drip system approvals: county perspective october 19, 2010 2010 onsite water conference anne lowry,...
TRANSCRIPT
Drip System Approvals:County Perspective
October 19, 20102010 Onsite Water Conference
Anne Lowry, REHSChatham County Environmental Health
• Drip System Siting Criteria
• Drip System Sizing
• Drip System Design Criteria
• Drip System Installation & Testing
• Drip System Operation, Maintenance, and Monitoring Requirements
• Soils 18-20”:
– Fill System
– Anaerobic Drip
Type of Drainfield
Fill System
• Only American Manufacturing (Perc-Rite) has approval for Anaerobic drip system.
Anaerobic Drip Systems
**(Anaerobic drip is designed without pretreatment)
Siting Criteria for Anaerobic Drip Systems
Requires: Minimum of 18” of useable naturally occurring soil above an
UNSUITABLE soil horizon, rock, or a soil wetness condition.
12” vertical separation from bottom of trench to UNSUITABLE soil horizon, rock, or soil wetness condition.
A special site evaluation if Group IV soils are encountered within 18” of the naturally occurring soils surface.
Siting Criteria for Anaerobic Drip Systems
18”Suitable Soil
Group IV soils within 18” (need special site evaluation)
Installation depth 6”
12” vertical separation
Drip Video
• Soils 13-18”:
• Pretreatment with drip disposal
Type of Drainfield
Pretreatment Options
Gravel Bed Peat Filter
Fabric FilterSandfilter
Pretreatment Units
Effluent Treatment Standard
Minimum Soil Depth
Vertical Separation Distance
NSF 40 18” 12”
TS I 15” 9” (12” for rock or tidal water)
TS II 13” (for Perc Rite) 15” for Geoflow
6” (12” for rock or tidal water)
Aerobic Drip Siting CriteriaPretreatment Drip Soil Depth Requirements:
Aerobic Drip Siting Criteria
13’
18” NSF 40
Geoflow
Perc Rite15”
Aerobic Drip Siting CriteriaHorizontal Setbacks:
Public water supply
WS-1 Streams & S.A. Waters
Other Coastal Waters
Streams,canals surface water
Drainage systems: upslope/sideslope/downslope
Any other nitrification field
.1900Rules
100 100 50 50 10, 15, 25 20
NSF 40 100 70 35 35 10, 15, 25 20
TS I 100 70 35 35 7, 10, 20 10
TS II 100 50 25 25 7, 10, 15 10
Aerobic Drip Siting Critera
Reductions in horizontal and vertical setbacks cannot be taken concurrently when installing drip systems except for drainage systems setbacks (interceptor, foundation drains, diversion)
Aerobic Drip SizingSpecial Site Evaluation
• Detailed descriptions of soil profiles and soil morphological • Description of landscape position• Location and depth for placement of the trenches • Recommended LTAR• Hydraulic conductivity tests, lateral flow analysis, • Proposed site-specific requirements for system design,
installation, site preparation, modifications,
Additional Special Site Evaluation Requirements in .1970 (p)(2)
Aerobic Drip Sizing Drip systems treated to TS I or more stringent
standard on sites with less than 18” of suitable soil shall not exceed the lowest LTAR of the soil group:
Soils Group LTAR Maximum w/ Reduced setbacks (horizontal or vertical)
Group I .8
Group II .5
Group III .2
Group IV .1
Aerobic Drip Sizing
• Minimum square footage:
– Design daily flow ÷ LTAR = Square footage
– Ex. 360 design flow ÷ .1LTAR = 3600 sq.ft.
Aerobic Drip Sizing
• Minimum drip tubing length:
Square Footage ÷ 2 Feet = Drip tubing length
Ex. 3600 Sq.Ft. ÷ 2 Feet = 1800’ Drip tubing length
Aerobic Drip Design Criteria
Requires: Pretreatment prior to drip emitter system to reduce BOD
and TSS to 30mg/l each. Dosing tank must be the same size as is required for the
septic tank. Floats must be adjustable from ground surface with out
entering tank. Must have audio visual alarm. Must have self cleaning filters
Pretreatment Options
Gravel Bed
Peat Filter
Fabric Filter Sandfilter
Aerobic Drip Design CriteriaPretreatment prior to drip emitter system to reduce BOD and TSS to 30mg/l each.
Aerobic Drip Design Criteria
Floats adjustable from ground surface
Aerobic Drip Design Criteria
Audio/Visual Alarm
Self Cleaning Filters
Disc Filter Screen Filter
Headworks
Aerobic Drip Design CriteriaProcessing and Control Unit
• Requires:– Must be able to be programmed to deliver design
volumes to each field at specified intervals (flow equalization)
– Must include automatic flushing of filters and laterals– Must have ETM and CC for each zone– Must keep record of flow– Must be 36” above grade– Telemetry if design flow is above 600gpd
Control Panel
Aerobic Drip Design CriteriaHeadworks Box
• The Headworks box includes filters, backwash valves, field flush valve and flow meter.
• Headworks components shall be in a separate enclosure that is freeze protected, UV and corrosion resistant
• Design shall facilitate reasonable access to all internal components.
Aerobic Drip Design CriteriaDrip Field Design
• Drip tubing shall have pressure compensating emitters
• Drip tubing shall effectively inhibit root growth
• Pressures must be able to maintain a minimum of 7-60psi during dosing
Aerobic Drip Design CriteriaDrip Field Design
• Lines shall be installed level +/- 2” in any linear segment on 2’ centers. May reduce center to center spacing to 1.5’ to avoid field obstructions (trees, rocks)
• Connection lines shall be conveyed over earthen dams with at least 2” higher than drip lines.
• When slopes exceed 10% check valves shall be used in supply and return manifolds.
Aerobic Drip Design CriteriaDrip Field Design
• Scour velocity of 1.2 feet per second minimum during dosing & flushing
• Minimum pressure of 10psi during flushing ??• Maximum of 60 psi during dosing• Air vent, check valve, solenoid valves at high point of
each zone.• Pressure monitoring fittings at field inlet and outlet• Valves & cleanouts shall have protective vaults/boxes
Schrader Valves in Fieldto check pressure head in field
Drip System Installation
Aerobic Drip Installation & Testing Procedures
• Preconstruction conference required– Local Health Department– Engineer (Manufacturer Authorized)– System Designer (Manufacturer Authorized)– Grade Level IV Installer (Manufacturer Authorized)– Licensed Soil Scientist
Aerobic Drip Installation & Testing Procedures
• All tanks are to be water tested into risers• Field must be flagged prior to installation• 6” minimum soil cover over drip tubing
Aerobic Drip Installation & Testing Procedures
• Blanking:– Blanking sections are not be included in linear
footage total– 6” of soil cover must be maintained over blanking
sections.– Blanking should be installed at same elevation as
drip tubing• If blanking is not able to maintain same elevation then
the blanking shall go above in elevation around obstruction.
Aerobic Drip Installation & Testing Procedures
• Start up attendees:– Local Health Department– Engineer (Manufacturer Authorized) – System Designer, if applicable (Manufacturer
Authorized)– Grade Level IV Installer (Manufacturer Authorized)– Licensed Soil Scientist– Operator in Responsible Charge
Aerobic Drip Installation & Testing Procedures
Engineer LSS Installer ORC
Aerobic Drip Installation & Testing Procedures
• Start up:– Conduct required start up checks on pretreatment
unit.– Check alarms (audio/visual) for dosing tank and
recirculation tank, if applicable– Check grade around tanks– Check UV light, if applicable– Check Headworks box
Aerobic Drip Installation & Testing Procedures
Start up:
• Supply line shall be flushed prior to start up
• Run each zone dosing and flushing at design times
• Measure flow rates during dosing and flushing
• Measure field pressures during dosing and flushing
• Walk field during dosing and flushing to verify no leaks
Aerobic Drip Installation & Testing Procedure
• Start up:• Vegetative cover must be established over
field• Check for settled areas over drip tubing, add
soil as needed• Finished grade shall allow for shedding of
surface water
Aerobic Drip Installation & Testing Procedures
Prior to issuing Operation Permit:• Maintenance contract signed by manufacturer approved ORC and
property owner must be submitted to the LHD• Engineer/Designer must submit written certification that system
was installed as designed.• Manufacturer/Manufacturer Representative must submit
confirmation of their acceptance of the system installation.• Licensed Soil Scientist must submit written certification that the
installation was in accordance with their specified site/installation requirements.
Aerobic Drip Operation, Monitoring, & Maintenance
• Inspection frequency for the first year is quarterly, two times per year there after
• Inspections shall include:
Flushing rates & pressures Document flow meterChecking/cleaning filters Document ETM & CCMeasure dosing rate to each zone Visual observation of drip
field
Questions??