HomeMy WebLinkAboutFile Documents.58 Pitkin Way.0158.2019 (2).ARBK58 Pitkin Way-Minor Design March 12, 2019
502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704 -0311 • Fax (970) 704 -
0313
S OPRIS E N GINEERING • LLC civil consultants
Karen Wing
58 Pitkin Way
Aspen, CO 81611
karenjwing@gmail.com
c/o Bobby Peters
Structural Associates
RE: 58 Pitkin Way, Aspen, CO: Minor Drainage
Job No. 19046
Dear Mrs. Wing:
This letter has been prepared in support of obtaining a Building Permit for work associated with replacing the existing
driveway snowmelt system at 58 Pitkin Way in Aspen, Colorado. Per the City’s Urban Runoff Management Plan
(URMP) a project of this nature is classified as a “Minor Design” project which requires WQCV for the disturbed area
or drain hardscape area to green space. This letter summarizes the existing conditions, the proposed improvements
as well as a discussion of how the project conforms to the intent of the URMP for a “Minor Design” project.
Existing Site Description:
The Project Site is located at 58 Pitkin Way within the City of Aspen. The legal description for the property is: Lot 3,
Pitkin Reserve Subdivision as shown on the Second Amended Plat of Pitkin Reserve Subdivision Bk. 16 at Pg. 15. An
updated existing conditions survey dated March 6, 2019 was performed by SGM and is included as an attachment to
this letter. The existing site is approximately 1 acre and includes an existing residence, landscaping, impermeable
driveway and an extensive open space/lawn area along the southwest side of the residence. The ultimate receiving
river is the Roaring Fork River which lies approximately 450-ft south of the existing residence.
A site visit was performed on February 22, 2019 to evaluate existing drainage conditions associated with the driveway
and surrounding area. Exhibit A has been prepared to provide illustrative support of our findings. In summary, during
our site visit it was determined that the driveway conveys runoff to four different locations. The western portion (Area
A) which consists of about 300 s.f. of driveway conveys runoff down a steep landscaping hillside before entering the
expansive open space/lawn area located along the backside of the residence. The eastern 370 s.f. of existing
driveway (Area B) conveys runoff towards the south over landscaping stairs that run along the east side of the
residence before reaching the expansive open space area along the south side of the residence. The remaining
portion of the driveway (Areas C & D) conveys runoff towards two separate 4-inch ACO trench drains. Two
downspouts were also observed on the north end of the porte cochere. Each of these downspouts daylight into the
landscaping area north of the driveway where runoff is eventually routed to the east trench drain mentioned above.
Several other roof downspouts were observed along the north side of the residence that convey runoff into elevated
landscaping planters adjacent to the residence. Inlets were not observed within these landscaping areas given the
snow coverage however it is not likely that discharge from these downspouts contribute runoff towards either of the
two existing driveway trench drains given the freeboard between finished grade within the planters and top of planter
walls and therefore were excluded from the tributary areas to each of the existing trench drains.
06/20/2019
Reviewed by Engineering
07/16/2019 11:28:14 AM
"It should be known that this review shall not
relieve the applicant of their responsibility to
comply with the requirements of the City of
Aspen. The review and approval by the City is
offered only to assist the applicant's
understanding of the applicable Engineering
requirements." The issuance of a permit based
on construction documents and other data shall
not prevent the City of Aspen from requiring the
correction of errors in the construction
documents and other data.
58 Pitkin Way-Minor Design
SE Job No. 19046
March 12, 2019
Page 2
A follow up site visit was performed on March 6, 2019 to further investigate where the two existing trench drain lines
terminate. This was achieved by televising the lines from each of the trench drain outfall pipes. Upon inspection it
was determined that each trench drain is connected to separate dry wells that are located under the concrete
driveway. Although it was difficult to verify the size and depths of these existing structures the video seems to indicate
that each dry well is 4-ft in diameter and approximately 4-ft deep. No other pipes entering the structure were
observed during the video inspection.
Project Description:
The project includes the replacement of the electric snowmelt system with a hydronic snowmelt system. This will
require removal and replacement of the entire concrete driveway. The existing grades will not be altered. There
might be some slight adjustments to the overall footprint of the driveway to improve some curb returns for vehicle
turning movements however the intent will be to maintain the existing square footage of impervious area.
As mentioned above, and as illustrated on Exhibit A, the driveway conveys runoff to four different locations. This
section describes how each area adheres to the intent of the City’s water quality treatment requirements for a “Minor
Design” project.
The Western portion of the driveway (Area A) conveys runoff to the west down a steep landscaping hillside and then
conveyed over the well vegetated open space prior to entering the Roaring Fork River which complies with the intent
of “green” infrastructure approach to stormwater treatment.
The Eastern portion of the driveway (Area B) directs runoff to the south along the east side of the residence. Once
runoff clears the driveway flows are conveyed over landscaping stairs and patios and then directed over a well
vegetated open space area prior to entering the Roaring Fork River. Again, this meets the intent of the City’s
requirements as conveyance over “green” infrastructure.
The portion of the driveway that conveys runoff to the existing West Trench Drain and ultimately to the West Dry Well
(Area C) was estimated to be 863 s.f.. The total tributary area which includes surrounding landscaping was estimated
to be 1,932 s.f. Table 1 summarizes the resultant required water quality treatment volume for this basin.
The portion of the driveway that conveys runoff to the existing East Trench Drain and ultimately to the East Dry Well
(Area D) was estimated to be 770 s.f.. The total tributary area which includes surrounding landscaping areas and the
roof associated with the porte cochere canopy was estimated to be 1,967 s.f. Table 1 summarizes the resultant
required water quality treatment volume for this basin.
Table 1: Water Quality Summary
Upon review of Table 1 the existing dry wells provide the required water quality treatment volume as outlined within
the City’s URMP. It should also be noted that the estimated available volume within the existing dry wells outlined
06/20/2019
58 Pitkin Way-Minor Design
SE Job No. 19046
March 12, 2019
Page 3
above assumes a depth of 3-ft and not the assumed depth of 4-ft as estimated during the video inspection. The
reduction in depth was used as a conservative approach since obtaining actual depths was not feasible during the
video inspection of the dry wells. Actual sizes and depths will be confirmed during construction.
Based on discussions with the property manager the existing residence has not experienced any adverse effects from
the dry wells and based on the video inspection there were no stains observed on the sidewalls of the dry wells which
suggests that there hasn’t been extended periods of time where the structures have had standing water and therefore
the existing structures seem to be working effectively.
It is our recommendation that, as part of the driveway snowmelt improvements, the existing dry wells be cleaned and
the lids be brought to the surface with grade rings to provide future access for inspection and maintenance purposes.
If you have any questions or need any additional information, please call.
Sincerely,
Jesse K. Swann, PE
Project Manager/Principal
Encl: Existing Conditions Survey, dated March 6, 2019
Exhibit A: Existing Drainage Exhibit
06/20/2019
06/20/2019
PITKIN WAY58 PITKIN WAYMULT-STORY WOODFRAMEDSTRUCTUREOPEN SPACEUPPER PATIOLOWER PATIOEXISTING EASTTRENCH DRAINEXISTINGWESTTRENCHDRAINEXISTING PORTECOCHERE OVERHANGWITH GUTTERS ANDDOWNSPOUTSEXISTINGLANDSCAPESTAIRSEXISTINGHOT TUBEXISTINGBOULDERWALLEXISTINGDOWNSPOUTAPPROX. LOCATION OFEXISTING WEST DRY WELLBURIED UNDER CONCRETEDRIVEWAY; RE. TOSUMMARY TABLEAPPROX. LOCATION OFEXISTING EAST DRY WELLBURIED UNDER CONCRETEDRIVEWAY; RE. TO SUMMARYTABLEEXISTINGDOWNSPOUTAREA C:WEST DRY WELL TRIBUTARYDRAINAGE BASIN; RE. TOSUMMARY TABLEAREA D:EAST DRY WELL TRIBUTARYDRAINAGE BASIN; RE. TOSUMMARY TABLESCLSCLSCLSCLSCLINSTALL EROSIONCONTROL LOG OREQUIVALENT(TYP)CONSTRUCTIONACCESS; RE. TO NOTE14EXISTING LANDSCAPINGBOULDERS WITHLANDSCAPING POCKETS(TYP)Know what'sbelow.before you dig.CallREXISTING CONTOUREXISTING CONTOUR INTERVAL7900EXISTING PROPERTY LINELIMITS OF EXISTING CONCRETE DRIVEWAY TO BE REPLACED(LIMITS OF DISTURBANCE)LEGENDOPRISESNGINEERING, LLC.CIVIL CONSULTANTS19046JOB NO.DATE:03-12-19502 MAIN STREETCARBONDALE, CO 81623(970) 704-0311FAX: (970)-704-0313EXHIBIT AEXISTING DRAINAGECONVEYANCEDESIGNED BYDRAWN BYJS03/12/2019DATEREVISIONC-1.0DRAWING NO.TITLEMINOR DESIGN EXHIBIT
G:\2019\19046 58 PITKIN WAY\CIVIL\CIVIL DWGS\DE\19046-DE.DWG - Mar 12, 2019 - 12:25am
NORTH1 inch = ft.( IN FEET )GRAPHIC SCALE01010201040558 PITKIN WAY
CITY OF ASPEN, COLORADOEXISTING DRAINAGE FLOW DIRECTIONNOTES:1.EXISTING CONDITIONS AND TOPOGRAPHY BASED ON SURVEY PREPARED BY SGM.2.LOCATION OF EXISTING DRY WELLS IS APPROXIMATE BASED ON VIDEO INSPECTION PERFORMED ON MARCH 6, 2019.3.THE UTILITIES AS SHOWN, MAY NOT REPRESENT ACTUAL FIELD CONDITIONS. IT IS THE RESPONSIBILITY OF THE CONTRACTOR TO CONTACT ALL UTILITYCOMPANIES FOR FIELD LOCATIONS OF UTILITIES PRIOR TO CONSTRUCTION.CONTRACTOR MUST UTILIZE "BEST MANAGEMENT PRACTICES" (BMP), TOCONTROL EROSION AND SEDIMENTATION DURING CONSTRUCTION, TO INCLUDE THE INSTALLATION OF INLET PROTECTION AROUND THE NEARESTDOWNSTREAM RECEIVING INLET LOCATED WITHIN THE CITY'S ROW.4.CONTRACTOR IS RESPONSIBLE FOR INSTALLATION AND MAINTENANCE OF ALL TEMPORARY EROSION CONTROL MEASURES.5.DUST CAUSED BY EXCAVATION, TOPSOIL REMOVAL OPERATIONS, OR ROAD BASE PLACEMENT SHALL BE CONTROLLED BY THE CONTRACTOR AT HIS EXPENSE.THE ENGINEER OR CITY MAY REQUIRE THE CONTRACTOR AT ANY TIME TO DISCONTINUE CONSTRUCTION ACTIVITIES UNTIL DUST CONDITIONS ARE REDUCEDTO THE CITY'S SATISFACTION.6.THE CONTRACTOR WILL BE REQUIRED TO FURNISH AND APPLY A DUST PALLIATIVE ON THE SITE AS DIRECTED BY THE CITY. DUST PALLIATIVE MAY CONSISTOF WATER OR A NON-POLLUTING SOLUTION. SPREADING OF WATER OR WATER MIXTURE SHALL BE DONE WITH ACCEPTABLE SPRINKLING EQUIPMENT. ALLDUST CONTROL SHALL EXTEND BEYOND THE CONSTRUCTION AREA PROPER TO THE SIDE STREETS ENTERING AND EXISTING THE PROJECT, WHERE MUD ANDDIRT FROM CONSTRUCTION EQUIPMENT, AS WELL AS LOCAL TRAFFIC, MAY GET ONTO THE SIDE STREETS. CLEANUP OF THESE AREAS WILL BE REQUIRED ASNECESSARY OR AS DIRECTED BY THE CITY/OWNER/ENGINEER.7.BMP’S SHALL BE INSTALLED BEFORE ANY EARTH DISTURBING ACTIVITIES COMMENCE.8.SEDIMENT CAUSED BY ACCELERATED SOIL EROSION SHALL BE REMOVED FROM RUNOFF WATER BEFORE IT LEAVES THE CONSTRUCTION SITE.9.THE CONTRACTOR SHALL INSPECT THE CONSTRUCTION SITE (INCLUDING ALL BMP’S, STORAGE CONTAINERS, AND CONSTRUCTION EQUIPMENT) A MINIMUMOF EVERY 14 CALENDAR DAYS AND WITHIN 24 HOURS AFTER A PRECIPITATION EVENT OR SNOW MELT THAT MAY CAUSE SURFACE EROSION.10.THE CONTRACTOR SHALL KEEP A RECORD OF ALL INSPECTIONS ON SITE AND AVAILABLE FOR REVIEW BY CITY STAFF. INSPECTION REPORTS MUST IDENTIFYANY INCIDENTS OF NON-COMPLIANCE WITH THE TERMS AND CONDITIONS OF THE PERMIT.11.STRAW BALES SHALL NOT BE USED FOR PRIMARY EROSION OR SEDIMENT CONTROL (I.E. STRAW BALES MAY BE USED FOR REINFORCEMENT BEHINDANOTHER BMP SUCH AS SILT FENCE).12.BMP’S INTENDED FOR SHEET FLOW SEDIMENT RUNOFF SHALL BE PLACED PARALLEL TO THE SLOPE.13.ALL BMP’S SHALL BE CLEANED WHEN SEDIMENT LEVELS ACCUMULATE TO HALF THE DESIGN OF THE BMP UNLESS OTHERWISE SPECIFIED.14.THE CONTRACTOR IS RESPONSIBLE FOR PREVENTING TRACK-OUT ONTO CITY STREETS AND/OR PRIVATE SHARED ACCESS WAYS. IF TRACK-OUT DOESOCCUR, THE CONTRACTOR SHALL IMMEDIATELY SWEEP THE STREET OF DEBRIS.15.ALL PORTA-POTTY STRUCTURES MUST BE FIRMLY SECURED WITH #4 REBAR ANCHORS OR EQUAL. MUST BE PLACED AWAY FROM FLOW LINES OF STREET,SWALES, RAIN GARDENS & AWAY FROM INLETS.16.A CONCRETE WASHOUT AREA (CWA) MUST BE PROVIDED AND ROUTINELY MAINTAINED. NO WASHING OUT OF CONCRETE TRUCKS OR WASHING OFSWEEPINGS FROM EXPOSED AGGREGATE CONCRETE INTO STORM DRAINS, OPEN DITCHES, STREETS OR STREAMS IS ALLOWED.17.EXCESS CONCRETE IS NOT ALLOWED TO BE DUMPED ON-SITE, EXCEPT IN DESIGNATED TEMPORARY CONCRETE WASHOUT AREAS (CWA).18.ON-SITE TEMPORARY CONCRETE WASHOUT FACILITIES WILL BE CONSTRUCTED AND MAINTAINED IN SUFFICIENT QUANTITY AND SIZE TO CONTAIN ALL LIQUIDAND CONCRETE WASTE GENERATED BY WASHOUT OPERATIONS AND MUST BE CLEANED OUT OR REPLACED ONCE THE WASHOUT IS 75% FULL.TRIBUTARY BASIN TO EXISTING DRY WELLSSEDIMENT CONTROL LOG INSTALLATION NOTESSEDIMENT CONTROL LOG MAINTENANCE NOTESSECTION A - AUSE TWO STAKES 1 1/2 ' x 1 1/2 " xSUFFICIENT LENGTH TOEMBED AT LEAST 12" INTO SOIL AT EACH ENDOF LOGUSE A STAKE EVERY 24" AT ALTERNATE 90DEGREEORIENTATION THROUGHOUT THESEDIMENTATION LOG.SEDIMENTATION LOG - 12" MIN. DIAMETERSTAKE AT 90DEG.TO EACHOTHERWETLANDS ORFEATURESREQUIRINGPROTECTION(NOT TO SCALE)1.SEE PLAN VIEW FOR: LOCATION OF SEDIMENT CONTROL LOG.2.SEDIMENT CONTROL LOGS SHALL BE INSTALLED PRIOR TO ANY LAND DISTURBING ACTIVITIES.3.SEDIMENT CONTROL LOGS SHALL CONSIST OF STRAW, COMPOST, EXCELSIOR OR COCONUT FIBER.4.NOT FOR USE IN CONCENTRATED FLOW AREAS.5.THE SEDIMENT CONTROL LOGS SHALL BE TRENCHED INTO THE GROUND A MINIMUM OF 2-INCHES.1.THE SWMP MANAGER SHALL INSPECT SEDIMENT CONTROL LOGS DAILY, DURING AND AFTER ANYSTORM EVENT & MAKE REPAIRS OR CLEANOUT UPSTREAM SEDIMENT AS NECESSARY.2.SEDIMENT ACCUMULATED UPSTREAM OF SEDIMENT CONTROL LOGS SHALL BE REMOVED WHEN THEUPSTREAM DEPTH IS WITHIN 12 THE HEIGHT OF THE CREST OF LOG.3.SEDIMENT CONTROL LOGS SHALL BE REMOVED AT THE END OF CONSTRUCTION, ONCE PROPERVEGETATION HAS BEEN ESTABLISHED. IF ANY DISTURBED AREA EXISTS AFTER REMOVAL IT SHALL BECOVERED WITH TOPSOIL AND REVEGETATED/STABILIZED IN A MANNER APPROVED BY THE LOCALJURISDICTION.SEDIMENT CONTROL LOGPROPOSED SEDIMENT CONTROL LOGSSCLEXISTING DRY WELL WATER QUALITY VOLUME SUMMARYAPPROX. LIMITS OF OPEN SPACE/LAWN AREAREDUCED FOR ATTACHMENT TO REPORT(APPROX.HALF SIZE)06/20/2019