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Home My WebLink About1988-05-18 Storm Water Improvements Reporti Report Storm Water Improvements Casco Point Road Orono, Minnesota 1988 r: RIe 13941 Hi__ F May 18. 1988 Honorable Mayor and City Council City of Orono Box 66 Crystal Bay, Minnesota 55323 Re; Casco Point Road Storm Water Improvements Our File No. 13941 Dear Mayor and Council:LiesK: -- - - - - - runoff from the drainage area. The report proeide. . defiled co.t e.tlo.te of the «orh helnp cooeldered end a plan of the area. .. .ould be pleased to «eet .1th the Cit, Couhcil et your cooveolenoe to review the proposed project. Respect! illy submitted, BONESTROO. ROSENE. ANDERLIK h ASSOCIATES, INC. Glenn R. Cook, P.E. GRC:kf 1 hereby certify that this Report we.s prepared by me or u^der o^dlrLt sapervi.io.. fd th.t I ... . duly Registered Prolession.l Engineer under the levs of the State of Minnesota. A/I_ ^ Glenn R. Cook, P.E. 01391179 Date 1 May 18. 1988_Regs No. 9451 . 1 • 4 m .'r* %. . INTRODUCTION The City of Orono has requested this report to detemine the best nethod of handling the stons water runoff from a small watershed along Casco Point Road. During construction of a new house at 3061 Casco Point Roadt one of two existing outlet pipes were removed. The purpose of this study Is to determine the else of the replacement outlet pipe. The existing outlet pipe at 30SS Casco Point Road is not adequate to handle a significant portion of the runoff. The pipe runs under the existing hone and could not be repaired if a problem were to occur. Ve did not elect to consider the capacity of this pipe when determining the sixe of the new outlet pipe. The drainage area is landlocked with no safe overflow drainageway. The water will flow into the garage at 30S5 Casco Point Road before reaching a natural overflow. - 3 - 01391179 I i NiifiiiillilllllMiMil K f-*r- DISCUSSION The drainage area for this watershed is approximately 3.25 acres as shown on Figure 1. The topography is rolling and high rates of runoff would be expected. There is some temporary ponding available if the backyard areas are flooded. Ve reviewed three alternates for providing the storm water outlet capacity. Alternate I would be to design for maximum storage with minimum outlet capacity. Alternate II would be to design for a safe amount of storage with a modest outlet capacity. Alternate III would be to provide for minimal storage and a maximum outlet capacity. The environmental Impact for each of the altenu :ies significantly Alternate 1 would provide an eight inch outlet pipe with approximately O.S *cre-feet of storage required in a major storm. This could bring the water elevation above the garage floor at 3055 Casco Point Road. The construction of an overflow drainageway would be necessary with this alternate. Alternate II would provide a ten inch outlet pipe with approximately 0.35 ocre-feet oV storage required in a major storm. This would bring the water elevation to a point 0.5 feet below the garage floor at 3055 Casco Point Road. The r.onstructlon of an overflow drainageway would be desirable with this alternate. Alternate III would provide an eighteen inch outlet pipe and virtually no storage would be required. The construction of an overflow drainageway would not be necessary with this alternate . 4 . 01391179 I % i ifis - • The total water discharged to the lake is nearly the same for all three alternates. The rate of stom water runoff is greatly reduced for Alternates I and II. The following is a sususary of the outlet rates for each alternate. Alternate I Alternate II Alternate III Pine 8* 10' 18" Design Discharge 7 cfs 4 cfs 17.5 cfs Reducing the rate of runoff ioproves the water quality discharge to the lake by allowing solids to settle out. The floating debris can be controlled by constructing a baffle weir near the inlet. - 5 - 01391179 PROTECT COST AND ASSESSMEMT The project cost and assessment rates for the storm water improvement are outlined in this section with a detailed cost estimate provided in the Appendix. The indicated prices are as projected for the 1988 construction season (ENR 4500). Alternate I Alternate II Alternate III Estimated Project Cost $ 9.230 $10,100 $10,600 The project costs are proposed to be assessed to the benefiting property owners in the watershed on an acreage basis. There are 3.25 acres in the watershed with the cost per square foot for each alternate shown below. estimated assessment rates Project Cost Alternate I Alternate II Alternate III $ 9,230 10,100 10.600 Assessment Rate 0.065/sq.ft. 0.071/sq.ft. 0.075/sq.ft. The above indicated project costs do not include pending easements or pipe lire easement acquisition costs. These costs could be as high as the construction costs if condemnation is necessary. - 6 - 01391179 n \ ,- ’’-r^ CQNCLUSIOHS AND SfCOHHEHOATIONS The project as reviewed herein is feasible as it relates to general engineering principals and construction procedures. Based on information contained in this report, it is recommended that: 1. This report be adopted by the City of Orono as a guide for construction of a storm water improvement on Casco Point Road. 2. The City conduct a legal and fiscal review of the project prior to a public hearing. 3. A public hearing be held to determine further action to be taken. The property owners in the watershed which are proposed to be assessed should be notified for hearing purposes. 4. Alternate II be followed in constructing the improvements. 5. The following schedule be followed if the project is to proceed; Receive Preliminary Report May 23. 1988 Hold Public Hearing June 13. 1988 Order Plans 4 Specifications June 13, 1988 Approve Plans k Specifications June 27, 1988 Receive Bids July 8, 1988 Award Contract July 11, 1988 Start Construction July 18. 1988 Complete Construction August 15, 1988 - 7 - 01391179 The most desirable way for the project to proceed is to have the property owner at 3061 Casco Point Road install the selected outfall line. The City would then acquire the necessary easements and assess that cost over tne entire watershed - 8 • 01391179 01391179 - 9 - APPENDIX COST ESTIMATES ALTERNATE I 180 Lin.ft.8* PVC i $20.00/lin.ft.$3,600.00 2 Each Catch basin @ $1,000.00 2,000.00 10 Each Rip rap 6 $5i 00/cu.yd.500.00 LUMP SUM Grade overflow S $1,000.00/L.S.1.000.00 Total Construction $7,100.00 -I- 30Z Legal, Engr., k Admin.2,130.00 Total Project Cost $9,230.00 ALTERNATE II 130 Lin.ft.10* PVC i $25.00/lin.ft.$3,250.00 50 Lin.ft.8' PVC % $20.00/lin.ft.1,000.00 2 Each Catch basins i $1.000.00/ea.2,000.00 10 Cu.yds.Rip rap ^ $50.00/cu.yd.500.00 LUMP SUM Grade overflow Q $1,000.00/L.S.1.000.00 Total Cunstruction $7,750.00 + 30Z Legal, Engr., k Admin.2.350.00 Tot9l Project Cost $10,100.00 ALTERNATE III 130 Lin.ft.18* PVC i $35.00/lin.ft.$4,550.00 30 Lin.ft.15* PVC i $30.00/lin.ft.900.00 10 Lin.ft.8* PVC e $20.00/lin.ft.200.00 2 Each Catch basins 9 $1,000.00/ea.2,000.00 10 Cu.yds.Rip rap i $50.00/cu.yd.500.00 Total Construction $8,150.00 + 30Z Legal, Engr., k Admin.2,450.00 Total Project Cost $10,600.00 .i ■j ■J*' -------T ; 1. • V.%• , .♦1 'V‘ V •'v .' h • «• t**:>. ■ -ii • ’ * ; ^ • * t ' -4 •s>; ♦ ^ .r •-W ' ' /*' t- - • j^ ^ ' f. 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