HomeMy WebLinkAboutCorrespondence (10/30/2006) Donald Harmon- Re: Fire Station No. 3 Page 1
From: Lindsay Boyer
To: Donald Harmon
Date: 9/8/2006 11:41 AM
Subject: Re: Fire Station No. 3
CC: Carol Cotter
Hi Donald,
Fora site plan review, we need 12 copies of the site plan, 1 landscaping plan, 1 copy of the building
elevations, and a set of material and„,color samples forfhe exterior of building. For the Development
Permit, we require 1 drainage and'erosion control plan, and 2 Drainage Reports (the development
engineers may be able to better tell you if those would be required), and building plans require 3 sets of
building specs. Let me know if you need anything else.
Lindsay
Lindsay B. Boyer
Staff Planner
City of College Station
1101 Texas Avenue S.
College Station, Texas 77840
(979) 764-3570/ (979) 764-3496 Fax
Iboyer@cstx.gov
www.cstx.gov
>>> Donald Harmon 9/8/2006 10:28:26 AM >>>
Hi Lindsay,
As we did with fire station no. 5, we want to submit plans and specs for building to review in order to
have a permit ready for the contractor to sign and pick up without having him submit the plans and specs
and wait for building to review.
Would you please let me know what information you need submitted and how many copies you need for
review for site, building, etc. in order to secure a development permit, building permit, etc. ?
Thanks,
Donald
L110/3012006) Donald Harmon- Re: Fire Station No. 3 Page 1]
From: Lindsay Boyer
To: Donald Harmon
Date: 9/8/2006 11:41 AM
Subject: Re: Fire Station No. 3
CC: Carol Cotter
Hi Donald, ✓—
For a site plan review, we need 12 copies of the site plan 1 landscaping plan, 1 copy of the building
elevations, and a set of material and�°lor samples forfhe exterior of pe—building. For the Development
Permit, we require 1 drainage and- rosion control plan, and 2 t Drai gna'a Reports (the development
engineers may be able to better tell you if those would be required), and building plans require 3 sets of
building specs. Let me know if you need anything else.
Lindsay
Lindsay B. Boyer
Staff Planner
City of College Station
1101 Texas Avenue S.
College Station, Texas 77840
(979) 764-3570/ (979) 764-3496 Fax
lboyer@cstx.gov
www.cstx.gov
>>> Donald Harmon 9/8/2006 10:28:26 AM >>>
Hi Lindsay,
As we did with fire station no. 5, we want to submit plans and specs for building to review in order to
have a permit ready for the contractor to sign and pick up without having him submit the plans and specs
and wait for building to review.
Would you please let me know what information you need submitted and how many copies you need for
review for site, building, etc. in order to secure a development permit, building permit, etc. ?
Thanks,
Donald
BRW
BROWN REYNOLDS WATFORD ± ARCHITECTS
2700 Earl Rudder Fwy South
SUITE 4000
College Station,TEXAS 77845
979-694-1791
FAX 694-8293
WWW.BRWARCH.COM
TRANSMITTAL 33
5()
DATE: June 4, 2007 (�
TO: Lindsay Boyer ))C
City of College Station 'f) 1ADDRESS: 1101 Texas Ave. S.
College Station,TX 77840 I�
FROM: Tom Parker
RE: College Station Fire Station #3
PROJECT NO: 2465.00
SENT VIA: Hand Delivered
CC: File
QUANTITY DESCRIPTION
7 Full Sets of Drawings
2 Site Plan Drawings
1 Landscape Plan Drawing
1 11x17 Grading and Erosion Control Plan Drawing
MESSAGE:
1
(11111*,"11414
CITY OF COLLEGE STATION
4C'r y4.,
,kr,4-toul4,1 Planning 6.Development Services
1101 Texas Avenue,P.O. Box 9960
College Station,Texas 77842
Phone 979.764.3570 / Fax 979.764.3496
1
MEMORANDUM
- -
January 26,2007
TO: Donald Harmon,Public Works
FROM: Lindsay Boyer,Staff Planner
SUBJECT: COCS FIRE STATION NO.3(SP)- Site Plan
Staff reviewed the above-mentioned site plan as requested. The following page is a list of staff review
comments detailing items that need to be addressed. The next submittal will be the third and final review by
staff for this round of reviews. Please address the comments and submit the following information for
further staff review:
One (1) complete set of civil construction documents for the proposed development with
the revised site and landscaping plans attached
If there are comments that you are not addressing with the revised site plan,please attach a letter explaining
the details. If you have any questions or need additional information,please call me at 764-3570.
Attachments: Staff review comments
cc: Case file#06-00500109
CITY OF COLLEGE STATION
Planning dr Development Services
1101 Texas Avenue, P.O. Box 9960
College Station, Texas 77842
Phone 979.764.3570 / Fax 979.764.3496
MEMORANDUM
November 13, 2006
TO: Donald Harmon, via fax 764.3489
FROM: Lindsay Boyer, Staff Planner
SUBJECT: FIRE STATION # 3 (SP)- Site Plan
Staff reviewed the above-mentioned site plan as requested. The following page
is a list of staff review comments detailing items that need to be addressed.
Please address the comments and submit the following information for further
staff review:
One (1) complete set of construction documents for the proposed
development with the revised site and landscaping plans attached
If there are comments that you are not addressing with the revised site plan,
please attach a letter explaining the details. If you have any questions or need
additional information, please call me at 979.764.3570.
Attachments: Staff review comments
xc: Case file #06-00500233
Home of Texas A&M University
0-Q4°91-6)
BRW
BROWN REYNOLDS WATFORD ± ARCHITECTS 1\'
�
V60 1D
2700 EARL RUDDER FREEWAY
SUITE 4000
COLLEGE STATION, TX 77845
979-694-1791
FAX 979-694-8293
WWW.BRWARCH.COM
TRANSMITTAL
DATE: May 7, 2007
TO: Lindsay Boyer
CITY OF COLLEGE STATION
ADDRESS: 2613 Texas Avenue S.
College Station,Texas 77842
FROM: Ray Holliday, AIA
Project Manager
RE: College Station Fire Station No. 3
PROJECT: COLLEGE STATION FIRE STATION NO.3
BRW Project No.: 2465.00
SENT VIA: HAND DELIVERED
CC: File
QUANTITY DESCRIPTION
1 Set of Drawings
1 Set of Notes
1 Site Review
MESSAGE:
As requested
(111*,11111111111
•
CITY OF COLLEGE STATION
� r sg Pla using d Deve opment S,vuw
1101 Texas Avenue,P.O. Box 9960
College Station,Texas 77842
Phone 979.764.3570 / Fax 979.764.3496
MEMORANDUM
January 26,2007
TO: Donald Harmon,Public Works
FROM: Lindsay Boyer, Staff Planner
SUBJECT: COOS FIRE STATION NO.3 (SP) - Site Plan
Staff reviewed the above-mentioned site plan as requested. The following page is a list of staff review
comments detailing items that need to be addressed. The next submittal will be the third and final review by
staff for this round of reviews. Please address the comments and submit the following information for
further staff review:
One (1) complete set of civil construction documents for the proposed development with
the revised site and landscaping plans attached
If there are comments that you are not addressing with the revised site plan,please attach a letter explaining
the details. If you have any questions or need additional information,please call me at 764-3570.
Attachments: Staff review comments
cc: Case file#06-00500109
114'13/2006 9:41 AM GWFAX -> Page 1 of 4
1' 1107
3: 3`t-
0(p- a33
(*.4/1441
CITY OF COLLEGE STATION
Planning 6 Development Services
1101 Texas Avenue, P.O. Box 9960
College Station, Texas 77842
Phone 979.764.3570/ Fax 979.764.3496
MEMORANDUM
November 13, 2006
TO: Donald Harmon, via fax 764.3489
FROM: Lindsay Boyer, Staff Planner
SUBJECT: FIRE STATION #3 (SP)- Site Plan
Staff reviewed the above-mentioned site plan as requested. The following page
is a list of staff review comments detailing items that need to be addressed.
Please address the comments and submit the following information for further
staff review:
One (1) complete set of construction documents for the proposed
development with the revised site and landscaping plans attached
If there are comments that you are not addressing with the revised site plan,
please attach a letter explaining the details. If you have any questions or need
additional information, please call me at 979.764.3570.
Attachments: Staff review comments
xc: Case file #06-00500233
Home of Texas ABM University
CITY OF COLLEGE STATION
Planning cr Development Services
1101 Texas Avenue, P.O. Box 9960
College Station, Texas 77842
Phone 979.764.3570 / Fax 979.764.3496
MEMORANDUM
November 13, 2006
TO: Donald Harmon, via fax 764.3489
FROM: Lindsay Boyer, Staff Planner
SUBJECT: FIRE STATION # 3 (SP)- Site Plan
Staff reviewed the above-mentioned site plan as requested. The following page
is a list of staff review comments detailing items that need to be addressed.
Please address the comments and submit the following information for further
staff review:
One (1 ) complete set of construction documents for the proposed
development with the revised site and landscaping plans attached
If there are comments that you are not addressing with the revised site plan,
please attach a letter explaining the details. If you have any questions or need
additional information, please call me at 979.764.3570.
Attachments: Staff review comments
xc: Case file #06-00500233
Home of Texas A&M University
BRW
BROWN REYNOLDS WATFORD + ARCHITECTS
2700 EARL RUDDER FREEWAY
SUITE 4000
COLLEGE STATION,TX 77845
979-694-1791
FAX 979-694-8293
WWW.BRWARCH.COM
January 5, 2007
RESPONSES TO PLAN REVIEW
PLANNING
1. Sheet C1.1, provide legal description of the property in the title block.
Legal description of the property is provided on the site plan.
2. Sheet C1.1, provide ownership and current zoning of the parcel and all
abutting parcels.
Ownership and current zoning of the parcel and all abutting parcels is provided
on the site plan.
3. Sheet C1.1, provide total square footage of the proposed building.
Total square footage of the proposed building is provided on the site plan.
4. Sheet C1.1, provide note concerning floodplain.
There is no flood plain, and the confirming FEMA/FIRM map number is noted
on the site plan.
5. Sheet C1.1, please clearly identify the FDC connection.
The FDC connection is labeled on the site plan.
6. The west elevation does not have enough architectural elements, as required
by the Non-Residential Architectural Standards (UDO, Section 7.9).
Shading devices have been added over the 2 doors on the west elevation in
order to alleviate this problem.
7. The roofline on the north elevation may have no more than 66% of the
roofline on the same elevation.
This is not applicable as the building is less than 20,000 square feet.
8. Provide a general note that all roof and ground-mounted mechanical
equipment shall be screened from view or isolated so as not to be visible from
any public right-of-way or residential district within 150' of the subject lot,
measured from a point five feet above grade. Such screening shall be
coordinated with the building architecture and scale to maintain a unified
appearance.
This note is provided on the site plan.
LAN DSCAPI NG/STREETSCAPI NG/BUFFER
1. The buffer on the east and north side of the property should have an
accompanying 6' solid fence. Fencing may be eliminated completely if the
buffer yard and plantings are tripled. Otherwise, the existing plantings must
be located within the 10' buffer yard measured from the property line with a
fence provided (UDO, Section 7.6—Buffers).
On the north side of the property the buffer yard and plantings are now tripled.
On the east side of the property the buffer yard and plantings are tripled except
for the area to the east of the parking lot. In this area, a fence is substituted
with a solid plant wall that is greater than 6 feet in height with 100% opacity
(Re: Sheet C1.4).
2. The buffer on the west side of the property should have triple plantings to
remain in its existing location without the provision of a fence (UDO, Section
7.6—Buffers).
The buffer on the west now has triple plantings.
3. Show fencing details if a fence is to be provided.
No fence is to be provided.
4. Provide a general note that 100% coverage of groundcover, decorative
paving, decorative rock, or a perennial grass is required in parking lot
islands, swales and drainage areas,the parking lot setback, rights-of-way,
and adjacent property disturbed during construction.
Note provided on landscape plan.
5. Irrigation system must be protected by either a Pressure Vacuum Breaker, a
Reduced Pressure Principle Back Flow Device, or a Double-Check Back Flow
Device, and installed as per City Ordinance 2394.
A Double-Check Back Flow Device is shown on the Irrigation Plan 1/C1.5
and described in the irrigation legend. It is also mentioned in note 17 on sheet
C1.5.
6. All backflow devices must be installed and tested upon installation as per
City Ordinance 2394.
See note 17 on sheet C1.5.
ENGINEERING COMMENTS NO. 1
1. The location of the storm pipe along the rear of the property is shown on the
opposite side of the property line on Sheet C1.2 than on Sheet C2.1. Sheet
C2.1 shows the storm pipe located on the south side of the property line.
The storm pipe is now only shown on Sheet C2.1 on the correct side of the
property line.
2. Provide sizing of the driveway culvert.
Culvert shall be 8" diameter. Calculations are attached. 25-110 oeijoLg‘t_
3. Provide sizing of inlet grates. Ce2, ,
The grates are 30"x 30" and this is ind' ted on Sheet C2.4. W`)
4. I don't agree with the CN values used in the Drainage Report. Post 5
development is not natural grasslands, but landscaped areas with slopes. C) )4.)
See attached response from engineer. The storm water runoff design is not
required; however, we are addressing the issue in an attempt to be good
neighbors.
5. What are the velocities of the detention pond discharge?
The velocity is 4 feet per second.
Can you assure that the discharge from the detention ponds will be captured
by and not overshoot the inlets? What is the overflow route if a grate gets
clogged?
Based on the UDO,the Code of Ordinances, and Flood Hazard Protection a
dK) �---- letention pond was not required. The fire department has asked to have a
. //detention pond installed to be good neighbors. The neighbors are already
experiencing flooding in their back yards due to the topography of the
undeveloped site. The fire department also has the water draining from the
4 detention ponds into catch basins and then into the storm sewer which is also
1.4 not required. The catch basin openings are sized 1 %2 times bigger than that of
1 the v-neck opening in the detention pond. If the catch basins get clogged it
would have to be larger than tree leaves. The over flow of water would be
directed into a drainage swale in the rear as it is today and flow from west to
east to the street. The system is designed way beyond the minimal
requirements that are required to develop this site.
7. Would a larger turning radius on the south side of the drive around the
building as its turn off the main drive function better?
This radius was increased to 25'-0".
8. Please revisit the waterline connection detail. Is the blow-off necessary since
there is a fire hydrant? Are all the gate valves necessary? As shown,the
isolation of the meters will also turn off flow to fire suppression line. Is this
what is desired?
One gate valve has been removed and the other two are necessary. As shown,
the water supply to the fire suppression system is not metered and this is what
is desired.
9. The"Typical Water and Sewer Trench Detail" provided does not match BCS
Unified. Please provide letter for our review stating why it is better, or use
standard.
The detail has been changed.
10. Be aware that the 11 foot elevation difference between the Fire Station and
the adjacent residential properties is bound to cause outcry. Finished floor
of the station will be 5 feet above the adjacent properties' 6 foot fence.
This issue has already been addressed by the Fire Department.
ELECTRICAL COMMENTS REQUIRING IMMEDIATE ATTENTION
1. Developer provides temporary blanket easement for construction purposes.
This is not applicable because the City owns the property.
GENERAL ELECTRICAL COMMENTS
1. Developer installs conduit per city specs and design.
The contractor shall install conduit per city specs and design(Re: Sheet E3.1
detail 2).
2. City will provide drawings for conduit installation. Contact City prior to
bidding.
This is noted in detail 2 on Sheet E3.1.
3. Developer provides 30' of rigid or IMC conduit for riser poles. City installs
riser.
This is noted in detail 2 on Sheet E3.1.
4. Developer to intercept existing conduit at designated transformers and
extend as required.
This is noted in detail 2 on Sheet E3.1.
5. If conduit does not exist at designated transformer, developer to furnish and
install conduit as shown on electrical layout.
This is noted in detail 2 on Sheet E3.1.
6. Developer pours transformer pad(s) per city specs and design.
This is noted in detail 2 on Sheet E3.1.
7. Developer installs pull boxes as per city specs and design (pull boxes
provided by the city).
This is noted in detail 2 on Sheet E3.1.
8. Developer provides digital AutoCad 2000 or later version of plat and/or site
plan; email to sweido(a,cstx.gov.
This is noted in detail 2 on Sheet E3.1.
9. Developer provides load data for project.
This is noted in the "Load Summary" at the top of Sheet E3.1.
BUILDING PLAN REVIEW
1. Need to submit energy information on the envelope, mechanical, and lighting
of the building to comply with the 2003 IECC.
The report is attached.
2. Adjust handrail extensions at top and bottom of stair detail sections on sheet
C1.3 so that they comply with sections 505.10.1 —505.10.3 of the ANSI
A117.1-1998, see attached sheets.
The handrail extensions are now in compliance and are shown correctly on
sheet C1.3.
3. Change buildings codes on cover sheet to 2003 codes.
The codes are now shown correctly.
4. Submit a special inspections statement for structural steel bolted and welded
connections that covers the requirements of sections 1704.1.1 and 1704.1.2 of
the 2003 IBC.
The necessary information has been added to Specifications Section 01400.
5. Verify or provide a safe and clear path to ladder in tower.
Plywood decking is now shown on 1/S1.2 and 1/A2.5 in the attic in order to
allow a person to walk to and climb through the 3'-0" square clear opening in the
wood stud wall of the tower(shown on 1/A2.5) and then onto the ladder.
6. Provide a listed 1 hour fire-rated floor-ceiling assembly for separation of
floors for the incidental storage room on the second floor that is greater than
100 square feet to comply with table 302.1.1 of the 2003 IBC.
The floor-ceiling assembly in question is a 2 hour rated 2.5" concrete slab on
steel deck.
7. Provide additional cleanouts to the sewer branch lines in the front restrooms
and in the kitchen to comply with section 708.5 of the 2003 IPC.
Necessary cleanouts have been added to 1/P1.1.
8. Provide emergency lighting on second floor area and stairs to comply with
section 1006.3 of the 2003 IBC.
Emergency lighting has been added on the second floor and in the stair area
(Re: 2!E2.1).
9. Provide exterior emergency lighting at exit discharge locations for all exit
doors to comply with section 1006.3 #5 of the 2003 IBC.
Battery back-up has been added to exterior lights all exit discharge locations
(Re: Sheet E2.1).
10. Need Texas Accessibility Standards (TAS) registration number.
The TAS number is EABPRJA7803844.
LANDSCAPE & IRRIGATION COMMENTS
LANDSCAPE
1. Add note on tree detail that the root flare needs to be 2" above existing grade
(add to all planting details).
Note has been added to Sheet C 1.4.
2. Please specify a container size along with the tree caliper size. That would
insure that the landscape contractor will not install a B&B tree. B&B
material is not acceptable.
The UDO does not prohibit the use of B&B trees and in our professional
experience, B&B trees perform better than container trees.
3. Sophora affinis (Eve's Necklace tree) concerned about availability in 2" size
and whether this tree can take irrigation water hitting it.
This tree has been changed to a female yaupon.
4. Dwarf crepe myrtles on plant list...specify a variety. Some grow to 3' height,
some to 6', some to 10' height.
The Varieties are specified on the landscape legend on Sheet C1.4.
5. Viburnum rufidulum....is availability okay to obtain 2" size and will these
grow okay with salty irrigation water hitting them?
Availability is fine and this plant is on the preferred plant list.
6. Red oaks will grow here but gets problems from irrigation heads hitting
them with salty city water and quality of available stock is questionable.
Maybe use chinese pistache or water oak or lacebark elms.
Red oaks are on the preferred plant list.
7. Eliminate Rudy Haag Euonymous or substitute another evergreen shrub.
Euonymous shrubs get leaf diseases and scales here. Also this plant is not on
the plant list but is #2.51 on the plan.
This plant has been changed to nandina.
8. Use steel T posts vs. 4" perforated drain pipe for the tree stakes...Note#2.22
states that it is a 4" drain pipe.
Tree stakes are now labeled as"wood stake".
9. Add notes that the contractor is to leave tags on shrubs at installation.
Note has been added to Sheet C1.4.
10. Use same symbol and code for same plant material throughout all plan
sheets.
This correction has been made.
11. Roof drains should be tied into the site's storm drainage as per City of CS
landscape and irrigation design considerations, under Building Concerns,
item #1.
This has been done. See grading plan on Sheet C1.2.
12. Planters should be raised with masonry walls, brick, etc. as per COCS
Design Considerations. Steel edging is not acceptable as it does not give
adequate drainage.
Our design meets the requirements of the UDO.
13. Do not specify peat moss in soil mix. Specify a decomposed pine bark mulch.
Needs to be shown on plans and specs.
This is now shown in specifications and on Sheet C1.4.
14. Remove all mention of B&B plant materials on plan details or in specs.
The UDO does not prohibit the use of B&B trees and in our professional
experience, B&B trees perform better than container trees.
15. Sheet C1.4 Landscape. Where does the drain shown in detail#5 run to?
See the grading plan on Sheet C1.2 for drain pipe locations. This was done in
response to the City's request to provide drainage for the planting beds.
16. Screening areas have live oaks planted 25' on center. Too close for proper
tree and shrub development in these areas. Overcrowding will lead to
disease/insect problems and will reduce desired screening effect.
Red oaks were used per request by the fire department and spaced per the
UDO.
IRRIGATION
1. Rotary heads with 30-40' radius could be used and would require a lot fewer
heads and piping to cover the larger lawn areas (vs. the 18-20' radius heads).
18-20' radius heads were used due to the slope of the site.
2. Are the swing joints with pressure regulators needed? There is a pressure
regulator already near the main valve and tie in.
The pressure regulators have been removed.
3. Drip irrigation: AS BUILT DRAWINGS REQUIRED after construction is
completed. Show drip tubing and emitters on the tree planting detail to
make sure every tree gets drip irrigation. Specify a maximum length of drip
line allowed to be installed on one zone.
The as built drawing requirements are listed in the specifications. See note 12
on Sheet C1.5 for drip irrigation requirements for each shrub and tree. See
also detail 4a on Sheet C1.5. Maximum length of drip line shall be 275 feet
and is indicated in note 19 on Sheet C1.5.
4. Extra wires...2 extra red and 1 white needed at the end of the 2 furthest
valves. The plan only says one red. Verify which zones will get the extra
wires dependent on the path of the field wires. Plans specify zones 5 and 8,
but this may change dependent on the field wire installation.
Note 18 on sheet C1.5 has been updated.
5. Double check valve: please specify the make and model number.
Make and model number are given on legend on Sheet C1.5.
6. Rain sensor may need an outside antenna.
The specified model comes with an antenna(see detail 10 on Sheet C1.5).
7. Make sure all valves are outside of planter beds. 2 still shown in beds by
front parking lot.
Valves serving the planting bed are to remain where previously shown. Other
valves have been moved out of planting beds.
8. An independent electrical circuit should be specified for the irrigation
controller(no electrical plans were included in the review set so unable to
evaluate this item).
This has been done (Re: 1/E1.1).
9. Add drip specs to irrigation specs (as per Drip System requirements in
design standards, item#10. The irrigation plans should be 100% completed
by the Certified Irrigator completing the plans for construction—not left to
the installer).
Drip specs have been added.
10. Irrigation sleeves must be indicated on both concrete sheets and irrigation
sheets along with the maximum depth, size, location and marking with
carriage bolt to insure concrete contractor will install sleeves.
It is not required by the City to be shown on the concrete sheets—this would
cause confusion. The size and location are shown on Sheet C1.5. The depths
are shown on detail 11 of Sheet C1.5. See note 10 on Sheet C1.5 for
information on carriage bolts.
11. Sheet C1.5 Irrigation: need larger scale plan, 1"=10' in order to verify zone
piping, mixture of plant material per zone, etc.; as per COCS Design
Considerations, need to show all flow rates, pressure loss calculations, line
sizes, etc.; need cut off valves (2) at meter/backflow preventer location as per
COCS Design Considerations.
A larger scale plan is not required by the UDO. The flow rates and pressure
loss calculations are attached. The line sizes are on the irrigation plan. Cut
off valves have been added.
12. Spec book- irrigation: section 2.02 main lines to be sch. 40 PVC pipe.
Section 2.02 of 02810 updated to specify PVC schedule 40 pipe for main
irrigation lines.
13. Electrical: will there be area lights? Make sure tree locations are
coordinated with lights.
Tree locations do coordinate with lights.
DEGELMAN ENGINEERING GROUP, INC.
2206 Quail Run
College Station, TX 77845-6232
Phone/Fax: (979) 696-2506
15 December 2006
To: BRW Architects,Inc.
2700 Earl Rudder Freeway South, Suite 4000
College Station,TX 77845
Attn: Diana Smith
From: Larry 0. Degelman, P.E. a f
Project: Fire Station #3, College Station, TX (BRW Job No. 2465.00)
I'm responding to your inquiry of whether the storm runoff coefficients for the subject
property should have been used as "Landscaped Area" values, rather than the"Natural
Grassland Area"values use in my runoff report. Though the report refers to the College
Station Drainage Policy Manual, and though the procedures of the manual were followed,
I actually used runoff coefficients from Table 2-2 of the manual from City of Austin,
Watershed Engineering Division. This table is more sensitive to storm return periods as
well as to more definitive soil types and site slopes.
The term"Landscaped Areas"would seem to infer a possible mixture of mulch, bare soil,
shrubbery, grass and gravel. The Austin manual used a category called "Grass Areas
(Lawns, Parks, Etc.)", which seemed to be a better match to what we actually have. The
published values for"grass areas"were used in both pre- and post-development, but are
different for 10-yr, 25 yr, 50-yr and 100-yr storm return periods. The values I used were
for a"good condition" site, meaning that at least 75% of the open area(excluding the
paved areas) has grass cover. Those values were 0.35, 0.39, 0.42, and 0.45 respectively
for the different return periods, for a slope in the range of 2 to 7%. The subject site is
actually 3.5% slope, so these values are somewhat conservative in that the real slope is
toward the bottom of the range. In other words, we could have used the same runoff
coefficients values even if the site were twice the slope that it is.
Our obligation is to assure post-development runoff is no greater than the pre-
development runoff. I was careful to not attempt to exaggerate the pre-development
runoff to ease the job of sizing the detention basin to capture the "excess" storm water, so
I used the same grass area coefficients in pre- and post-development. In realty, the pre-
development site could have been classified as"Pasture/Range", which has slightly
higher coefficients (0.38, 0.42, 0.45, and 0.49 respectively.) This would have made the
pre-development runoff higher,thus easing the burden of capture and detention. Here
again, the design becomes slightly conservative in sizing of the catch basins.
I believe the design values chosen to be based on sound engineering data sources, and
therefore, they should be as reliable as we can expect for the storm conditions published
for our area.