Skamania County
Community Development Department
Building/Fire Marshal Environmental Health Planning
Skamania County Courthouse Annex
Post Office Box 1009
Stevenson, Washington 98648
Phone: 509-427-3900 Inspection Line: 509-427-3922
WINTER WATER TABLE EVALUATION APPLICATION
INTAKE CHECKLIST
(This checklist must be completed and submitted with all required documents for the
application to be considered complete. Review will not begin on the project until
all of the requirements below are submitted.)
STAFF
APPLICANT
A complete Winter Water Table Evaluation Application, signed by the property owner,
with non-refundable $925 fee (payable to Skamania County Treasurer). Fees are
subject to change by resolution of the County Commissioners.
Late Application Submittal Understanding – required if submitting Winter Water Table
Evaluation Application after January 1.
Attach the site plan checklist submitted with the Site Analysis Level II application.
Winter Water Table Evaluation Checklist.
Reviewed by
Complete:
Yes
No
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Date:
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Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Skamania County
Community Development Department
Building/Fire Marshal Environmental Health Planning
Skamania County Courthouse Annex
Post Office Box 1009
Stevenson, Washington 98648
Phone: 509-427-3900 Inspection Line: 509-427-3922
Winter Water Table Evaluation Application &
Information Packet
Why do I need to have a Winter Water Table Evaluation (WWTE)?
Protect ground water and public health.
Verify the site has a minimum of 12 inches or more of undisturbed soil above the
seasonal ground water table. It is important that all sites have a minimum of 12 inches
of undisturbed soil to properly remove pathogens using the proper OSS treatment level.
To determine the type of OSS system to be used based on unsaturated depth opposed
to just using moderate mottles on soil depth to water table (typically the difference
between using a pressure distribution (PD) system vs. a sand filter (SF) or Glendon®)
When does a WWTE occur?
Winter Evaluations may be necessary when there is evidence of a seasonal water table
within eighteen (18) inches of grade or when there is seasonal surface water within less
than seventy-five (75) feet, although these parameters may be reduced at the discretion
of Skamania County Community Development Department (SCCDD) staff depending on
the type of system proposed and the characteristics of the soil and site.
If redoximorphic features (moderate soil mottles) are noted less than 18 inches in one
of the excavated pits the applicant may:
1. Submit an application for a Winter Water Table Evaluation (WWTE) or proceed with
the WWTE, as part of a standard site evaluation, when required by the
Environmental Health Specialist (EHS).
2. Request a waiver from the winter evaluation if adequate justification is provided that
the site has a minimum of 12 inches or more of undisturbed soil above the moderate
mottling level(s). This information shall be provided by the licensed designer.
Adequate justification may include but is not limited to the following site
characteristics and mitigation stratagies:
The greater the depth to soil before moderate mottles would help provide
justification that the site has a minimum of 12 inches or more of undisturbed
soil above the seasonal ground water table.
Confidence of the moderate mottling depth as indicated by level of
agreement between the licensed designer and EHS.
Land forms (convex topography, upland, open vs. closed depression).
Convex topography is most desirable, as it is less likely to have seasonal
surface water or seasonal ground water depth issues. Concave topography is
not desirable, especially on the base of a hill.
Depth of roots. Roots observed below 12 inches in depth would help support
justification that the site area has a minimum of 12 inches or more of
undisturbed soil above the seasonal ground water table.
Additional design mitigations such as curtain drains, etc.
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Proposed treatment level. In all cases where justification is requested,
Treatment Level A (obtained without disinfection) is required.
Surface water is greater than 75 feet from the proposed drainfield.
 The submitted justification will be reviewed by SCCDD staff. SCCDD staff will
render a decision within 14 working days of receiving the application. The final
decision will be communicated to the applicant in a Site Evaluation Results
Letter.
 If SCCDD staff does not consider the justification adequate to demonstrate that
seasonal ground water is greater than or equal to 12 inches then the site shall
complete the WWTE.
What is the process for a WWTE?
A completed application must be submitted between October 1 and December 31.
However, after January 1, SCCDD will accept applications as long as the WWTE - Late
Application Submittal Understanding form (attached) is completed by the
owner/applicant.
Winter Evaluation Application shall include:
1. Winter Water Table Evaluation non-refundable $1,100 fee (payable to Skamania
County Treasurer - includes the review of up to 8 piezometers/excavated pits. Any
additional piezometer/excavated pit will require an additional fee). Fees are
subject to change by resolution of the County Commissioners.
2. A Soil and Site Evaluation fee when the WWTE is submitted in connection with a new
site evaluation application;
3. WWTE request letter from the licensed designer. This letter should detail any special
circumstances SCCDD needs to be advised of;
4. Design layout prepared by a licensed designer - see attachment #1 Winter Water
Table Evaluation Checklist for design layout requirements. Planned curtain drains
must be clearly indicated in the application and constructed by the time of
application submittal. Refer to attachment #2: Typical Illustration of Curtain Drain.
5. Stake, flag and label the locations of (see attachment # 2):
Excavated pits/piezometers
Proposed area of tank and pump chamber placement
Corners of all other proposed initial and reserve system components
6. Piezometers are recommended over excavated pits and must be constructed per
attachments #3 & 4: Standard Installation of a Piezometer.
7. Additional piezometers/excavated pits added during the winter evaluation must be
concurrently agreed upon by the licensed designer and SCCDD staff.
8. Before wintering data is collected, a construction visit by both the EHS and licensed
designer is required to confirm proper construction of the site. All construction
issues must be raised by the EHS during this site visit. Construction issues must be
resolved prior to the first evaluation.
Winter Water Table Evaluation Process:
 Winter water table evaluations shall occur on a weekly basis by the EHS during
the months of January, February, and March immediately following the
construction visit. The WWTE may extend into April if more data is needed
based upon precipitation totals.
 Water level measurements are made to the top of the water level in a
piezometer minus the 6” riser height.
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
How will SCCDD interpret and present the data for my WWTE?
 Daily rainfall data is to be plotted on a graph through each month monitored.
The date the water table data was gathered shall be indicated on the plotted
graph. Data is reviewed at the end of the WWTE period.
Conditions for non-approval: sites will be denied if the water table is
measured consistently less than 12 inches below grade 48 hours or
more after significant precipitation events or if surface water setbacks
cannot be maintained (provided precipitation conditions have been typical
for the region).
Conditions for approval: sites where the water table consistently is
measured greater than 12 inches below grade 48 hours or more after
significant precipitation events and surface water setbacks are maintained
PASS the WWTE (provided precipitation conditions have been typical for
the region). SCCDD will verify observed vertical separation limits and
appropriate levels of treatment expected upon submission of a complete
design.
 SCCDD will issue a decision by May 1st of the following year, provided
precipitation conditions have been typical for the region. The decision will
include specified design depth to seasonal water table for each pit/ piezometer
evaluated and horizontal setbacks.
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
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Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Skamania County
Community Development Department
Building/Fire Marshal Environmental Health Planning
Skamania County Courthouse Annex
Post Office Box 1009
Stevenson, Washington 98648
Phone: 509-427-3900 Inspection Line: 509-427-3922
Attachment 1
Winter Water Table Evaluation Application
APPLICATION TYPE
New System
Repair System
Expansion and/or Replacement System
Description of Proposal: __________________________________________________________
______________________________________________________________________________
APPLICANT AND SITE INFORMATION
Applicant Name: ________________________________________________________________
Mailing Address: ____________________ City: _________________ State: _____ Zip: _____
Phone Number: _________________________ E-mail Address: ________________________
Owner Name (Complete if different from the applicant): ________________________________
Mailing Address: ____________________ City: _________________ State: _____ Zip: _____
Phone Number: _________________________ E-mail Address: _________________________
Site Address: __________________________________________________________________
Tax Parcel Number: ______________________ Lot Size: _______________________________
Detailed directions to the site: _____________________________________________________
_____________________________________________________________________________
List any access restrictions (gates, dogs, cattle, etc.). Access problems restrict the ability to
evaluate property in a timely manner: ______________________________________________
______________________________________________________________________________
List any known encumbrances on this property (i.e., neighbor’s well, easement, flood zones,
etc.): _________________________________________________________________________
______________________________________________________________________________
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
FLAG SITE
To easily locate your property and soil test pits, place your name on a sign and affix to a post or
tree in front of the site marking access from the main road. Mark property corners, property
lines (every 100 feet), etc. If the site has property lines clearly marked (fence, roadway, etc.), it
will not be necessary to flag these lines. Clearly mark the location of the soil test pits. Describe
the soil test pit’s location: ________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
SOURCE OF SEWAGE/USE
Residential
Multi-family
Commercial
Food Service
Other - If “Other” explain: ____________________________________________________
No. of Bedrooms Proposed: ___________
Garbage Disposal:
Yes
No
Existing System: No. of Existing Bedrooms: ______
Proposed Additional Bedrooms: ______
WATER SUPPLY
Existing
New
Future
Public Water System
System Name: ______________________________________________________________
Private Water System (Please attach a copy of the private water system review.)
Spring
Individual Well
Shared Well
No. of Homes Served: _______
SOIL TEST PITS
Date soil test pits were dug: _____________________________________________________
OWNER/APPLICANT STATEMENT: I will comply with the rules and regulations of the
Skamania County Community Development Department (SCCDD) for on-site sewage
systems in the installation and maintenance of this system. I understand that any alterations
of the building size or location, or any filling or grading in or below the drainfield area may
invalidate any approval granted for this application. I further understand that in order to
process my application, I hereby grant SCCDD access to the site for inspection purposes and
that additional inspections will be required where any part of the installation is performed
by someone other than a person licensed.
____________________________________________________ ________________________
Applicant Signature
Date
____________________________________________________ ________________________
Property Owner Signature
Date
For Department Use Only:
Records included: Yes / No
File No.
Date received:
Fee:
Receipt #:
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Attachment 1:
WINTER WATER TABLE EVALUATION CHECKLIST
(Design layout must be prepared by a licensed OSS Designer)
WWTE LAYOUT DRAWING:
___ Use minimum scale of 1” = 60’
___ Show all proposed initial and reserve system components, including septic tank(s).
___ Show test holes/piezometers and curtain drains and label.
___ Show proposed and existing wells (drinking, irrigation, decommissioned or otherwise nonused)
___ Show proposed and existing water lines and all other underground utilities
___ Show proposed footprints of residence, driveway, outbuildings, etc.
___ Show test holes/piezometers and curtain drains previously evaluated by SCCDD.
___ Show soil test pit locations.
SITE PREPARATION:
___ Construct test holes/piezometers and curtain drains as per approved methodology
___ Stake, flag and label the locations of the following:
___ Test holes/piezometers
___ Corners of all other proposed initial and reserve system components*
___ Maintain required minimum setbacks between curtain drains and test holes/piezometers
(see attachment #4: Typical Illustration of Curtain Drain):
___ 30’ between edge of initial/reserve disposal components and down-gradient curtain
drain
___ 10’ between edge of initial/reserve disposal components and up-gradient curtain
drain
___ Safety recommendations:
___ Cordon off holes and curtain drains with yellow “caution” tape
___ Limit width of curtain drains to 2’
* Note: more detailed staking may be required on some “difficult” sites
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Attachment 2
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Attachment 3:
Standard Installation Instructions for a Piezometer
Equipment List:
1.
Piezometer (4” white PVC pipe, perforated or non-perf)
2.
Drill for adding ¼” holes to pipe
3.
Post hole digger or bucket auger
4.
Wire brush to break up smeared soil walls, if soil conditions require
5.
Pea gravel
6.
Bentonite chips
7.
Steel measuring tape
8.
White cap for top of piezometer
9.
Permanent marker or paint marker to label cap
10.
Water to moisten bentonite
Piezometer Installation:
1.
Dig the hole:
Since the piezometer pipe will ultimately extend to a depth 12” below your measured
moderate mottling level and will rest on 1” or 2” of pea gravel, your hole needs to be
dug to 13” to 14” below your measured mottling depth. Note that a post hole digger is
recommended since an auger is more likely to smear the sidewalls. In finer textured
soils, piezometers should be installed when soils are dry to minimize smearing; if holes
are dug in wet conditions, the sidewalls must be scarified (see #3 below).
2.
Prepare the pipe:
a. If using perforated pipe, extra holes need to be drilled. Perf pipe typically has two
vertical rows of 3/8” to ½” orifices with an orifice spacing of 6”. Starting at the
bottom of the pipe, drill a series of ¼” holes within each of the two rows of
existing holes. Stop drilling when you reach a point within 12” of the top of the
pipe. The final product will have two vertical rows of holes with orifices spaced 2”
apart.
b. If using non-perforated pipe, drill two vertical rows of ¼” holes, with an orifice
spacing of 2”. Drill these from the bottom of the pipe to a point within 12” of the
top of the pipe. The final product will have two vertical rows of holes with orifices
spaced 2” apart.
3.
Scarify the sides of the hole over the area that will surround perforated section of
pipe, if smeared while digging the hole.
4.
Shall be installed in undisturbed soil. Not in a backfilled excavated pit.
5.
Place 1”or 2” of pea gravel in the bottom of the hole.
6.
Insert the piezometer into the hole, but not through the layer of pea gravel. Make
sure the piezometer is vertical.
7.
Pour pea gravel into the annular space around the pipe until it reaches a level 3” to
6” below ground surface.
8.
Pour and gently tamp bentonite chips above the pea gravel to the ground surface.
9.
Record height of riser on riser pipe or cap. (i.e. the section of pipe extending above
ground surface).
10.
Make a mound of bentonite chips around the riser at the ground surface, shaped to
prevent puddling around the base of the riser. Moisten before leaving.
11.
Add cap to the riser with a method that allows for easy removal.
12.
Label top of cap with piezometer number.
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Attachment 4:
Sample Minimum Construction Standards for Piezometer (October 2008)
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012
Skamania County
Community Development Department
Building/Fire Marshal Environmental Health Planning
Skamania County Courthouse Annex
Post Office Box 1009
Stevenson, Washington 98648
Phone: 509-427-3900 Inspection Line: 509-427-3922
Winter Water Table Evaluation –
Late Application Submittal Understanding
Winter evaluations are typically required on sites that have marginal vertical separation (dry dirt
near the surface) during the winter months. In order to protect public health and ensure
proper operation of a septic system on this property, a winter evaluation is being required to
ensure required setbacks from seasonal water can be maintained.
Applications for winter evaluations must be submitted to Skamania County Community
Development Department by January 1st. This cut-off date allows the site to be evaluated for a
significant percentage of the winter months. Applications submitted after January 1st may not
allow enough time during the rainy season to make a determination on the appropriateness of a
septic system for the property.
Furthermore, unseasonably rainy or dry weather conditions may prohibit a reasonable
evaluation of the property during an “average” rainfall winter.
By requesting a winter evaluation after January 1st, I, the undersigned, understand that there
may not be adequate time and/or rainfall during the remainder of this season to make a
determination on the adequacy of an on-site system for this property.
Site Address:
Parcel Number:
Name (printed):
Signed:
Date:
__________________
Skamania County Community Development Department – Winter Water Table Evaluation Application
Updated as of June 14, 2012