Administrative Code

Virginia Administrative Code

Chapter 410. Occoquan Policy

9VAC25-410-10. Introduction.

A. Purpose and authority. To provide a policy that protects the Occoquan watershed from point source pollution. The Occoquan Policy specifically regulates jurisdictional domestic sewage and sets forth requirements for high performance regional treatment plants. The policy was adopted pursuant to authority vested in the State Water Control Board (board) by § 62.1-44.15 of the State Water Control Law.

B. Water quality standard. This "Occoquan Policy" also constitutes special standard "g" in the board's water quality standards for sections 7a through 7h of the Potomac River Basin's Potomac River Subbasin (9VAC25-260-390), which sections are delineated geographically in the "Basin and Section Description" portion of the water quality standards publication (9VAC25-260-10 et seq.). In addition, the text of this policy is referred to under special standards and requirements (9VAC25-260-310), entitled "Occoquan Watershed Policy," of the water quality standards (9VAC25-260-10 et seq.).

C. Background. During the 1960s there was a great deal of concern generated about the large amount of treated sewage effluent being discharged in the Occoquan watershed, since the receiving streams feed the Occoquan reservoir, a drinking water supply for over 600,000 people in Northern Virginia.

In response to this, the board commissioned the firm of Metcalf & Eddy to study the problems of the Occoquan reservoir and to recommend a course of action to preserve the Occoquan as a valuable water resource for future generations.

The results of the Metcalf & Eddy study stated that point source pollution was the primary cause of water quality degradation in the Occoquan watershed and that a high degree of waste treatment would be necessary to prolong the life of the drinking water supply.

In 1971 the board adopted a policy for waste treatment and water quality management in the Occoquan watershed (the Occoquan Policy) that outlined a course of action to control point source pollution in the watershed.

The Occoquan Policy provided for the construction of regional high-performance treatment facilities in the watershed and a monitoring program to obtain water quality data both before and after construction of any of the high-performance plants.

The Occoquan Watershed Monitoring Program (OWMP or monitoring program) was established in 1972 which gathered an extensive amount of information and found that water quality problems in the Occoquan watershed were related directly to point source pollution and to non-point source pollution.

In 1978, a regional high-performance treatment facility (the Upper Occoquan Service Authority, UOSA, formerly known as the Upper Occoquan Sewage Authority) was placed in operation. This facility eliminated 11 major point sources of pollution in the watershed.

Shortly after UOSA began operations, costs and charges for sewage treatment in systems tributary to UOSA increased rather sharply. To date a significant part of those high costs have been associated with large amounts of infiltration and inflow being sent by the user jurisdictions to the regional facility for treatment.

In an attempt to control non-point source pollution the Commonwealth of Virginia adopted an erosion and sediment control law in 1973. In accordance with this law, all of the watershed jurisdictions have adopted erosion and sediment control ordinances. In addition, a number of best management practices (BMP) handbooks were written and published in 1979 by the board. In mid-1980 Fairfax County adopted a BMP ordinance.

In 1978, the board contracted the firm of Camp Dresser & McKee (CDM) to reevaluate certain aspects of the Occoquan Policy. Their report was presented to the board and to the local communities in 1980 and recommended that few changes be made to the policy.

As a result of the CDM report, input from the local communities and the board's staff, an updated version of the Occoquan Policy was drafted.

D. References.

1. A Comprehensive Pollution Abatement Program for the Occoquan Watershed, Metcalf & Eddy Engineers, March 18, 1970.

2. Record of public hearing on March 31, 1971, concerning State Water Control Board's Occoquan Policy.

3. Occoquan Policy Reevaluation, Phase III Report, Camp Dresser & McKee, June 1980.

4. Record of public hearing on November 20, 1980, concerning amendments to the Occoquan Policy.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from VR680-11-05 § 1, eff. December 5, 1990; amended, Volume 36, Issue 25, eff. September 2, 2020.

9VAC25-410-20. Long-range policy.

A. Number and general location of regional treatment plants.

1. The number of high-performance regional plants which shall be permitted in this watershed is not more than three, but preferably two, generally located as follows:

a. One plant in the Fauquier County/Warrenton area.

b. One plant in the Manassas area to serve the surrounding area in Prince William, Fairfax, and Loudoun counties.

2. All point source discharges of treated sewage effluent will preferably be located at least 20 stream miles above the Fairfax County Water Authority's raw water intake. In no case shall a plant be located less than 15 miles above the raw water intake.

3. The provisions of 9VAC25-410-20 A 1 and A 2 shall not limit the consideration of land disposal systems for waste treatment in the watershed, provided such systems shall have no point source discharge to state waters and shall have the approval of the Department of Environmental Quality (department).

B. Regional plant capacity allocations for the Occoquan basin.

1. The initial allotment of plant capacity for the Upper Occoquan Service Authority treatment facility was approximately 10 MGD, based on all effluent being from high-performance plants meeting the requirements of subsections D, E, and F of this section and all those treatment facilities belonging to the City of Manassas, the City of Manassas Park, the Greater Manassas Sanitary District, and Sanitary District 12 of Fairfax County being abandoned.

2. Incremental increases in the regional plant capacity may be approved by the department based on the results of a monitoring program that shows that current and projected discharges from the high-performance plants do not create a water quality or public health problem in the reservoir. The department advises that since severe infiltration/inflow stresses the performance reliability of the regional treatment plants, jurisdictions must pursue I/I correction within their individual systems.

C. Prerequisites for preliminary plant approval. Prerequisites before the department gives approval to preliminary plans for a regional high-performance plant are:

1. A monitoring program for the receiving waters shall be in effect; and

2. The authority who is to operate the proposed plant shall enter into a written and signed agreement with the department that the authority shall meet the administrative requirements of subsection F of this section.

D. Design concept for high-performance plants on the Occoquan.

1. Plant design requirements are:

a. The design of the high-performance sewage treatment plants discharging to the Occoquan Watershed shall meet all the requirements specified here as well as those specified in the most recent edition of the Sewage Collection and Treatment Regulations (9VAC25-790-10 et seq.); and

b. The basic sewage plant design concept for the regional plants discharging to the Occoquan watershed shall be based on the Upper Occoquan Service Authority Wastewater Reclamation Facility.

2. Changes in plant design requirements will be made according to these criteria:

a. Changes to the plant design described here shall only be acceptable if the change does all of the following:

(1) Improves or equals the plant performance and final effluent quality;

(2) Increases or equals plant reliability and maintainability; and

(3) Has a demonstrated performance in a plant of at least five to 10 MGD size for an operating period of not less than one, but preferably two years.

b. Before such changes are incorporated in the plant, specific written approval shall be obtained from the department; and

c. Changes to the plant design solely to reduce cost and which jeopardize plant performance and reliability will not be approved.

E. Plant performance requirements.

1. The plant performance requirements for high performance plants discharging to the Occoquan watershed are given in Table I.

2. Operation of the nitrogen removal facilities is required when the ambient nitrate concentration (as N) is 5.0 mg/l or higher in the Occoquan reservoir in the vicinity of the Fairfax County Water Authority intake point. The owner of the regional sewage authority is responsible for knowing ambient results of nitrate and when operation of nitrogen removal facilities is necessary.




COD mg/1 - 10.0

Suspended solids mg/1 - 1.0

Nitrogen mg/1 - 1.0**

Phosphorus mg/1 - 0.1

MBAS mg/1 - 0.1

Turbidity NTU - 0.5***

Coliform per 100 ml Sample - less than 2.0

*As measured on a monthly average unless otherwise noted. Since these are minimum requirements, the normal average would be expected to be substantially better.

**Unoxidized nitrogen (as TKN) Refer to 9VAC25-410-20 E 2 for further information.

***Measured immediately prior to chlorination.

F. Administrative and technical requirements for the control of the sewer system tributary to a regional, high-performance plant in the Occoquan watershed.

1. The owner to whom the permit is issued for operation of a regional plant shall meet the general and administrative requirements covered below. These requirements shall also be contractually passed on by the owner to any parties or jurisdictions with which the owner may contract for the processing of wastewater.

These requirements are applicable to regional sewage treatment plants.

2. The high-performance regional treatment plant shall be manned by an appropriate number of trained and qualified operating maintenance and laboratory personnel and manned continuously 24 hours a day, seven days a week throughout the year.

3. The owner shall include, as part of his preliminary and final plans and specifications submitted to the department for approval, a detailed statement indicating how each of the technical and administrative requirements in this policy has been met. Any proposed deviation from any of these requirements shall be clearly identified and technically justified, and shall require formal department approval. These submittals shall also include:

a. Simplified fluid system diagrams that clearly identify the following:

(1) The average and peak capacity of each unit;

(2) The number of units of each type needed to handle the normal average flow and the peak of flow; and

(3) The number of spare units and their capacity for both average and peak flow cases shall also be identified.

In addition, a brief narrative summary description shall be submitted to identify what has been done to ensure that each unit and major subsystem can be maintained and expanded without release of effluent that does not meet the minimum standards.

b. A simple one-line power distribution system diagram showing how outside power is brought into the plant and how power is distributed within the plant proper shall be submitted. This diagram shall also show as a minimum:

(1) Ratings and characteristics of electrical components, such as transformers, circuit breakers, and motor controllers making up the system;

(2) Protective devices such as thermal overloads, under frequency, or under voltage relays;

(3) Voltages supplied by all fuses;

(4) Normal circuit breaker and switch conditions (notes shall also be provided as required to cover abnormal, casualty, and emergency operating modes); and

(5) How electrical loads are combined into switch gear and load center. (The use of cubicle outlines in phantom or dotted line is suggested.)

4. The final submittal of plans and specifications for the plant to the department shall include a systematic failure mode and effects analysis on the mechanical and electrical portions of the plant so as to demonstrate that a single failure of a mechanical or electrical component will not interrupt the plant operations which are necessary to meet the effluent requirements of Table I of this policy.

5. Pumping stations on the collection systems that are located in the Occoquan watershed and are tributary to a regional treatment works shall:

a. Have stand-by pumping units;

b. Have at least one "on-site" backup power supply;

c. Have at least one "off-site" power supply;

d. Be designed so that no single failure of a mechanical or electrical component could degrade pumping capability;

e. Have pumps and valves arranged so that these units can be removed and replaced without the by-passing of sewage;

f. Have flow measure devices with provisions for recording flow; and

g. Have retention basins of a minimum one-day capacity.

If these pumping stations are remote and unmanned, an alarm system shall be provided at manned stations to indicate that problems are developing and to direct maintenance assistance to the affected pumping station. The owner of each pumping station shall be required to obtain a department certificate.

A waiver may be sought from requirement g above, particularly in new collection systems exhibiting no I/I problems. However, the jurisdiction requesting such a waiver must submit documentation to the department for review that the sewer system tributary to the pump station meets the criteria established by the most recent edition of the Sewage Collection and Treatment Regulations (9VAC25-790-10 et seq.) for infiltration/inflow, and any other such information that the department may require.

6. The major junctions in the collection system (e.g., at least at the one to two MGD collection points) shall have continuous recording flow measuring devices to help in the early identification of problem portions of a collection system in the event of unexplainable high flows (e.g., excessive infiltration). Also, such flow measuring devices and isolation valves shall be provided between jurisdictions as well as any others contracting for the services of the regional plant. The flow measuring devices and isolation valves between jurisdictions shall be under the control and responsibility of the owner to whom a plant certificate is issued.

7. Each sewage treatment plant shall have a pretreatment program approved by the department.

8. Waste being processed in any existing small plants shall have the first priority on treatment capacity and such capacity shall be specifically reserved for them in the new high-performance regional plants. New developments are to have second priority.

9. If any of the various administrative procedures of the owner of the regional treatment plant or of jurisdictions served by the plant prove ineffective under actual operating conditions, the department shall have the right to place new requirements on the owner and jurisdictions and to require any necessary action by these parties to physically correct the damage done to the reservoir due to ineffective implementation of the administrative requirements covered here.

10. The owner's interceptor and collection systems of the jurisdictions in the Occoquan watershed shall be designed, installed, inspected, and tested by the respective owner to limit infiltration to 100 gal/inch-dia/mile/day as a maximum. The test results shall be certified and submitted to the department.

11. Whenever the owner enters into an agreement with a jurisdiction for services of a regional plant, the owner shall be responsible for seeing that such jurisdictions have ordinances and rules to meet all the applicable requirements covered by this policy. These ordinances and rules shall meet the owner's approval and the owner shall monitor and spot-check to see that the jurisdictions are effectively implementing their ordinances and rules to meet the requirements covered here. The department, at its discretion, can request the owner to submit to the department for its approval the ordinances and rules that will be used to meet the department's requirements covered here.

Further, any time a user violates any of the administrative or technical requirements of the contract between the user and the owner which can affect the plant operations, hydraulic loading, or effluent quality or which affect the reservoir's water quality due to urban runoff (e.g., siltation), the owner shall not allow the user to discharge additional wastewater to the owner's plant until the problem has been resolved to the owner's satisfaction.

12. Up-to-date "as-built" drawings and manuals shall be available at least once a year for department inspection and review. These documents shall include as a minimum:

a. Up-to-date as-built electrical and fluid system diagrams;

b. Detailed as-built and installed drawings; and

c. Normal operating and casualty procedures manual. The documents shall be updated at least once a year to reflect all changes and modifications to the plant.

13. The design engineer shall have the responsibility of meeting the proposed effluent quality as shown in Table I. To demonstrate that the plant as designed by the engineer can meet the effluent standards, the plant is to be operated under the supervision of the design engineer for a minimum of one year of continuous operation after the "debugging" period.

G. Other point source discharges.

1. Point sources other than regional plants will be permitted as regulated or required by the Virginia Pollutant Discharge Elimination System (VPDES) permit regulation (9VAC25-31-10 et seq.).

2. VPDES permits may be issued:

a. For single family homes with failing septic tanks, stormwater, pollution remediation projects, and minor industries. The permitting of major discharges (as defined in 40 CFR Part 122) other than regional sewage treatment plants is strictly prohibited with the exception of pollution remediation projects that are shown to be feasible and no other alternatives are available.

b. To an existing sewage treatment plant constructed and placed into service prior to January 1, 2001, serving no fewer than 10 homes but no more than 25 homes if such sewage treatment plant has a documented history of substantial noncompliance and it is not feasible to connect to a publicly owned sewage treatment plant.

3. No permit as authorized in subdivisions 1 and 2 a of this subsection shall be issued or reissued unless the applicant demonstrates that it is not feasible to connect to a regional plant and that there is not a feasible alternative except to discharge.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from VR680-11-05 § 2, eff. December 5, 1990; amended, Volume 36, Issue 25, eff. September 2, 2020; Volume 38, Issue 25, eff. August 31, 2022.

9VAC25-410-30. Expansion of existing plants in the Occoquan watershed.

A. One of the objectives of the Occoquan Policy is to reduce water quality problems in the Occoquan watershed due to pollution from point sources. To date the means of accomplishing this objective have been the construction and utilization of a high-performance regional plant - the Upper Occoquan Sewage Authority (UOSA) - and the elimination of 11 low-performance treatment plants in favor of the UOSA facility. The 11 low-performance treatment plants constituted the major point sources of pollution in the Occoquan Watershed; however, there are a number of smaller sewage treatment facilities which are still discharging. These facilities were not connected to the regional facility for at least one of the following reasons: (i) a collector system to the regional plant was not constructed in close enough proximity to provide service, or (ii) the small facility was outside of the service area for the regional plant. At some point in the future, these remaining plants may wish to expand and increase their flows.

B. Existing waste treatment facilities may be expanded to receive increased sewage flows; however, the degree of treatment must also be upgraded so that there will be no increase in the quantity of pollutant loadings discharged to the receiving stream. A no-discharge land-application system may be considered in lieu of upgrading a facility.

C. Plants not meeting approved design performance limits will not be allowed additional capacity until the owner has installed additional treatment and demonstrated by means of a minimum of three months of performance data that the plant has been brought within its approved design performance levels and can accept additional waste loads without exceeding such approved design performance levels.

D. No expansion or continued discharge shall be approved if it is feasible for the flow to be directed to a regional plant.

E. Proposed interim expansion of plants shall be reviewed with the appropriate regional sewage authority to assure that such expansions are coordinated with the authority regional plans and can be readily incorporated into the regional system.

F. The plans and specifications for expansion of collection and interceptor systems shall be reviewed with the appropriate regional sewage authority for its comments before they are submitted to the Department of Environmental Quality (department) and the Virginia Department of Health for approval. Any proposed expansion of collection and interceptor systems shall meet the technical and administrative requirements of 9VAC25-410-20 F, and the jurisdiction proposing such an expansion shall submit a formal letter to the department stating that its expansion will meet the requirements of 9VAC25-410-20 F.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from VR680-11-05 § 3, eff. December 5, 1990; amended, Virginia Register Volume 38, Issue 25, eff. August 31, 2022.

9VAC25-410-40. Occoquan Watershed Monitoring Program (OWMP).

Due to the critical nature of the receiving waters, intensive monitoring will be required to ensure that plants achieve desired performance levels at all times, and the effects of point sources and nonpoint sources on the receiving waters are measured and projected.

1. Watershed monitoring subcommittee.

a. In order to ensure that performance levels are maintained and that the effects of point sources and nonpoint sources on receiving waters are known, a watershed monitoring subcommittee shall be established and shall be convened at least once each calendar year. A subcommittee of this type must necessarily be composed of high-caliber personnel knowledgeable in the field of water and wastewater treatment and management. Accordingly, the subcommittee shall consist of two ex-officio members or their designated representatives as follows:

(1) Director of Virginia Department of Health's Division of Water Programs;

(2) Director of Virginia Department of Conservation and Recreation's Division of Soil and Water Conservation; and three other members or their designated representatives as follows:

(a) A representative of the Environmental Protection Agency;

(b) A representative of a state university in Virginia; and

(c) A nationally recognized consultant in the water and wastewater treatment or water quality management fields.

b. The ex-officio members shall select and submit to the Department of Environmental Quality (department) for approval the names of the other members of the subcommittee. The subcommittee shall elect a chairman.

c. From time to time the subcommittee may seek additional expert advice.

2. Monitoring subcommittee's responsibilities. The watershed monitoring subcommittee shall have the following responsibilities:

a. To oversee that there is adequate monitoring of the regional plant effluent and process control testing at the regional plant;

b. To develop a water quality monitoring program for the Occoquan reservoir and its tributary streams to ensure that there is a continuous record of water quality available. To further ensure that projections are made to determine the effect of additional waste loading from point sources as well as nonpoint sources;

c. To ensure that the stream monitoring program is separate and distinct from plant process control testing and effluent monitoring;

d. To review data collected from the monitoring program and submit to the department and the various jurisdictions reports on the status of plant performance and water quality in the watershed at least once each year;

e. To report to the department immediately significant changes in plant performance or water quality due to either point source or non-point source pollution;

f. To maintain close liaison with the Fairfax County Water Authority in order to ensure satisfactory raw water which can be adequately treated at the authority's facilities; and

g. To establish the Occoquan Watershed Monitoring Laboratory (OWML) to conduct sampling and analyses to fulfill the above responsibilities.

3. Provision for restructuring of the OWMP.

a. The Occoquan Watershed Monitoring Program (OWMP) and the Occoquan Watershed Monitoring Laboratory (OWML) were established in accordance with the above provisions. This was done on July 1, 1972. Since that time a large body of information regarding the functioning of the Occoquan reservoir system has been accumulated. Major point sources have been consolidated into and eliminated by a high-performance sewage treatment facility (UOSA). As growth increases in the watershed, this trend is expected to continue.

b. The work performed by OWML has indicated that the key to water quality is a two part issue. Those parts are point source pollution and non-point source pollution. Point source discharges in the watershed are currently regulated by the department's VPDES permit program. Non-point sources of pollution are currently being addressed by state and local voluntary and mandatory control programs. However, in the future it may be necessary that additional mandatory programs be adopted.

c. The program shall be evaluated periodically for restructuring to account for shifts in monitoring trends and funding and any recommended restructuring approved by the department prior to implementation. The regional sewage plants are ultimately responsible for the monitoring program with the exception of the non-point source elements.

4. Financing the OWMP.

a. It is recommended that the cost of the OWMP be split equally between water supply and sewage uses. This would mean that the Fairfax County Water Authority would have to fund half of the OWMP budget while the counties of Fairfax, Prince William, Loudoun, and Fauquier and the cities of Manassas and Manassas Park would be responsible for jointly funding the other half. That portion of the OWMP budget funded by the counties and cities would be divided so that each jurisdiction would be charged in proportion to its allotted sewage capacity in the Occoquan watershed. The budget shall be reviewed by the jurisdictions prior to approval by the subcommittee.

b. Written agreements shall be obtained from each of the jurisdictions which shall commit them to supply the above funds yearly to finance the OWMP. This monitoring program is for their protection and benefit. If for some reason a county or city does not wish to retain its sewage allotment in the Occoquan watershed or will not fund the monitoring program, then its allotment can be divided up among the remaining participating jurisdictions, with their portion of the cost of the monitoring program rising accordingly. The regional sewage plants are ultimately responsible for monitoring with the exception of non-point source elements.

c. If federal funds and assistance can be obtained, the cost to the counties and the Fairfax County Water Authority will be reduced proportionally. The funding of the program without federal funds is to be assumed, so as not to further delay or complicate the initiation of this program.

d. The Office of Sponsored Programs, Virginia Polytechnic Institute and State University, has agreed to be responsible for billing, receiving, and disbursement of funds to the OWMP.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from VR680-11-05 § 4, eff. December 5, 1990; amended, Virginia Register Volume 38, Issue 25, eff. August 31, 2022.

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