Occoquan and Dulles Policies
Potomac DWSP Partnership
Meeting
February 21, 2008
An Overview of:
• The Occoquan Policy
• Occoquan Watershed Monitoring
Laboratory (OWML)
• Occoquan Non-Point Source Program
• Dulles Policy
Special Water Quality Standards in
Virginia
Reservoirs and Service Areas
Watershed Facts
• Area: 592 Square Miles
• Streams: 1,300 Miles
• Major impoundments:
–
–
–
Lake Manassas
Lake Jackson
Occoquan Reservoir
• Land Use (estimate):
–
–
–
–
–
–
–
14%
8%
4%
1%
13%
9%
51%
Low Density Residential
Medium and High Density Residential
Commercial and Industrial
Institutional
Agricultural
Pasture
Forest and Idle
• Residents: 390,000 (estimate)
Source: OWML -1998, NVRC - 2000, 2005
The Problem
• Late 1960s – WQ problems in the Occoquan Reservoir:
– Massive algal blooms
– Periodic episodes of taste and odors in drinking water
– Shortened filter runs due to clogging during periods of high algal
growth
– Periodic fish kills due to oxygen depletion
– Hypolimnetic de-oxygenation due to accumulation of organic material in
the sediments
• The State Water Control Board (Board) commissioned a Study to
recommend a course of action to preserve the Occoquan as a
valuable water resource for future generations.
• The Study results stated that point source pollution was the primary
cause of water quality degradation
• A high degree of waste treatment would be necessary to prolong
the life of the drinking water supply.
Summer 1973 – Algal Bloom (Source: OWML)
The Policy
1A
1
Policy for Waste Treatment and Water Quality Management in the Occoquan Watershed
• Formed UOSA (Upper Occoquan Sewage Authority) to
Consolidate Older WWTPs
• Established Occoquan Watershed Monitoring Program
• Established Indirect Potable Reuse as Sustainable Water
Supply for Northern Virginia
• Regulation administered by Virginia Department of
Environmental Quality (VDEQ)
Policy Requirements – WWTP Plants
• Preferably only two high-performance regional plants
• All point sources preferably 20 stream miles from Fairfax
•
•
Water intake
Incremental increases in regional plant capacity must be
approved based on results of the monitoring program
All future plants must meet or exceed UOSA design
standards
Policy Requirement - Effluent
• Discharge Limits:
– COD (mg/l) - 10.0
– Suspended solids (mg/l) - 1.0
– Nitrogen (mg/l) - 1.0 (as TKN)
– Phosphorus (mg/l) - 0.1
– MBAS (mg/l) - 0.1
– Turbidity (NTU) - 0.5
– Coliform per 100 ml Sample - less than 2.0
UOSA Process Treatment (from OWML)
Policy Requirement – Wastewater
Operation
All pumping stations in the watershed must have:
–
–
–
–
Stand-by pumping units
At least one “on-site” back-up power supply
At least one “off-site” back-up power supply
Be designed so that no single failure of a mechanical or electrical
component could degrade pumping capability
– Have pumps and valves arranges so that these units can be removed
and replaced without by-pass pumping
– Have retention basins of minimum one-day capacity
– Have flow measurement devices
• Nitrate removal required when NOx conc. Reach 5 mg/l at Intake
Policy Requirement – Collection Systems
• Certified and submitted to Board –
Inflow/Infiltration (I/I) limited to 100 gal/inchdia/mile/day
• Approved pre-treatment program
• Up-to-date and maintained (subject to annual
inspection) electrical and fluid system diagrams
• Detailed as-built and installed drawings
Occoquan Watershed Monitoring
Program
• Occoquan Watershed Monitoring
•
•
Lab (OWML)
– Sampling and Analysis
– Stream Gages and Reservoir
Stations
Overseen by Occoquan Watershed
Monitoring Subcommittee
Objective: to Ensure that
performance levels are maintained
and that the effects of point and
non-point sources are known
Occoquan NPS Programs
• Technical Investigations and Support
– Northern Virginia BMP Handbook
– Nonstructural Urban BMP Handbook
– Land Use Inventory and Updates
• Fairfax County Water Supply Overlay District
• Historic Fairfax County Down-zoning to
•
Protect Occoquan Reservoir
Occoquan NPS Model
Summary
• Occoquan Policy was a milestone in Water
Quality Management in the
Commonwealth of Virginia
• Water Quality improved dramatically after
UOSA came on-line
• Reservoir Water Quality has remained
stable for decades
Special Water Quality Standards in
Virginia
SWCB Adopts in 1975
(revised in 2004)
LCSA Broad Run WRF
on-line soon
SWCB Adopts in
1971 (revised 1981
and 1991)
UOSA on-line in
1978
Evolution of Dulles Policy
• Wastewater issues of 1970s
• Adopted by SWCB in 1975 as a ‘planning’
document for regional sewage treatment
in northwestern Fairfax and eastern
Loudoun Counties
• Policy revised in 2004 to update for new
LCSA Water Reclamation facility
Dulles Policy – Regional Plants
• Limits Regional Plants to 2
• Discharge in the Broad Run and Goose Creek
•
•
•
•
Watersheds
No discharges within 10 stream miles upstream from
Water Supply Intakes
High-performance effluent requirements based on
Occoquan Policy
Nitrate removal required when NOx conc. reach 5 mg/l
at Intake
LCSA and Fairfax Water to coordinate monitoring
program
Collaborative Updates (2000-2004)
• DAWP Stakeholder Meetings: FW, LCSA,
Fairfax Co., VDEQ, OWML, VDH, NVRC,
City of Leesburg
• Craft reasonable and protective Policy
modifications
• Objective: Ensure Protection of FW Intake
Dulles Policy Revisions (2004)
• Effluent Quality Limits for COD, TKN, TP,
Turbidity, Coliform (now E.Coli limit), and
TSS – same as Occoquan Policy
• Collaborative process was successful
Questions?