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DRAINAGE ASSESSMENT
Allura at Tiffany Park
Lot 93
Prepared for:
MainVue WA LLC
1110 - 112th Avenue N.E., Suite 202
Bellevue, Washington 98004
June 21, 2018
Our Job No. 16055
CIVIL ENGINEERING, LAND PLANNING, SURVEYING
18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX
BRANCH OFFICES ¨ TUMWATER, WA ¨ LONG BEACH, CA ¨ ROSEVILLE, CA ¨ SAN DIEGO, CA
www.barghausen.com
PR13007339
B18003399
V3-Revision to Issued
REVISION
Received: 09/21/2018 / aalexander
BUILDING DIVISION
APPROVEDBUILDING DIVISION
THIS SET OF APPROVED PLANS MUST BE ON THE JOB AT ALLTIMES DURING CONSTRUCTION. THIS BUILDING IS NOT TO BEOCCUPIED UNTIL AFTER FINAL INSPECTION BY THE RENTONBUILDING DIVISION AND RECEIPT OF CERTIFICATE OFOCCUPANCY.
APPROVAL SHALL NOT BE CONSTRUED AS THE AUTHORITY TOVIOLATE OR CANCEL ANY PROVISIONS OF CODES, ORDINANCES,OR OTHER REGULATIONS ENFORCED BY THIS CITY.
DATE: 10/09/2018
16055.025 - Drainage Assessment.doc
PROJECT OVERVIEW
The project, Lot 93, is located just east of the intersection of SE 18th Street and Monroe Ave SE,
in the recently constructed plat called Allura at Tiffany Park. The Allura at Tiffany Park project
(a.k.a. Reserve at Tiffany Park) was deemed complete on November 25, 2013 and therefore
subject to the zoning code in effect at that time. The project is zoned R-8. Impervious surfaces
will be constructed on the lot. Driveways and walks will account for 354 square feet. Roof top
area will be 2,791 square feet, for a total amount of 3,145 square feet.
Lot 93 is situated on the south side of the newly constructed SE 18th Street. To the east and
west are the newly constructed single family lots. To the south is Tract A, the drainage facility.
The lot is 5,000 square feet in size. The front and rear setbacks are 15 feet. The garage setback
is 20 feet, and the side yard setbacks are 5 feet.
The lot has been graded level from side to side and front to back. There are short modular block
retaining walls on each side, approximately 3.5 feet in height. A 6-inch PVC stormwater stub has
been provided at the front of the lot for connection of the roof and footing drains. This connection
conveys stormwater to the drainage facility constructed for the plat within Tract A.
The plat infrastructure plans were prepared and submitted to the City of Renton in December
2016; therefore, the plat is vested to the 2009 King County Surface Water Design Manual
(KCSWDM) and the 2010 City of Renton Amendments. As such, Individual Lot BMP's are
required to be implemented in accordance with Appendix C of the KCSWDM.
ON-SITE BMP ANALYSIS FOR FEASIBILITY
Individual onsite BMP's were analyzed during the plat improvement process. Given the site
constraints and onsite soils, the Restricted Footprint BMP was chosen. The R-8 zone allows 75%
maximum impervious coverage. The allowable impervious for each lot was reduced by 10% to
65% maximum. A covenant is on the Allura at Tiffany Park Final Plat Map restricting the amount
of allowable impervious. Lot 93 is 5,000 square feet in size. Based on 65% coverage, the
allowable impervious amount is 3,250 square feet. In addition to the Restrictive Footprint BMP, a
Perforated Pipe Connection will be provided immediately upstream of the 6-inch PVC storm stub.
EROSION CONTROL EVALUATION
In order to prevent erosion and trap sediments with the project site, the following BMPs will be
used approximately as shown in the Erosion Control Plan.
· Clearing limits will be delineated by installation of Silt Fence around the entire perimeter
of the site.
· A construction entrance will be installed at the location of the driveway.
· Soil will be stockpiled in the rear yard area.
· Mulch will be spread over all disturbed areas of the site when they are not being worked.
Mulch will consist of air-dried straw.