Vol. 36 Iss. 25 - August 03, 2020

Chapter 410
Final Regulation

REGISTRAR'S NOTICE: The State Water Control Board is claiming an exemption from Article 2 of the Administrative Process Act in accordance with § 2.2-4006 A 3, which excludes regulations that consist only of changes in style or form or corrections of technical errors. The State Water Control Board will receive, consider, and respond to petitions by any interested person at any time with respect to reconsideration or revision.

Title of Regulation: 9VAC25-410. Occoquan Policy (amending 9VAC25-410-10, 9VAC25-410-20).

Statutory Authority: § 62.1-44.15 of the Code of Virginia.

Effective Date: September 2, 2020.

Agency Contact: Melissa Porterfield, Department of Environmental Quality, 1111 East Main Street, Suite 1400, P.O. Box 1105, Richmond, VA 23218, telephone (803) 698-4238, or email


The amendments, which are a result of a periodic review, make technical corrections to update the regulation.

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 (9VAC25-300-10) (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) which 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 Sewage Authority-UOSA) 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.

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 State Water Control Board.

B. Regional plant capacity allocations for the Occoquan basin.

1. The initial allotment of plant capacity for the Upper Occoquan Sewage 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 below 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 board based on the results of a monitoring program which 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 board 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 board 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 board 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 Commonwealth of Virginia Sewerage 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 Sewage 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 5 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 board; 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 board 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 board approval. These submittals shall also include:

a. Simplified fluid system diagrams which 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, etc., 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 (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 board 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 which 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 State Water Control Board 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 board for review that the sewer system tributary to the pump station meets the criteria established by the most recent edition of the Virginia Sewerage Sewage Collection and Treatment Regulations (9VAC25-790-10 et seq. ) for infiltration/inflow, and any other such information that the board may require.

6. The major junctions in the collection system (e.g., at least at the 1 to 2 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 board.

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 board 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 board.

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 board, at its discretion, can request the owner to submit to the board for its approval the ordinances and rules that will be used to meet the board'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 run-off 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 board 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 (9VAC25-30-10 et seq.) (9VAC25-31-10 et seq.).

2. VPDES permits may be issued 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 which that are shown to be feasible and no other alternatives are available.

3. No permit as authorized in subdivisions 1 and 2 above 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.

VA.R. Doc. No. R20-6176; Filed July 9, 2020, 3:47 p.m.