07-0276 Shea Carr 060608HEA
ARRJEWELL~~~.
June 6, 2008
Mr. Jim Gibson, P.E.
Development Review Engineer
City of Yelm Community Development Department
P.O. Box 479
Yelm, WA 98597
Re: Peer Review -Site Construction Documents
Yelm RV/Boat and Mini-Storage
Dear Jim:
Per your request, Shea, Carr & Jewell, Inc. has performed a peer review of the Yelm
RV/Boat and Mini-Storage engineering construction plans and stormwater drainage report.
Our comments are as follows:
Storm Drainage Report:
1. Storm Drainage Report Section 2 -The minimum requirements listed do not appear to
follow the requirements per the 1992 DOE Manual Section I-2.4 New Development and
Redevelopment -Application of Minimum Standards. Most of the main points have been
identified but not in the same order or same title. It would appear, perhaps, another
manual may have been used to identify the minimum requirements.
2. Storm Drainage Report Section 2 - It is stated that Construction stormwater Pollution
Prevention is not required because all runoff is infiltrated. It is correct that the DOE
would not require a NPDES General stormwater Permit for sites with 100% infiltration
and, therefore, a SWPPP would not be required. However, construction stormwater
pollution prevention is always applicable despite the method of runoff disposal. Each
site will still require construction entrances to prevent soil track out, silt fences to
contain and filter drainage, inlet protection to prevent sediment from clogging the
conveyance systems, etc. Please revise the drainage report to include a brief section on
erosion control requirements.
3. Storm Drainage Report Section 2 - It is stated that source control pollution controls are
not required. Source control is typically always required. Trucks and/or construction
equipment could have oil leaks while on-site, building construction typically will require
storage of products such as paint and solvents, etc. Please revise to include a brief
section on requirements for source control prevention during construction.
4. stormwater Drainage Report Section 2 -The operation and maintenance information is
required to be part of the drainage report. Please include.
RE.f's'~111~,
JUN ~' 9 ~~nq
2102 Carriage Drive SW, Bldg. H Office 360.352.1465 www.5heacarrJewell.com
Olympia, WA 98502 Fax 360.352.1509
HEA
ARR~EWELL..
Mr. Jim Gibson, P.E.
June 6, 2008
Page2of7
S. Storm Drainage Report Section 4 -Please provide more discussion of how the drainage
system design provides the required amount of water quality and quantity control.
Please relate the manual requirements to what has been provided. Absolutely no
information has been provided to allow evaluation of the design and how it meets the
requirements of the stormwater manual. At minimum, please provide:
• The assumed rainfall depth for each storm event.
• A discussion about the water quality system proposed including how sizing
was established and relate sizing back to manual requirements.
• Calculations of the 6 month design flow and/or volume used to size required
water quality systems.
• Sizing calculations for water quality system.
• A discussion about the streambank erosion control system proposed including
how sizing was established and relate sizing back to manual requirements.
• Calculations demonstrating the required size and provided size of streambank
erosion facilities.
6. Storm Drainage Report Section 4 -Please provide all of the stormwater model input and
output information demonstrating that the manual requirements have been met. It is
not possible to evaluate the storm drainage design of the porous asphalt without this
information.
7. Storm Drainage Report Section 4 -What portion of the asphalt section is providing
treatment? Please indicate where treatment is occurring and provide computations
indicating the volume provided within this area. Further, please provide information on
the required volume for the treatment portion of the section. A summary of these
calculations including model information needs to be provided.
8. Storm Drainage Report Section 4 - 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. A summary
of these calculations including model information needs to be provided.
9. Storm Drainage Report Section 4 -Per Section III-3.6.8 of the 1992 DOE Manual, the
porous asphalt system shall infiltrate the 10 year storm in 24 hours and the 100 year
storm in 48 hours. Please provide calculations demonstrating the required drawdown
has been provided..
10. Storm Drainage Report Section 4 -Per Section III-3.6.7 of the 1992 DOE Manual, the
porous asphalt system shall infiltrate the 6 month storm in 24 hours. Please provide the
calculations demonstrating this drawdown has been provided.
il. Storm Drainage Report Section 4 - It is indicated that the pervious asphalt alone will
provide the required water quality treatment. However, according to Section III-3.6.7 of
the 1992 DOE Manual, a pretreatment BMP must precede the pervious asphalt. Please
review this section and revise the design to meet all of the requirements.
12. Storm Drainage Report -Excessively drained soils are not appropriate for use as a water
quality treatment BMP (see Section III-3.3.3 of the 1992 DOE Manual). Typically, if an
infiltration system is appropriate for use as a water quality system, it is not appropriate
for use as the streambank erosion control system. Please review this section and revise
the design to meet all of the requirements. The geotech report recommends 20 inches
Mr. Jim Gibson, P.E.
HEA June 6, 2008
ARR~EWELL Page 3 of 7
per hour for design which is in excess of what is recommended by the Manual for water
quality infiltration.
13. Storm Drainage Report Section 4 -Per Section III-3.6.7 of the 1992 DOE Manual,
porous asphalt is typically only recommended for certain traffic loading conditions.
Given the nature of the site, it is expected that large, heavy vehicles will be traversing
the pavement section (RV's, moving trucks, large trucks pulling boat trailers with boats,
etc.). Please provide a geotechnical report supporting the use of pervious asphalt for
this application and that provides a recommended minimum thickness for vehicle
support.
14. Storm Drainage Report Section 4 -This section should include a summary of the
infiltration rate that has been used for stormwater sizing. It should also include an
estimate of the high groundwater elevation as provided by a hydogeologic report. The
bottom of the infiltration systems shall be a minimum of 6 feet from the estimate high
groundwater elevation per the SEPA conditions. If this cannot be provided, please
include a discussion summarizing the results of the groundwater mounding analysis.
15. Storm Drainage Report Section 4 -Please address the drainage path runoff will take if
the pervious asphalt were to clog. It appears likely the buildings may flood if this were
to occur.
16. Storm Drainage Report Section 5 -Please provide a discussion on required erosion
control measures including requirements for installation and inspection.
17. Storm Drainage Report Section 6 - It is not clear why a groundwater mounding analysis
has been provided. Is the bottom of the infiltration facility less than 6 feet from the
estimated high groundwater depth? If so, please include a discussion regarding this
within the groundwater mounding analysis report. In addition, the 1992 DOE Manual
does not provide guidance on groundwater mounding. Therefore, groundwater
mounding analyses should follow the methodology currently recommended by DOE, not
criteria of Thurston County.
18. Storm Drainage Report Section 6 -The mounding analysis that has been provided is
incomplete. The appendices shall also be included.
19. Storm Drainage Report Section 7 -Please provide operation and maintenance
information for the proposed stormwater facilities.
Please note, the drainage report that was provided was incomplete and difficult to follow.
Absolutely no calculations were provided to indicate that the proposed stormwater facilities
meet the requirements of the 1992 DOE stormwater Manual. What little information has
been shown clearly indicates that the stormwater design proposed is unacceptable with
regards to water quality. Further, a groundwater mounding analysis has been provided but
with no explanation. The drainage report should discuss why there was a need for
mounding as the mounding analysis does not provide this information. In addition, the
groundwater mounding analysis itself is incomplete (appendices not included) and difficult
to follow. It is based on a Thurston County Drainage Manual requirement rather than a DOE
requirement. All stormwater design in the City of Yelm shall be based on the 1992 DOE
Manual. If that manual does not address an issue, then the current DOE Drainage Manual
HEA
ARRJEWELL,~
Mr. Jim Gibson, P.E.
June 6, 2008
Page 4 of 7
shall be followed. Overall, it would seem that the drainage system proposed will not work
for the site conditions and shall be revised. Please ensure that all future drainage reports
that are submitted are complete and contain all required information to adequately review
the proposed drainage systems.
Construction Plans:
All Sheets:
The following comments apply to all sheets:
20. Some minor redline comments have not been called out in the letter but need to be
addressed in the revised plans.
21. Please revise the approval block to read Development Services Engineer instead of
Director of Public Works.
22. The plans as currently shown are not stakable. Structure location information needs to
be tied to something such as a benchmark.
Sheet i of 7:
23. The site plan review conditions of approval need to be on the cover sheet. Please revise
to include the SPR conditions in addition to the SEPA conditions.
24. The existing legend shows the same line type for several existing facilities. It appears
that a layer may have been turned off with a letter for each type of facility. Please
revise.
Sheet 2 of 7:
25. An existing sanitary sewer line is indicated but the line shown is unclear. Also, please
indicate the size of the existing sewer line.
26. Please indicate the size of the existing water main shown.
27. The construction entrance needs to be a minimum of 100 feet long. Please revise the
plan and corresponding notes.
Sheet 3 of 7:
28. Revise the construction entrance detail to indicate a minimum 100 foot length.
29.One of the main causes of failure of pervious paving systems is clogging. They are
especially susceptible to clogging during construction. Please include notations
regarding prevention of sedimentation onto the pervious asphalt section once installed.
Also, includes notes regarding required cleaning if sedimentation or spills occur.
30. An inlet protection detail and notes are provided but no inlet protection is shown on the
plans. Is inlet protection to be provided? If so, please indicate the location.
HEA
ARRJEWELL,,.
Sheet 4 of 17:
Mr. Jim Gibson, P.E.
June 6, 2008
Page 5 of 7
31. Please provide proposed contours in addition to spot grades. Although the site is fairly
flat, it is necessary to show the contours to demonstrate how proposed grading will tie
back to existing contours. It will also demonstrate areas of steep grading. Steep
grading is of concern along Rhoton Road. It appears that a fill slope in excess of 3:1 will
be required between the building (FFE 332) and the new right of way line (elevation
329).
32. The pervious asphalt is shown to be directly adjacent to the buildings. According to
Section III-3.6.7 of the DOE Manual, pervious asphalt shall be 20 down slope of any
building. Please revise.
33. The proposed asphalt paving section shows a sand base to act as the water quality
treatment layer. This suggests that the proposed pervious asphalt section proposed
may be based on the requirements specified in the LID Technical Guidance Manual for
Puget Sound. If the design criteria of that manual are proposed, then the sizing
methodologies must also be followed including using a continuous simulation model for
sizing. The storm drainage report must address all of the criteria specified in this
manual for both the water quality and water quantity sizing. The criteria for the 1992
DOE Manual may not be mixed with the criteria for the LID Manual. Please select one
design criteria and follow all of the requirements including sizing calculations etc.
34. Infiltration facilities may not be located within the 100 foot well protective radius. The
pervious asphalt is within this radius area. Please revise.
35. The driveway entrances are shown as pervious asphalt. Will these be pervious or
standard? Given the slopes that are shown, it would seem that standard asphalt would
be more appropriate.
36. Please show proposed re-grading of existing ditch including proposed contours and
required cross section.
37. With the grades shown at the entrances, the proposed culverts will either be within
inches of the top of asphalt or will be a speed bump within the driveway. Further, the
pipe would also be within the paving section for either the pervious or standard paving
section. Please revise the proposed grading to accommodate the culverts. Be sure to
also accommodate the proposed pavement section.
38. Please provide a detail of the roof drain splash blocks proposed. Currently, the drive
aisles between buildings are about 25 feet wide. The splash blocks will presumably
encroach into this width. Please show that the splash blocks will not impede traffic flow
between buildings.
39. How will solid waste be handled on-site? According to SPR Condition of Approval #10, a
refuse collection area is required. Please revise the plan to include an area for refuse
collection per the SPR condition.
40. The sidewalk ramp adjacent to the handicap parking stall requires a minimum 5 foot
landing beyond the ramp. The ramp shown only has a 3 foot landing. Please revise.
HEA
ARR~EWELL,M
Mr. Jim Gibson, P.E.
June 6, 2008
Page6of7
41. Please provide a detail of the proposed handicapped ramp at the handicapped parking
stall.
42. Per the spot grades and slope arrows shown, it appears that the low spot on the south
end of the site is at the joint between the standard pavement section and the pervious
paving section. As such, the runoff from the standard paving section will sheet flow to
the low spot and will then have to pond before it will reach the pervious asphalt area.
Please revise.
43. There are conflicting slopes in the parking area adjacent to the office. On one side of
the drive aisle, the slope is to the east. On the other side it is to the west. Therefore
the cross slope of the drive aisle will vary which may be awkward for drivers.
44. There are a few parking stalls in the area of the standard paving section that appear
substandard. Please review the City of Yelm requirements for angled parking stall
dimension requirements and revise.
Sheet 5 of 10:
Water
45. As a note, the City of Yelm allows PVC pipe for water mains of 8 inches. Please consult
the City of Yelm Development Guidelines for specific requirements.
46. Per City of Yelm Standard Detail Number 6-7, the 6 inch gate valve for fire hydrant
assemblies shall be FLxMJ. Please revise all notations indicating the gate valve shall be
FLxRJ to FLxMJ. Further, the hydrant notations also indicate that the 6 inch pipe shall
be RJ. RJ is a joint reference and would not be applicable on a pipe notation. Please
revise.
47. A gate valve on the main line is not required for fire hydrant connections. The 8 inch
gate valves referenced can be removed.
48. The minimum required width for the water line easement is 15 feet, please revise.
49. A water service connection is not shown for the office building. Please show the
domestic water service, the water meter, and the required backflow prevention device.
Also please include appropriate details for these items on the detail sheet.
50. Is irrigation proposed for landscaping? If so, please show the required irrigation meter
and appropriate backflow prevention device.
51. The water line stationing needs to be tied to something such as a monument in order to
be stakable.
52. Fire hydrants are proposed directly adjacent to the buildings. Typically they should be
located away from the building to allow safe access should that building be on fire.
Please consult the applicable fire code for hydrant placement.
~HEA
ARRJEWELL,:
Mr. Jim Gibson, P.E.
June 6, 2008
Page 7 of 7
Sewer
53. Please provide station information for all structures from the STEP tank to the mainline.
(Note -stations shall be tied to something such as a monument.)
54. Please indicate the STEP tank size on this sheet.
55. It would appear from the invert elevation provided that the proposed STEP tank will be
within the proposed pervious asphalt paving section. Please revise so the top of the
STEP tank does not extend within the proposed stormwater management area. Please
note that the maximum allowable depth is 5 feet from invert to finished grade.
56. The 2 inch STEP force main pipe shall be PVC IPS 1120 SDR 21 Class 200 pipe. Please
revise.
57. A hose bib must be installed within 50 feet of the proposed STEP tank. This can be on
the building. Please indicate the location of the hose bib.
58. Please show the location of the Carson box to be installed for the new service line.
Sheet 6 of 7:
59. Please provide the following standard City of Yelm details in addition to those already
included: 6-3 (or applicable detail for required water meter size), 6-6, 6-13, and 6-14.
60. Please provide a water system map.
Sheet 7 of 7:
61. Please provide the appropriate standard City of Yelm detail for float level.
Should you have any questions or comments, please contact me at (360) 352-1465 at your
earliest convenience.
S' cerely,
h ,Carr & Jewell, In .
Amy M ead,
Projec anager
N:\Projects\605 City of Yelm\605-OS Civil Plan Reviews\Phase 20- Yelm RV-Boat & Mlnl-
Storage\Correspondence\060308firstreviewcommentltr.doc