drip system approvals: county perspective october 19, 2010 2010 onsite water conference anne lowry,...

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??