HomeMy WebLinkAbout11015 Kern Canyon - Payless Mini Storage Off-Site Basin Calculations
OFF-SITE DRAINAGE BASIN CALCULATIONS FOR PAYLESS MINI STORAGE PURPOSE The purpose of this study is to develop a plan to expand an existing temporary drainage basin (Basin) to provide
adequate capacity for the runoff produced by PayLess Mini Storage (PayLess). The Basin is located south of Tract No. 6193 near the intersection of Chase Avenue and Blue Cloud Street.
SUMMARY AND CALCULATIONS PayLess is located on Kern Canyon Road (State Route 184) north of Mesa Marin Drive within the boundaries of the Breckenridge Planned Drainage Area (PDA). The
site is designed to connect to an existing 24” storm drain pipe that is stubbed to the site from the back of an existing catch basin at the northeast corner of the intersection of Kern
Canyon Road and Mesa Marin Drive. Per the PDA, runoff from PayLess is designed to drain through Tract No. 6193 to the Basin. Currently, the Basin does not have the capacity to take the
drainage from the PayLess site and the 24” storm drain is not being utilized. The Basin was constructed constructed concurrently with Tract No. 6193 and was sized in the Supplemental
Drainage Study – Tract No. 6193 (Tract No. 6193 Study). The Basin was only sized to take runoff from Tract No. 6193 and Tract No. 5804. At this time, PayLess is not constructed to its
ultimate build-out because of the insufficient capacity of the Basin. A temporary drainage basin was built on the PayLess site to handle the runoff. In order to finish the construction
of the site, the on-site storm drain will need to connect to the existing system and the capacity of the Basin will need to be increased to take the runoff from the site. As stated previously,
the Basin was not designed to take runoff from the PayLess site. The design of the Basin used values taken from the Updated Master Drainage Plan for Nickel Enterprises Properties within
Section 20, 29/29 (Nickel Study). In the Nickel Study, Tract No. 6193 and Tract No. 5804 were assumed to be R-1 with 6,000 s.f. lots. The total cA for the two tracts was 28.52 (see Junction
22 on on attached map for Nickel Enterprises Drainage Plan), so the required storage for the Basin was calculated to be 4.28 acre-feet. The design of the basin provided a storage capacity
of 4.31 acre-feet. A typical Breckenridge PDA outlet structure with an 8” outlet pipe was constructed in the Basin which discharges into a natural drainage channel. A Temporary Flowage
Easement was recorded to cover the area of the Basin and the area in which the outlet pipe discharges. We have calculated the additional capacity needed in the Basin based on the current
site design of PayLess. The total site encompasses 20.28 acres. The current design will have
10.83 acres of impervious area and 9.45 acres of pervious area (see attached On-Site Drainage Area Map). A c-factor of 0.90 was used for the impervious area and 0.15 for the pervious
area per City of Bakersfield Standard Dwg. D-2. The required storage for the PayLess Mini Storage is 1.67 acre-feet, so the total storage required for the Basin is 5.95 acre-feet (see
attached Off-Site Temporary Drainage Basin Calculations). The Temporary Flowage Easement that is currently in place is larger than the Basin, so the Basin can be enlarged to 5.96 acre-feet
while staying within the limits of the easement (see attached Drainage Basin Plan). The bottom of the Basin will remain at the same elevation so the outlet structure and 8” pipe will
not be disturbed. CONCLUSIONS The storage capacity of the Basin can be increased to hold the runoff from the PayLess Mini Storage site in addition to the runoff that it is currently
designed for. The expansion of the Basin will remain inside the Temporary Flowage Easement. Since the the required storage was calculated with specific pervious and impervious areas
on the PayLess Mini Storage site, any site plan changes which increase the impervious area will increase the required storage. The expansion of the Basin does not provide enough capacity
for an increase in impervious area on the site, so a covenant shall be put in place on the property so the impervious area can not be increased without providing remediation for the
increased runoff.
PAYLESS MINI STORAGE OFF-SITE DRAINAGE BASIN CALCULATIONS
Porter & Associates, Inc. Engineering & Surveying Prepared by: MVC Date: 19-Apr-10 1200 21st Street Job No: 2230 Bakersfield, CA 93301 Sheet 1of 1 Sheets Calculations for Expansion of
Off-Site Temporary Basin Payless Mini-Storage DRAINAGE BASIN CALCULATIONS Average Accumulated Accumulated Elevation Area Area Volume Volume Volume ft sq. ft. sq. ft. cu. Ft. cu.ft. ac-ft
676.0 26337 27069 27069 27069 0.62 677.0 27800 28547 28547 55615 1.28 678.0 29293 30054 30054 85669 1.97 679.0 30815 31592 31592 117261 2.69 680.0 32368 33159 33159 150419 3.45 681.0
33949 34755 34755 185174 4.25 682.0 35561 36382 36382 221556 5.09 683.0 37202 38038 38038 259593 5.96 684.0 38873 5.96>5.95 OK
PAYLESS MINI STORAGE ON-SITE DRAINAGE AREA MAP
PAYLESS MINI STORAGE DRAINAGE BASIN PLAN
PAYLESS MINI STORAGE NICKEL ENTERPRISES DRAINAGE PLAN