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1a1. Riley lake Meadows,Plans & Specs I 7. CITYOF ____. ., 1 .. ' lio '' CHANHASSEN . , 1 _ t 690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317 (612) 937-1900 MEMORANDUM ;.cl.i- ,,__`/_—_ 1 TO: Don Ashworth, City Manager . . , °y- %j; FROM Larry Brown, Staff Engineer ,•.0 IDATE: February 5 , 1988 1 SUBJ.: Approval of Plans and Specifications for Riley Lake Meadows Richard and Gail Vogel, Planning File No. 87-5 IAttached are the plans for Riley Lake subdivision dated "Received February 3 , 1988" . This subdivision contains 11 lots located outside the M.U.S.A. on the north side of Pioneer Trail approxi- 1 mately one-half mile east of Highway 101. The final plat was approved by the City Council on December 7, 1987. I The initial submittal of the plans included a maximum proposed street grade of 10 .0% such that construction of the road would have a minimal impact to the site. This grade was reduced to II 8 . 0% to address concerns of this office of the steep grade and approach to Pioneer Trail. The applicant' s engineer has indi- cated that the 8 .0% grade would have a greater impact to the asthetics of the site as compared to a 10 .0% grade. The trade 1 offs of decreased speeds to climb the grade during inclimate weather and increased sight distance for the crest of the hill warrants the 8 . 0% grade. Although the 8 .0% grade exceeds the I City' s recommended standard of 7 . 0%, it is recommended that the grades be accepted as shown on the subject plans. The driveway access of Lot 1, Block 1, should be located a mini- 1 mum distance of 125 feet north of the intersection of Pioneer Trail and Meadowlark Lane to allow for proper turning movements and proper stacking distance for cars at the approach. Private 1 driveway accesses will not be allowed onto Pioneer Trail . Driveways of Lots 1, 2 , 3 and 11 of Block 1 should maintain ade- quate sight distance for a 25 M.P.H. speed limit according to the 1 design standards of the Minnesota Department of Transportation. A 25 M.P.H. design speed is used for this area versus a 30 M.P.H. posted speed limit due to the proximity of the intersection. 1 Side slopes for the proposed roadbed should not exceed a 3 :1 slope. 1 I Don Ashworth r February 5 , 1988 Page 2 r As per the recommendation of the soils consultant ( refer to attachment 2) , geotextile fabric shall be placed from station 3+00 to the end of the cul-de-sac to accomodate the existing poor soil conditions . In addition, a minimum of 12 inches of granular material is to be placed underneath the rock base. The report also states that the roadway should not be paved for one construction season such that any settlements that may occur may be repaired. Construction traffic over an open gravel road would not only create a problem of tracking material onto Pioneer Trail, but also would contaminate the base material, thus requiring its removal and replacement with new class V. It is therefore recom- mended that the bituminous mat be placed in two separate lifts (a 2-inch base course and a 1-inch wear course) , with the wear course being placed after a seasonal freeze/thaw cycle. This method would accomodate any necessary repairs while reducing contamination of the rock base. The applicant has provided for a retention/sedimentation basin such that the predeveloped runoff rate is maintained. Construction of the pond and all pertinent storm sewer systems to render the pond functional should be constructed prior to any other grading, to ensure protection of Lake Riley from off-site migration of silt. The grading plan should also be revised to indicate roadway ditches . The proximity of the steep side slopes in excess of 15% near the r proposed septic system sites of Lots 1 , 2 and 11 of Block 1, warrants the construction of diversionary berms or equivalent to direct drainage away from these sites . An acceptable grading and erosion control plan for each lot will be required as part of the building permit application process . The proposed erosion control as shown on the grading plan should be Type II ( staked hay bales and snow fence) . It is therefore recommended that the plans and specifications be approved with the following conditions : 1 . The developer shall enter into a development contract with r the City and provide the necessary financial sureties to guarantee the proper installation of these improvements . 2 . The developer shall obtain and comply with all conditions of the Watershed District and Department of Natural Resources permits. , II 3 . All erosion control measures shall be in place prior to the initiation of any grading, and once in place, shall remain in 11 Don Ashworth February 5 , 1988 ' Page 3 place throughout the duration of construction. All of the erosion control measures shall remain intact until an established vegetative cover has been produced at which time removal shall be the responsibility of the developer. 4 . All detention ponds and drainage swales shall be constructed and operational which includes all pertinent storm sewer systems to have the ponds functional prior to any other construction of the project. ' 5 . Wood fiber blankets or equivalent shall be utilized to stabi- lize all slopes greater than 3 :1. 6 . Working hours shall be between the hours of 7 : 00 a.m. to 6 : 00 p .m. with no work allowed on Sundays or holidays . 7 . All proposed septic system sites shall be staked and roped off as per the grading plan dated "Received February 3 , 1988" prior to the commencement of any grading to protect them from construction activities . 8 . The applicant shall obtain an access permit for access onto Pioneer Trail from the office of the Carver County Engineer, and shall comply with all conditions of the permit. ' 9 . All streets shall be constructed consistent with the City' s standards for rural construction. ' 10 . Private driveway accesses will not be allowed onto Pioneer Trail. The driveways of Lots 1 , 2 , 3 and 11 of Block 1 shall have adequate sight distance for a 25 M.P.H. design speed according to the standards of the Minnesota Department of Transportation. ' 11. The driveway access of Lot 1 , Block 1 shall be located a minimum distance of 125 feet north of the centerline inter- section of Meadowlark Lane and Pioneer Trail. 12 . The grading plan shall be revised to show proper roadside ditches . 13. The proposed erosion control as shown on the plan shall be Type II erosion control ( staked hay bales and snow fence) . The City' s standard detail for Type II erosion control shall be shown on the plans . 14 . The bituminous mat shall be placedin two lifts; a li-inch base course and a 1-inch wearing course. The wear course shall not be placed until the base course has been through a freeze/thaw cycle, at which time approval must be received by the City Engineer prior to placement. I Don Ashworth February 5 , 1988 Page 4 1 15. A diversionary berm or equivalent shall be constructed on Lots 1, 2 and 11 of Block 1 to direct drainage away from building pads and septic system sites . An acceptable grading and erosion plan for each lot shall be required as part of the building permit application. 1 16 . As per the recommendation of the soils consultant, Meadowlark Lane shall be posted by the developer to prohibit vehicles over a total weight of 4 tons during the roadway load restriction period of springtime as determined by the Minnesota Department of Transportation. Attachments : 1 . Location Map 2 . Soils Report 3 . Plans 1 1 1 1 i 1 1 1 1 ' 1 1 1 -- ,, LII 7 , ' _ ._ ,______, 8� VARY t W I A2 ' 7aurillYi RD P: z,.... ,// . — a� i/ I Alleigpf"--- .7•7 ,/ � �j1 LA�YE I . i E `flp � _ �„ �SF R/LEY avo -=!.' ,_ _____ 1 \f V ____. .;-: , _ i tr.- N. x- padis POND ��` ______ "--W) k . I 1 / C.":".z:> )Q. 1014 -II NI1144(1 t 1 V K, 1 <>// .: II a a f II f 9 Div i - . .__________ - , Ala. For. , kk fro,E.Ard-- itspor,„. 2., ... ._.. __. ..._ � ,6 : '>1�E By J� AcT r. Geotechnical Services ALLIED TEST DRILLING COMPANY Commercial, Residential 4000 Beau DRue Drive, Eagan, MN 55122 (612)452-6913 \AVIF Municipal, DHUD I SUBSURFACE SOIL INVESTIGATION FOR Block 1 , Proposed Vogel Addition Chanhassen, Minnesota 2 February 1987 Project 87006 INTRODUCTION This report summarizes the findings of a subsurface soil investigation completed by Allied Test Drilling Company on a proposed residential development in Chanhassen, Minnesota . Said work was performed for Richard and Gayle Vogel , referred to hereafter as the "Owner" . Six soil borings were performed within the project area to establish soil profiles , water table elevations , and other ' information . From this data , certain recommendat3ons , mostly pertaining to roadway design , are made regarding site suita- bility For the intended purpose of roadway grading and pave- y ment design for residential development access. The area of investigation is Block 1 of the proposed I Vogel Addition to the City of Chanhassen. It is located most- ly in the east half of the northeast quarter of Section 25, between the shore of Lake Riley to the north and Pioneer Trail (Scott County State Aid Highway No 14) to the south. Site terrain is rolling , with almost 50 feet of elevation I difference between highest and lowest points. Lowest terrain occurs at the Lake Riley Shoreline and in a lowland located 1 near the center of the parcel in question. Highest land AT'/'AC oime yr z It 1 a 3 1 87006 . . -2- occurs in the south portion , along CSAH 14. it IIISite vegetation consists mostly of grasses , weeds , - and crop residue . Some woody vegetation occurs in bands or Ir clumps in drainage areas or steeply sloped areas . The site appears to have once been used for agricultural crop k purposes . '. A farmstead presently exists on the south side- of ,F. - CSAH 14 , which appears to be Block 2 of the proposed Vogel Iraddition . This area is not a part of this investigation. Proposed site development is eleven residential lots. IConstruction of a roadway for access to these lots and II some lot grading , apparently for the purposes of obtaining borrow material , is the construction activity for which Ithese borings are necessary . From preliminary indications, the proposed roadway will lie at a centerline elevation of slightly above existing ground surface . I . BORING LOCATIONS AND ELEVATIONS The boring locations and depths were generally chosen illby the Owner ' s consultants and communicated to Allied Test Drilling Company by means of a sketch . Insofar as could be determined through field measurements , borings were per- fII ormed as specified . Each boring was originally estimated to be accomplished to a depth of between 5 and 10 feet. IIHowever , progressive results of the investigation lead to a judgment by field crews that some of the borings should r II y be performed to a greater depth (see "Soil Boring Re- ii 4 sults") below . II 11-d 87006 -3- i Refer to the attached drawing for a sketch of boring locations . In addition , boring locations were marked in the field with lath for future reference . These locations should be determined with greater accuracy by survey crews ' of the Owner or his consultant. Ground surface elevation at each boring location was estimated by reference to topograpchic data contained on a preliminary grading plan furnished by the Owner ' s consul- tent. These elevations are shown on boring logs and upon the referenced boring location sketch. Again, ' gain, these eleva- tions tions should be determined with greater accuracy by survey , crews . FIELD INVESTIGATION The borings were performed using the Power Flight Auger (FA) method method of investigation. Refer to the attachment (color-coded blue) for a description of this method . Also contained on that attachment are descriptions 1 of methods of soil classification and groundwater measure- 1 ment . 1 SOIL BORING RESULTS Attached is a log for each boring together with a key explaining terms and entries . The depth of individual lay- ers of soil may vary somewhat from those indicated on the logs due to the inexact nature of auger sampling and the occurence of transition between soil layers . Boring 1 evidences a normal depth of topsoil , below II • 1 1 r4 87006 -4- ' which is a silty clay to termination of the boring. Subse- tquent borings , however , reveal extensive deposits of sur- face organic soil . In Boring 2 , true organic soil extends to 2. 5 feet of depth, and is somewhat organic , but soft , to 5 feet . Basal soil is a soft (5 to 6.5 feet) to stiff (6 . 5 to 10 feet) gray silty clay . The gray color is prob- ably the result of leaching and staining from the overbur- dening organic soils. ' Boring 3 indicates the same general pattern , but with a slightly peaty tendency in the organic soil . That is , ' short partly decomposed fibers of plant vegetation are ob- served in soil samples . Boring 5 , located near the lowest point of the central lowland and at its outlet to Lake ' Riley , shows organic soils to 17. 5 Feet of depth. Soil to 20 feet is a silt loam . Gradually , basal soil becomes a stiff silty clay . Boring 6 shows a reversal of this trend, with organic soils to approximately 10 feet of depth and c gray silty clay basal soil . Boring 4 indicates organic soil to at least 20 feet in depth. This boring was termi- nated without reaching non-organic basal soil due to time ' constraints. Groundwater is evident in Borings 2 through 6 , at ' depths between 2 and 5 Feet . Elevation varies from 868 to 866 , and appears to slope downward towards the surface of ' Lake Riley (approx elev 864) . Organic soils at surface levels often appear stiff. ,• ' However , once groundwater level is encountered, these II 1 1 87006 -5- 'soils become soft . Refer to each individual boring log for a more de- ' tailed description of soils encountered. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are ' based upon interpreted results of boring logs and other data . Because the borings represent a small portion of the site in relation to the proposed area of work , ongoing re- view of construction should be carried out. Actual excava- tions may reveal subsurface soils and conditions of a dif- , ferent nature than those observed in the borings , and groundwater levels may vary with geological influences , in which cases the Soils Engineer may want to be contacted for revised recommendations (see the following "Limita- tions of Investigation") . , 1 . General Site Suitability : The borings generally indicate that the site has ' very severe limitations regarding site suitability for construction of a roadway and possibly single family residences . These limitations include high groundwater combined with significant deposits of organic and soft soils over a majority of the proposed roadway route. A ' roadway built over these soils at the elevations and in the manner shown on the preliminary grading plan would fail almost immediately due to poor support offered by II inplace soil and severe frost action due to the high groundwater combined with the nature of this soil . It II87006 -6- ' is assumed that traditional site correction methods , such as excavation and replacement of some or all un- suitable soil would be either ineffective or prohibi - tively expensive . Alternative construction techniques may be utilized to correct site limitations , however . 2 . Borrow Area : The area of Boring 1 which is apparently to be used I ' as a source of borrow material may not be suitable for ' the intended purpose . This is because moisture sensi- tive material should not be placed over stabilizing fabric . Material in this area is a silty clay , which may be somewhat difficult to work with, especially in cold or wet weather , and requires very thin lifts to ' achieve proper compaction. 3. Embankment Construction: ' Soils upon the site should be stabilized with a geo- textile fabric (also called civil engineering fabric , or ground stabilization fabric) prior to embankment construction . This fabric will act as a barrier to sep- arate subgrade and fill material , as a load distributor 11 to spread wheel loads over wider subgrade areas and somewhat as a structural barrier that will help resist the destructive action of seasonal frost boils. These guidelines are based upon the proposed roadway being a "minimal deformation" system as it will be paved with an asphalt wearing surface . (A high deformation system is capable of tolerating considerable rutting in the 1 { 1- I 87006 -7 I course of its design life . ) Heaviest loads that are likely to occur on the roadway will be during construc- tion , when dump trucks and construction machinery tra- vel over completed or partly completed sections , and during residential construction periods when concrete trucks and on highway tractor-trailer combinations de- liver construction materials. ' The fabric should be of the "high performance" woven variety due to the very poor nature of inplace soils and the very high groundwater table . Recommended prop- erties are as follows : Grab Tensile Strength, lb 300 Puncture Strength, lb 130 Approximate Weight, oz/sqyd 6 Equivalent products are TerraTex HO , Mifafi 600X , Fil- I terweave 400, or equal . Insofar as possible , the existing ground surface should not be disturbed prior to fabric and fill place- ment. This is because the existing vegetation mat may add some support during the construction process and I shortly thereafter . Sharp objects , such as protruding stumps and rocks , should be removed to prevent Fabric puncture . Minor leveling as necessary may be accom- plished by spreading wood chips. Fabric should be laid in the direction of construc- tion traffic and overlapped at least 3 feet (this can be reduced by field sewing of * I Y 8 joints) . It should be anchored onto Firm mineral soil where available. Fabric 1 87006 -8- should extend laterally to a point where a 1 .5: 1 slope Ifrom the shoulder PI meets existing ground surface . Trucks delivering Fill material should backdump onto ' the Fabric. Spread of material should be made with a tracked dozer . Compaction may be achieved by the Ordin- ary Compaction Method according to the Minnesota De- partment of Transportation (Mn/DOT) Standard Specifica- tions For Construction. This method rather than the ' Specified Density Method would avoid excessive compac- tion effort that could disturb the subgrade an undue ' amount. IRoadway Fill should be a non-moisture sensitive ma- terial meeting Mn/DOT requirements for Granular Borrow . Basically , this requires that no more than 20% by weight may pass the .72200 sieve. This lift should be a ' minimum of 12" in thickness. From available preliminary grading data , this may require that the planned roadway ' elevations be raised somewhat . The roadway section should not be paved for one con- /41/4 # struction season after fabric and Fill lacemen Some stabilizing aggregate may be necessary if the roadway is to be used in the meanwhile . During springtime , this ' roadway should be posted to disallow any vehicles over ' a total weight of 4 tons . Any settlements , ruts , etc, should be leveled and/or ' Filled so that the fill thickness minimum is attained. Edges of the roadway construction area should be 1 1 87006 monitored for the occurance of "mud waves", displace- ment of adjacent soil due to subgrade stress which ' causes underlying soil to move away and upwards . Mud waves should not be of significant concern unless they heave above the fill surface . In this event, the office of Allied Test Drilling Company should be contacted for additional recommendations. ' Additionally , the fabric should be installed in ac- cordance with the manufacturers recommendations. ' In areas where extensive organic soils are not pres- ent , such as in the vicinity of Boring 1 , fabric may not be required. In this event, organic soil should be not be present in the upper three feet of subgrade . Below this level , soils of low to medium organic con- t tent may be left in place ; heavy (peaty) soils should be covered with Fabric in accordance with the above recommendations . Excavated unsuitable soils should be disposed of offsite , or in landscaping areas. 11 4 . Pavement Design Values : I The pavement should be designed using a Soil Resis- tance Strength (R-value) of 12 due to the controlling 1 influence of silty clay soils in the vicinity of Boring 1 and the somewhat peaty soils below fabric level in other areas . An example of a pavement structure that would provide a S-ton design is as follows (total II { granular equivalency required = 9.5") : Bituminous Surfacing , Mn/DOT Spec 2341 2" Aggregate Base , Class 5, Mn/DOT Spec 2211 6 I 1 87006 -10- ' Total GE provided = 10.5" ' If a 7-ton design is desired, then a granular euiva- lency of 13" would be required, which could be provided with an overlay to the above section. Other designs based upon other factors , such as ' economy , can be used provided that the above guidelines are followed . ' The roadway should be seasonally posted for s prang- ' time road restrictions in accordance with Minnesota Statutes and the above design limitations . ' 5. Culvert Installation: Special attention should be paid to pipe culvert in- stallations that appear to be necessary on this pro- ject . Past experience indicates that culverts placed upon subsoils of the type and extent evidenced here tend to sink into unprepared subgrade , resulting in Frequent replacement or adjustment , pavement patches , and depressions in the interim . Spot excavations to mineral basal soil and refilling for the purpose of providing a stable pipe culvert Foundation would tend ' to accomplish the opposite effect , however . That is , while the culvert vicinity remains stable , adjoining roadway sections would otherwise uniformly heave and subside with changing seasons . To mitigate this situation , excavations as necessary For pipe culvert installation should be performed into i existing soil . The geotextile Fabric should be laid in w - '' 11 87006 -11- , two thicknesses 30 Feet either side of culvert center- line, with no roll end joints present in this vicinity . , LIMITATIONS OF INVESTIGATION The Soils Engineer has prepared this report in ac- cordance with generally accepted soils engineering prac- tices . Because the borings represent only a small portion of the total site and for other reasons , Allied Test Drilling Company does not warrant that the borings are ' necessarily representative of the entire site but only of the boring locations at the time of investigation. No warranty of the site is made or implied. The scope of this report is limited strictly to es- tablishment of soil profile together with only those con- clusions expressly made . The site investigated is not certified with respect to any requirements such as buil- ding codes , local or state ordinances , federal rules and regulations , etc , which may or may not be applicable . Allied Test Drilling Company has backfilled and com- pacted all boring holes as well as possible under then ex- isting conditions . However , some continuing settlement may ' occur if construction does not take place in the near fu- ture . The Owner should check boring holes (frequently at ' First, then after each chance of season) For signs of set- tlement. Any settling that does occur should be back- 11 Filled , preferably with a free-Flowing granular material . II This monitoring should continue for at least one season until no additional settlement is evidenced. I 87006 -12- Samples of soil from the borings will be retained in the office of Allied Test Drilling Company for a period of 1 90 days from the date of testing. After 90 days , the Y � sem- ipies may be discarded unless a request is received to re- tain them for a longer period. ENGINEER 'S CERTIFICATE ' I hereby certify that this plan , specification or re- port 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 . ALLIED TEST DRILLING COMPANY Patrick J Hines , PE Date Registration No 12086 I 1 i 1 I 1 1 1 1 1 1 1 1 1 i 1