage by the 4 most economical means and with the least possible h azard to persons, property and the 5 environment. 6 intercropping . The growing of two or more different species of c rops simultaneously, as in 7 alternate rows in the same field or single tract of land. 8
interstitial . The matrix of air or liquid between sediment part icles. 9
inverts . The bottom of a drainage facility along which the lowest flows would pass. 10
labile carbon . The highly reactive fraction of soil organic carb on with the most rapid turnover 11 times; its oxidation drives the flux of CO 2 between soils and atmosphere. Labile organic carbo n 12 decomposes rapidly in the water column or in sedime nts, on a time scale of days to weeks; 13 refractory organic carbon requires more time. 14 land applied . The reuse of reclaimed water or the use or dispos al of effluents or wastewater 15 residuals on, above, or into the surface of the gro und through spray fields, land spreading, or 16 other methods. 17 landing . A place in or near the forest where logs are gath ered for further processing or transport

. 18 large wood structures (LWS) . See large woody debris. 19 large woody debris . Also called large wood structures. A large tree p art, conventionally a piece 20 greater than 10 cm in diameter and 1 m in length. 21 leaching . The process by which soluble constituents are dis solved and filtered through the soil 22 by a percolating fluid. 23
leaf litter . Also called duff. Leaves and twigs fallen from fo rest trees. 24 livestock exclusion fencing . Fencing that keeps livestock away from rivers and streams. 25
load . The quantity of sediment transported by a current . It includes the suspended load of small 26 particles and the bedload of large particles that m ove along the bottom. 27 longitudinal rutting . Ruts formed along the length of the road from tir e pressure. 28 longitudinal zones . The longitudinal zones of a river corridor includ e the headwaters (zone 1), 29 the transfer zone (zone 2), and the depositional zo ne (zone 3). 30 lotic system . Flowing waters, as in streams and rivers. 31 low-input turf . Turf that requires little or no maintenance, i.e. , fertilization, irrigation, pesticide 32 applications. 333/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 13 low mow turf . Turf that is only infrequently mowed. Turf under this category would be mowed 1 as little as possible and mowing frequency would be based on issues such as security, pests, fire 2 hazard, or suppression of woody species. 3 macroaggregates . A relatively large particle (as of soil). 4

macropores . Secondary soil features such as root holes or des iccation cracks that can create 5 significant conduits for movement of NAPL and disso lved contaminants, or vapor-phase 6 contaminants. 7 matrix based fertilizers (MBFs) . Fertilizers formulated to reduce nitrate, ammoniu m, and total 8 phosphorus leaching through binding of N and P, and in some cases via mixtures with aluminum 9 sulfate, iron sulfate, starch, chitosan, or lignin. When N and P are released, the chemicals 10 containing these nutrients in the MBF temporarily b ind N and P to an aluminum sulfate and/or 11 iron sulfate starch- chitosan- lignin matrix. 12
mats/tree collars . These are used to block the growth of grass or we eds immediately adjacent to 13 a newly planted tree commonly made of 2.5-mil, UV-s tabilized, carbon-black plastic; about 3’ x 14 3’ (1 sq. yard) slit to easily fit around a newly p lanted tree that prevents weeds and other plants 15 from growing around the new seedling by blocking al l sunlight. 16 mechanical site preparation . The cutting of all standing material with blades or choppers to 17 prepare an area for the establishment of a future f orest either by artificial or natural means. Other 18 practices include disking, bedding, and raking. 19
mesohabitat . Distinct units of habitat within an ecosystem. 20
microfauna . Soil-dwelling micro-organisms (animals) that cann ot be seen with the naked eye. 21
microfiltration . Microfiltration uses a filter media to physically prevent biological 22 contamination from passing through. Ceramic and sol id block carbon are commonly used to 23 provide microfiltration. 24
miter drain . A drain that is at an angle (e.g., 45 degrees) to the surface that is being drained 25 (e.g., a grassed swale), as opposed to a drain laid flat on the surface that is being drained. 26 morphology . The branch of geology that studies the characteri stics and configuration and 27 evolution of rocks and land forms. 28 mouldboard ploughing . Conventional tillage using a moldboard plow. Turn s over the soil and 29 typically leaves less than 15 percent residue cover after planting. 30 native landscaping . Landscaping that is designed to use native plants adapted to the specific 31 geographic location of their origin are used. 32
nitrate flux . The flow of nitrate (the most soluble and mobile form of nitrogen) out of a system, 33 as from groundwater to streams, streams to rivers, and rivers to bays or oceans. 34
nitrification . The process whereby ammonia in wastewater is oxid ized to nitrite and then to 35 nitrate by bacterial or chemical reactions. 363/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 14 no mow turf . Grasses that do not need mowing and are allowed t o reach their mature state, e.g., 1 switch grasses and other native grasses. 2
no till . Planting crops without prior seedbed preparation, into an existing cover crop, sod, or crop 3 residues, and eliminating subsequent tillage operat ions. 4
no-till disk aeration . Disk aeration uses methods similar to no-till or conservation tillage 5 seeding of crops, which disrupts the soil surface i n a series of parallel rows. The soil is aerated 6 using an aeration device fashioned by attaching cor es, tines, or metal flashing (disk aeration) to 7 rows on a metal plate and pushing the implement int o the soil. 8
nonessential turf . Turf not necessary to achieve the intended goals of the facility or jurisdiction. 9 nonpoint source . Diffuse runoff (i.e., without a single point of o rigin or not introduced into a 10 receiving stream from a specific outlet). This docu ment uses the term “nonpoint source” broadly, 11 as EPA has in the past, to refer to sources that cu rrently are treated as nonpoint sources in EPA's 12 implementation of section 319 of the Clean Water Ac t. Some of these sources may legally be 13 made subject to regulation as point sources under s ection 402(p) of the Clean Water Act. EPA 14 has designated several categories of these stormwat er sources for regulation, such as small 15 municipal separate storm sewer systems, and may des ignate others for regulation in the future. 16
nutrient . Any substance assimilated by living things that p romotes growth. The term is generally 17 applied to nitrogen and phosphorus in wastewater, b ut is also applied to other essential and trace 18 elements. 19 nutrient use efficiency (NUE) . A measure of how much crop is produced per unit o f nutrient 20 supplied. A greater NUE leaves less N and P availab le for transport to waterbodies. 21 on-site system . Wastewater treatment system relying on natural pr ocesses and/or mechanical 22 components to collect and treat sewage from one or more dwellings, buildings, or structures and 23 disperse the resulting effluent on property owned b y the individual or entity. 24 organic turf management . Turf managed without the use of inorganic fertili zers or pesticides. 25 organic matter . The organic component of the soil consisting in l iving organisms, dry plants 26 and residues of animal origin. In a mass unit, this organic component is the most chemically 27 active of the soil. Such component stores several e ssential elements, estimulates the proper 28 structure of the soil, it is a source with capacity for the exchange of cations and regulates the pH 29 changes, supports the relationship between air and water in the soil, and is a huge geochemical 30 storage of carbon. 31 oxidation-reduction potential . The electric potential required to transfer elect rons from one 32 compound or element (the oxidant) to another compou nd (the reductant); used as a qualitative 33 measure of the state of oxidation in water treatmen t systems. 34
P-saturation . The amount of P in soil divided by the amount of P that can be fixed by the soil. 35 particulate bound . The condition in which a pollutant constituent at taches physically, strongly 36 or weakly, to sediments within a stream system. 373/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 15 pasture . Land used primarily for the production of domesti cated forage plants for livestock (in 1 contrast to rangeland, where vegetation is naturall y-occurring and is dominated by grasses and 2 perhaps shrubs). Rotation pasture or cropland under winter cover crops is not included in this 3 definition. The 1992 national resources inventory r ecorded 126 million acres of pastureland, 9 4 percent of all nonfederal rural lands. 5 peak flow . Maximum flow through a watercourse that will recu r with a stated frequency. The 6 maximum flow for a given frequency may be based on measured data, calculated using statistical 7 analysis of peak flow data, or calculated using hyd rologic analysis techniques. 8 permeable reactive barriers . A subsurface emplacement of reactive materials de signed as a 9 preferential conduit for treating contaminated grou ndwater flow. 10 phase construction. Disturbance of small portion so f a site at a time to prevent erosion from 11 dormant part. 12 phreatic surface. The free surface of ground water at atmospheric pre ssure. 13 phytoremediation. Practice used to reduce soil contaminant loadings t hrough the use of plants 14 selected to uptake and/or breakdown the contaminant s. In cases where plant cannot metabolize 15 and breakdown the contaminants, vegetative matter m ay need to be removed for further 16 processing or disposal. 17 phytotechnology. The term phytotechnology refers to technologies tha t use living plants. 18 planter box. A small, contained vegetated area that is used to c ollect and treat stormwater 19 through the mechanisms provided by bioretention des igns. There are three general types of 20 planter boxes: 1) contained planter that is used fo r planting trees, shrubs and ground cover that is 21 placed over an impervious surface; 2) infiltration planter that is a structural landscaped reservoir 22 used to collect, filter and infiltrate stormwater r un-on; and 3) flo-through planter that is similar t o 23 an infiltration planter except it has a waterproof lining allowing it to be used next to foundation 24 walls. Other terms used for this practice include: stormwater planter, vegetated planter, tree box. 25 plume . A definable, three-dimensional region of effluent created by the movement of 26 groundwater beneath its source. 27 plunge pool. A natural or sometimes artificially created pool th at dissipates energy of free 28 falling water. The basin is located at a safe dista nce downstream of the structure from which the 29 water is being released. 30 pore water pressure. The pressure exerted on its surroundings by water h eld in pore spaces in 31 rock or soil. 32 porosity. Degree to which soil, gravel, sediment, or rock is permeated with pores or cavities 33 through which water or air can move. 34 pre-development hydrology. The runoff characteristics in a watershed prior to urban 35 development in respect to the volume, rate, duratio n and temperature of runoff. 363/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 16 push outs. A type of road drainage structure that drains topog raphic lows or saddles on a road by 1 directing runoff away from the road from both road directions. 2 rain garden. A rain garden is a depressed area of the ground pla nted with vegetation, allowing 3 runoff from impervious surfaces such as parking lot s and roofs the opportunity to be collected 4 and infiltrated into the groundwater supply or retu rned to the atmosphere through evaporation 5 and evapotranspiration. Rain gardens are typically cheaper to build and design than bioretention 6 or bioinfiltration cells since they are often built without specific performance standards and 7 without the assistance of a certified professional to design them. 8 recirculating media filter. Wastewater treatment system component featuring a l ayer of sand, 9 gravel, or other material, upon which effluent is a pplied and treated via microbial growth on the 10 surface of the media, allowing the effluent to tric kle through. A portion of the effluent is returned 11 to another system component for further treatment o r to facilitate a treatment process. 12
reforestation. The establishment of a forest through artificial pl antings or natural regeneration. 13 reinforcement planting. Additional trees and shrubs that are planted durin g the short-term 14 maintenance phase (approximately 2 years after init ial plantings) of a riparian forest buffer 15 restoration to replace any plants that did not surv ive and to enhance the buffer. 16
retrofits. Installation of a new or redesigned stormwater faci lity to treat stormwater from 17 existing impervious area, including, but not limite d to, roofs, patios, walkways, and driving or 18 parking surfaces. 19
return walls. Walls constructed at the ends of seawalls, bulkhead s, or revetments perpendicular 20 to the shoreline to prevent flanking of the primary shore protection structure. 21
revetment. A facing of stone, concrete, etc., built to protect a scarp, embankment, or shore 22 structure against erosion by wave action or current s. 23 ridge tillage. A type of soil conserving tillage in which the soil is formed into ridges and the 24 seeds are planted on the tops of the ridges. The so il and the crop residue between the rows 25 remain largely undisturbed. The practice offers opp ortunities to reduce crop production costs by 26 banding fertilizers and pesticides and reducing the need for field trips. 27
riffle. A shallow part of the stream where water flows swif tly over completely or partially 28 submerged obstructions to produce surface agitation

. 29
rill. A small channel eroded into the soil by surface run off; can be easily smoothed out or 30 obliterated by normal tillage. 31 riparian area. Vegetated ecosystems along a waterbody through whic h energy, materials, and 32 water pass. Riparian areas characteristically have a high water table and are subject to periodic 33 flooding and influence from the adjacent waterbody. These systems encompass wetlands, 34 uplands, or some combination of these two land form s, although they will not in all cases have 35 all of the characteristics necessary for them to be classified as wetlands. 36 riparian buffer. A specific area to be managed within a riparian are a. 373/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 17 riparian habitat. Areas adjacent to rivers and streams with a differi ng density, diversity, and 1 productivity of plant and animal species relative t o nearby uplands. 2
road failure. A portion or location along a forest road where gen erally erosion or poor 3 construction has resulted in the surface of the roa d falling away and leaving the road impassable 4 or compromising the intended drainage of the road s urface. 5 road prism. All parts of a road including cut banks, ditches, r oad surfaces, road shoulders, and 6 road fills. 7 road profile. The cross-sectional shape of the road surface in re lation to the road corridor 8 traversing the surrounding landscape. 9
root wad revetments. Logs with root masses attached placed in and on str eambanks to provide 10 streambank erosion, trap sediment, and improve habi tat diversity. 11 row crop agriculture. The rows or planting beds are far enough apart to p ermit the operation of 12 machinery between them for cultural operations. 13

scour. Soil erosion when it occurs underwater, as in the c ase of a streambed. 14 scour pool. Removal of underwater material by waves and current s, especially at the base or toe 15 of a shore structure. 16
seawalls. A structure separating land and water areas, primar ily designed to prevent erosion and 17 other damage due to wave action. 18
sediment. Topsoil, sand, and minerals washed from the land in to water, usually after rain or 19 snow melt. 20
sediment basin/rock dams. Barriers, often employed in conjunction with excava ted pools, 21 constructed across a drainage way or off-stream and connected to the stream by a flow diversion 22 channel to trap and store waterborne sediment and d ebris. 23
sediment fences (also called silt fences)

. A temporary sediment control device used on 24 construction sites to protect water quality in near by surface waters from sediment (loose soil) in 25 stormwater runoff. A typical fence consists of a pi ece of synthetic filter fabric (also called a 26 geotextile) stretched between a series of wooden or metal stakes. 27 sediment transport capacity and competence. The ability or efficiency of a stream system to 28 move sediment. 29 sediment trap. A structure or vegetative barrier designed to colle ct soil material transported in 30 run-off and also to reduce water flow velocity and therefore scouring and erosion. Sediment traps 31 mitigate siltation of natural drainage features. 32 seeding. The establishment of vegetated cover on a disturbed site though the application of plant 33 seeds and as appropriate, fertilizer, lime, or othe r amendments. 34 septage. Liquid and residuals removed from a septic tank or other sewage pretreatment device or 35 holding facility, such as a seepage pit, cesspool, or portable toilet. 363/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 18 septic tank effluent gravity (STEG) collection syst em. Collection system that uses septic tanks 1 to separate solids and allow gravity flow of efflue nt to a subsequent component. 2 septic tank effluent pump (STEP) collection system. Collection system that uses a septic tank 3 to separate solids and incorporates a pump and asso ciated parts to convey effluent under pressure 4 to a subsequent component. 5 sequencing batch reactor. A series of components designed to treat wastewater in batches, one 6 process at a time. Typically, this involves activat ed sludge and other processes carried out in the 7 same tank in stepwise order (e.g., fill, treat, set tle, decant, and draw). 8
setback. A distance between a water resource and an activity (e.g., manure spreading) within 9 which the activity cannot be carried out. The purpo se of a setback is to reduce the potential for 10 contaminants to reach ground or surface water. Prop erly managed setbacks improve water 11 quality by acting as filters for water passing over or through the soil toward a water resource. 12 shear strength. The internal resistance of a body to shear stress, which typically includes 13 frictional and cohesive components and expresses th e ability of soil to resist sliding. 14
sheetflow. Term used to describe the movement of water lateral ly across the surface of the 15 ground, rather than flowing in defined channels or depressions. 16
silt fence (also called sediment fence). A temporary sediment control device used on 17 construction sites to protect water quality in near by surface waters from sediment (loose soil) in 18 stormwater runoff. A typical fence consists of a pi ece of synthetic filter fabric (also called a 19 geotextile) stretched between a series of wooden or metal stakes. 20
silviculture. Management of forest land for timber production. 21 silvopasture. An agroforestry application establishing a combinat ion of trees or shrubs and 22 compatible forages on the same acreage

. 23 single-pass. Wastewater flow configuration wherein effluent move s through a treatment 24 component only once. 25 site fingerprinting. 1. Site clearing and development using minimal dist urbance of existing 26 vegetation and soils. 2. Restricting ground disturb ance to these areas where structures, roads, and 27 rights of way will exist after construction is comp leted. 28
skid trail. A temporary, nonstructural pathway over forest soil used to drag felled trees or logs to 29 the landing. 30 slag filter. Filters filled with electric arc furnace steel slag , a byproduct of making steel, to treat 31 barnyard runoff and milkhouse waste. 32
slash. The unwanted, unused, and generally unmerchantable accumulation of woody material, 33 such as large limbs, tops, cull logs, and stumps, t hat remains as forest residue after timber 34 harvesting. 353/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 19 slit aeration. Soil aerators are predominately slicers or plug-pul lers, with slicer types being most 1 common for agronomic use. In the slicer type (slit aeration), tines are pushed into the soil to 2 make elongated holes. 3 slough. Sloughs contain areas of slightly deeper water and a slow current. 4 sludge. Accumulated solids and associated entrained water w ithin a wastewater pretreatment 5 component, generated during the biological, physica l, or chemical treatment; coagulation; or 6 clarification of wastewater. 7 sluicing. The practice of releasing water through the sluice gate of an impoundment rather than 8 through the turbines. 9 sodding. A permanent erosion control practice involving layi ng a continuous cover of grass sod 10 on exposed soils. 11 soil dispersal field (soil treatment area). Physical location where final treatment and dispers al 12 of effluent occurs; includes drainfields, drip fiel ds and spray fields. 13 spur road. A short road that branches from a major forest road and that is generally used to 14 access specific areas for harvesting. 15
stormflow. The portion of streamflow attributable to precipita tion that enters the channel 16 (generally as overland flow or shallow subsurface f low) within a short time frame in association 17 with storms (as opposed to baseflow, which enters t he channel slowly from groundwater 18 sources). 19 storm return period. The recurrence interval or an estimate of the inter val of time between 20 storms of a certain intensity or size. See also Des ign Flow. 21
stream corridor. The area that consists of the stream channel itsel f, as well as the floodplain, 22 and a transitional zone between the floodplain and the surrounding landscape. 23 stream geometry. The physical form assumed by a stream system which includes channel depth, 24 width, longitudinal slope and planform. 25 stream morphology. The science of analyzing the structural makeup of r ivers and streams and 26 how they change over time. 27
streamside management area. A designated area that consists of the stream itsel f and an 28 adjacent area of varying width where management pra ctices that might affect water quality, fish, 29 or other aquatic resources are modified. The SMA is not necessarily an area of exclusion, but an 30 area of closely managed activity. It is an area tha t acts as an effective filter and absorptive zone 31 for sediments; maintains shade; protects aquatic an d terrestrial riparian habitats; protects 32 channels and streambanks; and promotes floodplain s tability. 33 street sweeping. The use of self-propelled and walk-behind sweeping and vacuum equipment to 34 remove sediment and other debris from streets, road ways, parking lots and sidewalks. 353/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 20 struvite formation. Struvite is the common name for magnesium ammonium phosphate hexahy1 drate (MgNH 4 PO 4 · 6(H 2 O)). Struvite can naturally form and clog pumps and pipes when 2 recycling lagoon liquid, and struvite accumulation is also a common problem in pumping 3 systems for anaerobic treatment portions of municip al waste treatment systems. Although 4 components designed to promote struvite formation a nd collection have been previously used to 5 remove phosphorus from municipal waste treatment sy stems, the idea of promoting struvite 6 formation and collection is a relatively new concep t for livestock wastewater treatment and 7 nutrient management. 8 subirrigation. Application of irrigation water below the ground su rface by raising the water 9 table to within or near the root zone. 10 surface roughening (also called soil roughening). Increasing the relief of a bare soil surface 11 with horizontal grooves by either stair-stepping (r unning parallel to the contour of the land) or 12 using construction equipment to track the surface. 13 suspended growth or fixed film reactors. Configuration wherein the microorganisms 14 responsible for wastewater treatment are maintained in suspension within a liquid. 15 suspended sediment. Very fine soil particles that remain in suspension in water for a 16 considerable period of time without contact with th e bottom. Such material remains in 17 suspension because of the upward components of turb ulence and currents and/or by suspension. 18
swales. Vegetated, open-channel management practices design ed specifically to treat and 19 attenuate stormwater runoff for a specified water q uality volume. 20
tailwaters. The channel or stream below a dam, often characteri zed by waters with low 21 dissolved oxygen. Many NPS pollution problems in re servoirs and dam tailwaters frequently 22 result from sources in the contributing watershed ( e.g., sediment, nutrients, metals, and toxics). 23
tank. Watertight structure or container used to hold wast ewater for such purposes as aeration, 24 equalization, holding, sedimentation, treatment, mi xing, dilution, or addition of chemicals, or 25 disinfection. 26 thalweg. In hydrologic terms, the line of maximum depth in a stream. The thalweg is the part 27 that has the maximum velocity and causes cutbanks a nd channel migration. 28 thinning. A tree removal practice that reduces tree density a nd competition between trees in a 29 stand. Thinning concentrates growth on fewer, high- quality trees, provides periodic income, and 30 generally enhances tree vigor. Heavy thinning can b enefit wildlife through the increased growth 31 of ground vegetation. 32 three-zone buffer system. A technique for establishing a buffer, consisting o f an inner, middle, 33 and outer zones. The zones are distinguished by fun ction, width, vegetative target, and allowable 34
uses. 35
tile drains. Pipe made of perforated plastic, burned clay, concr ete, or similar material, laid to a 36 designed grade and depth, to collect and carry exce ss water from the soil. 37 tillage. Plowing, seedbed preparation, and cultivation pract ices. 383/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 21 time-dosed pressure drip dispersal (flow equalizati on). System configuration that includes 1 sufficient effluent storage capacity to allow for u niform flow to a subsequent component despite 2 variable flow from the source. 3 time-dosing. Configuration in which a specific volume of effluen t is delivered to a component 4 based upon a prescribed interval, regardless of fac ility water use. 5 topography. The shape and contour of a surface, especially the land surface, usually 6 characterized by slope, aspect and elevation. 7 total maximum daily load (TMDL). A calculation of the highest amount of a pollutant that a 8 water body can receive and safely meet water qualit y standards set by the state, territory, or 9 authorized tribe. 10 total suspended solids. A measure of the suspended solids in wastewater, ef fluent, or water 11 bodies, determined by tests for "total suspended no n-filterable solids." 12
turf. A surface layer of earth containing a dense growth of grass and its matted roots; sod. 13
turnouts (aka bleeders or cutouts)

. A drainage ditch that drains water away from roads and road 14 ditches. 15 urban forest canopy. The land surface area that lies directly beneath th e crowns of all trees and 16 tall shrubs. 17 vegetated swales. A shallow drainage conveyance that has vegetative t urf (typically grasses) 18 with relatively gentle side slopes, generally with flow depths of less than one foot. 19 vertical stability (degradation/aggradation). The ability of a stream system to maintain a 20 constant or balanced profile without deposition of sediment (aggradation) or incision 21 (degredation). 22
vortex rock weirs. A structure designed to serve as grade control and create a diversity of flow 23 velocities, while still maintaining the bed load se diment transport regime of a stream. 24 waste treatment lagoon. Impoundment made by excavation or earth fill for bi ological treatment 25 of wastewater. 26 water quality standards. State-adopted and EPA-approved ambient standards fo r water bodies. 27 The standards prescribe the use of the water body a nd establish the water quality criteria that 28 must be met to protect designated uses. 29
weir. 1. A wall or plate placed in an open channel to mea sure the flow of water. 2. A W-Weir is 30 an in-stream structure constructed for the purpose of reducing shear stress on streambanks, 31 controlling the grade of the streambed and establis hing fisheries habitat. W-Weirs are typically 32 constructed with two rock vanes on opposing sides o f the stream channel forming the outside 33 legs and two opposing vanes in the center of the ch annel to complete the W-Weir. 343/15/2010 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote —

Glossary 22 weighted usable area (WUA). The total surface area having a certain combination of hydraulic 1 and substrate conditions, multiplied by the composi te probability of use by fish for the 2 combination of conditions at a given flow. 3
wetland. An area that is saturated by surface or ground wate r with vegetation adapted for life 4 under those soil conditions, as swamps, bogs, fens, marshes, and estuaries. 5
windbreaks. A living barrier that usually includes several rows of trees, and perhaps shrubs, 6 located upwind of a farm, field, feedlot or other a rea and intended to reduce wind velocities. 7 Windbreaks, also called shelterbelts, can reduce wi nd erosion, conserve energy or moisture, 8 control snow accumulations, and provide shelter for livestock or wildlife. 9
windrow. Logging debris and unmerchantable woody vegetation that has been piled in rows to 10 decompose or to be burned; or the act of constructi ng these piles. 11
WTR addition. The addition of iron-rich or aluminum-rich drinking water treatment residuals 12 (WTR) to soils to bind with P and reduce losses of P via leaching and runoff. 13

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