HomeMy WebLinkAboutResponse to Staff CommentsResponse to Engineering Comments No. 1
1. There is a pending LOMR by Walter P. Moore dated November 6, 2009 which includes revisions
to this portion of Spring Creek. This should be used as best available data and reflected in the
construction plans and drainage report.
The 100 -year floodplain pending per LOMR has been shown in the construction drawings and
on the drainage exhibit.
2. Sh. 2 — The drainage easement between Lots 9 & 10 should be public.
The drainage easement between Lots 9 & 10 has been change to public.
3. Sh.2 — There needs to be a public drainage easement adjacent to Lot 36.
A 40' drainage easement has been added on and adjacent to Lot 36.
4. Sh. 3 — Should there be a barricade at the edge of Channel 2 that prevents traffic from driving on
it?
2 -6" pipe bollards have been added to prevent traffic from driving on channel 2
5. Sh. 4 — It looks like there's quite a bit of proposed fill on Rocky Briar Ct. & Deep Stone Ct. What
is the impact of this on the adjacent conservation area and floodplain?
The fill placement and grading will be limited to the Castle Rock property and the velocities in
the channel are such that there should be negligible impact to the conservation zone. The
Walter P. Moore & Associates LOMR data was reviewed and the floodplain in this area for the
minor tributary was not developed by modeling the flow in the tributary, but by using the
Base Flood Elevations in the LOMR and following the contours to develop the limits of the
floodplain. This portion of the floodplain is due to the backwater effect of Spring Creek, not
actual conveyance of runoff. Placement of fill in this non - effective flow area will have
negligible effect on the water surface elevation since the flow conveyance is entirely in the
Spring Creek main channel. The storm sewer for Phase 6 was designed for this floodplain
backwater condition.
6. Sh. 5 — Please verify that the drainage channels in public drainage easements are being built to
public standards.
The 25 -year storm runoff values were developed for each channel and the data has been
added to the drainage report and included as an addendum to the report. All the channels
have subcritical flow, have a 1' minimum freeboard and have velocities less than the
maximum allowable by the Design Guidelines, for the 25- year storm event. Figure D, Standard
Drainage Details, does not show a channel section using rock riprap as a channel lining which
we have used for Channel 1. Rock Riprap is commonly used for channel lining so if it is
acceptable to the City, then we feel that the drainage channels are being built to public
standards.
7. Sh. 5 — Please match soffits of pipes at Inlet 607.
The soffits of the pipes at Inlet 607 have been revised to match.
8. Sh. 5 — Please add a note specifying how the proposed RCP will tie onto the existing.
Note 4 has been added on sheet 5.
9. Sh.6 -(Sta. 1 +23.43) Please specify two gate valves at the tee.
A gate valve has been added on the 4" waterline next to the fire hydrant. The 2n gate valve
will be included in the fire hydrant assembly.
10. Sh.6 - (Sta. 1 +23.43) Please label the required fire flow at the fire hydrant.
The fire flow has been labeled at the proposed fire hydrant.
11. Sh. 6 - Would it be possible to move the water service so that it connects to the main before or
after it dips below the storm sewer?
The water service has been moved so that it connects to the main before it dips below the
storm sewer.
12. Sh. 6 &12 - In areas where the waterline is being deflected, please provide additional flowlines
every 20 -ft in order to verify the specified radius.
Additional flowlines every 20-ft have been provided.
13. Sh. 7 - Sanitary sewer services should be no deeper than 3.5 ft. Please adjust.
All services deeper than 3.5' have been adjusted. A table showing the depths of each service
has been attached.
14. Sh. 9 - Were you trying to build the temporary turnaround to permanent standards? If so, there
should be 1.5 -inch asphalt.
The temporary turnaround does not need to be built to permanent standards, however, we
have changed the asphalt from 1" to 1.5"
15. Sh. 10 - Please show the limits of the floodplain and floodway.
The limits of the floodplain has been shown. There is no floodway established for this area.
16. Sh. 11- Is the Pipe 602 labeled correctly on the profile for P601 or P602 & P603.
The all pipe labels for Pipe 601 -603 have been checked and corrected in the plan and profile
views.
17. Sh. 11- Are pipes 602 & 603 proposed to be 24 -inch or 30 -inch as shown in the plan view?
Pipe 602 & 603 will be 24". The labels in the plan view have been corrected.
18. Sh.11 - We are concerned about the 48 -inch pipe tying into the 10'X5' Box Culvert and affecting
it's structural integrity. Please verify.
A detail has been added to Sheet 9 addressing the connection to the box culvert and its
structural integrity.
19. Sh. 11- Plan view and profile label show Pipe 604 as 36 -inch. Please revise.
The labels have been revised.
20. Sh. 11- The 48 -inch RCP flowline shown in the Box Culvert profile doesn't match the flowline
shown on the profile for P604 & P606.
The 48" flowline has been added to the Box Culvert profile.
21. Sh.12 — Please label the separation distance between the water and storm sewer lines.
The separation distance has been labeled.
22. Sh.12 — how far away is the next closest fire hydrant. An additional hydrant may be needed
along the street.
The next closest fire hydrant is 89' from the start of this phase and 649' from the end of the
waterline. An additional hydrant is not needed.
23. Water Report — The portion of waterline being extended across the bridge should be included in
the water report.
This portion of the waterline has been added to the water report. Two revised copies of the
water report are being submitted.
24. Water Report — Its difficult to read what elevation is labeled for J15 on Exhibit A, but it doesn't
appear to be 281 as used in the model.
The label has been moved so that it can be read. And the elevation has been corrected.
25. Sanitary Sewer Report — Exhibit A shows several manholes from other phases that are labeled
as "proposed."
All manholes shown on the exhibit are existing, and the labels have been updated.
26. Drainage Report — The report and our guidelines specify 4:1 side slopes for open channels, but
the detail for Channel 1 on Sh. 5 shows 2:1. Please revise.
The side slopes for Channel 1 have been changed in 4:1.
27. The detail shows Castle Rock Pkwy. As an 80 -ft. ROW, but it is shown as an approx. 77 -ft ROW in
the plan view.
Castle Rock Pkwy. has an 80-ft ROW and it has been verified that it measures 80-ft in the plan
view.
28. Per Water/Wastewater Dept., Please make waterline material Ductile Iron for portion not
meeting our minimum 4 -ft cover.
Ductile Iron pipe has been specified for the portion of the waterline that does not have 4' of
cover.
29. Please show and label established BFE's.
The established BFE's have been shown on the overall sheets.
Sewer Line 5-1 (Deep Stone Court)
Sewer Line Station
Proposed Grade Elevation
FL at end of service
Depth of Service
0 +29.72
277.46
273.96
3.5
0 +40.72
277.35
273.85
3.5
1 +75.04
277
273.5
3.5
1 +98.33
276.48
273.23
3.25
2 +19.45
276.36
273.11
3.25
2 +74.69
276.75
273.5
3.25
3 +30
277.23
273.98
3.25
3 +94.69
277.59
274.2
3.39
4 +96.22
278.77
275.6
3.17
5 +01.97
278.77
275.8
2.97
5 +91.84
280.44
277.5
2.94
5 +91.84
280.44
277.7
2.74
Sewer Line 5 -3 (Rocky Oak Court)
Sewer Line Station
Proposed Grade Elevation
FL at end of service
Depth of Service
1 +14
281.9
278.5
3.4
1 +14
281.9
278.5
3.4
2 +04.18
278.5
275.7
2.8
2 +04.18
279.03
276
3.03
2 +04.18
277.75
275
2.75
Sewer Line Station
Sewer Line S-4 (Rocky Briar
Proposed Grade Elevation
Court)
FL at end of service
Depth of Service
0 +79.29
280.85
277.5
3.35
0 +79.30
280.85
278.7
2.15
1 +55.78
280.06
276.6
3.46
1 +55.78
1 +55.78
279.62
276.2
3.42
278.75
275.3
3.45
Response to Engineering Comments No. 2
May 27, 2010
1. There was more recent LOMR data submitted by Walter P. Moore in April 2010. The floodplain
boundary and water surface elevations shown on the plans and in the drainage report may be
affected.
The floodplain boundaries and the water surface elevation at the stream cross sections from the
April 2010 Walter P. Moore data are shown on the drawings. Sheets 1, 2, 4, 8, 9, and 10 have
been revised.
The 100 -yr storm events peak flows at the proposed box culvert structure did not change. The
water surface elevation in the stream section downstream of the box culverts are lower in the new
HEC -RAS model from Walter P. Moore, but the data new the structure did not change. The change
in the water surface elevation at the culvert structure using the new model data will be
insignificant when compared to the model run with the culverts.
The design of the storm sewer system in the residential section of Phase 6 is still valid as the
maximum water surface in the adjacent stream, Spring Creek Upper, is lower in the April 2010
model than in the previous model. A comparison of the water surface elevations follows:
Spring Creek Upper— Water surface elevations
X- Section 2009 data 2010 data
774 272.65 271.85
881 272.68 271.81
1049 272.82 272.23
1278 273.42 273.02
1417 273.51 273.18
2. Water report — Please clarify the demand of 1,174 gpm placed at Node 20 as there is not a proposed
fire hydrant or service connections in that area.
That portion of the water line does not have services or hydrants for a demand but there will be a
hydrant on the line when it is extended in the future so we assumed a fire hydrant at the end with
1,000 gpm plus 174 gpm additional demand and ran the model to show the 8" line is adequate
3. It doesn't appear that the BFE's from the LOMR were shown on the plans. Please revise.
The BFE's at each stream cross section from the April 2010 data are shown on the plans as well as
the BFE's from the 1999 LOMR.
4. What is the 100 -yr water surface just past the box culverts on the downstream side?
At the downstream end of the culverts the 100 yr water surface is 278.62 for the existing
conditions model and 278.93 for the ultimate conditions model
5. FYI...Additional Development Permit fees of 3/4% of the total public infrastructure costs is due prior
to issuance of the development permit.
Noted
6. FYI... The Temporary Blanket Easement is still pending and will need to be filed prior to issuance
of the development permit.
Noted
Schultz Engineering, LLC,
P.O. Box 11995
College Station, Texas 77842
979.764.3900 office
979.764.3910
June 1, 2010
Erika Bridges
Graduate Civil Engineer
City of College Station
1101 Texas Avenue
College Station, TX 77840
Re: Castle Rock Phase 6 — Construction Drawings
Dear Ms. Bridges:
Attached are 1 copy of the construction drawings and the response to the staff review comments.
If you have any questions, please do not hesitate to call.
Very truly yours,
Schultz Engineering, LLC
Joethultz, P.E.
Civil Engineer