05-0750 Review No. 1 083007
City of Yelm
Community Development Department
105 Yelm Avenue West
P.O. Box 479
Yelm, WA 98597
October 4, 2007
Clint Pierpoint
KPFF Consulting Engineers
4200 6th Ave Suite 309
Lacey, WA 98503
RE: Tahoma Terra Fairway Multi Family – SPR 05-0750-YL
Initial Review of Site Construction Drawings
Mr. Pierpoint:
The City of Yelm has completed the initial review of the proposed 3 multi-family residential buildings with a total of 48 units on 5.04 acre site. Your application included:
Transmittal Letter
11x17 Plans
Full Size Plans
Civil Plan Review Application
Drainage Report
We have reviewed the plans for compliance with the City of Yelm Development Guidelines, the DOE Stormwater Manual and general standards of civil engineering practice. The following
comments need to be addressed before the plans may be approved for construction. Our comments are summarized below:
Storm Drainage Report:
Many of the comments below may or may not apply depending on the design manual that the designer ultimately utilizes.
Storm Drainage Report – Section 3 states that the soil report indicates that an infiltration rate of 6 to 20 inches is appropriate for the on-site soils. Although a rate of 2 inches
per hour is used for design (with appropriate safety factor), the soil report rates indicate that the on-site soils have too high an infiltration rate to be used as a water quality device.
Per the Low Impact Development Manual, a separation and water quality treatment layer should be included. According to this manual, it appears this sand layer would need to be approximately
18 inches thick. This could increase the total pavement section to a point where the roadway section would need to be built in a manner that would preserve 3 feet of separation between
the bottom of the pavement section and the high water table.
Erosion Control Plan – Please provide a section on what should be done should sediment be tracked on to pervious asphalt and how to prevent this occurrence.
Storm Drainage Report Appendix 1 – This entire section as it relates to the pervious asphalt design appears to mix the requirements of the 1992 DOE Manual with the requirements of the
Low Impact Design (LID) Manual. A mixture of requirements will likely result in a substandard design.
Storm Drainage Report Appendix 1 – There is a computational error in determining the value of f. One inch per hour equates to 0.083 ft per hour, not 0.042 ft per hour. Subsequent computations
are likely to be effected by this error.
Storm Drainage Report Appendix 1 – Please provide the Storm Shed input and output information. It is not possible to evaluate the storm drainage design of the porous asphalt without
this information.
Storm Drainage Report Appendix 1 – The computation for pervious pavement sizing is incomplete for its use as the stormwater treatment device. No computations have been shown indicating
the amount of treatment volume provided. Please note that this volume should be in addition to the volume required for storage.
Storm Drainage Report Appendix 1 – The computation for pervious pavement sizing is incomplete for its use as the storage reservoir. No computations have been shown indicating the volume
provided within the pervious asphalt base course. Further, no information has been provided on the required volume for the pervious asphalt base course. The only volume indicated is
45,138 cubic feet. This volume is not available within base course. A summary of these calculations including model information needs to be provided.
Storm Drainage Report Appendix 1 – Please provide the WWHM model output for the sediment trap sizing computations.
Storm Drainage Report Appendix 1 – Sizing computations for the sediment traps shall be based on the criteria of the 1992 DOE Manual and require modeling to determine the required volume.
Please revise the computations to conform with Section II-5.8.6 of the 1992 DOE Manual.
Storm Drainage Report Appendix 2 – Per Figure III-3.18 of the 1992 DOE Manual, the typical section for porous asphalt paving includes a porous asphalt course, a filter course, and a
reservoir course. Please revise the section provided to include the filter course if the DOE Manual will be the source of design computations. Otherwise, follow the recommendations
of the section per the LID manual.
Storm Drainage Report Appendix 5 – The geotechnical investigation does not appear to make a recommendation regarding infiltration rates. The main storm report indicated that rates of
6 to 20 inches per hour were recommended. Please provide a revised geotech report indicating the recommended rates.
Construction Plans:
All Sheets:
The following comments apply to all sheets:
Some minor redline comments have not been called out in the letter but need to be addressed in the revised plans.
Please add Conditions of Approval on cover.
Sheet 3 of 19:
The site plan conditions of approval require that the pathway around the multi-family units shall connect to the pathways provided throughout the open space. The pathways shown don’t
appear to meet this intent. There are a couple of pathways that appear to end abruptly just outside or inside the buffer area. In addition, one pathway appears to conflict with a
proposed retaining wall. It is unclear from the grading plan whether this pathway will be possible to construct from the grading.
The conditions of approval also require a pocket park be located on the site plan. Please indicate where this pocket park is to be located.
Please show pavement markings details with offset and stationing on plans.
Please include call outs for sidewalks with dimensions on plans.
Please show and call out access point on Terra Valley right of way. Also show concrete driveway accessing from cul-de-sac at Terra Valley.
Please include curb ramps and Wsdot details.
Callout dumpster locations on the plans.
Call out the mail box cluster locations and get approval for locations from Yelm Postmaster.
Call out edge of pavement.
Sheet 4 of 19:
The site plan conditions of approval indicate that the Oregon White Oak Trees located in the proposed open spaces shall have chain link fencing installed around the tree drip line.
This fencing should serve as the temporary protection during construction. These fences shall be installed as part of the erosion control preparation. Please show these fences on the
erosion control plan. Please also indicate the trees that shall be retained. A detail of the fence should also be provided.
Please show the grading associated with the construction of the northern most sediment trap. This trap is proposed along a slope and it is not readily apparent whether it can be constructed
in this area.
The interceptor ditches must be installed outside the wetland buffer. It appears that grading of these swales will cause a fair amount of disruption of the wetland buffers. No disruption
within the buffer areas will be allowed.
Sheet 5 of 19:
Please indicate the slope required for the interceptor ditch.
Sheet 6 of 19:
This sheet was not provided in the plan set.
Sheet 7 of 19:
See the drainage report comments regarding porous asphalt section.
Sheet 8 of 19:
It appears that the grading between Building #2 and #3 will create direct drainage to the retaining wall. Please add provisions to the plans for the conveyance of the water.
Please label all proposed contours.
The drainage report indicates that the roof drainage will be collected and directed to the base course of the pervious asphalt. Please provide details and/or notes illustrating the
design for the roof drainage.
The grading shown does not address the proposed pathways. There are a few areas where the proposed pathways would be at too steep of a slope to be traversable. Please show pathways
on the grading plan and show the associated grading.
The wall along the entrance drive may encroach in to the wetland buffer. Construction equipment will not be allowed within the boundary of the buffer. Any construction that occurs
within the buffer will require the use of hand tools.
Pervious asphalt can have a tendency to clog if not properly installed or maintained. The current drainage system has no backup or emergency overflow system in place in case of failure.
During our discussion we agreed on having a reserve area for a stormwater pond if the asphalt area clogged up. Please show this area as a reserve area for stormwater and also show
how the stormwater would be conveyed to this location.
Sheets 9 thru 15 of 19:
Label the separation distance between water and sewer (all water and sewer sheets). A minimum of 10 feet of separation needs to be provided.
The minimum cover for water lines is 42 inches. Please revise all water plans.
It appears deflection will be required to construct the water lines as shown. The City of Yelm does not allow pipe deflection. Please revise design to eliminate all deflections shown.
The proposed fire hydrants and fire department connection locations for all three buildings need to be relocated to the edge of the parking lane.
Please provide the standard City of Yelm Detail for an appropriate back flow prevention device for the domestic services.
The domestic and fire services are unclear for all buildings. The 6 inch lines that connect to the 10 inch line have fire hydrant and domestic service connections. Please clarify which
is main line and where the fire line begins for all buildings.
Please indicate where the post indicator valve will be for the fire service for each building.
Please indicate the size of the fire lines in and out of the buildings.
Please indicate the size of the domestic water line, water meter, and backflow preventer for the domestic service for all buildings.
Please label the proposed easement for the water line.
Please indicate the connection type for all fittings – FL, FLxMJ, etc.
Note #2 is labeled as a 90 degree bend but appears to be a 22 ½ degree bend.
Please add a gate valve on the Tee at Note 17.
The developer is responsible for the cost of the fire hydrant locks and the City of Yelm will order and install them.
The water connection to the north appears to require excavation within a wetland buffer from the wetland located south of the golf course. (GeoData). It appears that the encroachment
in to the buffer for water line construction will require tree removal and related buffer impacts.
Thrust Blocking is required at all fittings and in-line valves. Please show thrust blocks on plans.
Sheet 16, 17 and 18 of 19:
The plan view and profile view show different numbers for the length of the STEP main.
A gate valve is needed at the connection point to the existing sewer main.
An Air Release Assembly is required at the high point approx STA # 2+00.97 of this main line
An “End of Line Clean-Out” is required at the end of this main line.
The Step Table item # 10 refers to a detail on sheet C7.2 for service Connections. This is not on sheet C7.2
The Step Table item #12 refers to City of Yelm Std. Drawing 7-12, for service connections. 7-12 is a drawing of an Air Release Assembly.
Please show the location of all Pump Control Panels.
Please show the location of hose bibs within 50 feet of each tank for servicing tanks etc.
Please show all Side sewers and Clean-outs.
All Side Sewers enter the tanks at the end of the tank, not the side.
Details need to be shown for Duplex pump systems not simplex.
Sheet 19 of 19:
There are no landscaping details for the site. The plan submitted appears to contain only the tree preservation plan, showing oak trees to be saved or removed. Please add a detailed
landscaping and irrigation plan for review and approval.
Please review and revise the plans to address the above referenced comments. When the project is resubmitted you will need to submit 4 sets of plans, 2 stormwater reports. The project
engineer should include a written response with the resubmittal, indicating how all the review comments above have been addressed or responded to. This will significantly expedite our
review of the project. If you have any additional questions or comments please do not hesitate to call or contact me at jimg@ci.yelm.wa.us.
Community Development Department
Respectfully,
Jim Gibson P.E.
Development Review Engineer
cc: Tahoma Terra Phase 3-8, LLC