18025 Reply Ltr 1.7.19Engineering
DESIGN ) PERMIT ) MANAGE
January 7, 2019
Tami Merriman
City of Yelm Community Development
105 Yelm Avenue W.
Yelm, WA 98957
tamimCr�velmwa.cov
Re: NPR Recycling Reply to 1� Review Comments
RBE NO. 18025
Dear Tami:
We have revised the civil consGuction plans per the redline comments. Below is our response to each of the comments
listed in order of received on the peer reviewed comment letter and then from the City of Yelm redline markups.
SCJ Alliance Comments
Sheet C0.1
1. Based onthetopographyshown onthe west propertyline itappears thatsomeoff-sitedrainage
is directed to the site in the vicinity of the storm pond. Sufficient contour information is not
shown to determine the extent of this offsite flow. Please provide additional information to
determine if off-site flow is directed to the site. If it is, then this drainage will need to be
addressed.
A berm has been added to ensure offsite flows do not enter the pond. The soils are
extremely well draining and from our site visit, there does not appear to be any runoff onto
the site due fo the well -draining soils.
Sheet C7.1
2. NoteBindicates thatadetailfor the trash enclosure will be provided onsheet Cl.2.Adetail has
not been provided.
Dimensions detail provided.
3. Drivewayaprons are required to beconcrete upto the ROWline.
Driveway aprons along Northern Pacific Rd have been revised to be 6" concrete up to the
ROW line.
4. Is curb proposed along the north side of the pavement? Grading proposed along this
edge seems to assume a curbwould hold drainage from the yard area, bui it does not
.......... is proposed. Ifflows are directed as shown and there is no structure to either
hold the drainage on the asphalt ordirectflowthrough a channel, there will be erosion
between the pavement and the gravel. Please clarify.
An extruded curb has been called ouf in this location.
91 SW 13�^ Street -Chehalis, WA 98532 - (3fi0) 740-8919 - Civilpros@RBEngineers.com
Page 2 of 9
Sheet C7.2
5. A detail is provided for wheel stops for compact stalls, but no compact stalls are
indicated on the site plan. Please clarify.
The concrete wheel stops are now called out on Sheet Cl. i and the detail was revised to show
standard stall.
Sheet C2.1
6. There should be silt fence placed along the property border with Northern Pacific Road.
Based on the proposed grading, there is potential for silty water to get onto the adjacent
road. Silt fence should also be placed along the private road on the west as shown on the
attached.
Silt fence has been revised as requested.
7. There needs to be silt fence along the north property line.
Silt (ante added in the locations requested.
8. The silt fence symbol for the 1,640 feet of silt fence on the east property line is hard to read
and exact location cannot be determined. Based on the grading, the silt fence should be
located along the entire boundary adjacent to development.
Silt fence revised as requested.
9. As all of the drainage facilities are infiltration facilities, the infiltrative pond bottom surtaces
should be protected from silty water during construction. Please clarify how this will be
achieved. Usually inlet protection and silt fence are insufficient to provide sufficient
protection. Notes indicating that infiltrative surtaces be protected from silty waters can be
sufficient.
Construction note added as requested.
Sheet C2.2
lo. Adetailforagrass lined channel has been included onthis sheet but is not noted on Sheet
C2.1. Pleaseclarify.
This has been deleted.
11. UndertheTESC construction sequence, therearemultiple referencesto pervious asphalt.lt
appears this sequence was writlenforadifferent project. Please revise.
Revised as requested.
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Page 3 of 9
Sheet C3.1
12. Is the intent for the yard storage area drainage to sheetflow directly into the V -ditches and
bioretention cells? Per the 2014 DOE Stormwater Management Manual for Western
Washington BMP T7.30, velocities of entering flows must be 1(Vsecond or less to minimize
erosion potential ofside slopes ofthe ditches and bioretention cells. Calculations of expected
velocities should be provided in the drainage report. Ifvelocities exceed 1 ft/second, then a
design modifcation will be needed.
A collecting system has been designed to capture sheet flow runoff and convey to tha bio -
retention system over rip -rap to protect from erosion. Ditch protection and inlet protection
details have been added on Sheet C3.4.
13. Howare therocfdrainage systems beingconnectedtothesitedrainagesystem7
The roof drainage systems are connected to the main drainage system in the respective
basins. A note has been added to the plans to clarify which CB's the downspouts will be
connected.
14. Provide more information on the v -ditch on the east side of the site (as noted on plan). In
addition, this ditch is proposing a 90 -degree turn. It is likelythat this area will erode, and water
will escape the ditch. The v -ditch on the west side has a turn as well. Although this turn is less
severe, it should also be checked to see if velocities will cause flow to erode the ditch at this
turn. Perthe 2014 DOEStormwater Management Manual for Western W ashington BMP C201,
sharp changes in alignment, bends orchanges in grade should be avoided.
V -ditch has been ro-designed and clarified in the plans.
15. It appears that Basin #1 is forthe future road frontage improvements as well as some currently
proposed landscaping. Italso appears that Basin4 is also for the future road improvements and
the landscaped areas. It is understood the road frontages will be deferred as well as related
drainage improvements. What will happen with the proposed landscape area drainage in the
interim? Basin 4 is an especially large area with no plan for drainage flow. It appears that the
Basin 1 drainage will flow onto the adjacent private road and [he Basin 4 drainage will become
part of the Basin 3 drainage. Please address what will happen with Basin 1 and 4 drainage until
such time that the future facilities are constmcted.
Basin #1 and #4 storm systems will be built with this phase to handle storm runoff
16. It is assumed CB#'s 73 and 14 will also be deferred. Please note on the structure table.
These structures are not tleferred.
17. PerChapter5oftheYelmDevelopmentGuidelinestheonlyallowedpolyethylenepipeisADSN-
12 pipe. Please note this on the plans. Other allowed pipe types include PVC, plan and
reinforced concrete, and ductile iron.
All pipes have been called out as ADS N-12 unless otherwise noted.
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Page 4 of 9
18. There are several lines noted on the attached redlines. What are these? Is it some type of
drainage structure? These lines were not legible enough to understand. They show up on
multiple sheets, but they are never noted.
These are grade break lines and the scale has been changed to clarify.
19. Please provide cross section and slope information for all proposed v -ditches. Please provide
ditch lengths as well.
Provided cross secG'on, slopes and lengths.
Sheet C3.2
20. Provide an emergency overtlow for the Basin 2 infiltration pond.
Provided emergency overflow.
21. Outfall protection needs to be added where noted.
Outfall protection added as requested. See Ditch Protection detail on Sheet C3.4.
zz. The note on this sheetforthe gravel indicates thatthe gravelyard shall befine-graded but no
grading information has been provided on this plan. Please clarify.
The existing grades will be utilized. No proposed contours are necessary. Fine grading is
required to smooth the surtace.
z3. The note on thissheet forthegravel indicated tha[CSBC be added as needed. Given the highly
permeable nature of the native soils and the plan to store vehicles in this area, the gravel area
should be hardened sufficiently to prevent direct infiltration and promoie runoff to the
bioretention cells. Therefore, the entire area should becompacted and covered with CSBC of a
uniform depth.
A 6"section of C. S.B.C. compacted to 95% has been added.
Sheet C3.3
24. The information for Section AA for Section 1 does not match information from Section 3 on
Sheet C3.3. The section on Sheet C3.3 shows that the top of the berm separating the
bioretention cell and the infiltration cell comes to a paint and does not have a width. The detail on
Sheet C3.4 shows and 8 -foot wide berm. The overflow spillwaywill not work as designed if the
detail on Sheet C3.3 is correct. The grading plan on Sheet C3.2 seems to show a 3 -foot width.
Please provide consistency between the plan views and cross sections.
Updated cross section detail.
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Page 5 of 9
25. Same as previous comment for the other bioretention cell and infltretion cell internal spillway. The
information shown on the grading plan and various cross sections do not align. Please
correct.
Updated cross section.
26. Bioretentioncellsshould beplanted with morethan grass. Seethe 2014 DOE Manualfor
Western Washington for additional information on planting requirements.
Landscape Architect fo provide planting plan for Bioretention Cells.
Sheet C3.4
27. Itis assumed [hat detail 6 is for the deferred stormwater facilities. If so, then itshould be noted.
The infiltration trench will be installed in this phase.
za. The berm widths noted in detail 1 and 2 do not match the widths noted on Sheet C3.3 details
3 and 4.
Updated cross section detail.
Sheet C4.1
29. The water pipe iscloserthan l0feet to the STEPtank. Please revise.
Line is now 10' from STEP tank.
so. There isanote9shown on the plan but no note9has been provided. Isthisasawcut?
Note #9 has been added to callout sawcdt and pavement restoration.
3t. Restoration ofthe road pavementwhere it will beaffected for utility installation should be noted
on this sheet and details provided including required pavement depth per the road type.
Road restoration callout and detail have been added.
3z. Provide information regarding existing hydrants. Depending on amount and location of existing
hydrants, additional hydrants) may be required to provide sufficientfireprotection.
Three existing hydrants have been called out with Note #10
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Page 6 of 9
General Comments
33. Lawn and landscaped areas shall be restored in accordance with BMP T5.13—Past Construction
Soil Quality and Deplh. Please add the applicable specifications, notes, details, etc. to the plans.
Added soil amendment call out and notes to the plans. See Sheets C2.1 & C2.2.
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Page 7 of 9
Drainage Report:
34. Please provide an operation and maintenance plan and a SWPPP.
A dm# operation and maintenance plan has been prepared and submitted with this letter. The
SWPPP has been added to Chapter 7 of the Drainage Report.
35. Please provideasummaryofcalculation resultsforpondsizingand conveyance sizingwithinthe
main body of the report. Summary of conveyance results should include a comparison of the
.....................
ctualflowtoconveyance capacity.
A summary of facilities is located in Section #5 of the Drainage Report. All conveyance
calculations are located in the Appendix. Conveyance calculations were checked against 100
years #ows. A comparison to full flow capacity is unnecessary.
36. Please provideconveyance calculations forall pipesizes within each basin. Forinstance, only
the 12 -inch pipe was calculated for Basin #2 butthere is also 8 -inch pipe. All pipe sizes for all
basins must have conveyance calculations. This calculation can be limited tothe worst-case
scenario far each pipe size.
All of the worst-case scenario pipes antl V -ditches have been calculated in each basin.
37. Only one v -ditch conveyance calculation has been provided but there are additional v -ditches
proposed. Please provide calculations for all conveyance ditches.
All of the worst-case scenario V -ditches have been calculated in each basin.
3E. The slope of the v -ditch for Basin #2 is identified as 2%. All information for the ditch is not
provided on the drawings but it .............
ppearstoerou500 feet long and have an elevation drop of
roughly 5 feet which would only be a 1 %slope. Please either revise the ditch design to 2 % or
correct the conveyance calculations.
All ditch slopes have been cladtied in the plans.
39. Actual pond elevations instead ofassumedelevations should be usedinthe MGS Flood model.
Using assumed elevations makes it difficult to assess and follow.
Pond elevations have been updated in the MGS Flood model.
40. Please use actual pond dimensions instead of equivalent dimensions for all models.
Actual pond dimensions have been used.
41. Please provide a discussion about emergency overFlow and what would happen with drainage
should itovertlow out of both infiltration cells. A safe path of failure that does not cause the
threat of flooding for neighboring residences or businesses should be discussed.
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Page 8 of 9
An offsite overflow map has been added fo Section k,? of the Drainage Report.
42. Perthegeotechnical report, testpits#1,#2 and#7 which are the pits within thefootprintofthe
stormwater facilities for the Basin #2 pond have evidence of high groundwater at elevations
about 8.5 feet below grade. The proposed infiltration pond bottom is at a depth of about 4 feet
below finished grade. Therefore, the separation between the pond bottom and the high
groundwater is only about 4.5 feet. Per the 2074 DOE stormwater Management Manual for
Western W ashington Section 111-3.3.7, SSC -5, the depth to groundwater must be greater or
equal to 5 feet. Lowerseparationsdown to 3 feet may be allowed but onlywith a groundwater
mounding analysis. Please either revisethe design or provide a mounding analysis.
Raised infiltration and biorefention facilities 1' in this basin.
43. Per comment #1, it appears that off-site drainage is directed to the site. This needs to be
clarified and potentially addressed. This will potentially inFluence the design of the stormwater
facility along this property line.
Added berm to keep /laws out of infiltration facility.
City of Yelm Plan Redline Comments
SheetC0.1
1. The refuse enclosure size was revised to be 8' x 20'.
2. A pedestrian access striping was added from parking to office building.
3. Mail will be delivered to the new office building. A CBU location has been added to the site
plan. See Sheet C1.1
4. Building elevations will be provided by the Client and are not part of this submittal.
5. Site lighting has been added to the cover sheet C0.1.
6. The existing fire hydrants were called out on C1.1 with distance call outs to proposed
buildings. All buildings are less than 250 from a fire hydrant.
7. The storage area will be vehicles void of any liquids as all fluids are drained out prior to
placement in the storage yard. Weare not aware of any additional fire protection required
for the storage area.
a. The Landscape Plans are being revised to show the 8 -foot landscape buffer and perimeter
fencing. Fencing was also added to sheets C3.1 and C3.2.
9. The relocation of the City's gate was added to sheet C1.1.
Sheet C2.1
So. The infiltration swales were moved to provide 10+feet of separation from the property line
and make room for perimeter landscaping.
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Page 9 of 9
Sheet C4.1
11. The main office building will be the only structure connected to the City water and sewer
services.
S2. Redline notes 1 l0 5 were added to the sheet and design noses.
Please proceed with final review oft ivil construction plans.
Sincerely,
Obert W. ar ells PE
President
Cc: Client
Enclosure: 3 copies of revised plans
2 copies of revised final drainage report
CD of all drawings and reports
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