§ 24.35.030. Special reports requirements.

Special report required in critical aquifer recharge areas shall include the following when relevant.

A.

Drainage and Erosion Control Plan. This plan shall address methods to minimize erosion and contain soil within the project boundaries during construction and to provide for stormwater management from the site and its surroundings during and after construction, consistent with the Drainage Design and Erosion Control Manual for Thurston County, as amended (Chapter 15.05 TCC).

B.

Hydrogeological Report.

1.

The hydrogeological report shall identify the proposed development plan and the risks associated with on-site septic systems and other on-site activities which may degrade the ground water beneath or down gradient from the site.

2.

The hydrogeological report shall be prepared by a licensed professional engineer or hydrogeologist, licensed in the State of Washington, qualified to analyze geological and hydrological information and ground water systems.

3.

The approval authority may waive the requirements of this section when there is persuasive evidence and reason that the issue(s) pertinent in a specific case, either site conditions or project mitigations, have been or can be adequately addressed in the technical report and supporting documentation.

4.

The hydrogeological report shall contain:

a.

A description of the soil, geological and hydrological characteristics of the area under permit application consideration, including the relationships between ground water and surface water including stream flows and wetlands; the character of the unsaturated zone, the depth to groundwater and, if reasonably possible, direction of groundwater flow.

b.

A site plan depicting the location of all existing and proposed structures; the boundaries of the property proposed to be developed; adjoining roads and site access; topography with two-foot contours; the hydrogeologic context including water bodies, wetlands, springs, seeps, wells, ditches, culverts, stormwater facilities and other relevant features; and the location of all existing and proposed public and on-site utility structures and lines, including on-site sewage systems, sewer lines and water lines.

c.

A discussion of how the characteristics described in subparagraph (a) above will influence drainage and the movement of water and contaminants in the ground water, and a discussion of how the proposed project will influence surface water including instream flows and wetlands.

d.

A description of conditions prior to project development, which may include baseline conditions for water quality and quantity.

e.

A description of conditions as they are likely to exist after complete development of the proposed project, and their impact on ground water quality and quantity.

f.

If determined to be necessary to evaluate the proposed activity or use, the approval authority may require the following information regarding the hydrogeologic characteristics of the site and the predicted behavior of contaminants: background water quality compiled over at least a one-year period, contaminant transport modeling based on potential releases to ground water, and modeling to determine the effects of ground water withdrawals.

g.

A list of those recommendations to be used to mitigate any of these potential ground water impacts. This shall include the effects of sewage disposal, lawn and yard activities, agricultural and animal husbandry, household chemical use, stormwater impacts and any other impacts reasonably associated with the project type described.

h.

The post development description shall include the effects of the activities likely to occur as a result of the complete development and use of the project at final equilibrium.

5.

Review and evaluation of the report may be delegated to other county departments and to qualified private consultants, at the applicant's expense, under the direction of the approval authority.

C.

Pier Foundations in Critical Aquifer Recharge Areas. The applicant shall submit the following information, certified by a qualified engineer, for foundations subject to review in accordance with TCC 24.10.170.

1.

The proposed depth of the foundation below the ground surface.

2.

The depth to the aquifer that any well within two hundred feet of the proposed foundation draws upon.

3.

If the aquifer drawn upon is less than fifty feet below the bottom of the hole proposed to be excavated to accommodate the foundation, then the applicant shall submit the following additional information.

a.

The distance from the proposed foundation to the subject wells.

b.

The foundation design and materials, including the concrete mix and the specific components of any additives, and the composition of any sealer/slurry proposed to be employed in construction of the foundation.

c.

Proposed construction techniques, such as use of a casing to mitigate potential groundwater contamination.

(Ord. No. 14773, § 3(Att. B), 7-24-2012)