Cochise, Maricopa, Mohave, Navajo, Pima, Pinal, Yavapai and Yuma

Counties

Septic percolation testing for the various counties within Arizona under the direction of ADEQ are neither consistent nor uniformly enforced. This has led many firms such as Vann Engineering, Inc. to conduct these tests inaccurately.

The most common septic percolation test we conduct is for single-family homes that are more than 400 feet away from any existing sanitary sewer lines. Most of these systems are either conventional or leach beds.

The purpose of this presentation is to review and become familiar with the requirements of various counties for septic investigations.

According to the counties testing for disposal trenches is the same as conventional systems or leach beds.

Although not as common, seepage pits will also be covered.

Essentially, we want to start conducting septic percolation tests everywhere and with 100% conformance to the local governing standards.

We figure by doing the above we will retain more clients, gain more new clients and develop strong relationships with governing agencies.

Note: 7” max

30” deep; does not allow : Cochise, Mohave, Navajo, Yavapai

During Site Investigations for Septic Projects we shall visually identify and report (on the Driller’s Report) any of the following limiting conditions discovered at the subject site:

Presence of rock outcrops/boulders Presence of fill (deep and pervious) Presence of visible earth fissures Site topography Washes 50’ is needed for a wash

Note: Use ADEQ form stapled to folder

While advancing exploratory test borings or conducting test pits for Septic Projects we shall identify and report any of the following limiting conditions discovered during the subsurface investigation:

Depth to bedrock or other “hard” stratum which may be impermeable (slower than 60 minutes per inch)

Presence of groundwater Presence of free-draining soil layer

(faster than 1minute per inch) Deep non-engineered fill Clay

There is an Arizona Administrative Code requirement of 3 points of exploration for conventional/leach beds/disposal trench systems: 2 in the primary area and 1 in the reserve area (in hopes that at least 2 locations will achieve acceptable results)

The reasoning for this is to assure at least 2 locations will yield acceptable results

The depth for the test borings/pits is to 12 feet below the surface

The average depth range for the percs is 3 to 7 feet below the surface, depending on the average septic discharge depth and any particular county requirements (to follow)

The exploration depth (12 feet) allows for an examination of the stratigraphy that exists a minimum of 5 feet below the discharge depth, which should approximate the bottom of the perc test

Seepage pits are not a part of the above but are discussed later in the presentation

Note: 12” deep percolation test hole has a 15” diameter

Assuming you have chosen an appropriate discharge elevation for the percolation testing to be conducted………we move on to:

Planning and Preparation A.A.C. R18-9-A310(F)(1)Tests to be conducted in proposed discharge soil layer (native

undisturbed soils)Hand dig 12” x 12” x 12” cube OR 15” diameter x 12” deep test

holeScarify smeared soils within the test hole and remove any

loosened materials from the bottomUse buckets with holes in the sides to support the sidewalls, if

necessary (it must be noted in the final report if this method was used)

Presoaking procedures A.A.C. R18-9-A310(F)(2)Fill hole with water up to 12”Observe & record the water level decline in minutesRepeatIf water drains in less than 60 minutes

Repeat for a third time and if still draining in less than 60 minutes perform the percolation test

If water drains in more than 60 minutesAdd water after 60 minutes and maintain a water depth of 9”

for at least 4 hoursWait 16-24 hours to perform the percolation test

Seepage Pit ProceduresPlanning and Preparation A.A.C. R18-9-

A310(G)(1)Drill a test hole at least 18 inches in

diameter and a minimum of 30 feet deepScarify smeared soils within the test

hole and remove any loosened materials from the bottom

Presoaking Procedures A.A.C. R18-9-A310(G)(2)Fill the bottom 6 inches of the test hole with gravel, if

necessary to prevent scouringFill the test hole with water to 3 feet below the surfaceObserve the decline of water and determine the amount of

time in hours and minutes for it to completely drainIf water drains in less than 4 hours

Repeat for a second time and if still draining in less than 4 hours perform the percolation test

If water drains in more than 4 hoursAdd water to the hole to maintain the level at 3 feet below the

surface for at least 4 more hoursWait 16-24 hours to perform the percolation test

Field Testing For Field Testing For Conventional/Leach Conventional/Leach Bed/Chamber and Bed/Chamber and Disposal Trench Disposal Trench

Systems – By CountySystems – By County

Site Investigation 3 Test Pits or Test Borings to 12 feet 2 in the primary, 1 in reserve location Pits should be 60 feet apart This remains constant no matter the type of septic system to be

usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -5 feet

(remember the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

The results of the pilot boring are key in determining the test interval above

Exceptions If refusal before 12 feet for Test Borings use Pits Remember, there must be 4 feet between the bottom of the test

hole and the limiting condition (5 feet if the limiting condition is ground water)

Site Investigation 3 Test Pits to 12 feet 2 in the primary, 1 in reserve location Pits should be 50 feet apart from each other This remains constant no matter the type of septic system to be usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -5 feet (remember

the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

Recommended that percs are conducted at varying depths in the discharge soil layer (i.e. 3.0’, 4.0’ and 5.0’)

The results of the backhoe pit are key in determining the test interval above

Must be observed by a County Official with a 24 hour noticeExceptions Seepage Pits are not allowed Hillside lots with greater than 15% grade are not allowed on-site systems

(due to back hoe inaccessibility ) (double check with Civil Engineer) Remember, there must be 4 feet between the bottom of the test hole and

the limiting condition (5 feet if the limiting condition is ground water)

Site Investigation 3 Test Pits to 12 feet 2 in the primary, 1 in reserve location Pits should be 50 feet apart from each other This remains constant no matter the type of septic system to be usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -5 feet (remember

the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

Recommended that percs are conducted at varying depths in the discharge soil layer (i.e. 3.0’, 4.0’ and 5.0’)

The results of the backhoe pit are key in determining the test interval above

Must be observed by a County Official with a 24 hour noticeExceptions Seepage Pits are not allowed Hillside lots with greater than 15% grade are not allowed on-site systems

(due to back hoe inaccessibility) (double check with Civil Engineer) Remember, there must be 4 feet between the bottom of the test hole and

the limiting condition (5 feet if the limiting condition is ground water)

Site Investigation 3 Test Pits or Test Borings to 12 feet (use 15 feet depth test

borings using 4.5-inch auger) 2 in the primary, 1 in reserve location This remains constant no matter the type of septic system

to be usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -5

feet (remember the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

The results of the pilot test hole are key in determining the test interval above

Exceptions If refusal before 12 feet for Test Borings use Test Pits A 4 foot separation must exist beneath the base of the perc

test and the limiting condition

Site Investigation 3 Test Pits or Test Borings to 12 feet (use 15 feet) 2 in the primary, 1 in reserve location This remains constant no matter the type of septic system to be usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -4 feet

(remember the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

The results of the pilot boring are key in determining the test interval above

A Pinal County representative must be given adequate notice and the opportunity to inspect the holes prior to perc testing

Sand in the base of the hole although an ADEQ requirement is paramount for Pinal County

Exceptions If refusal before 12 feet for Test Borings use Pits If more than 35% rock fragments must use Test Pits A 4 foot separation must exist beneath the base of the perc test and

the limiting condition

Site Investigation 3 Test Pits to 12 feet (will not require percs) OR 3 Test Borings to 12 feet* 2 in the primary, 1 in reserve location Pits should be 60 feet apart from each other This remains constant no matter the type of septic system to be

used

Percolation Tests Not required when work is supervised or performed by an Arizona

registered Engineer or Geologist *Note: If only performing test borings and the county is not

satisfied with the data collected they will require percs to be performed

Exceptions Hillside lots may require trenches to be farther than the

recommended 60 feet apart

Site Investigation 3 Test Pits or Test Borings to 12 feet (use 15 feet deep test

borings) 2 in the primary, 1 in reserve location This remains constant no matter the type of septic system to be

usedPercolation Tests 2 in the primary, 1 in the reserve location Assuming that the bottom of the test interval will be at -5 feet

(remember the typical depth range of 3-7 feet), keep in mind that the entire test interval must be within the discharge layer

The results of the pilot hole are key in determining the test interval above

Exceptions If refusal before 12 feet for Test Borings use Test Pits A 4 foot separation must exist beneath the base of the perc test

and the limiting condition

Site Investigation for Subdivision: A Soils Test Plan must be submitted to the County and

approved prior to testing for the subdivision. The Soils Test Plan consists of: Proposed locations of testing on a plat map The method of testing (boring/pit/perc) Name of firm Depth to seasonal high groundwater Site-specific geology Site-specific topography Information to be included in final report

A ‘set of tests’ is required for 30% of the lot coverage of the subdivision.

Each set consists of 1-50.0 foot pilot test boring and 1 percolation test (usually at 5.0 feet)

The primary and reserve criteria do not apply at this point

These results are used to determine if on-site septic systems will be possible or acceptable for the subdivision overall…….

If not……..The developers will need to make arrangements for sanitary

sewer system throughout the subdivision.If the results are acceptable….Then the individual homeowners will be responsible for

individual lot testing (3 pits/3 percs-primary/ reserve criteria). They have the option of relying partly on the report generated for the subdivision and my be able to have less septic testing done for the individual lot. This depends on the test locations (primary/reserve) versus their septic system location.

Site Investigation for an Individual Lot: 3 Test Pits or Test Borings to 12 feet. For conventional / leach field and

disposal trenches, the test hole depth is required to reach at least 5 feet below the discharge depth (resulting in a 10 foot boring usually-15 feet will be assumed by Foree and Vann so we have one less variable to mess with). 12 feet is the maximum depth attainable with a conventional backhoe. If borings are used it makes perfect sense to use 15 feet (3 sections of auger). Borings shall be small diameter auger i.e. 4.5 inches.

2 in the primary, 1 in reserve location Pits or Borings should be 10 - 25 feet apartPercolation Tests 2 in the primary, 1 in the reserve location A 1 cubic foot test hole is excavated in the test pit, while a minimum of 15

inch diameter auger is used for drilling efforts Assuming that the bottom of the test interval will be at -5 feet (remember the typical depth range of 3-7 feet), keep in mind that the

entire test interval must be within the discharge layer The results of the pilot boring or test pit are key in determining the

percolation test interval aboveExceptions A 4 foot separation must exist beneath the base of the perc test and the

limiting condition if encountered shallower than 12 feet

Field Testing For Field Testing For Seepage Pit Seepage Pit

Disposal Systems – Disposal Systems – By County (where By County (where

accepted)accepted)

Seepage Pits are No Longer Allowed in

this County

Seepage Pits are No Longer Allowed in

this County

Seepage Pits are No Longer Allowed in

this County

Site Investigation for an Individual Lot: Using 4.5 inch diameter continuous flight auger, complete a

pilot test boring to a minimum depth of 50 feetPercolation Tests One in the primary area only One 18 inch diameter test hole to a minimum depth of 30

feet Typically the bottom of the test interval will be from 3 feet

below the current grade to the bottom of the test (keep in mind the entire perc test must be within the discharge layer for the seepage pit system)

Exceptions A 4 foot separation must exist beneath the base of the perc

test and the limiting condition

Site Investigation for an Individual Lot: Using 4.5 inch diameter continuous flight auger, complete a

pilot test boring to a minimum depth of 50 feetPercolation Tests One in the primary area only One 18 inch diameter test hole to a minimum depth of 30

feet Typically the bottom of the test interval will be from 3 feet

below the current grade to the bottom of the test (keep in mind the entire perc test must be within the discharge layer for the seepage pit system)

Exceptions A 4 foot separation must exist beneath the base of the perc

test and the limiting condition

Seepage Pits are No Longer Allowed in

this County

Site Investigation for an Individual Lot: Using 4.5 inch diameter continuous flight auger, complete a

pilot test boring to a minimum depth of 50 feetPercolation Tests One in the primary area only One 18 inch diameter test hole to a minimum depth of 30

feet Typically the bottom of the test interval will be from 3 feet

below the current grade to the bottom of the test (keep in mind the entire perc test must be within the discharge layer for the seepage pit system)

Exceptions A 4 foot separation must exist beneath the base of the perc

test and the limiting condition Required to maintain a 60 foot separation between the

bottom of the proposed pit and aquifer

Site Investigation for an Individual Lot: Using 4.5 inch diameter continuous flight auger, complete a

pilot test boring to a minimum depth of 50 feetPercolation Tests One in the primary area only One 18 inch diameter test hole to a minimum depth of 30

feet Typically the bottom of the test interval will be from 3 feet

below the current grade to the bottom of the test (keep in mind the entire perc test must be within the discharge layer for the seepage pit system)

Exceptions A 4 foot separation must exist beneath the base of the perc

test and the limiting condition

ReportReport

Major Components of the Major Components of the ReportReport

Test Locations (Site Plan)Test Locations (Site Plan) Boring LogsBoring Logs Groundwater dataGroundwater data Field Data SheetField Data Sheet Completion of ADEQ formsCompletion of ADEQ forms Presentation of SARPresentation of SAR

Test Test LocationsLocations

Typical Typical Boring LogBoring Log

Groundwater MapGroundwater Map

Field Data Field Data SheetSheet

Typical Typical Form Form

SectionSection

Soil Absorption Rate (SAR)Soil Absorption Rate (SAR)