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Item 6A and 6B Drainage Study ST.LOUIS ST.CHARLES DALLAS PHOENIX ® Power House at Union Station 1520 S.Fifth Street 6175 Main Street 2701 E.Camelback Road 1 S.18th Street, Suite 307 Suite 367 Suite 175 cole 314 984 88 61103 St.Charles,Suite 200 636.978 75 MO tei 3 972.624X60 034 Phoenix,AZ te1 60�795.41181 tel 6 June 24, 2016 Mr. Steven Anderson, P.E., C.F.M. City of Southlake Public Works Administration 1400 Main Street, Suite 320 Southlake, TX 76092 Re: Preliminary Drainage Study White Chapel Village — 15.865 acres Dear Steve, This preliminary drainage study was prepared in accordance with City of Southlake zoning and subdivision requirements with respect to development of 15.865 acres at the southeast corner of SH 114 and North White Chapel Boulevard (the Site). The purpose of this study was to assess the impact of site development on existing drainage infrastructure and to determine the need for improvements. More specifically, the study was performed to address four primary concerns: 1. Is stormwater detention required? 2. Does existing TxDOT infrastructure have adequate capacity to convey the proposed runoff under SH 114 towards the Carillon regional detention ponds? 3. Does the conveyance system north of SH 114 to the Carillon regional detention ponds have adequate capacity to convey the increased runoff? 4. What size storm sewer would be required to reroute the drainage conveyed through the unnamed Dove Creek tributary that transverses the northwest corner of the site? In performing this study, the following information was reviewed: • Flood Study for Dove Creek for the Carillon Tract, August 2010, by Jacobs Engineering Group, Inc. (Jacobs) • As-Built Plans for SH 114 Highway Improvements, June 2001, by TxDOT (TxDOT) • Tributary to Dove Creek Drainage Study SH 114 at White Chapel Blvd, January 2007, by Halff Associates, Inc. (Halff) • White Chapel Blvd Improvements, Interim Review Plans, August 2010, by Nathan D. Maier Consulting Engineers, Inc. (Maier) • Forest Park Medical Center at Southlake, Land Development Plans, February 2012, by Cross Engineering Consultants (Cross) • Preliminary Master Drainage Plan Phase II for the City of Southlake, July 2007, by KSA Engineers (KSA) CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE Cole&Associates, Inc.is a Missouri Corporation d.b.a. Cole Design Group, Inc.in Arizona and Texas,herein referred to as"Cole" Texas Board of Professional Engineers Registration#F-10253 Texas Board of Professional Land Surveying Corporate Registration#10193871 Preliminary Drainage Study—White Chapel Village In order to address the primary concerns, we analyzed the documents listed and performed our own calculations and models as needed to reconcile the differences in order to develop our conclusions. Based on our analyses, we concluded that: 1. Stormwater detention for the development site has been accounted for in the design of the Carillon detention ponds. 2. The TxDOT drainage conveyance system under SH 114 has capacity to convey the 100-year developed runoff. 3. The conveyance channel north of and parallel to SH 114 is in disrepair and should either be improved, or the ultimate underground sewer should be constructed. It is understood that this work is the responsibility of others and will be completed prior to Site development. Once this work is complete, the conveyance from SH 114 to the Carillon ponds should have adequate capacity to convey the site developed runoff. Because of the current state of disrepair, the channel was not analyzed for capacity. 4. A conveyance system with a capacity of 305 cfs (or the approximate equivalent of an 8'x4' box sewer) will be required to reroute runoff from the unnamed Dove Creek tributary underground at the northwest corner of the site. Please review the summary of findings, analysis of data, and associated exhibits for an understanding of our procedures and reasoning for our conclusions. We request that the City accept our findings or let us know if any further analysis or information is needed. Please call if you have any questions. Sincerely, SandyjHSt;phe s, P.E.V.P. o ` perations r�P�E OFTEk��I .............. J0 SANDY H. STEPHENS j I.:.............................., 89483 cc: Mr. Lucien Tujague— Dominion Southlake Properties Mr. Carl Schwab — RREAF Southlake, LLP CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE Preliminary Drainage Study—White Chapel Village Table of Contents I. Summary of Findings II. Analyses of Data A. Drainage Area Analysis B. Runoff Analysis C. Capacity Analysis and Models III. Conclusion IV. Exhibits A. Jacobs - Regional Drainage Area Map B. TxDOT - Drainage Area to Culvert B C. Halff - Drainage Area Map to Culvert B D. Maier - Proposed Drainage Area Map E. TxDOT - Drainage Areas to Storm Sewer B F. Cole - Profile 1 System A G. Cole - Profile 2 System B H. Cole - Profile 3 Storm Sewer C (TxDOT Inlets) I. Cole - Concept Drainage Plan V. Appendices on CD 1 . Jacobs - Flood Study for Dove Creek for the Carillon Tract, August 2010 2. TxDOT - As-Built Plans for SH 114 Highway Improvements, June 2001 3. Halff - Tributary to Dove Creek Drainage Study SH 114 at White Chapel Blvd, January 2007 4. Maier - White Chapel Blvd Improvements, Interim Review Plans, August 2012 5. Cross - Forest Park Medical Center at Southlake, Land Development Plans, February 2012 6. KSA - Preliminary Master Drainage Plan Phase 11 for the City of Southlake, July 2010 7. Cole - Computer Models and Data CIVIL ENGINEERING / SURVEYING / PLANNING LANDSCAPE ARCHITECTURE Preliminary Drainage Study—White Chapel Village 1. Summary of • A. CARILLON PONDS DETENTION CAPACITY The Carillon regional detention ponds were designed with capacity for the 100-year developed runoff from the Site: • According to Jacobs, "The two proposed regional detention ponds will detain the 100-year flood for the Carillon development and the ultimate development conditions within sub-basins B-4a, B-b, and B-4c located south of SH 114." (Jacobs, page 17) • The Carillon regional detention ponds were designed to detain the ultimate runoff from areas that include the Site. The Site consists of 9.0 acres that falls within Jacobs sub-basin B-4a, and 6.8 acres that falls within sub-basin B4-b. • Both Carillon detention ponds have been constructed. However, neither an as-built survey nor a pond capacity analysis was performed as part of this study. B. TxDOT INFRASTRUCTURE CAPACITY There are two storm sewers that cross SH 114 and provide drainage for areas south of SH 114 that include the Site. These sewers were designated as Culvert B and Storm Sewer B, and were determined to have adequate capacity to convey the Site's proposed runoff under SH 114 towards the Carillon regional detention ponds according to TxDOT, Halff, Maier, and Cole: Culvert B • The total proposed 100-year runoff to Culvert B from the 15.865 acre site is 36 cfs. The total 100-year runoff to Culvert B from upstream areas is 253 cfs. • TxDOT Culvert "B" (8'x4' box culvert) was designed to convey 100-year developed runoff from drainage area B. Three acres of the site lie within drainage area B according to TxDOT. • Cole's analysis of the TxDOT Culvert B system, which includes lateral connections under SH 114, indicates that the available capacity of Culvert B at the upstream end is 342 cfs. • Halff analyzed the drainage channel in the northwest corner of the site as well as the capacity of Culvert B and determined Culvert B to have a capacity of 364 cfs, "under uniform flow conditions." • Maier depicts a drainage area of 78.81 acres flowing to Culvert B via three 6'x3' box culverts proposed for construction underneath North White Chapel Boulevard. Cole utilized Maier, the rational method, and a 0.70 C coefficient and found this acreage produces 252.66 cfs of runoff. The low runoff is partially due to the existing lot for single family homes and single family zoning designations, as well as plans to develop parks on a portion of the watershed. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 1 Preliminary Drainage Study—White Chapel Village • Combined runoff from Maier and the developed portion of the Site equates to 289 cfs. This is 75 cfs less than the 364 cfs capacity of TxDOT Culvert B according to Halff Storm Sewer B • TxDOT Storm Sewer "B" (8'x4' box sewer) was designed to convey developed runoff from drainage areas 133-15, B3-15x, 133-16, B3-16x, 133-17, B3-17x, and 133-18A. 12.8 acres of the site lie within these drainage areas according to TxDOT. • The Concept Drainage Plan (Exhibit 1) shows 83.75 cfs of Site runoff to be drained towards Storm Sewer B. This will leave up to 240 cfs to be discharged from TxDOT drainage area 313-18A which includes Forest Park and DeRose properties. It is anticipated 313-18A will drain only 123 cfs to Storm Sewer B. C. DRAINAGE CAPACITY FROM SH 114 TO CARILLON DETENTION PONDS There is an existing drainage channel on the north side of SH 114 which flows into a culvert underneath Southmont Drive. This system conveys runoff from SH 114 and upstream areas to the Carillon detention ponds. Drainage Channel from SH 114 to Southmont Drive The existing channel north of SH 114 that drains to the Carillon ponds is currently in disrepair. The channel needs to be repaired or the ultimate developed infrastructure needs to be constructed prior to development of the site. It is understood that this is the responsibility of others. Due to the current condition of the channel it was not included in this analysis. Culverts and Sewer from Southmont Drive to Carillon Ponds There are two 8'x4' culverts beneath Southmont Drive that convey runoff from the drainage channel to the detention ponds. Construction plans for this section of sewer were not analyzed. However, it is understood from discussions with City officials that this system either has adequate capacity to convey the ultimate runoff condition, or that it is the responsibility of others to provide adequate conveyance capacity D. DRAINAGE CHANNEL REROUTE The existing unnamed Dove Creek tributary in the northwest corner of the Site may be rerouted along the perimeter of the property by constructing an underground storm sewer system with a minimum capacity of 306 cfs, or approximately the equivalent of an 8'x4' box sewer. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 2 Preliminary Drainage Study—White Chapel Village 11. Analyses of Data A. Drainage Area Analysis The drainage areas flowing towards SH 114 as illustrated by the various consulting firms and TxDOT were compared in order to understand the relative accuracy of each. The following is a breakdown of the discrepancies that were found, organized with respect to TxDOT downstream infrastructure Culvert B and Storm Sewer B: Culvert B Jacobs Jacobs indicates that the Site lies within watershed sub-basin B-4a of the Dove Creek Watershed (Exhibit A). • Sub-basin B-4a (76.8 acres) includes approximately 9 acres of the site. B-4a ultimately drains to TxDOT 8'x4' box Culvert B. TxDOT TxDOT indicates that Site lies within drainage area "B" that flows to infrastructure along SH 114 service road (Exhibit B). • Drainage area B (88.74 acres), includes approximately 3 acres of the Site and drains to Culvert B. Note: Drainage area B includes 0.46 acres of the DeRose property. Halff Halff indicates that the Site lies within drainage area "DA" that flows to Culvert B (Exhibit C). Halff also referenced TxDOT in their study. • Drainage area DA (85.7 acres) drains to TxDOT Culvert B and includes approximately 6.6 acres of the Site. Maier Maier indicates that the Site lies within multiple drainage areas that flow to Culvert B (Exhibit D). • Drainage areas A, H, I, J, K, L, M, N, O, P, Q, R, and S (78.81 acres) including approximately 2.5 acres of the Site, ultimately drain to TxDOT Culvert B via three proposed 6'x3' culverts underneath North White Chapel Boulevard. Storm Sewer B Jacobs Jacobs indicates that the Site lies within watershed sub-basin B-4b of the Dove Creek Watershed (Exhibit A). • Sub-basin B-4b is 25.6 acres and includes approximately 6.8 acres of the site. B-4b drains to TxDOT 8'x4' box Storm Sewer B. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 3 Preliminary Drainage Study—White Chapel Village TxDOT TxDOT indicates that the Site lies within multiple drainage areas flowing to infrastructure along the SH 114 access road (Exhibit E). • Drainage areas 133-15, B3-15x, 133-16, B3-16x, 133-17, B3-17x, and B3-18A ultimately drain to TxDOT Storm Sewer B on the south side of the SH 114 access road (34.09 acres including approximately 12.8 of the site). Note: TxDOT accounted for fully developed flow in their conduit design for areas B3-15x thru B3-17x (TxDOT, sheet 84B). Note: Drainage area B3-18A includes 4.54 acres of the DeRose property. Cross Cross indicates that multiple drainage areas flow to TxDOT Storm Sewer B (Cross, sheet C7). • Drainage areas OS-1 and EE, 19.07 acres flow to Storm Sewer B. • Drainage area OS-1 includes 4.54 acres of DeRose Property under undeveloped conditions C=0.30 Note: Cross did not include any of the Site in their runoff calculations. Drainage Area Analysis Summary The discrepancies in drainage areas from the various reports may be explained by the varying levels of accuracy of the topographic data used and the scope of each study. The variations in area flowing to Culvert B range up to 13%. The greatest discrepancy - between TxDOT and Jacobs - appears to result from Jacob's exclusion of approximately 11 acres of Carroll High School. It is unclear why Jacobs may have excluded this acreage. • TxDOT, Halff, and Maier indicate similar acreages of land draining to Culvert B to within 11%. The variations in area flowing to Storm Sewer B range up to 25%. The greatest discrepancy - between TxDOT and Jacobs - is likely due to the size of sub-basin B-4a. Based on Cole's analysis of topographic data, including Cole's own field survey, the boundary between B-4a and B-4b does not extend as far east as Jacobs depicts. • TxDOT, Halff, and Maier indicate similar acreages of land draining to Culvert B to within 11%. • If Cross had included the 12.8 acres of the Development Site, the discrepancy between Cross and TxDOT would be 7%. • Exclusion of the Development Site in runoff calculations according to Cross is likely due to the intent to show these areas for illustration purposes only as no proposed runoff from Forest Park Medical Center drains to Storm Sewer B. • Jacobs study was regional in nature and covered over 1.7 square miles (1,088 acres). Table 1 displays the acreage discrepancies between the various plans and reports showing areas that drain to Culvert B, area of Site draining to Culvert B, and source of contour data used in each plan. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 4 Preliminary Drainage Study-White Chapel Village Table 1 SourceArea to Area of of Contour ource Culvert B Site to L (AC) Culvert B Data Jacobs 76.8 9 VARGIS 2001 TxDOT 88.74 3 Photogrammetry Halff 85.7 6.6 Field and Ortho Map Maier 78.81 1 2.5 1 Photogrammetry Table 2 displays the acreage discrepancies between plans and reports with areas that drain to Storm Sewer B, area of Site draining to Storm Sewer B, and source of contour data used in each plan. Table 2 Area to -900- Storm Area of Site to Source of Source SewerB Storm Sewer B Contour Data Jacobsj 25.6 6.8 VARGIS 2001 TxDOT 34.09 12.8 Photogrammetry Did not account Cross 19.07 for Development Photogrammetry Site CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 5 Preliminary Drainage Study—White Chapel Village B. Runoff Analysis All of the studies and plans provide runoff information. The various information was compared to better understand the relation of the hydrological conditions as calculated by the different entities; a breakdown follows. Runoff to Culvert B TxDOT TxDOT indicates that 100-year peak developed runoff to Culvert B will be 223.95 cfs using NRCS methodology (TxDOT, sheet 82). Halff Halff indicates that the 100-year peak developed runoff to Culvert B will be 242 cfs using the Rational Formula (Halff, page 2). Maier Maier indicates peak runoff for individual drainage areas (Maier, sheet 37). The cumulative peak runoff was not calculated. Many of these areas, highlighted in pink on Exhibit D, flow to Culvert B via three 6'x3' RCB culverts to be constructed with the North White Chapel Improvement Plans. Cole Cole performed calculations using the rational method to determine a cumulative peak for the watershed based on Maier. Cole's peak 100 year developed runoff was 252.66 cfs. Note: Time of concentration was calculated using TR-55 Time of Concentration methodology as the watershed was too large to apply the iSWM time of concentration estimation equation. Figure 1 represents runoff calculations performed by Cole with respect to Maier. Figure 1 Total Acreage A= 78.81 acres IMMS Runoff Coefficient For Watershed C = 0.7(P Rainfall Intensity l,00=4.58in/hr A . . cfs JIM Note: TxDOT, Halff, and Cole calculations based on Maier are accurate to within 11% with Cole being the most conservative of the three. Jacobs Jacobs indicates peak runoff to Culvert B is 379 cfs and 449 cfs under proposed and developed conditions respectively (Jacobs, page 12, 13). These peaks are not aligned with other plans. Runoff to Storm Sewer B Two plans showed peak runoff to Storm Sewer B, TxDOT and Jacobs. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 6 Preliminary Drainage Study—White Chapel Village Cole with respect to TxDOT TxDOT indicates 10-year peak runoff draining to Storm Sewer B under developed conditions as 166.175 cfs (TxDOT, sheet 84B). TxDOT did not provide calculations for 100-year peak under developed conditions, therefore Cole performed calculations to reflect the developed 100-year peak. The calculations resulted in a peak of 186.97 cfs using the Rational Method. Note: Runoff from 4.54 acres of the DeRose property was included in TxDOT runoff computations. Cole also included an additional runoff from DeRose property in the hydraulic model mentioned in section III-B. TxDOT also accounted for commercial development in their conduit design as well. Cross Cross indicates 100-year peak runoff to Storm Sewer B under existing conditions will be 45.63 cfs using the Rational Method (Cross, page 13). Note: Due to the exclusion of the applicable portion of the Site Cross calculations were excluded from the hydraulic analysis. Jacobs Jacobs indicates 100-year peak runoff to Storm Sewer B will be 152 cfs and 176 cfs under proposed and ultimate conditions respectively using NRCS TR-55 methodology (Jacobs, page 12 & 13). Cole believes these peaks to Storm Sewer B are aligned with what is appropriate for the watershed. Runoff Analysis Summary The discrepancies in runoff may be explained by the differences in drainage areas, runoff methodology used, factors of safety, and hydrological assumptions. Regarding runoff to Culvert B, peak calculations from TxDOT, Halff and Cole generally correspond and represent a realistic developed watershed condition based on the Southlake 2030 Future Land Use Plan (FLUP). Cole's assessment of the 2030 FLUP determined that a curve number in the range of 0.70 to 0.75 is more reflective of potential future developed conditions for watersheds to Culvert B and Storm Sewer B. It is unclear why Jacob's runoff calculation is significantly higher, but possible explanations are: • The factor of safety Jacobs included in the Carillon ponds design. • The potential for future infrastructure underneath SH 114 draining to the ponds (reflects peak runoff under ultimate conditions (449 cfs). • Jacobs being conservative and assuming the watershed will be developed enough to require the full capacity of Culvert B. This is reflected in the peak runoff under proposed conditions (379 cfs) that represents the max outflow of Culvert B according to Jacobs. Regarding runoff to Storm Sewer B, the capacity indicated by Jacobs and the analysis performed by Cole based on variables extrapolated from TxDOT correspond to within 6%. Tables 3 and 4 represent the runoff to Culvert B and Storm Sewer B respectively, runoff methodology used and assumed developed condition for the area to Culvert B. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 7 Preliminary Drainage Study-White Chapel Village Table 3 Runoff Runoff Assumed Source to Calculation Development MethodCulvert B Condition (cfs) Used Jacobs 449 NRCS TR55 Ultimate Jacobs 378 NR 55-TR Proposed TxDOT 223.95 NR 55-TR Proposed Halff 242 Rational Ultimate Maier by 254.20 Rational Proposed Cole Table 4 Runoff Runoff to Calculation Assumed Source Storm Method Development SewerB Used Condition Jacobs 176 NRCS-TR 55 Ultimate TxDOT by 186.97 Rational Proposed Cole Cross 1 45.63 Rational Existing CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 8 Preliminary Drainage Study—White Chapel Village C. Capacity Analysis & Modeling 1. Pre-Developed Conditions Capacity Culvert B Cole with respect to TXDOT TxDOT provides culvert computations for Culvert B for the 100-year storm event (TxDOT, sheet 83). TxDOT did not provide calculations for the maximum capacity of Culvert B or downstream infrastructure, therefore Cole performed a separate capacity analysis. A capacity analysis of Culvert B was performed based on TxDOT variables, including an upstream head condition of approximately 3.5 feet. A capacity of 342 cfs was determined (model included on CD in Appendix). Jacobs Jacobs indicates that Culvert B acts as a control structure with a maximum conveyance of 378 cfs (Jacobs, page 13). However, there were no detailed calculations provided. Halff Halff analyzed the capacity of Culvert B and found that the culvert can convey up to 364 cfs (Halff, page 4). Cole, Jacobs and Halff correspond to within 9% of each other. Slight differences in capacities are likely due to different methodologies, software, and assumed conditions. Storm Sewer B TxDOT TxDOT provides storm sewer calculations for the 50-year storm event for Storm Sewer B and applicable laterals (TxDOT, sheet 86E). TxDOT did not perform any calculations for the maximum capacity of Storm Sewer B or downstream infrastructure, therefore Cole performed a separate capacity analysis. Cole A capacity analysis of Storm Sewer B was performed based on TxDOT design variables. The existing inlets were modeled as collection points for the developed runoff from the site. A capacity of 244 cfs was determined. This represents the inlets 3B-15 thru 3B-18 at maximum capacity collectively conveying 131 cfs. 2. Developed Conditions Models Models were created to determine the maximum runoff that may be conveyed to the Carillon ponds under future proposed conditions by Culvert B and Storm Sewer B. These systems were modeled as Systems A and B, and are further described as follows: CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 9 Preliminary Drainage Study—White Chapel Village System A System A (Exhibit F) starts at the outfall of the future culverts under N. White Chapel (Maier), and continues into the proposed 8'x4' sewer (channel reroute), progresses through and into Culvert B and terminates at the outfall of Culvert B on the north side of SH 114. No back water conditions were assumed at this point. All laterals leading into Culvert B are accounted for in the model. A total of 305.66 cfs was input at the upstream end of System A. This runoff was successfully conveyed and determined to be the maximum capacity of the system. The 305.66 cfs maximum includes 252.66 cfs from the future North White Chapel culverts as calculated by Cole. Thus, 53 cfs is the total allowable runoff release between North White Chapel and Culvert B. As depicted on the Concept Drainage Plan (Exhibit 1), the proposed runoff will be approximately 38 cfs, or 15 cfs less than capacity. System B System B consists of: 1. TXDOT Inlets 313-15, -16, -17, and -18, and the storm sewer that connects these inlets (collectively referred to henceforth as Storm Sewer C, Exhibit H). 2. Storm Sewer B and all laterals connected thereto. System B terminates at the outfall of Storm Sewer B on the north side of SH 114. No back water conditions were assumed at this point. In the model runoff was released to the inlets of Storm Sewer C as depicted on the White Chapel Village Conceptual Drainage Plan. The total flow through System B at the south side of the SH 114 eastbound access road totals to 207.02. This includes 83.75 cfs from the Site, 123.27 cfs from TxDOT drainage area 313-18A (includes Forest Park Medical Center and DeRose property). Note: Storm Sewer C was designed by TxDOT to accommodate runoff from future commercial development (TxDOT, sheet 85 A). The total capacity of Storm System C was determined to be 132 cfs, or 48.25 cfs more than the total anticipated site runoff. Under proposed conditions shown on the Concept Drainage Plan, Storm Sewer B can accommodate up to 240 cfs from TxDOT drainage area 313-18A. This is more than adequate for demands of the area. It should be noted that although the culvert sizes are the same, System B has a lower capacity than System A due to hydraulic constraints and elevations of inlets within Storm System C. Certain inlets will flood if too much runoff is introduced to the system. To prevent flooding of the highway runoff must not exceed 323 cfs at the entrance of Storm Sewer B. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE 10 Preliminary Drainage Study—White Chapel Village Ill. Conclusion This study was performed in order to analyze the drainage impact of development of the 15.865-acre site. By reconciling the information previously prepared by other engineering firms and TXDOT, and performing our own modeling and analyses, it has been determined that: 1. Stormwater detention for the development site has been accounted for in the design of the Carillon detention ponds as stated in Jacobs. 2. The TxDOT drainage conveyance system under SH 114 has capacity to convey the 100- year developed runoff from the site. 3. The conveyance channel north of and parallel to SH 114 is in need of repair or reconfiguration. It is understood that this is the responsibility of others. It is assumed that the once repaired or reconstructed, this conveyance system will have equal or greater capacity than the system for which it served. 4. A storm sewer with a capacity roughly equivalent to an 8'x4' box sewer will be required to reroute the drainage from North White Chapel Boulevard underground and around the boundary of the site. CIVIL ENGINEERING / SURVEYING / PLANNING / LANDSCAPE ARCHITECTURE II IV- EXHIBITS u,�c3xs 3Ru—ca.ruo��oeaz,a riRodpiRr��wRrkmRP_reevRrRsu aar� LEGEND �6®Creek Centerline Property Boundary I 4[. 2-foot ContoursfV , Basin Boundaries { Basin Labels t • _ .{ti - s: r ;;� �' ' f ��-_ ., • t..-c�`..I :4����,.,,fi�� �� ��I t '���: I a.g� .�r a� ;� � tw� �-.-��1�, a b �--« I .� � �� c it ►, �., r Ai CARILLON REGIONAL DETENTION PONDS ke Val 9ACRES � 4+ �33 4 768 ACRES 26.6ACRES 6.8 ACRES SITE BOUNDARY `��� �v��; p, � i � ,,•P I 1vi- 71 �s i `�- — ' •{' r ktg ,;- e ` �V. a o V a a =A HINES - - CARILLON TRACT FLOOD STUDY A■w C A8= X City of Southlake,Tarrant County,Texas J/1VOBV egg _ -LAS, TEUS 75217 PROPOSED DRAINAGE AREA MAPPNRrvr zun-esa-Runs raxmAOA r<x D - E Omnm.lwiwms� 11 z� - oM/zo II m Q� W a g o W a as - O 110 7j� vi 0 n � P NX'8N1.7V0-\-£lD£0£S£0\AT711\Z7VYIN33\NS301N3.7'1 Figure 1. ©RA1 #GE gtEA MAPVIP 1 C' 17 1 Y k 85.7- 85.7 5.7 .:.S �S-. -. ._�� - ,d�b. •� .� ref^ - SITE BOUNDARY Yom, ,` _ }`I � : �3��•; x; ri rte ` �b All ibLb6£L(bLZ)/i£ZSL��.L'�Ile4 SVX31Hinos dO hllD - o°Ra3N�"�Naaa oo9�msi ��aoeoai-ewa��-ate¢ QyVAlin]d913dVH�311HM z/eo ova 08 GfCGOI'ON 3'd'%1 y$gj:'ON NOLLtlN1S7`J313 W}Il� s3nor a 3iirc �[�`S833NION3 JNLLI(1SN00 clM V]dV IOVNIVd(I 2131VW 'D NVHIVN 0 CIO X m - w � W w i ♦ �� cl / o o� 1 i- 77 1 a i Y w r L � z i 1 C14 I O H�3 H Y �I I 1 II I �o le d o / J T:\CENMESN\CENTRAL2\rW\035303072\CHANGE-ORDERS\DRAmBCO.DGN 625. 63 5 CD a, gm 8 6f 37.' o o 6 .9 635.1 g g 's 651.7 63 .7 m 34 8 0 1a 33. �6 6.3 32.3 of 649.8 64 .7 �+ m V - p 640. _{ �0 �p 6 3.0 64 r•' 'g AIS 638.7 643 1 w y_ m TXDOT CULVERT B N w I• .\, �b m k TXDOT STORM SEWER B 'm .46. g 7. �7.7 k w m 8.8 627 rz 628.1..~ 628.7 12.8 ACRES _ _ r 31. -- 629 .0 r� o .6 629 i�Vr u�l 62 5 rn 8 S;. 629. 627. 631. 83. 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