Weld County, Colorado On-Site Wastewater Treatment System Regulations Study Guide.

Specific Inspection Topics Ancillary Inspection Services
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No variances for economic gain.

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No city or county shall issue a permit to construct or an occupancy permit for a building until the Division has issued a permit for an OWTS.

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One cannot connect more than one dwelling to the same OWTS unless such multiple connection was specified in the application and the permit was issued for such a system.

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And now the fun stuff:

A site and soil evaluation must be conducted for each property on wich an OWTS is proposed. An evaluation consists of:

  1. Preliminary investigation
  2. Reconnaissance
  3. Detailed soil investigation
  4. Report and site plan
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Preliminary investigation:

  1. Property Information:

a. Address
b. Legal Description
c. Existing Structures
d. Location of existing or proposed wells

  1. Existing Division OWTS Records

  2. Published Site Information

a. Topography
b. Soil Data

  1. Location of Physical Features that will require setbacks. This includes features on surrounding properties.

  2. Preliminary soil treatment area size estimate.

  3. Other information required by the Division.

  4. Additional information that may be useful.

a. Survey
b. Easements
c. Floodplan Maps
d. Geology and basin maps
e. Aerial photos
f. Climate info
g. Wetland maps

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Reconnaissance:

A visit to the property to evaluate conditions must be conducted. Information to be gathered includes:

  1. Landscape position
  2. Topography
  3. Vegetation
  4. Natural and cultural features
  5. Current and historic land use
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Soil Investigation

A. Soil investigations to determine the long-term acceptance rate of a soil treatment area must be conducted.

  1. Visual and tactile evaluation of 2 or more soil profile test pit excavations to determin whether a limiting layer is encountered.

  2. Percolation testing may be conducted.

  3. If 1 & 2 don’t coincide, the designer must use the more restrictive LTAR in determining the size of the soil treatment area.

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B. Procedure for performing visual and tactile evaluations of soil:

  1. The soils evaluation shall be performed by a PE, PG, or other competent professional approved by the Division.

  2. Two soil profile test pit excavations and as many more as the PE wants.

  3. At least one of the profile test pit excavations must be inside the soil treatment area.

  4. Depth shall be to any limiting layer or four feet, whichever is encountered first.

  5. Layers of interference with the treatment and dispersal of effluent must be noted.

  6. Soil observations must be conducted at or near the location of the soil treatment area, but if possible, not where the trench or beds will go.

  7. Evaluations must be done with adequate light and not when frozen.

  8. Observation must allow observation of different soil horizons.

  9. Soil profile pit observations must be conducted prior to percolation tests to determine whether the soil is suitable and to what depth the percolation tests must be conducted.

  10. Use the most restrictive soil type found to calculate the long-term acceptance rate.

  11. Previous data can be used at the discretion of the public health agency.

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C: Soil descriptions for determination of a limiting layer:

  1. Depth of each sol horizon.
  2. Depth to bedrock
  3. Depth to saturated soil.
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D. Procedure for performing percolation tests:

  1. Under supervision of PE or PG.
  2. Number of test holes and location.

a. 3 test hols in the area where the soil treatment area is to be. Spaced evenly.
b. If proposed infiltrative surface is uncertain, do various depths.

  1. Dimensions.

a. 8-12" in diameter. Minimum of 6" and a maximum of 18" below the proposed infiltrative surface.

  1. Change in Soil.

a. 2 soil percolation hold must be terminated in the changed soil and percolation tests done in both.

  1. Percolation Tests.

a. Follow procedures below:
b. Preparation of Percolation Test Holes

 1.  Excavate the hole.
 2.  Scrape the bottom and sides.
 3.  Remove loose soil.
 4.  Add 2 inches of sand or fine gravel

c. Presoak:

d. Percolation Rate Measurement

 1.  Measurement must be done the day following the presoak.
 2.  If water remains after the swelling period, adjust the depth to 6 inches above the gravel.
 3.  If no water remains after the swelling period, add clean water to bring depth of water in the hold to 6 inches above gravel.
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Marking of Soil Profile Test Pit Excavations and Percolation Holes.

Flag them to allow easy location by others.

Soil profile test pit excavations may be backfilled after evaluation of the PE or PG.

Percolation holes must remain open until after evaluation by the Division.

Barricade for safety.

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Wastewater Flows

A: The Division may require the installation of a meter to measure the flow into the OWTS.

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B. Single-Family Residential Homes

  1. Design flow per person must be 75 gallons per day (gpd).

  2. The minimum design flow for a new home must be for a two-bedroom house (except for a repair or replacement of an OWTS of an existing one-bedroom house which can be one-bedroom.

  3. For homes up to and including 3 bedrooms, the assumed number of persons per bedroom is 2.

  4. For homes with more than 3 bedrooms, the assumed number of persons is 6 plus 1 additional person for each bedroom more than 3 bedrooms. A 5 bedroom house would be 8 persons, for example.

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C. Auxiliary Buildings

  1. If a home has an auxiliary building, the flow may be conveyed to the OWTS of the home or to a separate one.

  2. If the flow from the auxiliary building is only generated by the residents of the home, it will be assumed that the OWTS for the home will be adequately sized to include the building if flows are combined.

  3. If the auxiliary building will have users in addition to residents the design flow of the home must include the increased use.

  4. If the auxiliary building has a separate OWTS, the design should have a septic tank detention time of 48 hours.

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Accessibility for Inspection, Maintenance, and Servicing.

A. Septic tanks must have watertight risers over each access manhole and all risers must extend to or above final grade.

B. For new construction, the top of any septic tank, dosing tank or vault must be no deeper than four feet below finished grade.

C. Each treatment component of an OWTS other than the septic tank and soil treatment area shall be equipped with access manholes and risers that extend to final grade.

D. Riser Lids

  1. Each riser lid must be watertight, brought to or above the surface, and must have a secure closing mechanism, such as a lock, special headed bolts or screws, or sufficient weight (59 pounds or more) to prevent unauthorized access.
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A visual and audible signal device must exist.

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If sampling for testing is required for the permit, an accessible sampling point must be installed.

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Surface activity of the ground over any part of an OWTS must be restricted. No livestock, vehicles, recreational use, etc.

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An OWTS that will serve a business, commercial, industrial, or institutional property, or a multi-family dwelling must be designed by a P.E.

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Tanks, vaults, risers, and lids must be watertight.