1.2.2
For most projects resulting in 2,000 square feet or more of new plus replaced hard surface area or 7,000 square feet or more of land disturbing activity, the full range of minimum requirements contained in Volume I shall be evaluated for compliance through the drainage review process. However, for some types of projects, the scope of requirements applied is targeted to allow more efficient, customized review.
The review process and drainage requirements vary based on a project’s size, location, type of development, and anticipated impacts to the local and regional surface water system. There are five types of drainage review, as follows:
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Simplified Drainage Review
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Simplified Drainage Review – Engineered
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Abbreviated Drainage Review
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Abbreviated Drainage Review – Engineered
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Full Drainage Review
The permit or conditions that trigger each type of drainage review are described in Sections 1.2.2.1, 1.2.2.2, 1.2.2.3, 1.2.2.4, and 1.2.2.5. Figure II-1.1 provides a flow chart for determining which type of drainage review is required. Table II-1.1 summarizes the requirements that must be evaluated based on the applicable type of review, while Vol II–1.3 Submittal Processes and Requirements and Vol II–1.4 Submittal Documents outline the specific materials (i.e., plans, analyses, reports, and other documents) that must be submitted at various stages of permit review.
1.2.2.1 Simplified Drainage Review
Simplified Drainage Review applies to small (Chapter 12.08 KCC) Single Family Residential (SFR) projects for which Minimum Requirements #1 through #5 apply, located outside of critical areas and their buffers, and that do not implement a Threshold Discharge Area (TDA) approach (Volume I, Chapter 3). This type of drainage review is triggered by a building permit. The review process is streamlined by not requiring Preliminary Design Review (Vol II–1.2.3.2 Preliminary Design Review) and allowing for targeted submittal documents that do not require a professional engineer, as detailed in Vol II–1.4.2.3 Site Plans and Profiles (Simplified Drainage Review).
1.2.2.2 Simplified Drainage Review – Engineered
Simplified Drainage Review – Engineered applies to small (Chapter 12.08 KCC) SFR projects located inside critical areas (see KCC 12.28.020) or their buffers and to small (Chapter 12.08 KCC) SFR projects that implement a TDA approach (Volume I, Chapter 3). As with Simplified Drainage Review, this type of drainage review is triggered by a building permit, not by an SDAP. Preliminary Design Review (Vol II–1.2.3.2 Preliminary Design Review) is not required. Submittals must be prepared by a professional engineer. Additional mitigation beyond the minimum stormwater requirements in Volume I may be required to compensate for loss of critical drainage area habitat functions associated with activities inside the critical drainage area or critical drainage area buffers. See Vol II–1.4.2.3 Site Plans and Profiles (Simplified Drainage Review – Engineered) for detailed submittal requirements for this type of drainage review.
1.2.2.3 Abbreviated Drainage Review
Abbreviated Drainage Review applies to the following project types:
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Small (Chapter 12.08 KCC) non-SFR projects for which Minimum Requirements #1 through #5 apply, located outside critical areas and their buffers; and
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Grading only projects located outside critical areas and their buffers that involve the movement of between 150 and 5,000 cubic yards of material.
This type of drainage review is triggered by an SDAP. Preliminary Design Review (Vol II–1.2.3.2 Preliminary Design Review) is required, but the submittal process is streamlined by allowing targeted submittal documents that do not require a professional engineer, as detailed in Vol II–1.4.2.3 Site Plans and Profiles (Abbreviated Drainage Review).
1.2.2.4 Abbreviated Drainage Review – Engineered
Abbreviated Drainage Review – Engineered applies to the following project types:
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Small (Chapter 12.08 KCC) non-SFR projects for which Minimum Requirements #1 through #5 apply and grading only projects that involve the movement of between 150 and 5,000 cubic yards of material where the project:
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Connects into a drainage system in the right of way; or
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Constructs improvements in the right of way; or
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Constructs in a critical area or critical area buffer.
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This type of drainage review is triggered by an SDAP and requires a professional engineer. See Vol II–1.4.2.3 Site Plans and Profiles (Abbreviated Drainage Review – Engineered) for detailed submittal requirements.
1.2.2.5 Full Drainage Review
Full Drainage Review – Engineered applies to large (Chapter 12.08 KCC) projects for which Minimum Requirements #1 through #9 apply. This type of drainage review is triggered by an SDAP. See Vol II–1.4.2.3 Site Plans and Profiles (Full Drainage Review) for detailed submittal requirements.
Figure II-1.1. Flow Chart for Determining Type of Drainage Review Required.
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