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HomeMy WebLinkAbout11-00400096- 00076787 WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie 1.0 GENERAL LOCATION AND DESCRIPTION The subject tract (Plazas at Rock Prairie development) is located at the northeast intersection corner of the northbound feeder road of State Highway 6 and Rock Prairie Road in the Carter's Creek Watershed. The general location of the tract is shown on the vicinity map included in this report as Figure 1, and the subject property and adjacent tracts are shown in more detail in Figure 2. The subject tract consists of two parcels comprising a total area of 3.592 acres. Parcel 1 consists 1.787 acres fronting Rock Prairie Road on the south, and State Highway 6 along the west side of the parcel. The second 1.805 acre parcel consists of Lot 2 -C, Block One, of the Replat of 8.062 AC out of the Amending Plat of Cornerstone Commercial Subdivision Section One, which fronts State Highway 6 north of Parcel 1. The subject tract is bordered on the north by a shared private access drive to the Marriott Courtyard at Woodcreek Development, which is located east of the Lot 2 -C portion of the tract, and north of the Parcel 1 portion. Parcel 1 is bordered on the east by an undeveloped tract. As can be seen from Figure No. 2 the site is roughly "L" shaped and extends along the SH6 and Rock Prairie Road frontage. Surface cover of Lot 2 -C is comprised of grass, with a very few scattered trees, and has a small portion of paved access driveway along the north and east sides of the Lot which serve the Marriot development. Parcel 1 consists of a stand of cedar trees with scattered shrubs and grass cover. A portion of the Lot 2 -C property currently drains via sheet flow to the roadside ditch alongside SH6. The remainder of Lot 2 -C and all of Parcel 1 appears to drain to Rock Prairie Road via sheet flow and an onsite drainage swale located within Parcel 1, where it is collected by drainage inlets constructed with the Rock Prairie Road storm sewer system. The site is proposed to be developed as the Plazas at Rock Prairie Drive, an 18,661 SF commercial retail building with parking facilities to be constructed in Phase 1, along with two pad sites for future commercial retail construction. The General Site Development Scheme is shown on Figure No. 3. The building footprints and layouts shown for the future pads are preliminary and subject to change in the future. 2.0 DRAINAGE BASINS AND SUB - BASINS The 3.592 acre subject tract is shown by Figure No. 4 to be within the Carters Creek Drainage Basin near its' divide with the Lick Creek Drainage Basin. The 100 -year flood plain/floodway is not on or immediately adjacent to the subject property, which is shown to be in Zone X on Flood Insurance Rate Map Number 4804C 0201D effective date February 9, 2000. On site detention will be utilized to limit post development discharges from the tract to the adjacent lateral drainage systems of SH6 and Rock Prairie Road to levels at, or below the pre- development discharge rates to avoid impact to these systems due to development. - 1 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie 3.0 DRAINAGE DESIGN CRITERIA Analysis and design of storm drainage facilities for this project is in accordance with design criteria contained within the publication "Drainage Policy and Design Standards Stormwater Management Plan for the City of College Station" hereinafter referred to as the DPDS Manual. A previous study entitled "Drainage Report For Courtyard Marriott At Woodcreek Development Cornerstone Properties State Highway 6 Access Road At Woodcreek Drive College Station, Texas" prepared by CSC Engineering & Environmental Consultants, Inc. dated June 26, 2000 was utilized to design stormwater and detention facilities for the Marriott development adjacent to a portion of the site. The detention facility, which receives discharges from a 2.5 acre area of the Marriott development, discharges to the SH6 Frontage Road ditch via a 12 -inch concrete pipe sewer located within a 20 -Ft Public Utility Easement crossing Lot 2 -C along its' southern boundary. The spillway for the detention facility also discharges into a common access easement shared between the Marriott Development and Lot 2 -C. The existing topography indicates that spillway discharges into the Access Easement area are collected within an existing swale which crosses the Parcel 1 area south to Rock Prairie Road. At this point it is picked up by the public storm sewer system via an opening in the back of a curb inlet which also drains the road paving. Development plans will need to leave the 12 -inch outfall discharge pipe to SH6 in place, and maintain the emergency overflow from the pond for storms in excess of 25 -yr frequency. The Rational Formula has been utilized to calculate stormwater discharges as the tract area is less than 50 -acres in accordance with DPDS manual requirements. Manning's Formula has been utilized to analyze head losses and size storm sewer and drainage swales, and the triangular hydrograph method has been used to size detention facilities. Since detention is required for this development, the site storm sewer was designed to convey 100 -year frequency discharges for the site to the detention pond location without exceeding allowable ponding elevations in parking lots or driveways as specified in DPDS Manual, Item 3 Storage Depths, on Page 74. 4.0 DRAINAGE FACILITY DESIGN The existing site is currently undeveloped with the exception of some minor amounts of paving for a shared common access drive along the northerly and easterly sides of the Lot 2 -C portion of the project area. Figure 5A — Existing Drainage Conditions shows the pre - development drainage pattern for the property, which has a small drainage area discharging to the SH 6 Frontage Road ditch, with the rest of the area discharging to Rock Prairie Road. In order to comply with City of College Station requirements concerning impact to downstream drainage systems, the proposed drainage system has -2- WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie been designed to limit Phase 1 and Ultimate Conditions post - development 5, 10, 25, 50, and 100 -year frequency discharges to at, or below the pre - development level discharges determined for the property utilizing methods prescribed in the DPDS Manual. The proposed Plazas at Rock Prairie Road project is to be constructed in phases. The first phase of development is shown in Figure 5B — Phase 1 Drainage Conditions, which will include an 18,861 SF retail building with parking and driveways to Rock Prairie Road. Ultimate development conditions are shown on Figure 5C — Ultimate Drainage Conditions, and assume development of the entire project as commercial retail. Proposed Phase 1 Storm Sewers and Detention Facilities are being sized to provide capacity for the ultimate drainage condition. Drainage discharges for 5, 10, 25, 50 and 100 -year frequencies were computed using the Rational Method as required by the DPDS Manual. A Runoff Coefficient (C =0.30) for existing conditions was determined from Table III -1 for natural woodlands with land slopes of 3.5 to 5.5 percent for the Parcel 1 tract area, and also for the natural grassland area of Lot 2 -C which has slopes of around 1 %. For ultimate developed conditions a value of C =0.85 was used for the Commercial Reserve Areas, and C =0.70 was used for the grassed detention reserve area which has a bottom area sloped steeply down to a concrete pilot. The Time of Concentration for Existing Conditions was determined to be less than 10 minutes using an average overland sheet flow velocity of 1.0 FPS per Table III -2 of the DPDS Manual. Per manual requirements a minimum time of concentration of Tc = 10 minutes was therefore utilized for both existing and developed conditions in accordance with DPDS Manual Section III Paragraph B3c3. Rainfall intensities for a Time of Concentration of 10- minutes were determined utilizing the DPDS Manual Intensity Duration Frequency Curves of Figure III -1. A complete listing of the runoff coefficients, intensity factors, and discharges computed for the Existing Pre - Developed, Phase 1 and Ultimate Post - Developed Conditions are included in this report as Table 1 — Pre & Post - Development Stormwater Runoff Rates. A summary of allowable rates of discharge from the detention facility, design detention discharge rates, and total post development tract discharge rates is included in Table 2: Design Tract and Detention Discharge Summary Table. Required detention capacity to offset downstream impacts due to development of the subject property was determined by taking the difference in volume beneath the pre and post - development hydrographs which were derived using the Triangular Approximation method of the DPDS Manual. The 5, 10, 25, 50, and 100 -year hydrographs and required detention volume computations are presented in Figures 7A thru 7E respectively. A summary of the required allowable discharge rates, actual design detention discharge rates, total tract post development discharge rates, and detention storage volume and elevations is included in Table 3: Detention Pond Summary. Figure No. 8 — Detention Pond Schematic and Volume Computation shows the general detention pond layout and lists storage volumes between the pond bottom elevation of 302 Ft (min. elevation of the top of concrete pilot channel) and the emergency overflow weir elevation of 306 Ft. to be approximately 27,918 CF. This is sufficient to provide for both the required 5 -year thru 100 -year frequency detention volumes, and also for the 10% excess volumes required by - 3 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie the DPDS Manual to account for sedimentation. A graph of the proposed detention pond volume versus depth is shown in Figure No. 9. Table 2 shows the total allowable pre - development existing condition discharges to the public drainage systems in the right of ways of SH -6 and Rock Prairie Road. The table also shows the determination of both the allowable and design detention pond discharge, and the total post development design discharges from the tract to the public r -o -w for the 5, 10, 25, 50, and 100 -year frequency storm events. The net allowable detention pond discharges have been determined by subtracting the post - development discharges of the areas draining directly to the public systems in the adjacent roads from the total pre - project discharges for each of the storm frequencies investigated. Final design of the detention outfall limits pond discharges to a level equal to, or less than, the allowable detention discharge rates. Detention pond outflow is controlled by means of a 12- orifice installed in an 18 -inch outfall discharge pipe which connects to the Rock Prairie Road Storm Sewer Inlet located at the southeasterly corner of the project area. Emergency and extreme event overflow capacity is provided by a 15 -ft wide concrete weir structure with a weir elevation 306 feet. This structure directs overflow to Rock Prairie Road. Figure No. 10 is a graph of Pond Outlet Discharge Rate versus Pond Depth. The discharge rates shown indicate that at elevation 306.0 the discharge through the 12 -inch orifice from the detention pond is 7.80 CFS, which is slightly below the 25 -year frequency target rate of 7.98 CFS. Since the pond capacity below the emergency weir overflow elevation 306 exceeds the required detention volume for the 100 -year frequency design storm, and design outflows for each of the storm frequencies investigated have been limited to the pre- development outflow rate, or less, the detention facility will prevent negative impact to the downstream public drainage systems for all frequencies examined. Above elevation 306 feet the emergency concrete weir has been sized to convey the 100 -year frequency developed condition discharge of 30.07 cfs from the area which drains into the detention pond when the pond elevation reaches 306.75 feet. At this elevation the weir velocity is approximately 2.7 fps, and the storage surface provides 0.5 feet of freeboard below the minimum pond bank elevation of 307.25 feet. Emergency and Extreme Event Discharges from the Marriott Development detention pond discharge into the common access driveway behind the Phase 1 Building Structure and are to be conveyed south through the development via the driveway to Rock Prairie Road. Under normal conditions no flow is anticipated over the concrete spillway for storm frequencies up to the 100 -year event. The detention pond is proposed to be a grassed lined facility with minimum 4 -feet horizontal to 1 -foot vertical rise side slopes, and a grassed maintenance berm on three sides. The fourth side will consist of a paved driveway and future paved parking area. The bottom of the pond is sloped at a minimum of 5% from the toe of the pond side slopes to the proposed concrete pilot channels. The pond area can be readily accessed for maintenance. Maximum ponding elevations within the gutters of private onsite driveways, parking areas, and at inlets are not expected to exceed 6- inches for the 100 -year frequency event. -4- WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie This meets the requirements for maximum ponding depth specified in the DPDS Manual Item 3- Storage Depths on page 74. Erosion controls during site construction will consist primarily of a combination of silt fences, hay bale barriers, and sedimentation traps. The locations of the proposed control measures are shown on Figure 11. 5.0 CONCLUSIONS The proposed development of the subject site will require provision of detention to offset impact to downstream drainage systems due to construction of buildings, paved parking and driveway areas, and associated storm drainage improvements. Onsite swales and storm sewer have been designed to convey the majority of the development to a detention facility to be located along the northeasterly boundary of the development. The storm drainage and detention system have been designed in accordance with requirements of the City of College Station DPDS Manual, and provide capacity to alleviate development impact for the required 5, 10, 25, 50, and 100 -year design storm frequencies. The detention and drainage systems have been designed to provide adequate capacity for the ultimate planned development of the site, and limit total ultimate post - development discharges from the site to a level slightly below the existing condition discharge rates computed for the pre- development conditions. 6.0 CERTIFICATION "I hereby certify that this report for the drainage design of the Plazas at Rock Prairie Road Development located at the northeasterly intersection corner of the northbound Frontage Road of State Highway 6 and Rock Prairie Road was prepared by me (or under my supervision) in accordance with the provisions of the City of College Station Drainage Policy and Design Standards for the owners thereof" 4 v' % 64- }`' ... W. INIVORD 33170 40 r o - William M. Langford, PE . Registered Professional Engineer State of Texas Registration No. 53170 ✓/ /L/ e - 5 - TABLE 1 - PRE & POST DEVELOPMENT STORMWATER RUNOFF RATES (CALCULATIONS USING RATIONAL METHOD) Q = CIA RAINFALL INTENSITY I (inches /hour) Per Figure III - 1 Drainage Policy and Design Standards Manual at Time of Concentration T= 10 minutes Frequency 5 -YR 10 -YR 25-YR 50 -YR 100 -YR Rate I 7.68 8.36 9.86 11.15 11.64 rev.7 -05 -06 EXISTING CONDTIONS (PRE DEVELOPMENT) AREA AREA C 5 -YR 10 -YR 25 -YR 50 -YR 100 -YR COMMENTS No. (ACRES) CFS CFS CFS CFS CFS 0.51 0.3 1.18 1.28 ; < 1.71 1 78 , a 'e"" .. . 3.21 0.3 7.40 8.05 "p; 10.74 11.21 .y .,. w !s std ,„: -nt,; e r_ t'Atigitit 3.72 0.30 8.57 9.33 ' ? J ; . 12.44 1299 ot 31y + 2!s „ , PHASE 1 CONDTIONS (POST PHASE 1 DEVELOPMENT) AREA AREA C 5 -YR 10 -YR 25 -YR 50 -YR 100 -YR COMMENTS No. (ACRES) CFS CFS CFS CFS CFS Al 0.17 0.75 0.98 1.07 1.26 1.42 1.48 A2 0.03 0.3 0.07 0.08 0.09 0.10 0.10 A1-2 0.2 0.68 1.05 1. 14 1.35 1.52 1.59 AREA TO SH6 ROAD DITCH 61 0.94 0.85 6.14 6.68 7.88 8.91 9.30 B2 0.51 0.50 1.96 2.13 2.51 2.84 2.97 B3 0.11 0.85 0.72 0.78 0.92 1.04 1.09 B4 0.19 0.85 1.24 1.35 1.59 1.80 1.88 B5 0.18 0.85 1.18 1.28 1.51 1.71 1.78 B6 0.67 0.70 3.60 3.92 4.62 5.23 5.46 B7 0.48 0.75 2.76 3.01 3.55 4.01 4.19 81 -7 3.08 0.74 17.59 19.15 22.59 25.54 26.67 AREA TO DETENTION POND 01 0.24 0.30 0.55 0.60 0.71 0.80 0.84 C2 0.08 0.85 0.52 0.57 0.67 0.76 0.79 C3 0.12 0.30 0.28 0.30 0.35 0.40 0.42 C1 -3 0.44 0.40 1.35 1.47 1.74 1.96 2.05 AREA TO ROCK PRAIRIE ROAD ULTIMATE CONDTIONS (POST FUTURE ULT. DEVELOPMENT) AREA AREA C 5 -YR 10 -YR 25 -YR 50 -YR 100 -YR COMMENTS No. (ACRES) CFS CFS CFS CFS CFS Al 0.17 0.75 0.98 1.07 1.26 1.42 1.48 A2 0.05 0.3 0.12 0.13 0.15 0.17 0.17 A1-2 , : ", 0.22 0.65 1.09 1.19 , .'f A 1.59 1 66 ` xr> ` :.4 :R€?AD3 H , , ° - ?a B1 0.94 0.85 6.14 6.68 7.88 8.91 9.30 B2 0.37 0.85 2.42 2.63 3.10 3.51 3.66 B3 0.16 0.85 1.04 1.14 1.34 1.52 1.58 B4 0.11 0.85 0.72 0.78 0.92 1.04 1.09 85 0.19 0.85 1.24 1.35 1.59 1.80 1.88 B6 0.18 0.85 1.18 1.28 1.51 1.71 1.78 B7 0.48 0.85 3.13 3.41 4.02 4.55 4.75 B8 0.23 0.85 1.50 1.63 1.93 2.18 2.28 B9 0.43 0.75 2.48 2.70 3.18 3.60 3.75 ri 'z 3.09 0.84 19.84 21 60 i "' 28.81 30.07 A� �3E�74 1 01 0.2 0.3 0.46 0.50 0.59 0.67 0.70 C2 0.08 0.85 0.52 0.57 0.67 0.76 0.79 C3 0.12 0.3 0.28 0.30 0.35 0.40 0.42 =WA ,A 0.4 0.41 1.26 1.37 ;',^ 1.83 1.91 ,,,, ',;... ,a CL _1m CI. Ca � 0 w �2 g oo 1-- en e 66 �% d / C) CI // w c o =- o( k ®�� $ 2 LLI C.) o C o c w OW ¥ m m #® g 0 . ® >O @nco ®mom « Fix 666 \p k� IX /�/ °ƒ 2 0 P. 2 - § 0. 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The drainage infrastructure for this project cone of fo o . grate inlets and two segments of storm sewer pipe, p d rd is cha sg e designed into existing storm sewer system and then to a detention pond previously for the site. at the northeast corner of Rock Prairie Road at SH6 in north is located a The site new buildings College Station as seen on Exhibit 1. This project will not add any rather only additional p g arkin for the shopping center. This p arking was contemplated with the original drainage analysis, so this minor report is simply verifying that this parking lot design is in compliance with the original drainage assumptions. In addition, this drainage analysis p rovides. for the design that will connect calculations for the two new grate inlets and storm sewer pip to the existing infrastructure. GENERAL LOCATION & DESCRIPTION The Plazas @ Rock Prairie Road is located in a College on (See Station, Appendix B). The site and 2, Block 1 of the Plazas at Rock Prairie enter with the area at the corner of Rock ,. is partially developed as a shopping ed Lot 2, Block 1). Prairie Road and SH6 currently undevelop ' DRAINAGE DESIGN CRITERIA an g /College Station USDG. All drainage design is in accordance with the Bryan/College • Rational Method will be used to design storm � overfPow route. pipe with the 10 -year storm event and a check on the 100-ye factor was used for pipe sizing • Manning's equation and a 25% clogging calculations and can be found in Exhibit 5. As stated prevlo y usl , a drainage analysis was performed for this site dur tringt its initial design. That original design did plan for the subject area to analysis, as future parking. Appendix A is a complete copy of that original g performed by WLB Associates. In this drainage analysis, WLB designed a detention facility to detain the post - developed runoff from the ultimate i developed 3.592 acre site. I PRIMARY DRAINAGE BASIN DESCRIPTION The proposed project site is located within the Carters Creek Drainage Basin panel Basi asi (Foxfire Tributary). Exhibit 2 is a copy of a portion of the FEMA map effective February 2000, which shows that there is no floodplain contained on D the site. D p Plazas @ Rock Prairie Road Drainage Report STORMWATER RUNOFF ANALYSIS Pre - Development Drainage Basin (Additional Parking Area Only) The majority of Lot 2, Block 1 is currently vacant and consists of grass cover. This area along with the flow from the existing parking lot currently flows toward an open pipe inlet at the junction box at the southeast corner of the property. This pipe system carries flow to the existing detention pond. A small graded swale exists across Lot 2 to accommodate carrying this flow from the parking lot and the vacant lot to the pipe. From visual observation during rain events, a portion of the runoff that leaves the existing parking lot flows toward the storm sewer under Rock Prairie Road at the SH6 frontage road. This should not be occurring according to the original drainage report as this flow should be captured by the Swale and carried to the detention pond. This problem will be substantially improved with this additional parking construction. It is important to note that all building areas drain to the rear and are carried subsurface to the junction box at the southeast corner of the property. Post-Development Drainage Basin (Additional Parking Area Only) The post - development patterns for this additional parking will be to capture the runoff from the existing parking lot (DA1) and that from Drainage Area DA2 at Grate Inlet (G12) within the new parking lot. This flow will be carried by a 24 -inch RCP pipe on a .55% slope to Grate Inlet (GT4) and then in another 24" RCP pipe on a .85% slope to the existing junction box (JB1). As seen on Exhibit 3, Grate Inlet (GT4) will pick up flow from Drainage Areas DA3 and DA4. DA2, 3 and 4 were all assumed to have a C factor of .95 in this analysis for storm sewer and grate inlet sizing. Until a building footprint is designed for DA3, this total "C" is really unknown and could vary from .8 to .9. The assumptions made herein are conservative for the design of the grates and piping system and well within the assumptions of the overall "C" of .85 in the original drainage report. A final check should be made when the building is constructed to assure that the composite of Drainage Areas 2, 3 and 4 are no more than 85% impervious cover. As seen on Figure Number 6 in the WLB Drainage Report in Appendix A, the original design contemplated full buildout of Drainage Areas DA2, 3 and DA4. Therefore this additional impervious cover which is being added with this project has been accounted for in the original detention facility. On the WLB Figure 5C, the area draining to this new parking lot is .53 acres, and from these new calculations this area is .49 acres. The difference of .4 acres is likely the grassed area just outside the parking lot along SH6 and Rock Prairie Road, which will drain toward SH6 & Rock Prairie Road rather than toward the parking lot. The size of the new grate inlets are shown on Exhibit 6 and are sized based upon the 100 -year storm event with 25% dogging and checked for ponding depth and overflow. Exhibit 7 illustrates how high the water will pond over the grate inlet in the 100 -year event. In the case of GT2, the water surface elevation will only reach elevation 308.72', or .51 feet high and then will spill over the curb line Plazas @ Rock Prairie Road 2 Drainaae Report of the parking lot. In the case of GT4, the water surface elevation will only reach 309.47' or .56 feet high and then will spill over the curb line. The hydraulic grade line (HGL) calculations for the storm sewer can be seen in Exhibit 8.1 and 8.2. The downstream boundary condition for this HGL is assumed as a 100 -year water surface elevation of 306.00 within the pond. This assumption is from the WLB Associates drainage report. As seen on Exhibit 8.2, the HGL for the 100 -year storm at GT4 is 307.85' with a top of grate elevation of 308.91' illustrating that the 100 -year event is fully contained in the pipe system. The 100 - 9 year HGL @ GT2 is 308.70' with a top of grate elevation of 308.21' and a top of curb elevation of 308.77'. The 100 -year storm event is now fully contained in the parking lot with the HGL now below the top of curb and will be carried via storm sewer to the detention pond. The maximum ponding elevation at this location is .49' well within the Bryan /College Station Unified Stormwater Design Guidelines. CONCLUSION The development of the additional parking for the Plazas @ Rock Prairie Road is in compliance with the original assumptions provided in the original drainage design. This additional impervious cover will create additional runoff but that has been accounted for in the original detention pond design. The new grate inlets and storm sewer pipe have been adequately sized to meet the Bryan /College Station Unified Stormwater Design Guidelines. Plazas @ Rock Prairie Road 3 Drainage Report D fl ATTACHMENTS EXHIBIT 1: Project Location EXHIBIT 2: Firmette -FEMA Map Panel 142C (Effective July 2, 1992) EXHIBIT 3: Plazas @ Rock Prairie Road Drainage Area Map EXHIBIT 4: Rational Formula Drainage Area Calculations EXHIBIT 5: Pipe Capacity Calculations EXHIBIT 6: Inlet Capacity Calculations - 10 -Year Storm & 100 -Year Storm Capacity EXHIBIT 7: Inlet Ponding Depth Calculations - 100 -Year Storm WSE's EXHIBIT 8.1: Plazas @ Rock Prairie Road HGL Calculations EXHIBIT 8.2: Storm sewer HGL Data APPENDIX A: WLB Associates, Inc. Drainage Report "Drainage Report for Plazas at Rock Prairie State Highway 6 Access Road at Rock Prairie Drive" dated March 28,2006, Revised July 14, 2006. APPENDIX B: Replat Lot 2 & 2 -C Block 1 - Plazas at Rock Prairie APPENDIX C: Grading & Erosion Control Plan a Plazas @ Rock Prairie Road 4 Drainage Report 1 1 v , ,41,"...1". • 0 m m z — D A N 60'42'36" E 228.00' — — I i I I i ® N ■ co I i I I f_.__� — 1 V \ 1 i N I I 1 z m N W � N �p `` _i W I I tO i I * I r 1 �i' T 1 / [// !! ,,, a I o I -' r I i 1 1 ii u �/ - - - -- 1) -- ! IT i I I r1'-o J'° �; . I / I 1 ,, �I I I I 9-0 1' t - 1 I i I I I I I Il' i C i I� ;; 1I1, (n r' �I . z 1' I i 1 i . I l � C / I ) I ' ' N 44.12-4." � a 6' I i w I z iv z III . 1I 1 0 °' I" I of I ( _ —_ - - -- o I J 11 N 4 7a a 1 CO - -- * i G o D °' w CD I O 1 1 N 1 o to 0 D gi I I " I I v' 1 I c. a _ - 7...7. _ I I ti , I , N{ 1 1 29 5! 9 ' ~ OEM _ r� — — $ K, o 4, -_ - 60'33'13" 206.29' 0 S 60'33'1" W I I OMR ‘71 i \ \,._ I ? - - - -- S 60`33'13 " W 259.79' - - I 1 j Rock Prairie Road A" 1 . For Interim Review Only L � y j -1 _ T ,� € �1 Revisions mended for construction, w tp co q bidding, or permit purposes. DRAINAGE AREA MAPS !ill ; ° ° _ � P Prepared by • N N 70 �- _ ' m Joel J. Mitchell, P.E. O O n _ d'$m No. 80649 '& I P LAZA AT ROCK P - D -q N R4 /R /E ROAD _ 0 1 w z — ii9Ct §