Napa County Municipal Code Ch. 13.28 System Location and Soil Characteristics

The property owner or developer shall cause a site evaluation to be conducted which as a minimum will define the soil characteristics within the upper six feet, and shall include borings to encompass the drainfield and expansion areas.

(Ord. 1109 § 1 (part), 1996)

A. A site evaluation is a means of evaluating a parcel for its ability to provide an adequate sewage disposal system. A qualified professional shall perform a field textural analysis of the soil texture, structure and related variables, such as depth to water table, soil pores, root depth, and soil type to determine the percolation range at the sidewall of the proposed trench. The administrative authority shall review and approve the site evaluation and assigned results. The level of high seasonal groundwater shall be a minimum of three feet below the bottom of the proposed drainfield trench and there must be a minimum of three feet of soil with acceptable percolative capacity below the proposed drainfield trenches.

B. The site evaluation shall also include information particular to the area such as proximity to cuts, ditches, creeks, wells, steep slopes, reserve area, etc., which might impact the area's ability to properly treat and dispose of liquid wastes.

C. Where the qualified professional cannot adequately determine a percolation range, the property owner shall cause a percolation test to be conducted.

(Ord. No. 1337, § 17, 5-5-2010; Ord. 1109 § 1 (part), 1996)

Percolation tests shall be performed by a qualified professional and approved by the administrative authority. When required by Section 13.28.020 or the administrative authority, or requested by the qualified professional, a percolation test shall include the following:

A. The level of the seasonal high groundwater table, temporary or perched, shall be a minimum of three feet below the bottom of the proposed drainfield trench. Soil with an acceptable percolative capacity shall extend a minimum of three feet below the bottom of the drainfield trenches. The administrative authority may require additional percolation tests at such level when there is evidence of a soil change.

B. All percolation test result forms shall state what depth of trench is planned for the drainfield in the area tested. Evidence that the soil three feet below the trench bottom has acceptable percolation capacity must be submitted with the soil test.

C. Percolation tests shall be made in a standard test hole six inches in diameter, the depth to be based on the depth of the proposed leaching trench. Each test will require a minimum of six test holes in the area of the drainfield. The soil, to be acceptable, must show a stabilized percolation rate of at least one inch per hour.

D. A minimum of one core hole at least six feet deep shall be dug, preferably by a backhoe or similar equipment, in the drainfield area. Depth of the core hole is dependent upon proposed depth of leaching trenches.

E. Each percolation test shall be made in accordance with The Procedure for Percolation Tests, as outlined in the Manual of Septic Tank Practices, U.S. Department of Health, Education and Welfare, Publication No. 526, or the equivalent thereto and as modified by this division.

(Ord. No. 1337, § 18, 5-5-2010; Ord. 1109 § 1 (part), 1996)

A. Except as provided in Section 13.28.050, no building sewer, private or individual sewage disposal system, or parts thereof, shall be located in any lot other than the lot which is the site of the building or structure served by such sewer or sewage disposal system; nor shall any building sewer, private or individual sewage disposal system or part thereof be located such as to have less than the minimum clearance distance indicated in Table 13.28.040 (CPC § 721.1, modified).

Table 13.28.040

Notes

1. See subsection (C) of Section 13.20.080 for repairs.

2. Blue line shall mean any type of blue line on a USGS map.

3. Including porches and steps, whether covered or uncovered, breezeways, roof patios, carports, covered walkways, covered driveways, and similar structures and appurtenances.

4. This distance to be increased to four hundred feet if the sewage disposal system does not comply with the standards in this code. This four hundred feet may be reduced to a lesser distance (but no less than one hundred feet) if after inspection and evaluation by a qualified professional, a lesser distance is determined to be adequate for the purposes of protecting health and safety. Such distance shall be proposed by the qualified professional based on substantial evidence and is subject to approval by the administrative authority.

5. Unless easement is specifically for an onsite sewage disposal system.

6. These distances can be reduced to ten feet if the underground irrigation or drainage system is located upslope of the sewage disposal system.

B. The distance required by Table 13.28.040 may be (1) increased when a greater distance is required because of the existence of a special hazard or (2) decreased, except for water wells and springs, where the standard set forth in the table is impractical because of topological features and in all the circumstances no health hazard will be encountered. The administrative authority shall have the responsibility for making determinations called for by this subsection.

(Ord. No. 1337, § 19, 5-5-2010; Ord. 1252 § 9, 2005: Ord. 1109 § 1 (part), 1996)

(Ord. No. 1374, § 30, 9-11-2012)

A. Nothing in this division shall be construed to prohibit the use of all or part of an abutting lot or lots to either:

1. Provide access through a sufficient legal easement to connect a building sewer to an available public or private sewer, when appropriate cause has first been established to the satisfaction of the administrative authority; or

2. Provide space through a sufficient legal easement for a building sewer or private or individual sewage disposal system or part thereof.

B. "Legal easement," as used in this section, means easements and/or, where all parcels involved are in common ownership, contracts to convey easements upon severance of such ownership. Such easements and contracts shall be in a form approved by county counsel and shall be deemed effective for the purposes of this section only when recorded in the office of the Napa County Recorder (CPC § 721.2, modified).

(Ord. No. 1337, § 20, 5-5-2010; Ord. 1121 § 2, 1997; Ord. 1109 § 1 (part), 1996)