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Home My WebLink AboutReport on Municipal Services to the Annexation Area Extended August 1989 File No 5588I Report on Municipal Services To The Annexation Area Extended Oak Park Heights, Minnesota August, 1989 File No. 5588 JA1, Bonestroo Rosene Anderlik & Associates Engineers 8 Architects St. Paul, Minnesota REPORT ON MUNICIPAL SERVICES TO THE ANNEXATION AREA EXTENDED OAK PARK HEIGHTS, MINNESOTA AUGUST. 1989 FRANK SOMMERFELDT JACK R. DOERR DEAN KERN BARBARA O'NEAL RICHARD SEGGELKE LAVONNE WILSON LYLE ECKBERG ROGER G. BENSON MAYOR COUNCIL MEMBER COUNCIL MEMBER COUNCIL MEMBER COUNCIL MEMBER ADMINISTRATOR- TREASURER ATTORNEY PUBLIC WORKS SUPERINTENDENT BONESTR00, ROSENE, AND'RLIK & ASSOCIATES, INC. ENGINEERS /ARCHITECTS ST. PAUL, MINNESOTA I I 1 I 1 I 1 I 1 1 Engineers 8 Architects August 7, 1989 Honorable Mayor and City Council City of Oak Park Heights 14168 - 57th Street North P.O. Box 2007 Stillwater, Minnesota 55082 Keith A. Gordon, PE Rshard W Fouer PE Donato C BuRJardt PE Jerry A Bourdon. PE Mark A Hammn. PE Ted K Held. PE Michael T Rautmann PE Rohert R Ph4rers,, PE Dava O LOsww PE Thomas W Peterson PE Re: Municipal Services to the Annexation Area Extended Our File No. 5588 Dear Mayor and Council: Michael C Lynch, PE James R Ni land. PE Kenneth P Andench. PE Keith A Bachmann. PE Mark R. Rons. PE RCben C Russek. A I.A. Thomas E Angus, PE H.rcl A Sanford, PE Daniel J Edgerton, PE Mark A Seip PE Philip J. Caswell. PE Mark D Walhs. PE Thomas R. Mderson. A I A Gary F Ryrancie, PE Charles A Erickson Leo M Pawrisky Hadan M Olson Susan M Eherhn. CPA Submitted herewith is our Report on Municipal Services to the Annexation Area Extended in Oak Park Heights. The information presented in this report is intended to provide a basis for the extension of municipal services to the area recently annexed by Oak Park Heights, as well as the additional area bounded by Oakgreen Avenue, State Highway 36, State Highway 5, and the southern boundary of Section 5 and 6. Municipal services covered in the report include streets, sanitary sewer, water distribution system, and storm sewer. General routing and sizing is presented for the utilities. Cost estimates and corresponding assessment rates are presented for your consideration. We would be happy to discuss the findings of this report with you and any other interested parties at any mutually convenient time. Respectfully submitted, BONESTR00, ROSENE, ANDERLIK a ASSOCIATES, INC. Daniel J. Edgerton, P.E. DJE:kf I hereby certify that this Report was prepared by me or under my direct supervision and that I am a duly Registered Professional Engineer under the laws of the State of �Minnesota. �.dldr.OY _ �G Joseph C. Anderlik, P.E. OPH5588R Date: August 7, 1989 Reg. No. 6971 2335 West Highway 36 • St. Paul, Minnesota 55113 • 612 -636 -4600 Ono G Bonestma PE. JA Bones t roo R Joseph ert W Ronne. PE Jopn C Andalik. PE Rosene Anderlik & R A Lemberg. PE R ichard E Turner. PE G.ehnR Dlmn PE Glenn R Cook. PE Associates TM1a , E Noyes. PE sober Scnunicnt PE Marvin L Soh ala. PE Engineers 8 Architects August 7, 1989 Honorable Mayor and City Council City of Oak Park Heights 14168 - 57th Street North P.O. Box 2007 Stillwater, Minnesota 55082 Keith A. Gordon, PE Rshard W Fouer PE Donato C BuRJardt PE Jerry A Bourdon. PE Mark A Hammn. PE Ted K Held. PE Michael T Rautmann PE Rohert R Ph4rers,, PE Dava O LOsww PE Thomas W Peterson PE Re: Municipal Services to the Annexation Area Extended Our File No. 5588 Dear Mayor and Council: Michael C Lynch, PE James R Ni land. PE Kenneth P Andench. PE Keith A Bachmann. PE Mark R. Rons. PE RCben C Russek. A I.A. Thomas E Angus, PE H.rcl A Sanford, PE Daniel J Edgerton, PE Mark A Seip PE Philip J. Caswell. PE Mark D Walhs. PE Thomas R. Mderson. A I A Gary F Ryrancie, PE Charles A Erickson Leo M Pawrisky Hadan M Olson Susan M Eherhn. CPA Submitted herewith is our Report on Municipal Services to the Annexation Area Extended in Oak Park Heights. The information presented in this report is intended to provide a basis for the extension of municipal services to the area recently annexed by Oak Park Heights, as well as the additional area bounded by Oakgreen Avenue, State Highway 36, State Highway 5, and the southern boundary of Section 5 and 6. Municipal services covered in the report include streets, sanitary sewer, water distribution system, and storm sewer. General routing and sizing is presented for the utilities. Cost estimates and corresponding assessment rates are presented for your consideration. We would be happy to discuss the findings of this report with you and any other interested parties at any mutually convenient time. Respectfully submitted, BONESTR00, ROSENE, ANDERLIK a ASSOCIATES, INC. Daniel J. Edgerton, P.E. DJE:kf I hereby certify that this Report was prepared by me or under my direct supervision and that I am a duly Registered Professional Engineer under the laws of the State of �Minnesota. �.dldr.OY _ �G Joseph C. Anderlik, P.E. OPH5588R Date: August 7, 1989 Reg. No. 6971 2335 West Highway 36 • St. Paul, Minnesota 55113 • 612 -636 -4600 TABLE OF CONTENTS 2 - OPH5588R PAGE NO. LETTER OF TRANSMITTAL 1. TABLE OF CONTENTS 2. INTRODUCTION 3. FIGURE 1 - LOCATION PLAN 4 • LAND USE AND COLLECTOR STREETS 5. FIGURE 2 - LAND USE 6 STREETS 7 • SANITARY SEWER FACILITIES 8. TABLE 1 - AVERAGE SEWER FLOWS 8. TABLE 2 - SEWER FLOWS BY SUBAREA 10. TABLE 3 - SEWER FLOWS BY REACH 11. FIGURE 3 - TRUNK SANITARY SEWER 13. WATER SUPPLY AND DISTRIBUTION FACILITIES 14. TABLE 4 - WATER DEMANDS 15. TABLE 5 - WATER DEMANDS BY SUBAREA 18. FIGURE 4 - TRUNK WATER MAIN 19. STORM SEWER FACILITIES 20. TABLE 6 - HYDROLOGIC DATA BY SUBAREA 22. TABLE 7 - POND DATA 23. FIGURE 5 - TRUNK STORM SEWER 24 • ECONOMIC ANALYSIS 25. COST ESTIMATES 25. TABLE 8 - COST SUMMARY 25. ASSESSMENTS 26• TABLE 9 - ASSESSABLE AREAS 26• TABLE 10 - ASSESSMENTS 27 • SUMMARY AND RECOMMENDATIONS 29• 2 - OPH5588R INTRODUCTION This report addresses the service needs of the Annexation Area Extended in the City of Oak Park Heights, Minnesota. The report is intended to provide Oak Park Heights with a guide for providing municipal services to the area. A location plan is shown in Figure 1. The "Annexation Area Extended" is defined as the area bounded on the east by Oakgreen Avenue, on the north by State Highway 36, on the west by State Highway 5, and on the south by the southern boundary of Sections 5 and 6. It includes the area west of oakgreen Avenue which was recently annexed. The report covers the service needs of the study area under the assumption of full development in the area. The report is organized as follows: 1. Land Use and Collector Streets: A projected land use plan for the study area is presented, along with a proposed layout of collector streets. 2. Sanitary Sewer Facilities: The sewage requirements of the study area are investigated, and a layout of trunk sanitary sewers and lift stations is presented. 3. Water Supply and Distribution Facilities: The water demands of the study area are estimated, and a system of water supply, storage, and distribution is presented. 4. Storm Sewer Facilities: The stormwater runoff is analyzed, and a system of storm sewers and ponds is presented. 5. Economic Analysis: Cost estimates are prepared, and proposed assessments to meet the costs are presented. 6. summary and Recommendations: A summary and recommendations are presented. ' OPHS588R - 3 - .0 6onestroo Rosene ® Anderllk S Associates Erw, imm a ArddWu Twin Citiee Metropolitan Area LOCATION PLAN OAK PARK a Ir - - Ir%I ITrn 1 pW, Fig. No.I LAND USE AND COLLECTOR STREETS Northwest Associated Consultants, Inc. has prepared a conceptual land use plan for the study area. This is shown in Figure 2. The land uses shown in Figure 2 are a continuation of those uses designated in the City's recent Comprehensive Plan Amendment for the Oakgreen annexation area. The proposed land use plan consists of a strip of commercial area along Highway 36, with another strip of high density residential area immediately to the south. This strip of high density residential area acts as a buffer between the commercial area and low density residential area, which comprises the remainder of the study area. Two parks are also included in the low density residential area. The study area consists of a total of approximately 944 acres. A breakdown of the various land use areas is as follows: Land Use Acreage Low Density Residential 700 High Density Residential 94 Commercial 94 Park Land 32 Wetlands /Ponds 24 TOTAL 944 Significant areas of wetlands, marginal soils, and steep terrain exist within the study area. Because of this, the actual development in the study area will probably be less than the estimates above, which represent maximum - 5 - OPH5588R development potential for the area. However, the estimates provide a conservative yet reasonable basis for the purposes of utility planning. Proposed collector streets are also shown in Figure 2. They have a one - half mile spacing and are based on the proposed land use plan. The collector street network is very preliminary and should be adjusted as actual development occurs in the study area. OPH5588R _� J J CO .�' i s N 2 Z p i W w cc Lu Z w w F•- Jr Ix a+ Q fA } } J W LU u 11 ,,st Z Ix F- H < = LL W W V N y U ~ ° z ai () F" Z = X cr p — m W W W o ° w O J o d- C/) J - x Y Z < o : ao Go 0 V = V a h c:v. (D U ) Q o J 3nN3AV N33dJ )IVO • • • 1 I ... � � ,- ,fir ,�'�. �•,i,.r y ;� ., i o LU • • e { .' ; ••.•••• c \ L , 1. i I ,r W • • • • t J 1 ... { g W W Q • .� 1 - M , 111 cr • • • �• :: (: r, 1 •••YYYYIIII j ♦ • • • :. �:: :•: ;., I �' � , .. it 1 l .r �', t S �. � i t"� ``d ' � L Q •••••••• uj ,r•r •:•:•:•: I 'I, i � . {{ ' j; �1�1111,5•( _ � Q ::•. ::.: — r i s Y it •.••••• '' '/ I I E . yr 4 II L.' �il LL er • • • I - A .�,Y� a LLI LL .... r • • • • • • ':'i: i / ~ w ... • • • 1 I , .'1 ! � •.. � -_- , � } 111 S f .J I 1 , 'r l• I I I 11 Avenue. The total sewage flow from th•.: cudy area was determined based on the proposed land use areas and a iates of unit flow rates from each land use type. The unit flow rates were ba on typical values for the Metropolitan Area. The computation of the erage sewer flaw from the study area is presented in Table 1. TABLE 1 ;RAGE SEWER FLOWS SANITAP WER FACILITIES isity Density Avg. Day The proposed trunk sanitary se system for the study area is shown in (Persons/ Figure 3. It consists of a itary sewer layout based on the collector Land Use streets shown in Figure 2, as well two lift stations. The proposed sewer Person will tie in to the existing .__ ch Interceptor at Highway 36 and Oakgreen Avenue. The total sewage flow from th•.: cudy area was determined based on the proposed land use areas and a iates of unit flow rates from each land use type. The unit flow rates were ba on typical values for the Metropolitan Area. The computation of the erage sewer flaw from the study area is presented in Table 1. TABLE 1 - 8 - OPH5588R ;RAGE SEWER FLOWS isity Density Avg. Day Area sits/ (Persons/ (gpd/ Avg. Day Avg. Day Land Use acres ._ res ) Unit Person (gpd /ac.) (MGD) Low Density Residential 576.2 I..O 3.2 70.0 233.0 0.134 High Density Residential 94.0 ;.5 2.0 70.0 1050.0 0.099 Commercial 94.0 -- -- -- 1500.0 0.141 Parks, Public Use 51.5 -- -- -- -- 0.000 Total 815.7 0.374 - 8 - OPH5588R As can be seen in Table 1, the total average sewer flow from the study area is 0.374 million gallons per day (MGD). Based on the December 1980 Comprehensive Sewer Policy Plan, the North Interceptor has an excess capacity of 0.480 MGD available to serve the study area. Therefore, there is sufficient capacity in the interceptor to handle the flows from the study area. The proposed sanitary sewer layout is shown in Figure 3. It is based on the proposed land use and collector street plan. In order to determine required sewer pipe sizes, sewer flows at various locations along the sewer were estimated. For this purpose, the sewer was divided into 14 reaches between Point 1 and Point 13 (see Figure 3). The study area was then divided into 11 subareas (A through K) draining to the reaches. Land use areas and unit flow rates were used to compute average sewer flows in each of the 11 subareas. These are shown in Table 2. The resulting average flows in each reach of the sewer are shown in Table 3. Peak flow factors were used to convert average flows to maximum flows, upon which the pipe sizes were based. The peak flow factors and maximum flows in each reach of sewer are presented in Table 3. 9 OPH5588R TABLE 2 SEWER FLOWS BY SUBAREA - 10 - OPH5588R Residential Parks, Low High Commercial Pub. Use Total Avg.Day Subarea acres acres (acres) acres acres Flow (MGD) A 0.0 26.0 20.0 0.0 46.0 0.057 B 113.8 0.0 0.0 4.0 117.8 0.027 C 0.0 21.4 32.7 4.0 58.1 0.072 D 36.6 0.0 0.0 2.5 39.1 0.009 E 72.2 0.0 0.0 3.0 75.2 0.017 F 74.2 0.0 0.0 6.2 80.4 0.017 G 0.0 18.6• 34.7 0.0 53.3 0.072 H 74.2 28.0 6.6 0.0 108.8 0.057 1 46.6 0.0 0.0 3.0 49.6 0.011 J 100.0 0.0 0.0 14.8 114.8 0.023 K 58.6 0.0 0.0 14.0 72.6 0.014 Not Served 123.8 0.0 0.0 4.0 127.8 0.029 Totals 700.0 94.0 94.0 55.5 943.5 0.403 Total Served 576.2 94.0 94.0 51.5 815.7 0.374 - 10 - OPH5588R TABLE 3 OPH5588R - 11 - SEWER --------------- FLOWS BY REACH - ---- Subarea Contrib- Total or Pipe utory Average Peaking Total Pipe Contrib- Flow Flow Flow Max Flow Reach uting (MGD) -- - - -- (MGD) -- -- - - -- Factor -- - - - - -- (MGD) --- - - - -- --- - - - -- 1-2 -- - - - --- A -- 0.057 B 0.027 0.084 4.00 0.335 2- L.S. 11 1 -2 0.084 C 0.072 D 0.009 0.164 3.95 0.647 3 -4 E 0.017 0.017 4.00 0.067 4- L.S. #1 3 -4 0.017 F 0.017 0.034 4.00 0.136 5- L.S. 11 G 0.072 0.072 4.00 0.286 L.S. 11 -6 2- L.S. 11 0.164 4- L.S. #1 0.034 5- L.S. 11 0.072 0.270 3.70 0.997 6 -7 L.S. 11 -6 0.270 0.270 3.70 0.997 7 -12 6 -7 0.270 H 0.057 0.326 3.60 1.174 8 -9 I 0.011 0.011 4.00 0.043 9- L.S. 12 8 -9 0.011 J 0.023 0.034 4.00 0.137 10- L.S. 12 K 0.014 0.014 4.00 0.055 L.S. 12 -11 9- L.S. 12 0.034 10- L.S. #2 0.014 0.048 4.00 0.191 11 -12 L.S. 12 -11 0.048 0.048 4.00 0.191 12 -13 7 -12 0.326 11 -12 0.048 0.374 3.60 1.346 - 11 - The Manning equation assuming full pipe flow was used to size the sewer pipes. The maximum flows shown in Table 3 were used, along with a Manning's n of 0.013 and pipe slopes based on the existing topography in the area. The resulting design pipe sizes are shown in Figure 3. Because of the topography of the study area, two lift stations were determined to be required to convey the sewer flows to the North Interceptor. Lift Station 11 is proposed to be located at the western edge of the Oakgreen annexation area. With a design capacity of 1.0 MGD, it will serve the western and southwestern portion of the study area. Lift Station 12 is proposed to be located in the southeastern corner of the study area. It has a design capacity of 0.2 MGD and will serve the southeastern portion of the study area. Approximately 128 acres in the southwestern corner of the study area will not be served under the proposed sanitary sewer system. This is a low -lying area which will not drain by gravity to the system. One alternative which would allow this area to be served by the proposed sewer system is to provide a third lift station in this area. This alternative is not proposed or investigated further in this report, but is mentioned for the City's consideration. Note that if the 128 acres were added to the system, the average sewer flow from the study area would increase to 0.403 MGD, which is still less than the available 0.480 MGD capacity. - 12 - OP85588R .zc oo, 9 3nN3AV N338ONVO .9= ,009'9 O • M .. ^ • N II f 1 ,_ 0 Y'��" l r r u: 1 � I I r I I � � gr rvv � ..• `Iif I ' I' �r J� l ti` I� h r ?,+J /Q /j\ •..:.1 �.�I �fti• II k l �I t Li'• N . , lb R .�� I l 1 1 � , I`I ..1 I ♦ 1. 1� Jt�•. 1 �1 �1 r 1'v � I O p I VIC O j- • r , �. �r, +•~ 1 C . ` . T° "� �� ^(. fc J O r_ 1�Qq�! M �11 a ....r , i 1 K r+ .r. <<I .• f cj CD Co (n tI F :V"•Ij•�'�..:':J1 ! 1 .te �._ ,O T ti, , •s �, V r . ' • .'n �1 I i / t �I /! / I L. to I .. .� ` ^i• ' .1.11 1N\ = CIA �•. -• .6"` I ,•��,. -,;, _,._� .:,, `�; - J .f .. -) is �� . •�. ' r 0 ` � ' a 1 /ti II'�T�\,y. / {/�(�'+�1•- 4�ll�r -.1"" ' � � f 1 0 LU H zz O W CO w W Z W Z Q A z O 2 a W W z = Q Y °C O a. a 0 LU LL z LU LU _F U o U _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7�MiM' ILawluar+ c. qu. qrn. iYww. acaw.. e..•. wsy +Mw.}aww..:..:nw.- ._:.......,y M .._.:. -.... W cr w 2 CIO W w Z O o � U) Co z > cc ►= ° m O z o ¢ < °z Q, ~ ui li Z Z 0 O w O = IWL Z N m O Z C7 N < w O Q < < cr o Z L1J Y W W F- N O O W O) Q J Z U Z Q Z Q o Y e H co ¢ ¢ Q O CO 7 m O LL U 'o` ig vn cv F IL d N N J N • C N �n Y c p .v, z N OD t O is M INK Q 1 O � O � :Z: ( r , 41 cc O O O U H p r of I .zc oo, 9 3nN3AV N338ONVO .9= ,009'9 O • M .. ^ • N II f 1 ,_ 0 Y'��" l r r u: 1 � I I r I I � � gr rvv � ..• `Iif I ' I' �r J� l ti` I� h r ?,+J /Q /j\ •..:.1 �.�I �fti• II k l �I t Li'• N . , lb R .�� I l 1 1 � , I`I ..1 I ♦ 1. 1� Jt�•. 1 �1 �1 r 1'v � I O p I VIC O j- • r , �. �r, +•~ 1 C . ` . T° "� �� ^(. fc J O r_ 1�Qq�! M �11 a ....r , i 1 K r+ .r. <<I .• f cj CD Co (n tI F :V"•Ij•�'�..:':J1 ! 1 .te �._ ,O T ti, , •s �, V r . ' • .'n �1 I i / t �I /! / I L. to I .. .� ` ^i• ' .1.11 1N\ = CIA �•. -• .6"` I ,•��,. -,;, _,._� .:,, `�; - J .f .. -) is �� . •�. ' r 0 ` � ' a 1 /ti II'�T�\,y. / {/�(�'+�1•- 4�ll�r -.1"" ' � � f 1 0 LU H zz O W CO w W Z W Z Q A z O 2 a W W z = Q Y °C O a. a 0 LU LL z LU LU _F U o U _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7�MiM' ILawluar+ c. qu. qrn. iYww. acaw.. e..•. wsy +Mw.}aww..:..:nw.- ._:.......,y M .._.:. -.... WATER SUPPLY AND DISTRIBUTION FACILITIES The proposed water system for the study area is shown in Figure 4. It consists of a 12 -inch loop with one cross - connection, an 850 gpm well, and a 550,000 gallon water tower. The system will tie in to the City's existing water system at two locations, both on Oakgreen Avenue, as shown in Figure 4. The design of the water system facilities depends upon the water demands placed upon the system. The maximum daily demand is normally used to design the facilities. The maximum daily demand for the study area was estimated based on the proposed land use plan. Unit demand rates were applied to each land use area to compute both an average and a maximum daily demand. The computation of the demands is presented in Table 4. The maximum daily demand in the study area under conditions of ultimate development was estimated to be 1.32 MGD, or 916 gpm. - 14 - OPH558SR T^ I %0.10 0 1 0 td H I . . . - 01 0 0 1 00 u V1 I U 1 eT N O 1 e m I o�M 1 I � 1 , I W I td I Q I 1 H I I I I 1 N m I In In oo of > I m N N O H I 1 W B g b h Ul O; 1D 00 i d 10 rl 1 al > I I � I 1 T \ • 1 Y 1 W b 41 I . . 1 b 0. 1 01 0 0 1 00 u V1 I U 1 eT N O A I m 41 I N O O d N 1 I � 1 , I W I I Q I I O ✓1 I I pG I I I I W I T \^ 1 0 0 1 1 H I • G 1 I I 6 1 O 1 a Q b 0 0 , 1 I 00 N 1 O n " t I I > N 1 > v •.I w a1 (a . 1 000ln 1 y Ul 1 1 u v 1 oa�ln 1 M 6 N I o rn rn In I s � I W I J 1 W 1 6 , F 1 u 1 n a+ N N I I 1 • 1 N O G I G N O I d N 1 A a , a I T\ .-. I O ✓1 I I y N Q1 I I I •N N N, rl n I I tt1 -'1 U I G G m 1 d G , q � I (a . 1 000ln 1 y Ul 1 1 u v 1 oa�ln 1 M 6 N I o rn rn In I s � I W I J 1 W 1 6 , F 1 u 1 n 1 rn � 1 1 � I m •.J G v m ro v •.I •H N N W a O/ I a. 4 y a1 T p T I T s E I •.1 N td 7 N I W G • W N I G N U VI A I N A H A Cd N tl H W O G 3 0 8 w W I O -H O Itl F .a I 11 x U W Based upon discussions with the City staff, the existing maximum daily demand in the City was estimated to be 1.0 MGD, or 700 gpm. The ultimate maximum daily demand in the City, excluding the study area, was estimated by determining the available developable area in the City and making projections of probable future land usage. Unit demand rates were then applied to these land uses to calculate the additional maximum daily demand expected. The ultimate maximum daily demand in the City, excluding the study area, was estimated to be 1.21 MGD, or 840 gpm. The total maximum daily demand in the City and the study area, under ultimate development conditions, is 2.53 MGD, or 1756 gpm. The City is currently supplied by two 850 gpm wells. This provides the City with 850 gpm of dependable capacity, with one backup well. In order to meet the supply needs of the City and the study area under ultimate development conditions, it is estimated that an additional well of 850 gpm capacity will be required. This will provide the City with 1700 gpm of dependable capacity, with one backup well. Storage requirements for the City are based on the available supply, the maximum daily demand, which represents normal water usage in the area, and fire flow requirements, which represent high short -term water demands above and beyond the normal water usage. For the City, a fire flow requirement of 2000 gpm for a period of two hours was incorporated into the estimate of the storage requirements. - 16 - OPB5588R I I r] ' II II L The estimated total storage required for the City under ultimate development conditions was estimated to be 800,000 gallons. This is based on the ultimate dependable capacity of 1700 gpm, the ultimate maximum daily demand of 1756 gpm, and a fire flow of 2000 gpm for two hours. The City has an existing 250,000 gallon water tower, with an estimated high water level (HWL) of 1080. Therefore, it is estimated that an additional 550,000 gallon water tower at HWL 1080 will be adequate to meet the needs of the City and study area under ultimate development conditions. The location of the proposed water tower is shown in Figure 4. A computer model was used to design the water distribution system. Input for the computer model included pipe lengths, sizes, and roughnesses, as well as point demands and elevations. The model then computed pipe flows and water pressures throughout the system. The distribution of water demands across the study area was approximated by placing demands at discrete demand points on the system. The study area was divided into demand subareas, each requiring a certain water demand from its corresponding demand point. Land use areas and unit demand rates were used to compute the demands in each demand subarea. The demand points and subareas are shown in Figure 4. The subarea demands are summarized in Table 5. The proposed water distribution system is shown in Figure 4. It was found that a 12 -inch trunk water main loop with one cross - connection will be capable of delivering the maximum daily demand at acceptable pressures. OPH5588R - 17 - I � L TABLE 5 WATER DEMANDS BY SUBAREA - 18 - OPH5588R Residential Parks, Max Day Demand Low High Commercial Pub. Use TOTAL Demand Node (acres) (acres) (acres) (acres) (acres) (gpm) - - - -- -- - - -- - -- 101 - - ---- 19.0 - --- --- 14.4 -- - -- -- 1.6 - - - -- -- 0.0 - - - - - -- 35.0 44.1 102 115.0 35.0 44.2 4.0 198.2 258.0 103 119.0 44.6 48.2 9.7 221.5 288.4 104 223.0 0.0 0.0 9.0 232.0 162.3 105 174.0 0.0 0.0 19.9 193.9 126.8 106 50.0 0.0 0.0 12.9 62.9 36.4 --- - -- TOTALS - ----- 700.0 --- - -- 94.0 - -- - -- 94.0 ---- -- 55.5 ------ 943.5 916.0 - 18 - OPH5588R ', Q W Z M D M I..L CD c� Q W F V) Z < 2 Z O p ir ¢ O W Z W < Z 0 w W O 0 3 W Y J j ¢ W O f— W I— Q 1 O O \ O r • 3nN3AV N33HONVO , �� ) O '� , •.� ;tt� -� /;�1 � �'f _ ql • N...�, j -: 1 14 .. _ � I xr 1 1 J �• I, •O' ! inl r J'i , 1i1 �5 ,..� 1 IU' � 1 / /. ��_ �t `,� •� ,I -- u..J CY \ ! • t w + I :+ � IiTL_ r++- .., f .'Y-' i -} S n�`1 t. 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I � M t, -�� '' I lr 1,. 1 ��.' / �, � / \ x•j.,, / �f 1 , -- Ij' -r Sv. �i I; �� I`• / Y � ^_� � el, ' .P O'f.,, / ; t•• ! �. rlrl ' I T/ rl. \ ' � r \�x / h ; /11j I •t \I -�`i __o < k I; 1 r t(1 ` Y ;l ( '•�I I �X - 1 I � !�Z 4 i`: l ., LO LO cy ! � I ^ J/I �'., 1� i � /�1, �1 � �% ; i �� tl \ QI i t l! / � I V'T' -L• tA ,`` 1 O . inN \ 1 - \ , ' .. \ \ /fir 11 '. 'i µ.M11 ��: /.Ylt • irr.., S LU 0 0 W W LU Z M L M y C 0 L 1 2 0 Z uj W 2a °C 1..1. Q CL 0 Y Q CO 0 W LL Z LU >- w F 0 STORM SEWER FACILITIES The proposed trunk storm sewer system for the study area is shown in Figure 5. It consists of storm sewer pipes which will collect and convey stormwater runoff to a series of detention ponds. The study area is made up of varied terrain. The northern portion of the area drains northward, through culverts under State Highway 36 into Stillwater. The southwestern portion of the area drains southward into McDonald and Cloverdale Lakes. The southeastern portion of the area drains southeasterly into a landlocked wetland area south of Oak Park Heights. The soils in the area are generally well- drained. Storm sewer facilities depend on the volume and rate of stormwater runoff under design conditions. The stormwater runoff, in turn, depends on the rate and volume of precipitation, topography, soil type, land use, and size and shape of the drainage area. For design purposes, both the 24 -hour, 5 -year storm (3.55 inches) and the 24 -hour, 100 -year storm (5.90 inches) were used. The Soil Conservation Service (SCS) Type 2 rainfall distribution was used. A computer model was used to compute the stormwater runoff in the study area. The study area was divided into a number of subareas, as shown in Figure 5. For each subarea, the drainage area, the SCS curve number, and the time of concentration were determined. The curve number is based on land use and soil type and is a measure of how much precipitation is converted to stormwater runoff. The higher the - 20 - OPH5588R curve number, the greater the amount of runoff. The time of concentration depends on the size, shape, type of land surface, and topography in the area and is used to estimate the timing of the stormwater runoff. The lower the time of concentration, the earlier and higher the peak of the runoff will be. A summary of the subareas, curve numbers, times of concentration, precipitation amounts, and peak rates of runoff is presented in Table 6. The trunk storm sewer pipes in the study area were designed to carry runoff from the 5 -year storm with no surcharging of the pipes. Excess runoff above the 5 -year storm will be carried through surcharging of the pipes or as overland flow. The Manning equation for full pipes was used to size the pipes. Pipe slopes were based upon existing topography in the area. A Manning's n of 0.013 was used for the analysis. The resulting pipe sizes are shown in Figure 5. Detention ponds will be used to detain the stormwater runoff and reduce the peak flow rates. This reduces the required storm sewer pipe sizes downstream of the ponds. The detention ponds and their outlet pipes were designed for the 100 -year storm runoff. The computer model was used to compute the high water levels and peak outflows in the ponds. Design high water levels and pond volumes are summarized in Table 7. - 21 - OPH5588R N T N N �O 00 d O W J W d d Q� �O O O] 1 O+ ✓1 �/1 ✓1 � W M N N ✓1 S Q� O d Q� iA d M N I� N M m� b d W W O C 7 fG 1 U M N T 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0� rn rn rn rn rn rn rn rn rn rn rn rn rn rn rn rn rn rn rn 4J d a N T C V V u U ✓ u V ill ill v M M cn M M M r�1 M M m M M M M m M M M cn M W O C S U C d d -d O E3 E U N N N 0 7 U Z v b0 W m ,y N N D• (p � O d M O 1 O Q+ 1 I� S O N N� N ✓1 •.�1 C U N M 1 1 a0 �O � ✓1 N �/1 d 00 M M �O 1 d d c 0 N A ro N 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 W d N N N M M 1 ul ul ul `O I� O m O a` d d d A 7 N R w a m 6 H TABLE 7 OPH5588R - 23 - POND DATA High Water Pond Level Volume Pond (feet) ac -ft 1 908.0 69 2 923.0 2 3 900.0 59 4 938.5 10 5 909.0 35 6 909.0 16 7 935.0 2 8 24.0 44 9 931.5 8 10 932.0 12 11 923.0 2 12 933.0 4 - 23 - cc W LLJ U) LL CO v Z CC F— (O Cl) Q 2 F F- (1) z ¢ o > O W ° H Z 3 m cr Q < O W ° C) F U) F' Z 2 W 0 N 2 ir LZ m WO �O = LL O Z C < Q W y O W W W O O co W J a a ° z Z a Z Z U j j O O ¢ N co y a a t- O '0 ° ° 0 I O O r 3nN3AV N33aJ )4b0 o T . oo o .oc •o / . 0 Al 1p .1 co 1 1' '� 4 1., , •`, co o - _ � IMF I , .dl�� ` +. o z.� .� .' 0 QL at M N • &� 1 r o '\' I O 1 1 � / `�♦ .008 �r Z 1 1 0 / 1 0 0 rill/ r J j s v Y O a . p Y e c � e • e c m nz LO O Z rn Ol OD m O rn O � h W) a E E 0 0 O V 0 W H O W V) w z Q z w C _ � L Q Q ~_ F— W c� W z Y 2 a fr CC 0 LL Y �- Q U) O w LL Z O w LU a U o U II 1 Water Distribution System: 17,250 L.F. - 12 in. DIP @ $45 /L.F. 776,250 One 850 gpm Well @ $350,000 350,000 1 _ . 550,000 gal. Water Tower @ $687,500 687,500 SUBTOTAL - Water Distribution System $1,813,750 Storm Sewer: 3,400 L.F. - 12 in. RCP @ $45 /L.F. 153,000 2,200 L.F. - 18 in. RCP @ $50 /L.F. 110,000 3,950 L.F. ECONOMIC ANALYSIS @ $55 /L.F. Cost Estimates 1 600 L.F. - 27 in. RCP Costs for the proposed utility improvements have been prepared and are 1 presented in Table 8. The general locations of the facilities, as shown in in. RCP Figures 3 through 5, served as the basis for the cost estimates. TABLE 8 1 COST SUMMARY 1 Sanitary Sewer: 3,500 L.F. - 6 in. DIP @ $30 /L.F. $105,000 19,400 L.F. - 8 in. PVC @ $35 /L.F. 679,000 500 L.F. - 10 in. DIP @ $40 /L.F. 20,000 ' 4,300 L.F. - 12 in. PVC @ $45 /L.F. 193,500 1.0 MGD Lift Station @ $55,000 55,000 0.2 MGD Lift Station @ $40,000 40,000 1 SUBTOTAL - Sanitary Sewer $1,092,500 Water Distribution System: 17,250 L.F. - 12 in. DIP @ $45 /L.F. 776,250 One 850 gpm Well @ $350,000 350,000 1 _ . 550,000 gal. Water Tower @ $687,500 687,500 SUBTOTAL - Water Distribution System $1,813,750 Storm Sewer: 3,400 L.F. - 12 in. RCP @ $45 /L.F. 153,000 2,200 L.F. - 18 in. RCP @ $50 /L.F. 110,000 3,950 L.F. - 24 in. RCP @ $55 /L.F. 217,250 1 600 L.F. - 27 in. RCP @ $65 /L.F. 39,000 2,900 L.F. - 30 in. RCP @ $70 /L.F. 203,000 1 3,000 L.F. - 33 in. RCP @ $ 75 /L.F. 225,000 1,500 L.F. - 36 in. RCP @ $ 85 /L.F. 127,500 4,050 L.F. - 48 in. RCP @ $95 /L.F. 384,750 1 Pond Excavation: 30,000 C.Y. @ $4 /C.Y. 120,000 i SUBTOTAL - Storm Sewer $1,579,500 TOTAL COST $4,485,750 - 25 - ' OPHS588R The costs are based on 1989 construction costs and can be related to an ENR Index of Construction Costs of approximately 4,670. Future changes in the index are expected to reflect fairly accurately cost changes in the proposed facilities. The costs include a 25S allowance for contingencies, design, administration, inspection, and capitalized interest during construction. Assessments Assessments have been prepared to pay for the costs of the utility improvements. The assessments are in the form of area and connection charges, based on net assessable acres. The net assessable acres are the gross acres of low density residential, high density residential, and commercial area, as shown in the section on Land Use and Collector Streets, net of detention ponding area. The residential connections are based on the work done by Northwest Associated Consultants, Inc. The commercial connections are based ' on an estimated 4 connections per acre. The net assessable acres and number of connections are shown in Table 9. TABLE 9 ' ASSESSABLE AREAS Residential ' Low Dens. High Dens. Comm. TOTAL Gross Acres 525 70 70 665 Ponds 79 11 11 101 Net Acres 446 59 59 564 # Connections 728 705 236 1,669 I J OPH5588R - 26 - The assessment rates are presented in Table 10. For sanitary sewer, 75Z of the total cost was put on the area charges and 25Z of the total cost was put on the connection charges. For the water system, 60Z of the total cost was put on the area charges and 40Z of the total cost was put on the connection charges. Note that the connection charges for commercial areas are on a per -acre basis, assuming 4 connections per acre. TABLE 10 ASSESSMENTS v Area Connection Charge Charge acre ($ /conn.) Sanitary Sewer: Low Density Residential $1,453 $164 High Density Residential 1,453 �e �1a 164 J Commercial 1,453 655 l/ Water Service: Low Density Residential $1,930 $435 ' High Density Residential 1,930 ` J 1� 435 4 Commercial 1,930 1,739 l/ Storm Sewer: Low Density Residential $2,406 - - -- High Density Residential 3,937 - - -- Commercial 4,648 - - -- Note: l/ $ per acre. - 27 - OPH5588R For storm sewer, 1005 of the cost was put on the area charges. The area charges for each of the three land uses were based on estimates of the portion of stormwater runoff contributed by each. Based on the curve numbers presented in Table 6, each acre of high density residential land was estimated to be equivalent to 1.64 acres of low density residential land, and each acre of commercial land was estimated to be equivalent to 1.93 acres of low density residential land. The assessments have not been adjusted for lateral benefit. It is anticipated that some lateral benefit would result from the construction of the trunk sanitary sewer, water main, and storm sewer facilities. 28 _ OPH5588R SUMMARY AND RECOMMENDATIONS This report addresses the service needs of the Annexation Area Extended in the City of Oak Park Heights, Minnesota. Specifically, the following services were examined: 1. Streets 2. Sanitary Sewer 3. Water Service 4. Storm Sewer Northwest Associated Consultants, Inc. developed a conceptual land use plan and collector street layout for the study. This layout is shown in Figure 2. It is very preliminary in nature and should be adjusted as actual development occurs in the study area. The proposed trunk sanitary sewer system is shown in Figure 3. It was determined that two lift stations would be required to convey the sewage from the study area into the North Interceptor. The estimated cost of the sanitary sewer facilities is $1,092,500. Assessments to pay for the facilities were estimated to be: Area charge: $1,453 per acre Connection charge: $164 per connection - Residential $655 per acre - Commercial - 29 - OPH5588R The proposed trunk water system for the study area is shown in Figure 4. It consists of a 12 -inch loop of water main with one cross - connection, an 850 gpm well, and a 550,000 gallon water tower. The well and water tower are sized to meet the needs of both the study area and the remainder of the City under conditions of ultimate development. The estimated cost of the water system is $1,813,750. Assessments to pay for the facilities were estimated to be: Area charge: $1,930 per acre Connection charge: $435 per connection - Residential $1,739 per acre - Commercial The proposed trunk storm sewer system for the study area is shown in Figure 5. It consists of storm sewer pipes which will collect and convey stormwater runoff to and from a series of detention ponds. The estimated cost of the storm sewer facilities is $1,579,500. Assessments to pay for the facilities were estimated to be: Area charge: $2,406 per acre - Low Density Residential $3,937 per acre - High Density Residential $4,648 per acre - Commercial - 30 - OPH5588R