C.M.R. 01, 001, ch. 565, ATTACHMENTS, att. B
NRCS Codes 393 and 635
Filter Strips and Vegetated Treatment Areas Natural Resources Conservation Service
CONSERVATION PRACTICE STANDARD
FILTER STRIP
Code 393
(Ac)
DEFINITION
A strip or area of herbaceous vegetation that removes contaminants from overland flow.
PURPOSE
Reduce suspended solids and associated contaminants in runoff and excessive sediment in surface waters. Reduce dissolved contaminant loadings in runoff. Reduce suspended solids and associated contaminants in irrigation tailwater and excessive sediment in surface waters.CONDITIONS WHERE PRACTICE APPLIES
Filter strips are established where environmentally sensitive areas need to be protected from sediment, other suspended solids, and dissolved contaminants in runoff.
CRITERIA
General Criteria Applicable to All Purposes
Overland flow entering the filter strip will be uniform sheet flow.
Concentrated flow will be dispersed before it enters the filter strip.
The maximum gradient along the leading edge of filter strip will not exceed one-half of the up-and-down-hill slope percent, immediately upslope from the filter strip, up to a maximum of five percent.
Filter strips will not be used as a travel lane for equipment or livestock.
Additional Criteria to Reduce Dissolved Contaminants, Suspended Solids and Associated Contaminants in Runoff and Excessive Sediment in Surface Waters.
The filter strip will be designed to have a 10-year life span, following the procedure in Agronomy Technical Note No. 2, "Using Revised Universal Soil Loss Equation, Version 2 (RUSLE2) for the Design and Predicted Effectiveness of Vegetative Filter Strips (FVS) for Sediment," based on the amount of sediment delivery to the upper edge of the filter strip and ratio of filter strip flow length to length of flow path from the contributing area. The minimum flow length through the filter strip will be 20 feet for suspended solids and associated contaminants in runoff and 30 feet for dissolved contaminants and pathogens in runoff. http://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=18578.wba
The filter strip will be located immediately downslope from the source area of contaminants.
The drainage area immediately above the filter strip will have a slope of one percent or greater.
Vegetation. The filter strip will be established to permanent herbaceous vegetation.
Species selected will be-
Able to withstand partial burial from sediment deposition. Tolerant of herbicides used on the area that contributes runoff to the filter strip. Stiff stemmed and a high stem density near the ground surface. Suited to current site conditions and intended uses. Able to achieve adequate density and vigor within an appropriate period to stabilize the site sufficiently to permit suited uses with ordinary management activities.Plant species, rates of seeding (lbs/ac), vegetative planting (plants/ac), minimum quality of planting stock (pure live seed [PLS] or stem caliper), and method of establishment shall be specified before application. Only viable, high quality seed or planting stock will be used.
BPerform site preparation and seeding/planting at a time and in a manner that best ensures survival and growth of selected species. Successful establishment parameters, (e.g., minimum percent ground/ canopy cover, percent survival, stand density) will be specified before application.
Schedule planting dates during periods when soil moisture is adequate for germination and establishment. Seeding will be timed so that tillage for adjacent crop does not damage the seeded filter strip.
Where the purpose is to remove phosphorus, remove (or harvest) the filter strip above ground biomass at least once each year.
The minimum seeding and stem density will be equivalent to the seeding rate for a high quality grass hay seeding rate for the climate area or the density of vegetation selected in current water erosion technology to determine trapping efficiency, whichever is the higher seeding rate.
Additional Criteria to Reduce Suspended Solids and Associated Contaminants in Irrigation Tailwater and Excessive Sediment in Surface Waters.
Filter strip vegetation will be a small grain or other suitable annual plant.
The seeding rate shall be sufficient to ensure that the plant spacing does not exceed 4 inches (about 16-18 plants per square foot).
Establish filter strips prior to the irrigation season so that the vegetation is mature enough to filter sediment from the first irrigation. A minimum flow length of 20 feet is recommended.
CONSIDERATIONS
General Considerations.
Filter strip width (flow length) can be increased as necessary to accommodate harvest and maintenance equipment.
Filters strips with the leading edge on the contour will function better than those with a gradient along the leading edge.
Seeding rates that establish a higher stem density than the normal density for a high quality grass hay crop will be more effective in trapping and treating contaminants.
When needed, invasive plant species may be controlled through mowing, herbicides, and hand weeding.
Consideration for Reducing Suspended Solids and Associated Contaminants in Runoff.
Increasing the width of the filter strip beyond the minimum required will increase the potential for capturing more contaminants in runoff.
Considerations for Creating, Restoring or Enhancing Herbaceous Habitat for Wildlife and Beneficial Insects and Pollinators. Filter strips are often the only break in the monotony of intensively-cropped areas. The wildlife and pollinator benefits of this herbaceous cover can be enhanced by the following:
When appropriate, use native grass species that fulfill the purpose(s) of the practice while also providing habitat for priority wildlife. Adding herbaceous plant species (including native forbs) to the seeding mix that are beneficial to wildlife and pollinators and are compatible for one of the listed purposes. Changing the seeding mix should not detract from the purpose for which the filter strip is established. Increasing the width beyond the minimum required. The additional area can increase food and cover for wildlife and pollinators. Management activities on filter strips (mowing, burning, or light disking), should not be done more often than every other year with frequency dependent on geographical location to maintain the purpose(s) of the practice. Management activities should be completed outside of the primary nesting, fawning, and calving seasons. Activities should be timed to allow for regrowth before the growing season ends. Organic producers should submit plans and specifications to their certifying agent for approval prior to installation, as part of the organic producer's organic system plan.Considerations to Maintain or Enhance Watershed Functions and Values. Filter strips may be used to enhance connectivity of corridors and noncultivated patches of vegetation within the watershed, enhance the aesthetics of a watershed, and be strategically located to reduce runoff, and increase infiltration and groundwater recharge throughout the watershed.
Increase Carbon Storage. Increasing the width of the filter strip beyond the minimum required will increase potential for carbon sequestration.
PLANS AND SPECIFICATIONS
Specifications for establishment and operation of this practice will be prepared for each field or treatment unit. Record the specifications using the implementation requirements document. The specifications will identify at a minimum the following:
Practice purpose(s). Length, width (width refers to flow length through the filter strip), and slope of the filter strip to accomplish the planned purpose(s). Plant species selection and seeding/planting/sprigging rates to accomplish the planned purpose. Planting dates and planting method(s). Specific care and handling requirements of the seed or plant material to ensure that planted materials have an acceptable rate of survival. A statement that only viable, high quality, and adapted seed will be used. Site preparation instructions sufficient to establish and grow selected species.OPERATION AND MAINTENANCE
For the purposes of filtering contaminants and nutrients (phosphorus), permanent filter strip vegetative plantings will be harvested and removed as appropriate to encourage dense growth, maintain an upright growth habit and remove nutrients and other contaminants that are contained in the plant tissue.
Control undesired weed species, especially State-listed noxious weeds.
Inspect the filter strip after storm events and repair any gullies that have formed, remove unevenly deposited sediment accumulation that will disrupt sheet flow, reseed disturbed areas and take other measures to prevent concentrated flow through the filter strip.
Apply supplemental nutrients as needed to maintain the desired species composition and stand density.
Periodically regrade and reestablish the filter strip area when sediment deposition at the filter strip-field interface jeopardizes its function. Reestablish the filter strip vegetation in regraded areas, if needed.
If grazing is used to harvest vegetation from the filter strip, the grazing plan must ensure that the integrity and function of the filter strip is not adversely affected.
REFERENCES
Dillaha, T.A., J.H. Sherrard, and D. Lee. 1986. Long-Term Effectiveness and Maintenance of Vegetative Filter Strips. VPI-VWRRC Bulletin 153.
Dillaha, T.A., and J.C. Hayes. 1991. A Procedure for the Design of Vegetative Filter Strips: Final Report Prepared for U.S. Soil Conservation Service.
Foster, G.R. Revised Universal Soil Loss Equation, Version 2 (RUSLE2) Science Documentation (In Draft). USDA-ARS, Washington, DC. 2005.
Renard, K.G., G.R. Foster, G.A. Weesies, D.K. McCool, and D.C. Yoder, coordinators. 1997. Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE). U.S. Department of Agriculture. Agriculture Handbook 703.
Revised Universal Soil Loss Equation Version 2 (RUSLE2) Web site (checked May 2007): http://fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm.
M.G. Dosskey, M.J. Helmers, and D.E. Eisenhauer 2008. A Design Aid for Determining Width of Filter Strips. Journal of Soil and Water Conservation. July/Aug 2008-vol. 63, no. 4.
NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE STANDARD
VEGETATED TREATMENT AREA
CODE 635
(Ac.)
DEFINITION
An area of permanent vegetation used for agricultural wastewater treatment.
PURPOSE
Improve water quality by using vegetation to reduce the loading of nutrients, organics, pathogens, and other contaminants associated with livestock, poultry, and other agricultural operations.
CONDITIONS WHERE PRACTICE APPLIES
This practice applies where:
A vegetated treatment area (VTA) can be constructed, operated and maintained to treat contaminated runoff from such areas as feedlots, feed storage, compost areas, solid manure storage areas, barnyards, and other livestock holding areas; or to treat process wastewater from agricultural operations. A VTA is a component of a planned agricultural waste management system.CRITERIA
Size the total treatment area for the VTA on both the contributing site water runoff and vegetation nutrient balances.
Water balance is the soil's capacity to infiltrate and retain runoff within the root zone. Base the runoff determination on the most restrictive soil layer within the root zone regardless of its thickness. Use the soil's water holding capacity in the root zone, infiltration rate, permeability, and hydraulic conductivity to determine its ability to absorb and retain runoff. Nutrient balance utilizes the nutrients from the waste runoff to meet the nutrient removal requirements in the harvested vegetation. Base the nutrient balance on the most limiting nutrient (i.e. nitrogen or phosphorus).Divert uncontaminated water from the treatment area to the fullest extent possible unless additional moisture is needed to manage vegetation growth in the treatment area.
Establish permanent vegetation in the treatment area. Use a single species or a mixture of grasses, legumes, and other forbs adapted to the soil and climate. Select species to meet the current site conditions and intended use. Selected species will have the capacity to achieve adequate density, vigor, and yield within an appropriate time frame to treat contaminated runoff. Complete site preparation and seeding at a time and in a manner that best ensures survival and growth of the selected species.
Select vegetation that will withstand anticipated wetting or submerged conditions. Harvest vegetation as appropriate to encourage dense growth, maintain an upright growth habit, and remove nutrients and other contaminants that are contained in the plant tissue.
Design the VTA based on the need to treat the runoff volume from the 25-year, 24-hour storm event from the agricultural animal management facility. Infiltrate a portion or the entire volume of the design storm, based on management objectives. Unless discharge is permitted by applicable regulations, store the non-infiltrated portion of the design volume for utilization or treatment.
Exclude all livestock, including grazing, from the VTA.
Apply discharge into and through vegetated treatment area as sheet flow. To encourage sheet flow across the treatment area, provide a means to disperse concentrated flow, such as a ditch, curb, gated pipe, level spreader, or a sprinkler system. Complete land grading and install structural components necessary to maintain sheet flow throughout the treatment area.
Limit the natural or constructed slope of the VTA from 0.3 to 6 percent. The minimum entrance slope to the VTA is 1 percent.
Use NRCS Conservation Practice Standard (CPS) Code 632, Waste Separation Facility, to pretreat influent with waste separation (i.e., settling basin) to reduce organic loading and nutrients to levels that are tolerated by the VTA and to prevent excessive accumulation of solids in the treatment area.
Utilize inlet control structures to control the rate and timing of inflow during normal operations and to control inflow as necessary for operation and maintenance.
Locate VTA outside of floodplains. However, if site restrictions require location within a floodplain, provide protection from inundation or damage from a 25-year flood event, or larger, if required by regulation.
Install VTA where the water table is either naturally deep or artificially lowered so that the infiltrated runoff does not mingle with the groundwater at the bottom of the root zone. Subsurface drainage within the VTA is not allowed. Subsurface drainage may be used to lower the seasonal high water table to an acceptable level provided the subsurface drain lines are at least 10 feet away from the VTA boundary.
Unless soil moisture can be maintained to prevent drying and cracking, do not plan infiltration areas where soil features such as cracking will result in preferential flow paths that transport untreated runoff from the surface to below the root zone.
Ensure that appropriate erosion control measures and sheet flow control measures (i.e., gravel or rock spreaders) are adequately addressed over the entire length of the VTA.
MAINE DESIGN CRITERIA
For the purposes of this standard, the following definitions apply:
-Intermittent or Perennial Stream: Any stream with a watershed greater than 100 acres.
-Sensitive Habitat: Rare or Exemplary natural communities or ecosystems as designated by the Maine Natural Areas Program or the U.S. Fish and Wildlife Service (USFWS), a pond or a fully functioning forested wetland as determined by the State Soil Scientist (SSS) or representative.
A VTA shall not be located within 300 feet of an intermittent or perennial stream or other sensitive habitat when used for any of the following:
Treats runoff from a structure that services more than 15 animal units Treats runoff from a composting facility that contains carcasses, offal, or meat scraps This includes, but is not limited to runoff from heavy use areas, waste storage facilities, compost facilities or silos.If there are no other feasible means to address an existing water quality resource concern, exceptions can be made to the above criteria by the State Conservation Engineer (SCE).
All VTA's, regardless of number of AU served, shall use the following criteria based on water balance to size the VTA:
No VTA shall be wider than 60 feet. No flow length shall be greater than 100 feet. Therefore, no VTA shall be greater than 6,000 square feet.
To encourage sheet flow, provide retention of peak runoff, and allow for settling of incidental particulates, each VTA shall have a retention area prior to Level Lip Spreader. The retention area has to meet the same separation distances as the treatment strip. Use Table 1 to size the retention area.
Retention areas shall not be more than 60 feet long and should not be less than 6 feet wide. Maximum retention area width can be up to 10 feet wide to accommodate maintenance equipment needed to clean out the retention area. Use NRCS Conservation Practice Standard (CPS) Code 632, Waste Separation Facility, as needed, to pretreat influent with waste separation (i.e. settling basin) to reduce organic loading and nutrients to levels that are tolerated by the VTA and to prevent excessive accumulation of solids in the retention area. NRCS CPS Code 629, Waste Treatment shall also be followed when treating silage leachate.
Table 1: Volume of Retention Area
Impervious surface use | Area of impervious surface used to calculate VTA size (y) Units = sq. ft. | Volume of retention area prior to sheet flow release (V) Units = cu. ft. |
Animal feedlot | Area where animals have access | V = 0.125y |
Silage storage | Area where silage is stored | V = 0.125y |
Cull potato storage | Area where potatoes are stored | V = 0.125y |
Manure storage | Area where manure is stacked | V = 0.125y |
Compost amendment storage | Area where amendments are stacked | V = 0.125y |
Composting | Area for composting | V = 0.06y |
TREATMENT STRIP SITING CRITERIA
Consult with a Resource Soil Scientist to locate proposed VTA's and determine if any modifications are needed to meet separation distances and soils criteria.
* SOIL PERMEABILITY:
The design shall be based on the most restrictive soil layer within the root zone. The Maximum Permeability in the root zone shall be less than or equal to 2.0 in/hr, UNLESS:
1. A natural or constructed barrier within the soil profile mitigates the potential of ground water contamination. In Maine, a natural barrier would be a dense substratum such as a glacial till hardpan or heavy marine or lacustrine sediment that results in a seasonally perched water table.
OR
2. Greater than or equal to 18 inches of loamy fine sand or finer soil material (permeability < 2.0 in/hr) exists over soil material with permeability > 2.0 in/hr such as sand or gravel.
OTHER VTA SITE/SOIL CHARACTERISTIC REQUIREMENTS:
Minimum Depth to Bedrock: 18 inches Minimum Depth to Seasonal High Water Table: 15 inches Slope Range: 1 - 6 percentSETBACKS FROM RESOURCE CONCERNS:
Wells: 100 feet Receiving Surface Water: 100 ft. < 15 animal units, 300 ft. > 15 animal units OR carcass/offal/meat composting Public Water Supply: 300 feet Other options or modifications, such as ROOFED AREAS, will be necessary if the above unsuitable conditions exist in potential treatment areas. See NRCS CPS 367, Roofs and Covers for details.Use Table 2 to size the vegetated treatment area based on soil type.
Table 2: Vegetated Treatment Area Size Based on Soil Type
SOIL / PARENT MATERIAL TYPES | SOIL PERMEABILITY RANGE | SIZE RATIO OF IMPERMEABLE SURFACE (y) TO VEGETATED TREATMENT AREA |
1. COARSE LOAMY & SANDY GLACIAL TILLS 2. COARSE SILTY SEDIMENTS 3. COARSE SILTY ALLUVIAL DEPOSITS | 0.6 - 2.0 in/hr | 1 : 1 |
FINE LOAMY AND SILTY GLACIAL TILLS | 0.2 - 0.6 in/hr | 1 : 1.5 |
FINE SILTY SEDIMENTS | 0.06 - 0.2 in/hr | 1 : 1.8 |
ADDITIONAL CRITERIA FOR DOSING SYSTEMS
Distribute the effluent over the VTA through sprinkler irrigation or other pressure dosing system. Match the application rate of sprinkler nozzles to the most restrictive soil infiltration rate or other factors to prevent effluent from discharging from the VTA.
CONSIDERATIONS
Direct contaminated effluent to a waste storage facility during excessively wet or cold climatic conditions.
Additional nutrient and infiltration design guidance in Vegetated Treatment Systems for Open Lot Runoff, (Koelsch, et. al., 2006).
Provide more than one VTA to allow for resting, harvesting vegetation, and maintenance, and to minimize the potential for overloading.
If impervious area requires more than 6,000 square feet of vegetated filter area for treatment, then consider installing multiple filter areas and divide impervious area flow accordingly.
Provide additional storage in the basin collection area to minimize or eliminate discharge into the VTA during rainfall events. Delay application until rainfall has ended to improve infiltration and nutrient uptake.
To maximize nutrient uptake, use warm and cool season species in separate areas to ensure that plants are actively growing during different times of the year.
Supplement water as necessary to maintain plants in a condition suitable for the treatment purpose.
Consider suspension of application to treatment area when weather conditions are not favorable for aerobic activity or when soil temperatures are lower than 39° F. When soil temperatures are between 39° F and 50° F, consider reducing application rate and increasing application period while maintaining a constant hydraulic loading rate.
Manage the VTA to maintain vegetative treatment effectiveness throughout the growing season. Time the harvest of the VTA plants so vegetation can regrow to a sufficient height to effectively filter effluent late in the growing season.
Install a berm around the lower end of the VTA to contain excess runoff that may occur.
Effluent from the VTA may be stored for land application, recycled through the wastewater management system, or otherwise used in the agricultural operation.
Install fences or other measures to exclude or minimize access of the VTA to humans or animals.
Install a pumping system at the bottom of the VTA to either recirculate the effluent to the top of the VTA or transfer to a waste storage facility.
PLANS AND SPECIFICATIONS
Prepare plans and specifications that describe the requirements for applying the practice to achieve its intended use. As a minimum include:
Critical construction perimeters, necessary construction sequence, vegetation establishment requirements, retention area and level spreader mechanism requirements, associated practices and agronomic nutrient removal. Plan view showing the location of all components of the VTA. Details of the length, width, and slope of the treatment area to accomplish the planned purpose (length refers to flow length down the slope of the treatment area). Herbaceous species, seed selection, and seeding rates to accomplish the planned purpose Planting dates, care, and handling of the seed to ensure that planted materials have an acceptable rate of survival. Site preparation sufficient to establish and grow selected species.OPERATION AND MAINTENANCE
Develop an operation and maintenance plan consistent with the purposes of the practice, its intended life, safety requirements, and the criteria for its design. Include the following items as appropriate:
Inspect and maintain retention and spreader area to ensure that sheet flow loading is maintained for the VTA. Inspect and repair treatment areas after storm events to address gullies, reseed disturbed areas, and prevent concentrated flow. Control undesired weed species, especially state-listed noxious weeds, and other pests that could inhibit proper functioning of the VTA. Exclude livestock from VTA. Apply supplemental nutrients and soil amendments as needed to maintain the desired species composition and stand density of herbaceous vegetation. Maintain or restore the treatment area as necessary by periodically grading or removing excess material when deposition jeopardizes its function. Reestablish herbaceous vegetation. Routinely dethatch or aerate a treatment area used for treating runoff from livestock holding areas in order to promote infiltration. Conduct maintenance activities only when the surface layer of the VTA is dry enough to prohibit compaction. Monitor all treatment areas to maintain optimal crop growth and environmental protection.REFERENCES
USDA/NRCS, National Engineering Handbook, Part 651, Agricultural Waste Management Field Handbook.
Koelsch, R., B. Kintzer, and D. Meyer. (ed.) 2006. Vegetated Treatment Systems for Open Lot Runoff - A Collaborative Report. USDA, NRCS.
C.M.R. 01, 001, ch. 565, ATTACHMENTS, att. B