HomeMy WebLinkAbout24There are no upstream tributary areas to the project site. The majority of the nmoff Eton: the
project site discharges to the public storm system in Garden Ave. N. Ttie 72-inch storm drain m
Garden Ave N flows in a northerly direction and then turns east between N Park Ave. an Tm
Washington Blvd N approximately %z-mile dowmstream of the site. The drainage system
en
crosses Lake Washington Blvd N in two 48-inch culverts and discharges to a ROW ditch. Runoff
then flows through a series of ditches and culverts known as John's Creek for another
approximately 03 miles downstream prior to discharging to Lake Washington -
SITE HYDROLOGY
Core Requirements
This section will address the requirements set forth by the Core Requirements listed in Chapter I of
Lie 1990 King County Surface Water Design Manual (KCSW'DM).
I - Drscha'ge at the NaaoaL Location (1..11) -The deve'tooed storm rtmo$will be collected, conveyed_
and discharged at die natural discharge location-
2. off-Site.9nalysis (I-21) -The off -site arnalysas is discussed in the' �own5cearn Annalysis' secnon of
this report
3. RimofjControl (1.2.3) -
A_ Peak Rate Runoff Control: Detention will not be required for this project due to a negligible
increase in the peak runoff rate for the 100-year, 24-hour storm event. According to the
"Exemptions From On -Site Peak Rate Runoff Control" section of the KCSWDM, the site
is exempt from raioff control because the increase in the peak runoff rate for the 100-
yr/24-hr storm event is less than 0-5 cfs. Further discussion of this subject is covered in the
"Detention Analysis section of this report.
B. Biofiltration: Since developed conditions will not produce more than 5,000 SF of new
impervious area subject to vehicular use, the pro,--ct is not subject to this requirement This
project will actually decrease the amount of impervious area subject to vehicular use by
approximately 3.72-acres. Further discussion of this subject is covered in the "Water
Quality Analysis" section of this report-
4. Conveyivrce Facilities (1.2.4) - ThLs subject js covered in the -'Conveyance Analysis" section of this
report
5. E or.Sedunartatian Convnl P1mr (1.25) - This proj— will install a series of temporary erosion and
seduriertt control BMP's (Best Managenirnt Practices) related to speci5c conditions on -site. This
subject will be covered in the "fernparary Erosion and Sednnertt Control" section of this report
6. ktaumv.,m M and Operarion (1. ?- 6) - The pry cxrsite storm drainage system will be owed.
operated, and mairitamed by the owner.
DLR Group