Virginia Law

Article 11. Nonpublic Drinking Water Supply Systems Utilized in Conjunction with Onsite Sewage Disposal Systems

12VAC5-610-1140. General.

Article 11
Nonpublic Drinking Water Supply Systems Utilized in Conjunction with Onsite Sewage Disposal Systems

A. Authority for this article is found in § 32.1-164 B 6 of the Code of Virginia. This article pertains only to new construction where a nonpublic water supply, other than a private well, is to be constructed and utilized in conjunction with an onsite sewage disposal system. Approval of the water supply is an integral part of the issuance of an operation permit for a sewage disposal system (see 12VAC5-610-340) and no separate permit is required. An approval of a water supply under this section connotes a water supply meeting the quantity, quality and construction standards of a satisfactory water supply at the time of approval.

B. Quantity.

1. The system shall be capable of supplying water in adequate quantity for its intended usage. Failure to provide adequate capacity may cause intermittent flows and negative pressures which may cause contamination of the system through cross connections or other system deficiencies.

2. The source shall have a capacity to produce 150 gallons per bedroom per day for residential use.

3. The minimum system capacity (source plus storage) should be capable of delivering a sustained flow of five gallons per minute per connection for 10 minutes for ordinary residential use.

C. Quality.

1. Water sources described in this section shall be considered satisfactory if the water sample or samples test negative for coliform organisms. Sources with positive coliform counts, but with less than 100 MPN/100ml shall be provided with a means for continuous disinfection (chlorination).

2. A sample tap shall be provided at or near the water entry point into the system so that samples may be taken directly from the source; this requirement may be met by utilizing the first tap on the line near where the plumbing enters the house (may be a hose bib), provided the tap precedes any water treatment devices.

3. The entire water system including the well shall be disinfected prior to use. After operating the well to remove any remaining disinfectant, a sample of the water from the well shall be collected by the district or local health department for bacteriological examination. The sample may be collected by the owner, or an agent designated by the owner, provided the sample is submitted to a private, certified (by Division of Consolidated Laboratory Services) laboratory for analysis.

4. If tests indicate that the water is unsatisfactory and no other approval source is available, adequate approved methods of water treatment shall be applied. The district or local health department shall be consulted when treatment is necessary.

D. Approval. All water supplies covered by this chapter shall be approved by the district or local health department before being placed into service as a satisfactory water supply.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.49, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1150. (Repealed.)

Historical Notes

Derived from VR355-34-02 § 4.50, eff. February 5, 1986; amended, eff. May 11, 1988; repealed, Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1160. Springs.

A. Sanitary survey. Only springs which are found acceptable following a sanitary survey (12VAC5-610-1150 B) will be considered for use as a source of potable water. The following shall be considered when making the sanitary survey:

1. The spring's source should be an aquifer which is not subject to pollution;

2. The spring should not be subject to flooding;

3. Consideration should be given to fencing an adequate area completely around the spring to prevent contamination by people and/or animals;

4. Consideration should be given to diverting surface water away from the spring; and

5. The distance from other sources of pollution shall be the same as for subsurface soil absorption systems contained in Table 4.4 and 12VAC5-610-810 A.

B. Construction of springs and/or reservoirs.

1. The spring shall be completely enclosed. The walls and cover shall be constructed of durable watertight material.

2. All springs and/or reservoirs shall be accessible for cleaning and maintenance. When access is through the top, the opening shall have a minimum dimension of 24 inches. The opening shall be fitted with a solid, watertight cover which overlaps the framed opening and extends vertically down around the frame at least two inches (shoe box).

3. The top of the cover frame shall be at least two 12 inches above the surrounding ground surface.

4. Overflows shall be screened to prevent entrance of undesirable materials (See 12VAC5-610-1170 C 9).

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.51, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1170. Cisterns.

A. General. Cisterns shall be considered only when no other source of potable water is feasible.

B. Location and protection. The following precautions should be taken with regard to the location and protection of cisterns:

1. The distance from other sources of pollution shall be the same as for subsurface soil absorption systems contained in Table 4.4 and 12VAC5-610-810 A; and

2. Cisterns shall be located in a manner that will not subject them to flooding.

C. Construction.

1. The cistern shall be constructed of watertight, durable, structurally sound material, with a smooth interior surface.

2. When the cistern is filled by rainfall provisions shall be made to bypass, divert or otherwise remove the water that falls at the beginning of a rain.

3. Cisterns shall be accessible for cleaning.

4. Where a manhole cover is used, it shall be watertight and the manhole shall be at least 24 inches in diameter.

5. Where another type of cover is used, it shall be a solid, watertight cover which overlaps the framed opening and extends vertically down around the frame at least two inches.

6. The top of the cover frame shall be at least 12 inches above the surrounding ground surface.

7. All openings into the cistern shall be screened in order to prevent the entrance of insects, rodents and other animals and pollutants.

8. When screens and filters are utilized for filtering roof runoff, they shall be accessible for regular cleaning.

9. Drain and overflow pipes shall not be connected directly to any sewer, soil pipe, house drain or other waste pipe. An air-gap shall be provided on all drains and overflow pipes. Drains and overflow pipes shall be suitably screened.

10. Asphaltic roofing material or painted roofs should not be utilized in conjunction with cisterns because of the potential leaching of toxic materials.

D. Potability. Cisterns cannot be relied upon to provide potable water without adequate treatment. Adequate treatment consists of removal of solids washed from the roof and continuous disinfection.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.52, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1170:1. APPENDIX F. Field Guide To Soil Texture Classes.

APPENDIX F.

Field Guide To Soil Texture Classes

Field Guide To Soil Texture Classes (USDA)

Introduction-The purpose of this test is to provide a standard procedure for estimating soil texture in the field. The texture is estimated by the "feel" of moist soil. The texture of a soil cannot be estimated by "feel" if it is either dry or wet.

Definitions

Particle Size Classes

Sand-Sand has a particle size ranging from 0.05 millimeters (mm) to 2.0 millimeters (mm) in diameter. Sand imparts a gritty feel to soil due to the shape of the individual particles.

Silt-Silt has a particle size ranging from 0.002 millimeters (mm) to 0.05 millimeters (mm) in diameter. When moist, silt has a floury feel and does not ribbon when pressed between the thumb and forefinger due to the shape of the individual particles. When placed between the teeth silt has a gritty feeling.

Clay-Clay has a particle size less than 0.002 millimeters (mm) in diameter. Clay exhibits collodial properties, has a negative charge and is flat and platelike in shape. Moist clay is sticky and will ribbon readily when pressed between the thumb and forefinger. When placed between the teeth clay has a smooth slick feeling.

Soil Texture-Soil texture refers to the relative proportions of sand, silt and clay particles in a soil material that has a particle size less than two (2) millimeters (mm) in diameter. Soil texture is an indicator of infiltration capacity, permeability, degree of aeration and drainage as well as other physical characteristics of a soil material.

Soil Texture Classes-The United States Department of Agriculture (USDA) has identified twelve (12) soil texture classes as follows: sand, loamy sand, sandy loam, sandy clay loam, loam, silt loam, silt, silty clay loam, clay, clay loam, sandy clay and silty clay. Each texture class has a distinctive characteristic(s) which can be estimated in the field by trained personnel.

Distinguishing Characteristics-The following characteristics are based on moist soil.

Sand-Sand has a gritty feel, does not stain the fingers and does not form a ball when moist.

Loamy Sand-Loamy sand has a gritty feel, stains the fingers (silt and clay) and forms a weak ball but cannot be handled without breaking.

Sandy Loam-Sandy loam has a gritty feel, forms a ball that can be picked up with the fingers and handled with care without breaking.

Loam-Loam may have a slight gritty feel but does not show a finger print and forms only short ribbons of from 0.25 inch to 0.50 inch in length. Loam will form a ball that can be handled without breaking.

Silt Loam-Silt loam has a floury feel when moist and sticky when wet but will not ribbon and forms a ball that will tolerate some handling. Silt texture has not been found in any Virginia soils.

Sandy Clay Loam-Sandy clay loam has a gritty feel but contains enough clay to form a firm ball and may ribbon to form 0.75 inch to 1 inch long pieces.

Silty Clay Loam-Silty clay loam is sticky when moist and will ribbon from one (1) to two (2) inches. Rubbing silty clay loam with the thumb nail produces a moderate sheen. Silty clay loam produces a distinct finger print.

Clay Loam-Clay loam is sticky when moist. Clay loam forms a thin ribbon of one (1) to two (2) inches in length and produces a slight sheet when rubbed with the thumb nail. Clay loam produces a nondistinct finger print.

Sandy Clay-Sandy clay is plastic, gritty and stocky when moist and both forms a firm ball and produces a thin ribbon to over two (2) inches in length.

Silty Clay-Silty clay is both plastic and sticky when moist and lacks any gritty feeling. Silty clay forms a firm ball and readily ribbons to over two (2) inches in length.

Clay-Clay is both sticky and plastic when moist, produces a thin ribbon over two (2) inches in length, produces a high sheen when rubbed with the thumb nail and forms a strong ball resistant to breaking.

12VAC5-610-1170:2. APPENDIX G. Percolation Test Procedure and Percolation Test Data Forms.

APPENDIX G.

1. Percolation Test Procedure

2. Percolation Test Data Forms

Percolation Test Procedure

Definition-The percolation test is a field procedure conducted in the soil horizon(s) selected for installation of the proposed subsurface soil absorption system for the purpose of observing the rate that clean water will permeate the soil under saturated conditions. The test provides a method for approximating the actual movement of wastewater through the soil which will occur during operation of the subsurface soil absorption system.

Test Holes

1. Test holes shall be located at points and depths selected by and/or approved by the district or local health department.

2. The depth of the test hole shall be placed in the "slowest" portion of the horizon(s) selected for installation of the absorption trenches. (See § 4.03A).

3. The portion of the test hole penetrating the horizon(s) selected for placement of the absorption trenches shall be 7 (±) 2 inches in diameter. Minimum acceptable horizon thickness is twelve (12) inches. The diameter of the test hole above the selected horizon(s) may be as large as necessary to conduct the test and prepare the hole in the selected soil horizon(s).

4. Test holes shall, where possible, be constructed within four (4) to six (6) feet of an existing profile hole.

5. A portion of the material excavated from the test hole should be mounded around the test hole to prevent surface water runoff from entering the hole in the event of rainfall during the period preceding and continuing through the conduct of the test.

6. Where indicated the bottom and sidewalls of the hole shall be scarified with a sharp pointed instrument or knife to remove any smeared soil surfaces. Two inches of clean course sand or clean fine gravel (pea gravel) shall be added to the hole to protect the bottom infiltrative surface from scouring and sedimentation.

Presoaking

1. Swelling Procedure-When shrink-swell soils are suspected the soil surrounding the test hole shall be saturated for at least 24 hours by keeping at least 12 inches of water in the hole for the 24 hour period. An additional three days for swelling may be required during dry periods when cracking has occurred. After completion of the swelling procedure stated above the hole shall be left overnight before proceeding with the measurement procedure.

2. Saturation Procedure-All test holes not subject to the swelling procedure shall be kept saturated with at least 12 inches of water for a 4 hour period on the day preceding the measurement of the percolation rate. Residual water in the hole shall be left to provide overnight soaking.

Measurement of Percolation Rate-All measurements shall be made from a fixed reference point.

1. Test holes with 6 inches or less of water remaining after the overnight soaking period.

a. Carefully fill the hole with water to a depth of 6 inches over the sand/gravel.

b. Record water surface drop every 30 minutes for a 4 hour period.

c. After recording the water surface drop each 30 minutes estimate if, based on the last reading, the hole will go dry add sufficient water to maintain not more than one (1) inch water depth over the sand/gravel at the end of the test period.

d. The drop measured during the last 30 minute period shall be used to compute the percolation rate for the hole tested.

e. In soils where the first 6 inches of water seep away in less than 30 minutes after the overnight saturation period, add an additional 6 inches of water and the time interval between measurements shall be taken as 10 minutes and the test run to completion, i.e. hole goes dry. The drop that occurs during the final 10 minutes is used to calculate the percolation rate.

2. Test hole with more than 6 inches of water remaining after the overnight soaking period. The water depth over the gravel shall be recorded. More than 6 inches of water remaining in the hole after soaking procedure is prima-facie evidence of unsatisfactory for installation of a subsurface soil absorption system.

V0110037.JPG, SIZE-44 PICAS, TYPE-DPI

For , see Virginia Administrative Code print product.

12VAC5-610-1170:3. APPENDIX H. Land Disposal Criteria.

APPENDIX H.

Land Disposal Criteria

The following sections are reproduced from the Commonwealth of Virginia Sewerage Regulations, State Department of Health and State Water Control Board February 1977.

25.07 Sludge and Solids Disposal

25.07.01 General

A plan shall be provided for the disposal of sludge and solids from each treatment facility as part of the final engineering documents (cf. Section 2.04.02). Before sludge is disposed of by land application, its short term and long term chemical effects on the land and groundwater must be evaluated. The evaluation program should consider the existing industrial waste surveys and general characteristics of the land to be used as well as other appropriate information. Adequate provisions for residue disposal, air pollution control, soil contamination prevention and groundwater/surface water contamination prevention shall be provided. Sludge shall not be applied to root crops or crops intended for human consumption in the raw form. Disposal of sludge shall be in such a manner as not to cause health hazards, destroy vegetation, create odor and/or vector problems, render the soil unsuitable for future land use or create other nuisances. Land areas proposed for sludge disposal should be remote from inhabited dwellings, water supplies and shellfish areas. Disposal of sludge to open dumps is prohibited. Designs incorporating the use of sludge as a soil conditioner should be forwarded to the Department of Agriculture and Commerce by the Department for appropriate review and comment.

25.07.02 Land Acquisition or Control

When land application constitutes a primary means of sludge disposal for a facility and the facility does not possess sufficient alternate disposal means, the continued availability of the land shall be protected. Such land shall also be protected from improper concurrent uses during utilization periods. The means of such protection for land availability and from improper concurrent uses shall be determined by the Department, the Board and the owner at the preliminary engineering conference.

25.07.03 Sludge Stabilization and Pathogen Reduction Prior to Land Application

Sludge shall be subjected to a treatment process which will stabilize many of the organic materials present in raw sludge. Anaerobic digestion, composing, aerobic digestion, heat treatment, processes or chemical treatment processes such as high lime or chlorine dosages are considered to produce stabilized sludges. For some projects, it may be necessary to achieve additional pathogen reduction beyond that attained by stabilization.

25.07.04 Sludge Composition and Soil Evaluation

The following parameters for sludge and soil composition may be employed to determine the sludge classification and suitability of soils for sludge application. Determination of specific parameters to be run shall be made at the preliminary engineering conference and the results of the analyses shall be included as a portion of the sludge disposal plan required in accordance with Section 25.07.01.

Appendix J contains forms which are recommended for use by the owner of the treatment facility in providing the results of background sludge and soil analyses. A one-quart soil sample shall be taken from the top four inches of soil and retained indefinitely.

After the sludge disposal plans required in accordance with Section 25.07.01 is approved by the Department and the Board, the Department and the Board waive the requirement for the sludge composition analyses and soil evaluation at any new application site for which either of the two following criteria apply:

a. the sludge is applied as a single application not to be repeated for at least five years.

b. the sludge application area is no larger than 10 acres.

This waiver in no way limits the powers of the Board and the Department in the control of any sludge application practice, regardless of frequency of application or size of the application area, for which groundwater contamination, surface runoff, soil toxicity, health hazards or nuisance conditions are considered to be a problem or a potential problem. Additionally, all other requirements contained in Section 25.07 including protection from improper concurrent uses, stabilization, sludge classification, application and disposal methods, soils, application rates, runoff control, sludge transport, etc. shall apply to all sludge application sites, regardless of size. As a further condition of this waiver provisions, the plant owner shall provide advance notification for concurrence to the appropriate Regional Offices of the Department and the Board of any new site(s) for which sludge application is intended. The notification for concurrence may be made by phone call to be confirmed in writing or by letter mailed in time to ensure receipt by the Department and Board prior to utilization of the new site(s). As a minimum, the notification for concurrence shall provide the location and size of the area, owner's name, proposed application rate, percentage of solids and any special or unusual conditions which may exist.

25.07.05 Sludge classification

Prior to land application, sludge shall be evaluated in accordance with Section 25.07.03 and 25.07.04. The sludge shall be classified by its characteristics. For new projects, sludge characteristics may be approximated by data obtained from like treatment facilities receiving flow from similar waste contributors. Pilot studies for sludge characteristics may be required when deemed appropriate by the Department and the Board.

a. Class A-Class A sludge shall be suitable for land application at the approved site in accordance with the approved application conditions indefinitely under proper management. Sludge which is classified as Class A shall be stabilized and shall not contain heavy metals or other undesirable components in quantities that (1) may be harmful to the production of crops, trees or other vegetation; (2) may result in crops or vegetation containing components which may be harmful to the health of animals or humans when consumed; (3) may render the soil unsuitable for future land use and (4) degrade existing groundwater quality. Appendix K presents standards for Class A sludge based on maximum allowable levels of certain heavy metals.

b. Class B-Class B sludge is sludge which is raw, partially stabilized, chemically or bacteriologically contaminated or contains undesirable components which makes it unfit for land application. This shall include unstabilized pumpage from septic tanks. Disposal of Class B sludge may be implemented by (1) conveyance to sewage treatment plant having approved sludge handling facilities, provided that detrimental effects to the plant shall not occur; (2) stabilization of sludge such that it shall meet the requirements of Section 25.07.05a, above; and (3) other methods which will be evaluated on a case by case basis. Raw or partially stabilized sludge shall be mixed with solid waste for disposal in solid waste landfills.

25.07.06 Application and Disposal Methods

Spray application of Class A sludge to the land is acceptable when no transport of aerosols beyond the boundaries of the application area is predicted.

a. Liquid Sludge

Liquid sludge shall generally have a solids content of less than 12 percent. Liquid Class A sludges shall be applied to land by plowing, discing, or direct injection so that the sludges are immediately covered or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected for sludge application and approved by the Department and the Board may be used. Liquid sludges shall not be mixed with solid wastes for disposal in solid waste landfills.

b. Final Dewatered Sludge

Final dewatered sludge is sludge that is dewatered for the purpose of ultimate disposal and is defined as having a solids content usually ranging between 12 percent and 30 percent. Dewatered sludges including those dewatered through the use of centrifuges, vacuum filters and filter presses may be disposed with solid wastes if the ratio of sludge is high enough so as to prevent problems with compaction and extruding of sludges to the surface of the ground. These dewatered sludges may also be disposed in separate trenches at approved solid waste landfill sites or other approved sites. Dewatered Class A sludges may also be applied to the land by plowing or discing into the soil immediately after application or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected for sludge application and approved by the Department and the Board may be used.

c. Dried Sludge

Dried sludge is sludge that has a solids content greater than 30 percent. Dried Class A sludges from treatment processes may be disposed in solid waste landfills or atop the landfills to promote growth of vegetation, landfills selected for sludge disposal or plowing or discing into the ground or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected from sludge application and approved by the Department and the Board may be used.

d. Other Solids

Grit, rages and other debris or screenings from sewage treatment plants shall be stored in covered containers. These solids are classified as Class B, and subsequent disposal shall be by burial at solid waste landfill sites or other sites approved by the Department and the Board.

25.07.07 Soil

Soils shall be well drained. A minimum soil depth of two feet is preferred.

25.07.08 Application Rates

For land application systems, the engineer shall consider sludge composition, soil characteristics, climate, vegetation, cropping practices and other critical factors in determining application rates. Since sludge and site factors vary widely, application rates shall be determined for each specific site. Application rates shall be approved by the Department and the Board.

Nitrogenous substances are usually the limiting factor in determining annual application rates. Unless it can be satisfactorily demonstrated that the nitrogen uptake of crops to be harvested justifies a higher loading rate, the initial design application rate shall not exceed five tons of dry weight solids/acre/year. Guidelines for allowable application rates for specific crops are presented in Appendix K. Additionally, Appendix K presents guidelines on maximum loadings of cadmium, maximum cumulative levels for metals and acceptable soil pH levels. For any site receiving only a single application of sludge not to be repeated for at least five years, the maximum allowable loading rate for the on-time application shall be 15 tons of dry weight solids/acre. The above notwithstanding, at no time shall sludge be applied to a depth greater than 0.5 inches in any single application procedure.

No crops should be removed by harvesting or grazing less than 30 days after the last application of sludge. Pasture should be clipped immediately prior to sludge application.

25.07.09 Groundwater Quality

Land application sites, landfills, sludge lagoons and sludge holding facilities shall be designed and operated so that the utilization of sludge does not result in groundwater quality changes. If the presently existing concentration of any parameter is high in the groundwater than the level allowed for a raw water supply source (reference: Commonwealth of Virginia Waterworks Regulations), then the sludge utilization or disposal technique shall not result in an increase in the concentration of that parameter.

25.07.10 Holding Facilities

a. Emergency Holding

Raw sludges, septic tank sludges, sludges from upset digesters and sludges of similar nature may be stored in emergency holding facilities. Subsequent processing of the supernatant and sludge shall be provided in an approved manner. Such holding facilities should be located remote from human activity. The engineer shall provide a plan for approval by the Department and the Board. The plan shall address sampling, odor control, vector control, potential soil and water pollution, and security.

b. Routine Holding

During periods when application of sludges to agricultural land is not possible due to climatic or other conditions, a holding facility shall be provided. The engineer shall provide a mass balance which determines the amount of sludge storage which is to be provided. The location and protection of the holding facility shall conform to the requirements stated in Section 25.07.01a, above. Holding shall be utilized to enhance runoff prevention.

25.07.11 Incineration

Incineration of sludges and screenings from treatment facilities is an approved method of solids reduction. Such facilities shall meet all requirements for air pollution control. The ash from such processes may be buried or spread on land selected for such purposes and approved by the Department and the Board.

25.07.12 Sludge Lagoons

a. Long Term Storage Lagoons

Long term storage lagooning of stabilized sludges is allowable if provisions are made for ultimate disposal of the sludge in accordance with the requirements of the section. Decant liquid from the lagoon shall be conveyed to a plant by an approved method for treatment in a manner that will not upset the plant's operational efficiency. Adequate provisions shall be made to prevent seepage from the lagoon. Fencing and warning signs shall be required.

b. Ultimate Disposal Lagoons

Lagooning of stabilized sludges as a means of ultimate disposal is allowable if stored in accordance with Section 25.07.12a above and covered with soil upon completion of use to a depth of two feet.

25.07.13 Transport of Sludge

The engineer shall furnish the final engineering documents (Section 2.03) the equipment and materials needed for sludge handling, including nonspill, water-tight vehicles for transport, routes, quantities of sludge and procedures to be used. Transport vehicles should be equipped with tow hooks, and transport routes through heavily populated areas should be avoided.

25.07.14 Land Reclamation

Land reclamation is an accepted practice usually utilizing high application rates of liquid sludge. Class A sludges are acceptable for land reclamation. The sludge utilization program shall be developed between the owner, the Department, the Board, the Division of Mined Land Reclamation (when appropriate) and other agencies as appropriate.

25.07.15 Other Methods

Other methods of sludge and solids disposal, such as preparation and use as a soil conditioner, will be considered on a case by case basis.

25.07.16 Runoff Prevention

An area which has sludge applied by spraying or spreading shall be located a minimum distance of 50 feet from all surface water. Containment and controlled release of runoff from sludge application areas or effective erosion control methods should be practiced as necessary.

12VAC5-610-1170:4. APPENDIX I. Buffer Zones.

APPENDIX I.

Buffer Zones

A. All anaerobic lagoons shall provide the minimum buffer zone as shown below unless they qualify for reduced requirements as provided in (B) below. Buffer zones are areas of controlled or limited use. Within buffer zones residential uses or high density, human activities or activities involving food preparation are prohibited. The extent of the buffer zone perimeter is measured from the perimeter of the lagoon.

B. The Department shall consider reduction of up to one half of the above listed buffer zone requirements based on topography, prevailing wind directions, provision of covered units or the inclusion of an effective wind break in the overall anaerobic lagoon design.

1. The prevailing wind direction should be determined by on-site data. Local weather station records may be utilized if they are demonstrated to be applicable. Attention should be paid to both moderate and high speed winds since the high velocity winds often have a prevailing direction different from the prevailing direction of moderate winds.

2. A windbreak should be located on both sides of the anaerobic lagoon normal to a line projected through the plant and area which is to be protected as close to the plant as practical. An effective windbreak is comprised of manmade or natural barriers which extend from the ground surface to minimum height of 16 feet. A cultivated tree windbreak may be developed by planting at least four rows of fast growing evergreens (pine family preferred) planted on staggered 10 feet centers. Rows should be spaced no greater than 16 feet apart. The variety of tree used should be readily adaptable to the soil and climate at the plant site.

C. The required buffer zone shall be maintained by an adequate legal instrument throughout the life of the anaerobic lagoon.

12VAC5-610-1170:5. APPENDIX J. Sludge Dewatering.

APPENDIX J.

Sludge Dewatering

The following section is reproduced from the Commonwealth of Virginia Sewerage Regulations State Department of Health, State Water Control Board, February 1977

25.05 Sludge Dewatering

25.05.01 General

Drainage from beds and concentrate or filtrate from dewatering units shall be returned to the sewage treatment process at appropriate points preceding disinfection. These organic loads shall be considered in plant design, and alternatives for handling these loads may be considered similar to those for supernatant (See Section 25.01.06d).

25.05.02 Sludge Drying Beds

a. Area

The sludge drying bed area required for dewatering aerobic and anaerobic digested sludge shall not be less than the following:

For other types of sludge treatment, the drying bed area will be evaluated on a case by case basis.

b. Percolation Type

1. Gravel

The lower course of gravel around the underdrains shall be proper graded and should be 12 inches in depth, extending at the underdrains. It is desirable to place this in two or more layers. The top layers of at least three inches shall consist of gravel 1/8 inch to ¼ inch size.

2. Sand

The top course shall consist of at least 12 inches of sand with a uniformity coefficient of less than 4.0 and an effective grain size between 0.3 and 0.75 millimeters.

3. Underdrains

Underdrains shall be clay pipe, concrete drain tile or other underdrain material acceptable to the Department and the Board and shall be at least four inches in diameter and sloped not less than one percent to drain. Underdrains shall be spaced not more than 20 feet apart.

c. Impervious Types

Paved surface beds may be used if supporting data to justify such usage are provided.

d. Walls

Walls shall be watertight and extended 15 to 18 inches above and at least six inches below the surface.

e. Sludge Removal

Not less than two beds shall be provided and they shall be arranged to facilitate sludge removal. Concrete truck tracks should be provided for all percolation type sludge beds. Pairs of tracks for percolation type beds should be on 20-foot centers.

f. Sludge Influent

The sludge pipe to the beds shall terminate at least 12 inches above the surface and be arranged so that it will drain. Concrete splash plates shall be provided at sludge discharge points.

25.05.03 Rotary Vacuum Filtration

a. Where units will not operate on a continuous basis and the plant does not have digesters, aerated storage tanks should be provided for the sludge.

b. A maximum amount of flexibility consistent with reasonable economy should be designed into the system. Design flexibility should include, but not be limited to, the following:

1. sludge and chemical dilution facilities;

2. separate chemical conditioning tanks;

3. variable speed filter pan agitator drives; and

4. effective filter media cleaning facilities.

25.05.04 Centrifugation

a. Where units will not operate on a continuous basis and plant does not have digesters, aerated storage tanks should be provided for the sludge.

b. Successful application of centrifugation of municipal type sludges requires consideration of numerous factors. Therefore, proper scale-up data pertaining to the particular sludge to be dewatered shall be obtained and submitted to the Department and Board for approval.

c. Provisions for addition of coagulants to the sludge before or during introduction of the centrifuge shall be considered.

25.05.05 Pressure Filtration

a. The addition of and mixing of coagulants before filtration shall be considered.

b. Design data shall be collected from laboratory tests and be properly scaled-up to plant size.

c. Adequate storage should be provided for single unit systems for down time and for multiunit systems on one or two shift cycles.

25.05.06 Lagooning

a. Lagooning for dewatering may be used where suitable land is available for this use.

b. The soil shall be reasonably porous, or underdrains shall be provided. The maximum water table level shall be 18 inches below the bottom of the lagoon. The surrounding areas shall be grades to prevent surface water from entering the lagoon. The maximum depth shall be 24 inches or less. There shall be two or more lagoons. Any underdrainage fluids shall be returned to the treatment plant and be treated.

c. Loading rates, buffer zones, odor control and groundwater protection will be addressed in the preliminary engineering conference.

12VAC5-610-1170:6. APPENDIX K. Map of Physiographic Provinces.

APPENDIX K.

Map of Physiographic Provinces

12VAC5-610-1170:7. APPENDIX L. Suggested Scale and Contour Interval for Subdivision Plats.

APPENDIX L.