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Home My WebLink About10/29/2001, - SLO MARKETPLACE ASSOCIATES GENERAL PLAN AMENDMENT G010004M OCT-25-2001 22:50 Jan 8055412239 P.01i06 ' NGtp 29-oIAGM SAN LUIS OBISP MEM#--- '�° DEPARTMENT OF PUBLIC C WORKS Noel Klug,Director 'c. County Crovernment Center, Room 207• San Lula Obispo CA 93408• (805)781-5252 1 Fax(805)781-1229 email addre":engrVCo.6lo.ca.ub COUNCIL TIMID DIR SAO ❑ FIN DIR � L� uo�o [3 FIRE CHIEF October 15, 2001 ORNEY C3 PW DIR CLEftORIG- C1 POLICE CHF O Q%T NEA 3 ❑ REC DIR W ❑ UTIL DIR _ . MEMORANDUM ❑ HR DIR _ ,DeSarnetfC ✓Rica/ 1-"'":-"` ------. _ .. . r-90%w� '= I TO: Richard Marshall, Development Services Engineer Noel IGng, Director of Public Works FROM: Susan Litteral, Project Coordinator SUBJECT: SLO Marketplace Associates General Plan Amendment G010004M Flood Control and Water Conservation District, Zone 9 has been analyzing the San Luis Obispo Creek watershed to determine the extent of flooding and evaluate options to minimize or control flooding problems. The development of the Dalidio property raises many issues and potential impacts. All of this property is subject to flooding. In high flows, the waters of Prefumo Creek get backed up from high head in SLO Creek and culvert restrictions near Los Osos Valley Road and the Highway 101 southbound off-ramp and flood the lower portions of the property. In higher flows, water from SLO Creek flows over Highway 101 near Madonna Inn and flows through Madonna Plaza, the Promenade and the Dalidio properties on its return to the creek. Any structures placed in this flood plain will displace flood waters and cause increased depth of flooding elsewhere...Improperly located structures can block the flow of water and cause increased flooding (extentand duration)and may slow the waters enough to cause deposition of sediment. The creation of extensive impervious(or reduced pervious)areas will increase the runoff from this site and exacerbate the existing flooding problems. This property also currently functions as a recharge area for the San Luis Obispo groundwater basin. Although this basin is relatively small, it is an important component of the City.of San Luis Obispo`s water supply and this impact should be addressed. The City of San Luis Obispo is subject to NPDES Phase II requirements for storm water quality. Erosion and sedimentation control practices are designed for upland sites not for sites subject to complete innundation. Special mitigation methods will need to be identified to insure compliance with these regulations. Additionally,storm water quality from parking OCT-25-2001 22:51 Jan 8055412239 P.02i06 lot runoff is an NPDES concern. Typical treatment methods include detention and filtration of site runoff. The amount of water that can back up on to this site or flow across the site could be problematic and the project design should address these concerns. The Zone 9 study is producing a Stream Management and Maintenance Program for the San Luis Obispo.Creek Watershed. This includes the Watershed and Waterway Design Manual forthe City of San Luis Obispo and portions of San Luis Obispo County Within The San Luis Obispo Creek Watershed. A programmatic EIR is being prepared for these documents with plans for both the City and County to adopt the plan and manual. Based on this goal, it might be appropriate to include the draft requirements of these documents in the conditions of approval for a project that most likely will be constructed after formal adoption. The project site is specifically included in the plan as being in a special Floodplain Management Zone. I have attached to this memo the recommended mitigations for these lands that have been determined to "have a potentially significant effect on downstream flooding." The Stream Management and Maintenance Program also includes a number of projects designed to control or reduce flooding problems along various reaches of the creek. One of these sites is at the confluence of San Luis Obispo and Prefumo Creeks. The financing plan for these projects has not yet been developed, but it would be appropriate to require the applicant to pay an impact fee towards this project. Thank you for considering my concems. If you have any questions please call me at 5269. File: Planned Dev.-SLO Marketplace G010004M L•\UTILrrYlOct011Madcetplace.MMO.lndsl \ .' SLL,��> 1 �'/�' lit r flt � "a'^-� It,�,-�•Cv�T' t�rl�� fl'li�,l - p�`��}tis.Y1/�,��(;3''��V� �`'A''�''+/. .nom. � � rl�' `hL"^,}t; t�7►i;�•.. Y' y� _x7P fi'lf'` �v�a ��) ` 1 � 1 � ♦ , Iv � ?�.,��P � iCly 1YF ti- 2' 'lab1' '3'L`! n f ar� I a1'!!]�,�P�_ � � It�,?r� r 1 .f.w "'it �5•.-.�+. • '�� ' � s� S i i� ' n J - /oi�14[ (��1o.�Je"`2/`L�Y�p / / �/ �,,��`Y til .f ] ✓ 2 t �� 1.,. ' � //�i/ ///�, 'f $i +r ^IL lit • r �r�' s�jy,^f�'� rt j.. vI}}r. 8' {SIfI y r t��' !i `$r1f..., j- ° L� y . . . 'r.i `/�//i//ri%Qj.. r. /'� 1 ' S ?r ;^ 1im \`YQQt,1 .•rC . °Mlails,e�'��a y�y k c Iy'�FS 'Y7� ;� }'..� I.1. 1'!r); r a C /v Iw. ija w '- ,rs gy 'Ran•'{'r. 4�,, �+ • 1a i�. -A,°°s'l"`l p: a A11rtr' �e - �+y:i NMI in a1 t � � y %,. . 9 ' •i .�. ��• -�,, r'a.�$�t2y� �/iky/ ///%/�i/i/iii% %%�/ �---- � - ��f�n,�`','�{-,�•�i+4g�?I+'S,'a�lrf4al Cy ��a� /�j � �i.'�• `f }� � '' i �'�vTt1��x�} ,E�'�`��'��F''•i �'t��i��r ��C�"' ��]k-^��K r ai�1 � �i.- �.`..�^Y,V.2��G�!,1�`„ •a➢�✓'�<{.•r�^-��yc �3�' .��f,:/�jD,j � � �� t�y"" , �1 1/pa� w,,�{.�,1�1 �.i,✓'jf',r�,�xn fi' i�'L�'1�. t� ��..n.�'`�'�i I1;!iT�JR.�,'y .d'`..e�1�v� 1 � y��... '� _ �'f��°E4��it�'i�31aa� �cn�:.Cs'^'�•` %j��."y- �hsmap� t s .':t-•Y7. ^O�;'.�`'i '' rf�°"rc3'L ' i 5Y'aT ��1/ �� .• q f.; i�a a� �i! �ytY Eyf ! j� r !�,ii n�5�'.'t'•t mr OCT-25-2001 2253 Jan 13G7741GGJ7 r.r,�•�,o For any development or subi: OCT-25-2001 22:53 Jan 8055412239 P.05i06 • Excavation to uwakice fill shall be located on the same r,.rcel as the fill unless it is not reasonable or practicable to do so.In such cases,the excavation shall be constructed as a part of the same development project. Any excavation dug below the winter "low water" elevation shall not count toward compensating for fill since these areas would be full of water in the winter and not available to hold storm water following a rain.Winter"low water"elevation is defined as the wat&surface elevation during the winter when it has not rained for at least three days, and the flows resulting from-st=: have receded This elevation may be determined from records,hydrologic/hydraulk studies,or field observation.Any fill placed above the 100- year floodplain will riot count towards the fill volume. • Parking facilities providing for short term parking(motor vehicles remain parked for less than18 hours per day)in the floodplain may be located at an elevation of no more than one foot below the ten year floodplain.Long term parking (motor vehicles remain parked for greater than. 18 hours without being moved)•in the floodplain may be located at an elevation of no more than one foot below the 100-year floodplain . • Temporary fills permitted-daring construction shall be removed upon completion of construction prior to the close of the in-stream work window as defined by California Department of Fish and Game or other state or federal regulatory authority. • Excavation and fill required for the construction of detention facilities or other facilities, such as levees,shall be specifically designed to reduce or mitigate flood impacts. Levees shall not be used to create vacant buildable land. • Excavation and fill required to restore or enhance floodplains, riparian areas, wetlands, uplands-and streams, including�but not limited to the planting of vegetation, installing aquatic habitat enhancement structures, and"daylighting"existing storm drains, shall be permitted as long as the design complies with all applicable City, County, state and federal standards. • A minimum setback of 15 meters (50 feet) from the top of bank shall be adopted and maintained as a flood passage way.No new structures that could significantly block the downstream passage of floodwaters(inci4ng buildings,utility and trash closures,fences and landscaping walls) are permitted in this atea. This area shall be planted with native plants and maintained with an allowable Mannings roughness value of no lower than 0.050 and no higher than 0,065 as calculated using the procedures outlined in this Manual_ • For non-in fill areas the finished floors of all buildings shall be a minimum of 0.3 meters (one foot)above the 100- year FEMA base flood elevation. 13