Frequently Asked Questions
Mathews Soil Consultants, Inc.
What’s a perk test? Colloquially this refers to the suitability of a site for onsite sewage systems.

Governmental approval is the only means to assay a property’s suitability for development. This is the result of a series of actions including a site and soil assessment. Perk test is a common phrase to describe the process of evaluating a piece of land for drainfield development.  “Perk” is abbreviation of percolation, the movement of fluids (water) through the soil matrix.

Advanced Onsite Soil Evaluators (AOSE) and Certified Professional Soil Scientists (CPSS), and some engineering firms are qualified to conduct perk tests. There are several methods which have varied applications depending upon the questions arising from a soil profile evaluation.  Historically a standard perk test(known as a “falling head test) was conducted by a specialist from the VDH. This involved saturating a bore hole, and then noting the rate (time) the water spent soaking out of the hole. Thus was a born a rate (i.e. minutes per inch), however this was fraught with problems chiefly the variables of differences in procedure leading to significant changes in results. This method also does not establish the capacity of the soil to treat waste, nor the standoff to an impermeable or saturated horizon.

A perk test, due to it’s limitations transitioned to a procedure known as a drainfield site evaluation. A soil scientist  performs a thorough evaluation of soil properties and landscapes.  Using a hand auger (or excavator)  a Munsell color book,  measurement tools to assess depth, slope, distance, and the native tools of experience and interpretation the scientist will choose a suitable landscape position, with adequate setbacks to existing boundaries and setbacks (i.e. neighboring wells or springs) and create representative soil borings locate a drainfield site.

How long does it take to evaluate a piece of property for drainfield use?

Many factors affect the evaluation of a parcel, the scale, risk, scope and complexity of the site and soils are chief.  The landowner’s unique needs, as the  evaluator should be most concerned with adapting the design needs for your project to the he restrictions of the site and soil.

Generally an estimate can be made following a brief site visit, or occasionally a phone conversation. On average, it takes  2 to 4 hours to locate and document a drainfield for a single family home. To complete an application for a construction permit requires professional documentation- via a report for an engineer or other purpose, or to completely specify construction details for your site to ensure the design may be efficiently and successfully constructed. Therefore depending on complexity a complete permit application may take about a day to produce, as subdivision application takes less since there are abbreviated design requirements.  Commercial projects and evaluations to repair failing drainfields can take much longer.

Who should evaluate my property for drainfield use?

There are two classes of individuals who are certified, authorized or licensed by the Virginia Department of Health (VDH) or the Department of Professional and Occupational Regulations (DPOR).

An AOSE is qualified to perform a complete evaluation and design systems including “alternative systems” which can take advantage of devices which produce better effluent quality, and therefore can be installed on sites with greater limitations than conventional systems.

However, not all public or private sector consultants are equal.  Before you decide on a professional, check their credentials.  Ask them how long they have been evaluating soils for drainfield use.  Describe your project or challenge and ask them if they are qualified in that area of expertise. Employees of the Virginia Department of Health are titled Environmental Health Specialists (EHS). They must be licensed as an OSE to perform the evaluation and design of septic systems, however their services are limited by their employer. Inquire with the locality to determine these limits, such as how long they may spend on your site, whether you must provide a backhoe or utility marking, and how many sites they may evaluate. Also determine the consequence of a rejection, is this a case decision and will it affect the value of your property or subject the site to a higher burden of proof for future applications.   In general, the EHS is a regulator first and an onsite soil evaluator last.  If you want service with value, choose a competent AOSE.

CPSS generally have greater experience and knowledge soil factors, which affect septic systems, and are also experts in other areas, such as nutrient management or wetland delineation. However as with geologists these scientists are not qualified nor licensed to predict future performance of a built environment.

Why choose an AOSE over an EHS?

An EHS is an employee of the Virginia Department of Health (VDH) who is responsible for  protecting the public health and the environment from harm.

Health districts have policies limiting the number of site visits, soil borings or boring depth.  These restrictions can obviously limit the level of service provided, and delay the outcome of an application.  Some local health departments even recommend or require consulting with an AOSE from the very beginning.

There are  circumstances in which the health department requires an AOSE or an engineer.  If your property was rejected for conventional permitting  an AOSE is required to review your site and propose an alternative.  The VDH employee, is also not permitted to advise you on other site development questions. For example the planning of utilities, erosion control, construction access, integrating structure footprint, water development, preserving natural resources such as unique trees or vegetation, information about neighbors or communities, livestock or gardening are all areas in which a private consultant may be able to educate and inform you. Naturally we are interested in customized service which determines making the best choices, customer service is not an area in which government employees are rated.

Alternative systems employ “pre-engineered” treatment systems designed to improve the quality of the wastewater before disposal.  There are many competing treatment devices approved for use in the Commonwealth by the VDH which also regulates their use.   EHS are prohibited from designing alternative septic systems, they lack the knowledge and training, and to avoid a conflict of interest the VDH does not wish to be in the position of recommending a vendor’s system.

Second, community scale (more than 1,00o gallons/ day or multiple dwelling units, and commercial projects require a tremendous amount of consulting time and expertise to integrate the variables of a project.  An AOSE is selected by a client to find a solution to a problem or to complete a project within a certain time frame and budget.

A competent AOSE considers all issues and options available to make your specific recommendation.

VDH limits the resources that may be expended on a “bare application,” consequently in the event the EHS is frustrated by a site, they will reject the site rather than being able to allocate more time to this application. An AOSE has the freedom to make you his first priority and discuss a plan of inquiry to satisfy the site owners wishes.

What is an Certified Professional Soil Scientist?

A Certified Professional Soil Scientist, or CPSS, is an individual who possesses a special knowledge of soil science and the methods and principals of soil evaluation gained from education and experience in the formation, description and mapping of soils.  A CPSS is regulated by the Department of Professional and Occupational Regulations (DPOR) and certified by the Board of Professional Soil Scientists through education, experience and examination.  A CPSS is held to a high standard of practice and conduct in their field.  A CPSS evaluates, describes and maps soil types in order to predict their suitability for and in response to various land uses.  Such land use evaluations may include storm water, septic drainfields, residential and commercial development, sanitary landfills, forestry or agricultural production, soil erosion and sediment control, shrink-swell potential and hydric soils.

What is an Alternative Onsite Soil Evaluator or AOSE?

The AOSE is a site evaluator licensed by DPOR, and acting under the exemptions to the practice of engineering (Code of Virginia Section 54.1-402.A.11) VDH will accept evaluations and designs for onsite septic systems from an AOSE or Professional Engineer in consultation with an AOSE. Generally, VDH is required to take action on an AOSE submittal within 15 working days or the submittal shall be “deemed approved.”

What information is included in your AOSE permit application?

Typically the permitting application includes:

  • the cover page with site and client identification, certification statement and professional seal,
  • soil characterization summary and soil descriptions,
  • design criteria,
  • detailed site sketch and design drawing,
  • construction notes and specifications,
  • if applicable an operation and maintenance reference.
  • some designs may also include pump calculations and station schematics, product sheets, permeability test data and health department documentation.

AOSE packages for certification letters do not include complete construction specifications.

What is the difference between a Certification Letter and a Construction Permit?

A certification letter is a letter issued to certify a septic system which does not expire, though the actual design my vary with changes in regulation the site remains accepted by the local health department,  the site must be located on a plat by a licensed land surveyor and recorded to the deed. Applicants which do not intend to build within 18 months may choose to apply for a certification letter because the approval does not expire and conveys with the land.  Certification letters can be converted to construction permits by submitting an application and paying any required fees.  Certification letters are ideal for certifying that a property is approved prior to a sale.

A construction permit is written approval from the local health department to install, expand, repair, or modify an onsite sewage disposal system. Permits are nontransferable and are issued for a specific owner, site, and design.  Permits expire after 18 months, though they may be renewed under certain conditions.

What is the difference between a Conventional and Alternative System?

A conventional system is an individual sewage disposal system that consists of a septic tank or series of septic tanks and drainfield(s).  This type of system may include a sewage pump.

An alternative system is more complex  than a conventional system.  An alternative system is required when the site or soil conditions are limiting.  An alternative system typically includes advanced treatment and dispersal methods, equipment, and technology specifically designed for the marginal site.

What is an Engineered Onsite Septic System and why do I need a professional engineer?

An engineered onsite septic system is a special system designed by a professional engineer to meet particular design parameters.  An engineered system is a site-specific, custom design which may consist of a combination of specific components designed to performance standards established by the designer and dictated by the site conditions and design parameters.  A professional engineer may be required if the system is under pressure (such as a drip system, or a low pressure distribution system (LPD),  or must pump sewage more than 500′ horizontally,  or in excess of 50′ uphill, or for certain other special problems.
Occasionally a facilities wastewater varies from normal effluent as defined under the Regulations, in this event a characterization is necessary, and a system designed to accommodate abnormal wastes. A professional engineer (PE) may be necessary to design systems for such modified circumstances or if a project dictates a design outside the site, soil and design requirements of the Sewage Handling and Disposal Regulations.  The recommendation to consult a PE  is typically suggested by the AOSE in accordance with your situation and local Health Department guidelines.

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