In order to promote low impact development using creative approaches to site design, habitat and tree retention, significant reduction of impervious surfaces, changes in traditional site features such as roads and structures in favor of natural habitat features, the director may approve, or for those projects requiring review and approval by the city council, recommend approval of deviations from engineering design and the provisions of Clyde Hill's development regulations for all development, redevelopment, and construction site activities based upon the following factors:
A. The deviations will produce a compensating or comparable result in stormwater flow control and treatment that is in the public interest;
B. The deviations contribute to and are consistent with the goal of achieving low effective impervious surface area within a development;
C. The proposed development project offers reasonable assurances that low impervious surfaces will be achieved and maintained;
D. The deviations do not threaten public health or safety;
E. The deviations are consistent with generally accepted engineering and design practices and are prepared by a registered professional engineer licensed in the state of Washington with experience in LID design;
F. The deviations promote one or more of the following:
1. Innovative site or housing design;
2. Increased on-site stormwater retention using native vegetation;
3. Retention of at least 60 percent of natural vegetation conditions over the site;
4. Improved on-site water quality beyond that required by current applicable regulations;
5. Retention or recreation of predevelopment and/or natural hydrologic conditions to the maximum extent possible;
6. The reduction of effective impervious surfaces to the maximum extent practicable;
G. The deviations do not allow density greater than what would otherwise be allowed under city regulations then in effect;
H. The deviations do not present significantly greater maintenance requirements at facilities that will be eventually transferred to public ownership;
I. There shall be submitted in conjunction with each such project, covenants, conditions and restrictions which will be binding upon the property all necessary native growth protection easements, impervious surface restrictions and such other critical features as the director may require.
Use of LID facilities shall require approval by the public works director. Prior to plan approval of LID facilities, a soils report must be prepared by a professional engineer, geologist, hydrogeologist, or engineering geologist licensed in the state of Washington and submitted to the public works director for review and approval. If LID facilities are found to be feasible, the final signed/stamped soils report must include a statement that the use of the proposed LID facility will not result in springs, surface flooding, seepage into downstream basements or crawl spaces, or slope instability. |
Prior to final approval of the LID facility construction, a registered professional engineer licensed in the state of Washington and experienced in LID design shall submit to the city "as built" plans of the LID facility and certification that the facility has been constructed as shown on the "as built" plans. |
(Ord. 905 § 2, 2010; Ord. 947 § 1, 2016)