HomeMy WebLinkAboutBLD2008-00262 Stormwater I
I GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
New Home for Dustin Slimp
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Prepared for Bishop Brothers Construction
ISeptember 2008
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I For the Property
p y Described
c bed as
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Parcel 901-245-004
Located in
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Section 24, Township 29 North, Range 1 West,
Jefferson County
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Prepared by:
NTI ENGINEERING & SURVEYING
I 717 S. Peabody Street
Port Angeles, Washington 98362
360-452-8491
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I GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
I
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Contents
ABSTRACT 26
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I. OVERVIEW 27
IA. Pre-Developed Condition 28
1. Pre-Contact Condition 28
I 2. Existing Condition 28
B. Developed Condition 31
C. Proposed Improvements 31
I D. Stormwater Runoff 32
1. Pre-Contact Stormwater Runoff 33
2. Pre-Developed Stormwater Runoff 33
I 3. Post-Developed Stormwater Runoff 33
E. Controlling and Challenging Site Parameters 34
F. Natural Drainage System 35
I G. Drainage To and From Adjacent Properties 35
1. Bypass Flows 35
H. Vicinity Maps 35
I I. Site Map 35
J. Surface Soils 35
K. Geotechnical Report 39
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1. Site Description 39
2. Site Geology 40
3. Conclusions and Recommendations 40
I4. Limitations to Geotechnical Report 42
II. EXISTING CONDITIONS 43
IA. Natural Receiving Waters 43
B. Area-Specific Requirements 43
1. Local Plans 43
2. Ordinances 43
3. Water Cleanup Plans 43
IIII. OFF-SITE ANALYSIS 43
IIV. PERMANENT STORMWATER CONTROL PLAN 44
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I A. Methodology 44
B. Existing Site Hydrology 44
1. Design Sub Basin 45
I 2. Soils Hydrologic Group 45
3. Time of Concentration 45
(i) Pre-development Condition 45
I (ii) Pre-development Time of Concentration 49
4. Runoff Curve Numbers 49
5. Rainfall 51
I6. Pre-Contact Runoff Volumes 53
C. Developed Site Hydrology 53
Design Sub Basin 53
Ii.
2. Soils Hydrologic Group 54
3. Time of Concentration 54
(i) Post-development Condition 54
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(ii) Post-development Time of Concentration 56
4. Runoff Curve Numbers 56
5. Rainfall 57
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6. Post-Development Runoff Volumes 57
D. Performance Standards and Goals 58
I 1. Minimum Requirement #1: Stormwater Site Plan 59
2. Minimum Requirement #2: Construction Stormwater
Pollution Prevention Plan 59
3. Minimum Requirement#3: Source Control of Pollution 59
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(i) Landscaping 59
(ii) Vegetation Management 60
I (iii) Irrigation 61
(iv)Fertilizer Management 61
4. Minimum Requirement #4: Preservation of Natural
I Drainage Systems and Outfalls 62
5. Minimum Requirement #5: On-site Stormwater
Management 62
I 6. Minimum Requirement #6: Runoff Treatment 62
7. Minimum Requirement #7: Flow Control 63
8. Minimum Requirement #8: Wetlands Protection 63
I 9. Minimum Requirement #9: Basin/Watershed Planning 63
10.Minimum Requirement #10: Operation and
Maintenance 63
I E. Flow Control System 63
F. Water Quality System 64
G. Conveyance System Analysis and Design 64
IV. CONSTRUCTION STORMWATER POLLUTION
PREVENTION PLAN 65
IA. Clearing Limits 66
B. Construction Access 66
I C. Flow Rate Controls 67
D. Sediment Controls 67
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E. Soil Stabilization 67
F. Slope Protection 68
G. Drain Inlet Protection 68
' H. Channel and Outlet Stabilization 68
I. Control of Pollutants 68
1. Control of Toxic Substances 68
2. Petroleum Spills 69
(i) Driver Training 69
(ii) Fueling of Vehicles 69
' (iii)Parking of Fuel Tankers 69
(iv)Containment of Spills 69
J. Control of De-Watering 69
' K. Maintenance of BMPs 70
L. Project Management 71
1. Phasing of Construction 71
' 2. Seasonal Work Limitations 71
3. Coordination with Utilities and Other Contractors 71
4. Inspection and Monitoring 71
' 5. Maintaining an Updated Construction SWPPP 72
VI. SPECIAL REPORTS AND STUDIES 72
VII. OTHER PERMITS 72
VIII. OPERATION AND MAINTENANCE MANUAL 72
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' ji? If If 11
JEFFEk SUN LuUNIY uLU
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I
IGEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
IParcel 901-245-004
New Home for Dustin Slimp
I
Figures
IFigure 1 - Disturbed Soils Footprint 32
Figure 2 - 2 Year Isopluvials 51
I Figure 3 - 25 Year Isopluvials 52
Figure 4 - 100 Year Isopluvials 52
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Maps
Map 1 - Chimacum Vicinity 8
IMap 2 - East Chimacum Creek Valley 9
Map 3 - Neighborhood Overview 10
I Map 4 - Neighborhood Drainage Patterns 11
Map 5 - Site Sketch 12
Map 6 - Drainage Basins 13
Map 7 - USGS Topo Map Segment 29
' Map 8 - Soils 36
IPhotos
Photo 1 27
Photo 2 28
' Photo 3 30
Photo 4 31
I Photo 5 34
Photo 6 34
Photo 7 37
I Photo 8 38
Photo 9 44
Photo 10 46
I Photo 11 47
Photo 12 48
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I GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
I
ITables
ITable 1 - Pre and Post Development Land Uses 50
Table 2 - Threshold Flow Chart 58
Table 3 - Stormwater Pipe Design 65
IDetail Drawings
Detail Drawing 1 - Stormwater Collection System 14
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Detail Drawing 2 - Infiltration/Dispersion Trench 15
Detail Drawing 3 - Erosion Control 16
Detail Drawing 4 - Erosion Control Notes 17
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Detail Drawing 5 - Erosion Control Notes (cont.) 18
Detail Drawing 6 - Erosion Control Notes (cont.) 19
Detail Drawing 7 - Erosion Control Notes (cont.) 20
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Detail Drawing 8 - Silt Fence Protection of Catch Basin 21
Detail Drawing 9 - Filter Fabric, Gravel, and Wire Mesh
Protection of Catch Basin 22
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Detail Drawing 10 - Sediment Trap 23
Detail Drawing 11 - Erosion Control Wattles 24
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C H I MAC U M VICINITY MAP
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�I NTI ENGINEERING & SURVEYING
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Engineers — Land Surveyors — Geologists 1 1/2 C 1
� Construction Inspection — Materials Testing SCALE IN MILES
NTI T�'I 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452,9491
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1 GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
U
Parcel 901-245-004
New Home for Dustin Slimp
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Map 2 - East Chimacum Creek Valley
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I GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
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IMap 3 - Neighborhood Overview
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I
IGEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
1
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Map 4 - Neighborhood Drainage Patterns
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I
GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
I
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SCALE IN FEETb .
I CONTOUR INTERVAL - 5' 411* - .
NOTE - BACKGROUND IMAGERY WAS TAKEN FROM Ju-reKSON
COUNTY'S WEB SITE AND IS INCLUDED FOR ORIENTATION ONLY. 1
ITEMS SHOWN MAY NOT BE ACCURATELY LOCATED.
IMap 5 - Site Sketch
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I
IGEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
IParcel 901••245-00/,,,..,....7. ; ,
New Home for Dustin Slimp
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BASIN A ..;` y�' ;. ' ..,,A--
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SCALE IN FEET
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CONTOUR INTERVAL - 5' ,VOTE - BACKGROUND IMAGERY WAS TAKEN FROM JEFFERSON
COUNT 'S WEB SITE AND IS INCLUDED FOR ORIENTATION ONLY.
I MS SHOWN MAY NOT BE ACCURATELY LOCATED.
IMap 6 - Drainage Basins
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13
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DU
STIN SLIMP HOME
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STORMWATER INFIL_ TRA TION SYSTEM '�
FROM U '
RUNOFF BASIN B-2 IS TO
BE 100% INFILTRATED. CATCH BASINS TO BE TRAFFIC RATED kitI :i I Al I V ri r n
WHERE SUBJECT TO WHEEL LOADS U
I ROUTE ALL SURFACE FLOWS FROM FROM ERRANT VEHICLES. MIDDLE
BASIN B-2 OVERLAND TO CATCH CATCH BASIN MAY BE OMITTED IF
BASINS AS INDICATED BY BLUE ALLOWED BY GRADING AND ALIGNMENT
ARROWS. ROUTE FLOWS FROM ROOF OF STORMWATER PIPE.
I DRAINS DIRECTLY TO STORMWATER
PIPES. FOR DESIGN PURPOSES BASIN
B-2 HAS BEEN EXPANDED TO
I
/ i INCLUDE SOME AREA FROM THE
' ADJACENT PARCEL ABOVE.
BECAUSE TOPOGRAPHY LIMITS
1 +' FLOWS FROM THIS AREA, THERE 4( IS NO NEED TO CONTROL
�I \� + +' THESE FLOWS.
ONE OR MORE YARD DRAIN
CATCH BASINS MAY BE ;
PLACED IN BACK,,OF THE \ ;`
I
HOUSE AND CONNECTED \
TO THE STORMWATER j \ \ . .
PIPE AS NECESSARY JI \
TO PROVIDE V STORMWATER PIPE TO BE
POSITIVE DRAINAGE_- -'�� \\ 6" DIAMETER ASTM 03034
I OF THIS AREA TQ "� \, ' ; , �. PVC PIPE RATED TO SDR35
THE INFILTRATION i • -.;, .r ' • WITH GASKETED JOINTS, PLACED
DISPERSION THE • • / • y AND BEDDED PER THE MANU—
' ` � FACTURER'S RECOMMENDATION.
-� 'V / -,------- ',
'—! -L ROUTE STORMWATER PIPE AS
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INDICATED. ENSURE THAT
SURFACE FLOWS ARE NOT
,; -- �) ALLOWED TO FOLLOW THE
TRENCH DOWN THE SLOPE TO
+ THE SOUTH AND WEST OF
--- -- THE HOME
IPLACE 100' LONG INFILTRATION TRENCH AT THE POINT _
WHERE THE SLOPE OF THE GROUND BREAKS AT THEEROSIONCAUTION
S SEE NOTES ON
TOE OF THE SLOPE. TRENCH IS TO BE CURVED AS REG RDI CONTROL TON PLAN(S)F
I NEDESSARY TO FOLLOW THE CONTOUR. THE TRENCH REGARDING PROTECTION OF
IS DESIGNED AS AN INFILTRATION/DISPERSION TRENCH T U INFILTRATION SYSTEM
AND AS SUCH, THE TOP OF THE TRENCH MUST BE DURING CONSTRUC770N!
AT A CONSTANT ELEVATION.
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DETAIL DRAWING 1 - STORMWATER COLLECTION SYSTEM
I
40 NTI ENGINEERING & SURVEYING
•N_ Engineers — Land Surveyors — Geologists
I Construction Inspection — Materials Testing li6!6
/VTI 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491 100 SS ALE INO FEET 100
14
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I DUSTIN SLIMP HOM
E
STORMWATER INFILTRATION SYSTEM
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I PORTION OF FILTER FABRIC SLOPE OF GROUND
(6" MIN WIDTH) LEFT CONSTRUCT AND BACKFILL AT FINAL GRADE
EXPOSED TO THE ELEMENTS TRENCH SUCH THAT 2 - 4
IS INTENDED TO PROVIDE INCHES OF ROCK IS EXPOSED \
I PROTECTION FROM SILTATION AFTER REMOVAL OF THE y
OF THE TRENCH FOR THE TEMPORARY RAP OF FILTER
FIRST SEASON WHILE THE FABRIC
SOILS ABOVE BECOME WELL
I
VEGETATED . IT IS INTENDED
THAT THIS EXPOSED PORTION
OF FABRIC BE CUT OFF OR LINE OF TRENCH
LEFT TO DEGRADE IN THE EXCAVATION
SUNLIGHT AFTER THE FIRST BEFORE BACKFILL
I SEASON. \
d+ ` .%r • SLOPE OF PIPE CARRYING
I+• FLOWS TO THE DISPERSION
TRENCH IS VARIABLE
I PERFORATED PIPE
didoutiVa
(6" PVC, TYP.)
THROUGH ENTIRE
LENGTH OF TRENCH 36 INCH WIDE x 24 INCH DEEP
I FILTER FABRIC SUCH AS TRENCH BACKFILLED WITH CLEAN,
TREVlR?A SPUNBOND 1112WASHED DRAIN ROCK OR PEA GRAVEL
OR SIMILAR, PLACED
ACROSS BOTTOM, BACK,
1
AND TOP OF TRENCH
AS SHOWN
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ENTIRE DISPERSION TRENCH TO BE CONSTRUCTED AT A CONSTANT ELEVATION,
MEANDERING ALONG A SINGLE CONTOUR AS NECESSARY.
LENGTH OF DISPERSION TRENCH TO BE 100 FEET.
I
SCHEMATIC ONLY - NC) SCALE
ITHIS TRENCH WAS DESIGNED TO INFILTRATE 100X OF FLOWS AT THE 25 YEAR
STORM EVENT. THE DISPERSION CAPABILITIES ARE TO ALLOW GREATER FLOWS TO
BE DISPERSED AS SHEET FLOWS.
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DETAIL DRAWING 2 — INFILTRATION,/DISPERSION TRENCH
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4/17--
41. NTI ENGINEERING & SURVEYING_ Engineers - Land Surveyors - Geologists
VetConstruction Inspection - Materials Testing
INTI 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
I
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I DUSTIN SLIMP HOME
LEGEND EROSION CONTROL
IALL SLOPE TREATMENT \'N 1
PER NOTES ON OTHER /I
/
DETAIL DRAWINGS :� /
►•���� CUT SLOPE TREATMENT
��'
g•• PER NOTES ON OTHER :,.• i ,.
I
DETAIL DRAWINGS •�.�' ••• // i
. , /
UTILITY TRENCH TREAT- `%::::.� •'•
MENT PER NOTES ON •.•••:�
I
OTHER DETAIL DRAWINGS `.•••••• /
•
'•..• /
QUARRY SPALL LINED TEMPORARY (
SILTATION POND PER DETAILS ��' ''••.. .•,..•;.,,�. I •
••�
I ,
AND NOTES ON OTHER DETAIL
DRAWINGS 1 •
••�•A
I QUARRY SPALL LINED TEMPORARY
CONVEYANCE CHANNEL PER \ � .,
DETAILS ON OTHER DETAIL \ .••••••�
DRAWINGS \ \ 'iii•.
I
\ •••••
PROTECT CATCH BASINS ••4 \ \ .��••••••••
PER DETAIL ON OTHER �� •�: ••••••
DETAIL DRAWINGS ••�•i•�`� ••i••` o \ •••••••••••.
I ••••••••...•••,• O•••.�'iii
�•••••••••••Pi••••!�••••' 1••••••
LA SION •
CONTROL `�•••••••••••••`••-••.' \ \ �i i�••:i
WATTLES AS REQUIRED •.;�:❖•!•:•••••,• •.'••••••:
BY DETAILS AND TEXT ON '!••�;•• \ `�•�::
I
OTHER DETAIL DRAWINGS `:���! �•�:••
,41
:ii; /
II ....
/
/ :'
IEROSION CONTROL PLAN ,•••••••••••••••••,.
•
THESE DETAIL DRAWINGS ILLUSTRATE THE ••'••�••••••••••••••°` '••••••••
I SEDIMENT AND EROSION CONTROL FEATURES •••!•�o�•�.�•�•�•�•���•�•�•;••-'
OF THIS PLAN. SEE THE NOTES AND ••�-=� •
DETAILS ON OTHER DETAIL DRAWINGS
AND THE TEXT OF THE ACCOMPANYING
DRAINAGE, SEDIMENT, AND EROSION I
CONTROL PLAN.
DETAIL DRAWING 3 - EROSION CONTROL
I
41: + NTI ENGINEERING & SURVEYING
I _ Engineers - Land Surveyors - Geologists 50 25 0 50
.�� Construction Inspection - Materials Testing SCALE IN FEET
INTI 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
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DUSTIN SLIMP HOME
EROSION CONTROL
1
' EROSION CONTROL PLAN NOTES
' THE FOLLOWING SEQUENCE SHALL BE FOLLOWED:
1— STABILIZE FILL SLOPES BY COVERING WITH STRAW. SEE NOTES ON THESE DETAIL DRAWINGS FOR
ADDITIONAL INFORMATION. ADDITIONAL MEASURES MAY BE NECESSARY TO STABILIZE THESE SLOPES.
' 2— CONSTRUCT THE TEMPORARY CONVEYANCE CHANNEL AND SEDIMENTATION POND WHERE SHOWN ON
THE EROSION CONTROL MAP PER NOTES AND DETAILS ON THESE DETAIL DRAWINGS. COVER EXPOSED
SOILS RESULTING FROM CONSTRUCTION OF THE CHANNEL AND POND WITH STRAW AND THEN TREAT
THIS AREA AS A FILL SLOPE PER ITEM 1 ABOVE.
' 3— GRADE THE BUILDING SITE. SLOPE TO DRAIN TOWARD THE TEMPORARY SEDIMENT POND PER THE
EROSION CONTROL MAP WHILE PROVIDING FOR PERMANENT DRAINAGE TO THE CATCH BASINS WITH
ONLY MINIMAL REVISIONS.
' 4— COVER ALL EXPOSED SOIL ON THE BUILDING SITE WITH STRAW WITHIN 24 HOURS FOLLOWING
COMPLETION OF GRADING.
5— COVER THE CUT SLOPES SHOWN ON THE EROSION CONTROL MAP WITH WET SHREDDED STRAW.
SEE NOTES ON THESE DETAIL DRAWINGS FOR ADDITIONAL INFORMATION. ADDITIONAL MEASURES MAY BE
NECESSARY TO STABILIZE THIS SLOPE.
6— CONSTRUCT THE IMPROVEMENTS, INCLUDING THE INFILTRATION FACILITY. DO NOT ROUTE FLOWS
' DOWN THE STORMWATER PIPE TO THE INFILTRATION FACILITY AT THIS STAGE OF THE WORK. CONTINUE
TO COVER NEWLY EXPOSED SOILS WITH STRAW WITHIN 24 HOURS AND ROUTE FLOWS TO THE
SEDIMENT POND.
' 7— MAINTAIN ALL EROSION AND SEDIMENT CONTROL DEVICES, FACILITIES, AND COVERINGS
THROUGHOUT THE LIFE OF THE CONSTRUCTION PROCESS.
8— WHEN THE WORK IS COMPLETE AND ALL EXPOSED SOILS ARE PERMANENTLY COVERED, ROUTE
' FLOWS TO THE CATCH BASINS AND THE INFILTRATION FACILITY. MONITOR SEDIMENT DEPTH IN THE
CATCH BASINS FOLLOWING THE NEXT FIVE TO TEN RAINFALL EVENTS WHICH GENERATE SIGNIFICANT
FLOWS INTO THE CATCH BASINS.
9— REMOVE THE SILT PROTECTION FROM AROUND THE CATCH BASINS AFTER A MINIMUM OF FIVE
CONSECUTIVE RAINFALL EVENTS HAVE PASSED WHICH GENERATED SIGNIFICANT FLOWS WITHOUT
DEPOSITING MEASURABLE SEDIMENT IN THE CATCH BASINS.
I
DETAIL DRAWING 4 - EROSION CONTROL NOTES
EROS/ON CONTROL PLAN
N T I ENGINEERING & SURVEYING THESE DETAIL DRAWINGS ILLUSTRATE THE
SEDIMENT AND EROSION CONTROL FEATURES
OF THIS PLAN. SEE THE NOTES AND
DETAILS ON OTHER DETAIL DRAWINGS
_ Engineers — Land Surveyors — Geologists AND THE TEXT OF THE ACCOMPANYING
Construction Inspection — Materials Testing CONTROL PLAN.
N/T�I 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491 DRAINAGE, SEDIMENT, AND EROSION
17
DUSTIN SLIMP HOME
EROSION CONTROL
GENERAL SEDIMENT AND EROSION CONTROL NOTES
' THE MAPS, DETAIL DRAWINGS, AND NOTES INCLUDED ON THESE DETAIL DRAWING PAGES ARE
INTENDED TO SUPPLEMENT AND EXPLAIN THE FULL SEDIMENT AND EROSION CONTROL PLAN
WHICH IS CONTAINED IN THE ACCOMPANYING DRAINAGE, SEDIMENT, AND EROSION CONTROL
PLAN PREPARED FOR BISHOP BROTHERS CONSrRUCT10N.
' THE FULL SEDIMENT AND EROSION CONTROL PLAN CONTAINS ADDITIONAL PROVISIONS THAT
APPLY TO THIS PROJECT AS WELL AS PROVISIONS FOR DEALING WITH LESS COMMON OR
UNEXPECTED SITUATIONS AND EVENTS WHICH MAY OCCUR.
FILL SLOPE TREATMENT
' COVER FILL SLOPES WITH AN INI77AL HEAVY COATING OF STRAW. EXTEND THE STRAW TO
COVER AREAS WHERE UNVEGETATED SILT HAS COME TO BE LOCATED AT THE BOTTOM OF
THE FILL SLOPES. ALSO EXTEND THE AREA TO BE COVERED A MINIMUM OF THREE FEET
ONTO THE BUILDING SITE.
' AFTER THE FIRST MEASURABLE RAINFALL PLACE STRAW AGAIN OVER ANY AREAS WHERE THE
FIRST COVERING OF STRAW HAS BEEN WASHED AWAY.
REPEAT AFTER THE SECOND RAINFALL AND THE THIRD.
IF STRAW IS NOT SUCCESSFUL IN STABILIZING THE FILL SLOPES AFTER BEING REPLACED
TWICE, REPLACE THE STRAW A THIRD TIME AND COVER WITH JUTE MATTING STAKED INTO
THE SLOPE PER THE MANUFACTURER'S RECOMMENDATIONS. RUN THE JUTE UP AND DOWN
' THE SLOPE WITH A MINIMUM OF 12 INCHES OF OVERLAP BETWEEN RUNS. INSTALL EROSION
CONTROL WATTLES ON THE BOTTOM OF ANY AREAS COVERED WITH JUTE MATTING. PLACE
THE WATTLES AS SHOWN ON THE EROSION CONTROL MAP. EXTEND WATTLES A MINIMUM OF
TEN FEET BEYOND THE LIMITS OF JUTE MATTING.
' IN AREAS WHERE JUTE COVERED STRAW IS NOT SUCCESSFUL IN PROTECTING THE FILL
SLOPE FROM EROSION AS EVIDENCED BY THE CONTINUED FORMATION OF RILLS AND
RUTTING, PULL BACK THE JUTE AND COVER THE REMAINING EXPOSED AREAS WITH A
MINIMUM OF THREE INCHES OF COMPOST AND REPLACE THE JUTE AND RESTAKE.
IF THESE COVERINGS ARE NOT SUCCESSFUL IN ALLOWING A HEALTHY STAND OF GRASS OR
NATIVE VEGETATION AT THE END OF THE FIRST GROWING SEASON FOLLOWING THE INITIAL
COVERING OF THE SLOPE, HYDROSEED AND MULCH THE FILL SLOPES ONCE DURING THE
PERIODS OF APRIL 1 THROUGH JUNE 30 OR SEPTEMBER 1 THROUGH OCTOBER 1,
WHICHEVER OCCURS FIRST.
CONTACT THE ENGINEER, DAVID HANNA, PE AT 360-452-8491 IF REPEATED EFFORTS ARE
NOT SUCCESSFUL IN PREVENTING EROSION OR IF THERE ARE ANY QUESTIONS.
DETAIL DRAWING 5 - EROSION CONTROL NOTES (CONT.)
EROSION CONTROL PLAN
THESE DETAIL DRAWINGS ILLUSTRATE THE
' ,4 NTI ENGINEERING & SURVEYING SED/MENT AND EROSION CONTROL FEATURES
OF THIS PLAN. SEE THE NOTES AND
,�r- DETAILS ON OTHER DETAIL DRAWINGS
_ Engineers - Land Surveyors - Geologists AND THE TEXT OF THE ACCOMPANYING
N DRAINAGE, SEDIMENT, AND EROSION
Construction Inspection Materials Testing CONTROL PLAN.
' NT! 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
' 18
I
DUSTIN SLIMP HOME
EROSION CONTROL
ITEMPORARY CONVEYANCE CHANNEL AND SEDIMENT POND
THE CONVEYANCE CHANNEL AND POND SHALL BE EXCAVATED TO THE DIMENSIONS INDICATED
AND LINED WITH GEOTEXTILE RECOMMENDED BY THE MANUFACTURER FOR USE AS FILTER
I FABRIC. PLACE THE POND IN THE RELATIVELY FLAT AREA WHERE INDICATED ON THE EROSION
CONTROL MAP. EXTEND THE CONVEYANCE CHANNEL A MINIMUM OF FIVE FEET ONTO THE
BUILDING SITE. THE LOWER EDGE OF THE SEDIMENT POND SHALL BE CONSTRUCTED TO A
CONSTANT ELEVATION TO DISPERSE FLOWS AS SHEET FLOW.
THE CONVEYANCE SHALL THEN BE LINED WITH A MINIMUM OF TWO LAYERS OF QUARRY SPALLS
OR NINE INCHES, WHICHEVER IS THICKER. EXTEND THE QUARRY SPALLS A MINIMUM OF TWELVE
INCHES ONTO THE SURROUNDING GROUND.
ITHE SEDIMENT POND BOTTOM SHALL BE LINED WITH A SINGLE LAYER OF QUARRY SPALLS OR
SIX INCHES, WHICHEVER IS THICKER. THE SIDES OF THE POND (WITHIN THREE FEET OF THE RIM
INSIDE THE POND AND WITHIN 1 FOOT ON THE OUTSIDE) SHALL BE LINED IN THE SAME
IMANNER AS THE CONVEYANCE CHANNEL..
THE CONVEYANCE CHANNEL AND SEDIMENT POND SHALL BE MAINTAINED UNTIL FLOWS ARE
ROUTED TO THE CATCH BASINS AND INFILTRATION SYSTEM AS PROVIDED FOR ELSEWHERE.
I
REMOVE ACCUMULATIONS OF SILT FROM THE FOND WHEN THEY REACH A DEPTH OF SIX INCHES
OR MORE.
I
0•���� SITE GRADING
A....
THE BUILDING SITE, WHICH INCLUDES ALL OF THE LEVEL PORTION OF BASIN B-2, SHALL BE
GRADED CONSISTENT WITH THE PERMANENT STORMWATER PLAN WHICH REQUIRES ALL
I
STORMWATER TO BE ROUTED TO CATCH BASINS. TEMPORARY CONSTRUCTION PHASE GRADING
SHALL PROVIDE FOR A SHALLOW SWALE TO ROUTE FLOWS FROM THE AREAS OF THE CATCH
BASINS TO THE TEMPORARY CONVEYANCE SHOWN ON THE EROSION CONTROL PLAN.
CARE SHALL BE TAKEN DURING THE INITIAL SITE GRADING THAT NO FLOWS BE ALLOWED TO
I
PASS DOWN ANY OF THE FILL SLOPES TO THE WEST OR SOUTH OF THE BUILDING SITE.
WHEN INSTALLED, THE CATCH BASINS SHALL BE PROTECTED TO PREVENT SILT FROM ENTERING
THE INFILTRATION FACILITY UNTIL SOILS ON THE BUILDING SITE ARE FULLY COVERED.
IIT IS PREFERRED THAT ALL SITE GRADING ACTIMMTTES BE CONDUCTED AT THE SAME TIME AND
THEN THE EXPOSED AREAS BE COVERED AND PROTECTED BUT IT IS EXPECTED THAT SOME
AREAS WILL HAVE TO BE EXCAVATED LATER.
I EACH AREA OF EXPOSED SOIL SHALL BE COVERED WITH STRAW WITHIN 24 HOURS AFTER
COMPLETION OF THE WORK IN THAT AREA.
CARE SHOULD BE TAKEN THAT THE GRADING PROVIDES FOR LATER REROUTING OF FLOWS FROM
I THE TEMPORARY CONVEYANCE AND SEDIMENT POND TO THE CATCH BASINS WITH ONLY MINIMUM
DISTURBANCE OF SOIL.
THE CONTRACTOR IS DIRECTED TO THE FULL TEXT OF THE SEDIMENT AND EROSION CONTROL
I
PLAN WHICH IS INCLUDED IN THE ACCOMPANYING DRAINAGE, SEDIMENT AND EROSION CONTROL
PLAN. THAT PLAN CONTAINS ADDITIONAL PROVISIONS WHICH SPECIFICALLY APPLY TO SITE
GRADING ON THIS PROJECT.
I DETAIL DRAWING 6 - EROSION CONTROL NOTES (CONT.)
EROSION CONTROL PLAN
lli_114. THESE DETAIL DRAWINGS ILLUSTRATE THE
N T I ENGINEERING & SURVEYING SEDIMENT AND EROSION CONTROL FEATURES
I titifi/-----
OF THIS O. SEE THE NOTES AND
DETAILS ONN OTHER DETAIL DRAWINGS
Engineers Land Surveyors Geologists AND THE TEXT OF THE ACCOMPANYING
Construction Inspection DRAINAGE, SEDIMENT, AND EROSION Materials Testing CONTROL PLAN.
INT! 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
I19
DUSTIN SLIMP HOME
EROSION CONTROL
I
W; CUT SLOPE TREATMENT
COVER CUT SLOPES WITH A HEAVY COATING OF WET SATURATED SHREDDED STRAW.
AFTER THE FIRST AND AGAIN AFTER THE SECOND MEASURABLE RAINFALL, RECOVER ANY AREAS
' WHERE THE FIRST COVERINGS OF STRAW HAVE BEEN WASHED AWAY.
IF STRAW IS NOT SUCCESSFUL IN STABILIZING THE FILL SLOPES AFTER BEING REPLACED ONCE,
EXCAVATE A SEDIMENT TRAPPING DITCH A MINIMUM OF 12 INCHES DEEP AND 24 INCHES WIDE
AT BASE OF THE CUT SLOPE EXTENDING A MINIMUM OF TEN FEET BEYOND AREAS THAT REMAIN
' UNCOVERED. ROUTE FLOWS FROM THIS DITCH TO THE TEMPORARY CONVEYANCE AND SEDIMENT
POND. REMOVE ANY ACCUMULA77ONS OF SILT OF MORE THAN SIX INCHES FROM THE SEDIMENT
DITCH. THIS DITCH IS TO BE MAINTAINED IN PLACE TO PROTECT THE INFILTRATION SYSTEM UNTIL
THE CUT SLOPE IS SUCCESSFULLY REVEGETATED.
HYDROSEED AND MULCH THE CUT SLOPE ONCE DURING THE PERIODS OF APRIL 1 THROUGH
JUNE 30 OR SEPTEMBER 1 THROUGH OCTOBER 1, WHICHEVER OCCURS FIRST.
•9•
UTILITY TRENCH TREATMENT
' x UTILITY TRENCHES LOCATED OFF OF THE BUILDING SITE AREA, INCLUDING THOSE FOR POWER,
WATER, SEPTIC, STORMWATER, AND OTHER UTILIT'ES SHALL BE COVERED AND PROTECTED IN THE
SAME MANNER AS FILL SLOPES.
' PROTECTION OF CATCH BASINS
CATCH BASINS SHALL BE PROTECTED WITH SILT FENCING UNTIL EXPOSED SOILS ARE COVERED
OR REVEGETATED AS PROVIDED FOR ELSEWHERE IN THESE NOTES. IF PROTECTION OF CATCH
BASINS IS NECESSARY FOR MORE THAN THREE MONTHS, INSTALL FILTER FABRIC, GRAVEL, AND
WIRE MESH PROTECTION PER DETAIL.
DETAIL DRAWING 7 - EROSION CONTROL NOTES (CONT.)
EROSION CONTROL PLAN
THESE DETAIL DRAWINGS ILLUSTRATE THE
N T I ENGINEERING & SURVEYING SEDIMENT AND EROSION CONTROL FEATURES
OF THIS PLAN. SEE THE NOTES AND
DETAILS ON OTHER DETAIL DRAWINGS
_ Engineers — Land Surveyors — Geologists Construction Inspection — Materials Testing AND THE TEXT OF THE ACCOMPANYING
�1 DRAINAGE, SEDIMENT, AND EROSION
/ CONTROL PLAN.
' NT! 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
' 20
I
I DUSTIN SLIMP HOME
EROSION CONTROL
I
STAKES- - -
I ;•.
..... ......
:...... ........
L.:..•..• ► .:::::.::.:::::•I.:
......... ........
........ .. ......
......
:......:
.......... .........
............ ..........
...............
�.❖.❖.❖.•.s..:❖.. :::::•:❖••••••••••••••••:�
Wit.❖• .::.•1i•❖.;.*.
DROP INLET FILTER FABRIC
WITH GRATE MIRAFIC 100 NS
OR EQUIVALENT
I 2"x2"
WOOD STAKE
I
FILTER FABRIC -
RUNOFF WATER-
IIWITH SEDIMENT
IN I— I I— I
FLOW
IBURIED FILTER--
FABRIC
I
I
DETAIL DRAWING 8 - SILT FENCE PROTECTION OF CATCH BASIN
EROSION CONTROL PLAN
�jr -.' THESE DETAIL DRAWINGS ILLUSTRATE THE
I �` N T I ENGINEERING & SURVEYING SEDIMENT AND EROSION CONTROL FEATURES
OF THIS PLAN. SEE THE NOTES AND
DETAILS ON OTHER DETAIL DRAWINGS
Engineers — Lond Surveyors — Geologists AND THE TEXT OF THE ACCOMPANYING
N_ DRAINAGE, SEDIMENT, AND EROSION
Construction Inspection — Materials Testing CONTROL PLAN.
INT1 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452.8491
I21
DUSTIN SLIMP HOME
EROSION CONTROL
1
1
1
rWASHED ROCK
(12" MIN. DEPTH)
RUNOFF WATER .;o%vggSoi g000igiiio goii*g;,
WITH SEDIMENT °S%gog oeg4.2,40..0..... 00000°°
FILTERED
18"IUIN. WATER 1" x 1" WIRE MESH
' WITH FILTER FABRIC
ON TOP
NOTE: ALL FILTER FABRIC SHALL BE WRAF! 14ONS OR EQUAL
DETAIL DRAWING 9 — FILTER FABRIC, GR
AVEL, AND WIRE
MESH PROTECTION OF CATCH BASIN
EROSION CONTROL PLAN
THESE DETAIL DRAWINGS ILLUSTRATE THE
' N T I ENGINEERING & SURVEYING
Engineers — Land Surveyors — Geologists SEDIMENT AND EROSION CONTROL FEATURES
OF THIS PLAN. SEE THE NOTES AND
�1_
DETAILS ON OTHER DETAIL DRAWINGS
AND THE TEXT OF THE ACCOMPANYING Construction Inspection DRAINAGE, SEDIMENT, AND EROSION Materials Testing CONTROL PLAN.
' NTI 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
' 22
I
I DUSTIN SLIMP HOME
EROSION CONTROL
I
I
I -.0
15'
I
"'.- QUARRY SPALLS
4' MIN.
. 1' MIN. OVER LOW
�•-S- i
1' MIN.
�L
3.5"-5 I11' MIN.
I 1.5' MIN.
i'' — 1.5" QUARRY SPALLS
FLAT BOTTOM t WASHED GRAVEL
GEOTFXTILE
I
NOTE:
TRAP MAY BE FORMED BY —*0
BERCOMPLETE EXCAVATION PROFILE M OR BY PAR77AL
OR
III
law-8' MIN.
NATIVE SOIL OR \, / \�/ MIN. 1' DEPTH
COMPACTED BACKFILL •!, i� 2IN. " ROCK
I GEOTEXTILE .7 /,/ �/���/��/ /\� ,� \ MIN. 1' DEPTH i" —1.5"
,�,��/\�,�,, ,�� ,' ,x,� WASHED GRAVEL
SECTION A-A
I
III
I DETAIL DRAWING 10 - SEDIMENT TRAP
IEROSION CONTROL PLAN
07,
N T I ENGINEERING & SURVEYING THESE DETAIL THE
SEDIMENT AND DRAWINGS
CONTROL ILLUSTRATE FEATURES
i
OF THIS PLAN. SEE THE NOTES AND
DETAILS ON OTHER DETAIL DRAWINGS
Engineers — Land Surveyors — Geologists AND THE TEXT OF THE ACCOMPANYING
Construction Inspection — Materials TestingDRAINAGE, SEDIMENT, AND EROSION
P CONTROL PLAN.
INTI 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452.8491
I23
WATTLE CASING IS A BIODEGRADABLE 1" SQUARE STAKES DRIVEN THROUGH
TUBULAR PLASTIC OR SIMILAR ENCASING f WATTLE EVERY 3' — 4'
MATERIAL
8" — 10" STRAW
PLACE WATTLE IN 3" — 5" FILLED WATTLE
DEEP TRENCH
1 .:Al •
/ l ,
�/ / // / / / —ii
—//
1 // %/ ///
' STRAW WATTLE — STANDARD STAKING
NO SCALE
FOR SHORT DURATION PROJECTS
' WHERE THE CONTRACTOR DESIRES
TO REUSE THE WATTLES WITHOUT V
DAMAGING THE CASING THE ALTERNATE A
A—FRAME STAKING METHOD SHOWN
HERE MAY BE USED.
1
/ /-
// -i/i-/// -
//_/i-///_
STRAW WATTLE — ALTERNATE STAKING
NO SCALE
' I�J j NTI ENGINEERING & SURVEYING
Engineers — Land Surveyors — Geologists
EE1
•I Construction Inspection — Materials Testing
N/ I 717 SOUTH PEABODY,PORT ANGELES,WASHINGTON 98362,(360)452-8491
24
I
I
GEOTECHNICAL REPORT and STORMWATER SITE PLAN
I for
Parcel 901-245-004
INew Home for Dustin Slimp
IJEFFERSON COUNTY STANDARD STORMWATER SITE PLAN NOTES
I • All erosion and sediment control Best Management Practices shall be selected,
constructed, and maintained in accordance with the Washington Department of
Ecology Stormwater Management Manual for Western Washington (current
Iedition).
• The construction and maintenance of erosion and sediment control measures
Ishall be the responsibility of the contractor. The contractor shall not deviate from
the approved plans without prior approval from the Jefferson County Public
Works Department. The contractor shall have a set of approved plans on the
Isite whenever construction is in progress.
I
• The erosion and sediment control measures depicted on this plan are minimum
requirements to meet anticipated site conditions. As conditions dictate during
construction, the contractor shall implement additional measures as necessary
Ito ensure erosion and sediment control.
• Construction vehicle access shall be limited to one route, whenever possible.
I Quarry spalls or crushed rock shall be applied to the access in order to prevent
sediment from being transported onto roads. If this should occur, roads shall be
cleaned thoroughly by shoveling or sweeping.
I • Clearing shall be phased so that only areas that are being worked are exposed.
All exposed and unworked soils shall be stabilized by appropriate Best
I Management Practices. From October 1 through April 30, unworked soils shall
not be left exposed for more than 2 days. From May 1 through September 30,
unworked soils shall not be left exposed for more than 7 days.
• All erosion and sediment control measures shall be maintained in a satisfactory
condition until such time as land disturbing activities are completed and the
Ipotential for onsite erosion has passed.
• The contractor shall request inspection of temporary erosion and sediment
I control measures by the Jefferson County Public Works Department [(360) 385-
9160] as soon as practicable after installation.
I
I
25
I
IGEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
INew Home for Dustin Slimp
I
IABSTRACT
I
This project consists of the construction of a new home with a 60' x 60' footprint
I and related work on a 4.9 acre parcel located at 62 Spring Hill Road in
unincorporated Jefferson County. The new home will occupy only a small portion
of the parcel.
IThis Stormwater Site Plan (SSP or Plan) was prepared to examine and
recommend Best Management Practices (BMPs) to mitigate stormwater related
I impacts of the construction of this project as required by Jefferson County. It is
based on the 2005 Stormwater Management Manual for Western Washington,
published by the Washington Department of Ecology (DOE Manual).
IThe Geotechnical Report was prepared to document an assessment performed
in response to the property being listed as a landslide hazard area by the
I
Jefferson County Department of Community Development.
Ground disturbing work will be confined to the building site except for utilities.
I Runoff from the building site will be infiltrated and areas disturbed by utility
construction will be stabilized and returned to their natural state.
I The infiltration facility was designed based on a geotechnical evaluation of the
soils.
IConstruction phase erosion and sediment control measures are proposed to
prevent soil from leaving the site during construction of the improvements as well
as to protect the infiltration facility during the construction phase. Detail drawings
Ishowing the proposed BMPs and their location are included with this report.
This Plan includes the Construction Stormwater Pollution Prevention Plan
I (CSPPP) in its entirety. As a minimum, the CSPPP requires slope covering,
sediment control wattles and protection of inlets. Additional BMPs are included
for use in the event that unforeseen circumstances require additional measures.
I
I
26
I
I GEOTECHNICAL REPORT and STORMWATER SITE PLAN
for
Parcel 901-245-004
I New Home for Dustin Slim
,
I
I JtttthSUT CL'UNIY UCU
`a '' ,'` ,fit
T
I
i , . • a t
1• is
•6
rye.
Kr
y tea, 'i v 4,
11�yLI -,,, Y r fi"�,-",*} L!j!�` YF , > r 4 i fl-s�.7.
'p'` �i.
ai . t
IPhoto 1
II. OVERVIEW
IThis plan was prepared to provide a reasonable level of protection, as required
by Jefferson County ordinance, against damage being caused to properties
I within or without the project during construction or as a result of increased
stormwater runoff after development of the project. It follows the guidelines
contained in the 2005 Edition of the Stormwater Management Manual for
I Western Washington (2005 Manual), published by the Washington State
Department of Ecology (DOE).
I27
This project consists of the construction of a new home with a 60' x 60' footprint
and related work on a 4.9 acre parcel located at 62 Spring Hill Road in
' unincorporated Jefferson County. The new home will occupy only a small portion
of the parcel.
The building site is shown in Photo 1.
A. Pre-Developed Condition
' 1. Pre-Contact Condition
It is assumed that the pre-contact condition of the site is old growth timber,
as required by the 2005 Manual.
2. Existing Condition
The site is presently undeveloped except for the road and buildingsite.
P p
Photo 2 shows an overview of the parcel. The cleared building site can be
' seen on the right. The existing timber is quite large and more closely
resembles old growth forest than young second growth timber and brush.
This plan uses mature forest as the existing condition of the parcel.
Jar
Photo 2
28
I
IThe surrounding neighborhood consists of a high plateau to the east of the
project location with slopes to the north and south and through the parcel
I leading down to the valley floor to the west as shown on Map 4 -
Neighborhood Drainage Patterns on Page 11 and on the USGS topo map
segment included as Map 7.
I
. n I ` v '
'. i,
IIi - < i
U
I I ; ,)
�4s� t_ �a ,. . _ 13 '
I
- -C-— — A C
® � � I s DUSK'
I I� off
i LIN
SUMP
` �; 0.
o. HOME 1
SITE l 0
i/ 24 Q� '
, /0
0' ' f VI --fi. nO .4
) ( /11 i
i \, \), \‘,. IX
II ( .._ ---- +.
Vf. - .-4
I r:i.) i' tg ,
._..., ((-. ,,,,,
, :,. r f_
, ,..__,
• • . , . 2....4 .4 - t -4
IMap 7 - USGS Topo Map Segment
IMore detailed topographic information is shown on Map6 - Drainage
Basins on Page 13. Map 6 shows a small ridge which acts to isolate the
Iproject site from run-on from lands above.
The building site has been cleared and rough graded, creating a level pad
Iwhere the home will be constructed as shown in Photo 3 and on Map 5 -
Site Sketch on Page 12.
I
I
I29
I
I ff.'
y,,. s },
, - ., r .alE0.
fi' c
%-, 4.,,, ./ ( .'
�.[,�,�y,,I r.
4 - - .y"'� . ,i g
Photo 3
IA large cut slope above the building site is just beginning to sprout
vegetation but will not be entirely revegetated until one or more growing
I seasons have elapsed. Special procedures may be necessary to ensure
that this slope becomes stabilized as discussed in the Erosion Control
Map and Notes beginning on Page 16.
I
t A.
4 _
�,s• . .
I30
' The lands below the parcel to the west is undeveloped except for a narrow band
of fill slope and small areas just below as shown in Photo 4.
4:-,.
•
I
s^
•
F •x, •
! ^
' Photo 4
B. Developed Condition
' It is proposed to construct a single family home with necessary utility
connections, access, and landscaping. Map 5 - Site Sketch on Page 12
' shows the locations of the proposed improvements on the parcel. Additional
design information is included in the Appendices.
C. Proposed Improvements
The parcel area is approximately 4.9 acres. For the purposes of runoff
' calculations an area of 213,823 square feet (4.9078 acres) is used to more
easily handle rounding of some runoff areas and coefficients. The project will
disturb a footprint of up to 0.9356 acres of soil as shown on Figure 1 -
' Disturbed Soils Footprint on Page 32. If field changes to the project are
contemplated that may increase the area of this footprint, a new area should
be calculated. If the new area will be greater than 1.00 acres, a Construction
' Stormwater National Pollution Discharge Elimination System (NPDES) permit
will be required.
31
I
I
13'WIDE UTI[lry/-7'
I
CORRIDOR
I
i 0-4* ,..11,
,.i:.:t.
-z:z.... .....
_._
A.
„:„.
.:.:.:.
Iiiiik.
I \ / `:" .
TOTAL DISTURBED FOOTPRINT •••\ •.i :• •:;: §'.
40754 SQUARE FEET J.4❖:❖.. **..
= 0.9356 ACRES :i•❖:❖:
I
/ '
Iii
I
ACI x9'11,7"RON
FACILITY FOOTPRINT
I
I
Figure 1 - Disturbed Soils Footprint
The footprint of disturbed soils during the construction phase (shown in Figure
I 1) will be different from the area that will be permanently converted to lawn,
landscaping, driveway, roof or similar uses because much of the areas
disturbed during utility construction are narrow corridors which will revegetate
Iwith native species without changing the forested character of the location. A
total of 0.4792 acres (20,874 square feet) will be permanently converted. See
computer printouts in the appendices for full calculations. Both of these areas
Iare different from the total area (0.5235 acres) used to design the
infiltration/dispersion facility which includes 0.0443 acres of forested lands on
the ridge on the adjacent parcel to the east (uphill) of this project as shown in
IMap 6 - Drainage Basins on Page 13.
New (pollution generating) impervious surfaces (roof and driveway) will be
I0.1629 acres (7,096 square feet) while landscaping (pollution generating
pervious surfaces) will occupy the 0.3163 acres (13,778 square feet)
I
remainder of the converted area.
D. Stormwater Runoff
IBecause of the unique location of the building site near the top of a ridge, the
work can be accomplished significantly without adversely impacting the runoff
32
I
Ileaving the parcel. Map 4 - Neighborhood Drainage Patterns on page 11
shows the basins that affect this project. All but a small amount of runoff from
lands above are intercepted by natural landforms and routed around the
Iproject. The small amount that flows down the cut slope on the east is simply
included in the design flows for the infiltration facility.
IAll of these basins ultimately drain to the right of way for Highway 19 which
drains via roadside ditches, eventually reaching East Chimacum Creek as
shown on page 9.
I
1. Pre-Contact Stormwater Runoff
I It is assumed that the re-contact condition of
p o the site is old growth timber,
I
as required by the 2005 Manual.
There is no evidence of prior large scale grading activities on the site,
I
indicating that pre-contact stormwater runoff would have been similar to
the existing (pre-development) condition.
I
After leaving the site, pre-contact flows would have reached East
Chimacum Creek in a meandering flow path.
I2. Pre-Developed Stormwater Runoff
IIn its present, pre-developed, condition flows travel as sheet flows over
building site and then as a combination of sheet and dispersed flows to
I the bottom of the parcel. Some concentration of flows does occur at the
existing Spring Hill Road but the road is located in a natural drainage area
so the concentration mimics pre-Contact flows. The existing flow
I
conditions are shown in Map 6 - Drainage Basins on Page 13.
I3. Post-Developed Stormwater Runoff
Basins A, C, and D will remain unchanged by this project. Basin B has
I been split into Subbasins B-1 and B-2. Flows from B-1, the undeveloped
portion will remain unchanged. Flows from Subbasin B-2 will be 100%
infiltrated, which will reduce the total flows in Basin B sufficiently to
I account for the small increase in flows from the pre-contact condition
caused by the previous construction of Spring Hill Road. Full calculations
are included in the appendices.
I
I
I
33
I
1 E. Controlling and Challenging Site Parameters
The single major challenge was to provide for the control of erosion from the
I
building site. The site has already been cleared and a large soil stockpile,
shown in Photo 5, exists on the leveled building site.
I
i
I -
T
I
I
Photo 5
While this stockpile has been covered with plastic sheeting, soil has been
I
eroded and transported into the vegetation on the level area immediately
below the building site as shown in Photo 6.
I
r'° •!�`f.1 tl a 'i .. ,r
'.- a 4i'4 f
'y+ a
•
•
- . X •
I I .
I
Photo 6
I
34
1
One minor challenge was to find a location for the infiltration/dispersion
facility. If it were designed on the building site, the lower permeability of the
' Cassolary Soils would have required the trench to be more than 200 feet
long. It was decided to locate it further down the parcel in the Indianola Soils
where a conservative design still allows the trench length to be reduced to
' 100 feet.
' F. Natural Drainage System
The natural flow regime from this site consists of sheet flows to the west to
join with concentrated flows from the plateau above as shown on Map 4 -
INeighborhood Drainage Patterns on Page 11. The construction of Spring Hill
Road has increased runoff a small amount but this will be offset by infiltrating
all rain falling on Subbasin B-2. Other than these minor effects, there will be
' no changes in the natural drainage systems. Flows will leave the site in their
natural corridors.
' G. Drainage To and From Adjacent Properties
Drainage to and from adjacent parcels is shown on Map 4 - Neighborhood
' Drainage Patterns on Page 11 and Map 6 - Drainage Basins on Page 13.
This project will not change these drainage patterns.
' 1. Bypass Flows
There will be no bypass flows.
H. Vicinity Maps
' A vicinity map is included as Map 1 on page 8. The Area Map included as
Map 2 - East Chimacum Creek Valley on page 9 and the Neighborhood Map
included as Map 3 - Neighborhood Overview on page 10 also contain useful
information about the surrounding areas.
I. Site Map
A site sketch map is included as Map 5 on page 12. Other maps are included
in the same area at the beginning of this report.
J. Surface Soils
The site maybe found on mapnumber 49 of the
t e Soil Survey of Jefferson
' County Area (the Soil Survey) published by the U. S. Soil Conservation
Service, a portion of which is reproduced here as Map 8.
I
' 35
I
I
\ /SI
1 •• ,
\ CfD SnC SnD
N
CO
I Ill IPIN'�v ,
j� is
I Se
II
M
Sh
I
CID I°G Of¢ auly l,i ItpalY (1C(J
InD
24k
I \ CdB /—In�G
\ InD /
I
10E ) InD\
I
C\---'..-
,, \Bh'\ c,. S Se CfCP ,nC ,-----r
-' CEO : ..
oE /
� . \. r
I Sm
n �1 CfD IO i" ^ In
IIMap8 - Soils
I
Map 8 can be compared with the other maps at the beginning of this report for
additional orientation.
I Map8 shows that soils on the upperportion of theparcel are Type CfD
PP Yp
Cassolary sandy loam. These soils have a complex history which began with
Ithe basalt rocks of the Olympic Mountains. During the glacial period, glaciers
scoured away at the underlying basalt bedrock and carried the resulting
I
material downslope. As the glaciers melted they deposited glacial drift (glacial
drift is any soil carried and deposited by glaciers) over the landscape. The
weight of the continental glaciers actually depressed the underlying soil and
I rock formations so they were below sea level, They remained below sea level
long after the glaciers melted. The other parent material, marine sediments,
was then laid down as fine sediment under the sea. The land then slowly
I rebounded to near its original elevation over many hundreds of years. During
this process streams cut through the soils, mixing and redepositing them on
flood plains and stream bottoms. This caused the soils to be sorted by grain
I size with the larger particles being deposited first as the waters slowed and
the finer particles left in areas where slower velocities were achieved. The
deposition areas where Cassolary soils are now found are located at
36
I
Ielevations less than 500 feet. As the streams cut through these flood plains
and bottoms, they left flat areas known as terraces exposed above the new
stream elevations. These fine mixed soils on terraces with slopes ranging
Ifrom 15 to 30% form the present day CfD Cassolary soils. They are
somewhat fine grained with sufficient cohesion that they are very resistant to
erosion. They are only moderately well drained but do not have a shallow
Irestrictive layer such as hard pan. This results in a soil that is considered very
deep and will not retain moisture through the driest months of the year. A
I
shallow perched water table often occurs during the wet months of the year.
Drought resistant species of plants will commonly be found in these soils.
These soils have a permeability of 0.6 - 2.0 inches per hour through the upper
22 inches and 0.2 - 0.6 inches per hour through deeper soils. Cassolary soils
Iare in hydrologic group C.
Field investigation indicates that the soils exposed on the cut slope above the
Ibuilding site contain gravels as well as sands as shown in Photo 7.
r ar -iir.4' ,
if.
�' �F r s • v�� � �
t .
2 ,1. ;. • 11.A•. .k .;$1;"if ' l'.. _IL e•• ..„ "" ,„ :i:: ',hitt J.. ' 4,jib.: -
titft
ro * ..A ,, V r '� i r�
p
Photo 7
Observation of the building site indicates that most rain appeared to have
I infiltrated rather than running off. Rilling of the cut bank, while present in
some areas, is minimal as shown in Photo 8. While the grain sizes are
different, the permeability and resistance to erosion are consistent with the
I expected behavior of Cassolary soils. Because this report is concerned with
the hydrologic behavior of the soils, it assumes the soils on the upper part of
the site behave as Cassolary soils.
I
I
37
I
I it.1
,
J�i; y /aif r
•;.---- ' i. . . .r. ' -..,?, 4 14 t : ..1)te"\
,r:,: ,....-.7,..*:../:, :4:7.",,•,..r, ....:'.::4:,,,,,,E-:' 11/4 lb*.r.t4.:4‘`!1:;:,./..7*,.- , ii:31%)"... _I:N:i., c..:ik.''.';;C;77:' ' 1 -
.:, ...' • • ; '1", "I ft i tc p'
fi0F 4 a
.1 , ... z..„. . .. ,.,., , ~ �: .,...„ .tii.
.;0416- li ', *,:-.4'.,. s • iv. ,,,... : - 1 -. . .
,,.:. 1 .
•)
. iopv,.).„,iek ,„ ....4"r„,..t, It=';'-:,"74 .... .-:'4 40 i' -rj-'
IPhoto 8
IMap number 49 predicts that the soils on the lower portion of this site are type
InC, Indianola loamy sand on slopes ranging from 0 to 15 percent. These
sandy soils resulted from the flow of streams from glaciers. As the glaciers
Imelted, the meltwater carried sediments in streams flowing on top of and
under the glaciers. When the glaciers melted, sandy and gravelly sediments
were left behind as long (hundreds of feet) meandering deposits, known as
Ieskers, where these streams had flowed. Other fan shaped deposits, known
as alluvial fans, of similar material were left where the streams slowed as they
ponded on the surface of the glacier, left the glacier or entered a body of
Iwater. These deposits are known as kames. These processes resulted in the
sediments being sorted by the varying velocities of the flows. Larger gravels
and cobbles were deposited in areas of higher velocities and finer particles
I such as silts were carried further down the streams. Indianola soils were
formed in the sandy particles deposited by intermediate velocities. In some
I
instances, the sandy parent material of Indianola soils was deposited on
relatively level meltwater plains.
I
Later flows cut down through these various types of sandy deposits, leaving a
landscape of terraces and escarpments. Terraces are level areas remaining
and escarpments are the sides of the channels formed by the streams as they
I
cut into the deposits. As a result Indianola soils may be found on slopes
ranging from 0 - 50 percent although type InC Indianola soils are found on
slopes ranging from 0 - 15 percent. Indianola soils are found at elevations
ranging from sea level to 1000 feet. In some areas they may contain minor
I amounts of volcanic ash. Because of their very sandy nature they are
considered to be excessively drained. They do not retain water well, resulting
I in a droughty condition for vegetation. They pass water rapidly, especially
when saturated and are in hydrologic group A. Permeability can be expected
to range from 6.0 - 20 inches per hour.
I
38
I
I
Based on the predicted behavior of Indianola soils, this plan assumes a
Imaximum design infiltration rate of 10 inches per hour.
K. Geotechnical Report
As requested, NTI Engineering & Surveying (NTI) completed a geotechnical
Iassessment of the above referenced property consisting of research of
available literature and geologic maps of the area, and a site visit on
September 17, 2008, for visual observations. This assessment was in
Iresponse to the property being listed as a landslide hazard area by the
Jefferson County Department of Community Development.
1. Site Description
IThe subject property is located on Spring Hill Road off of S.R. 19, south of
Chimacum in Jefferson County (Map 2 - East Chimacum Creek Valley on
Page 9). The hilly wooded property is bounded on the north, east and
Isouth by wooded residential property, and on the west by SR 19. Existing
improvements to the property include a driveway and benched home site.
IThe property is situated on a west facing slope overlooking Chimacum
Valley. The eastern two thirds of the property has an overall average
I
natural slope angle of approximately 18°, and the western one third has a
slope of 13°. These slope angles are below the "angle of repose" which is
defined as the maximum slope or angle at which loose, cohesionless
I
material remains stable, and commonly ranges between 33 and 37
degrees on natural slopes. Three west and southwest trending ravines cut
through portions of the property (Map 6 - Drainage Basins on Page 13).
IThe benched home site is nearly flat and encompasses an area about 200
feet by 120 feet (Map 5 - Site Sketch on Page 12). The cut slope has a
I maximum height of approximately 29 feet with an average slope of 40°
and the fill slope is about 23 feet high with a slope of 30°. The material
exposed in the cut slope is dense silty sand and gravel.
IExcept for the benched home site, the property is well vegetated with
young to mature trees and brush. Predominant species include fir, cedar,
I maple, alder, and madrona, with an understory of salal and sword fern.
The property has been logged probably twice in the past as evidenced by
old growth stumps with spring board notches as well as second growth
I stumps. Some of the trees exhibit curved trunks, suggesting that
downslope creep of the surface soil is occurring in places. No groundwater
seeps were observed on the slopes, however, seeps were visible at the
I west side of the property near SR 19. No evidence of past landslides was
noticed on the slopes.
I39
I
2. Site Geology
IThe Department of Ecology's "Geology and Ground-Water Resources of
Eastern Jefferson County, Washington" maps the soil in the area of the
Iproperty as Lodgement till (Qvt) and as Undifferentiated glacial, fluvial,
glaciofluvial, lacustrine and glaciolacustrine deposits (Qu). The till is
described as boulders, cobbles and pebbles in a matrix of sand, silt and
Iclay; a compact and unsorted mixture. The undifferentiated deposits are
older than the Fraser glaciation and include sediments from pre Fraser
glaciations. This unit contains a variety of soil types and is generally
Imapped when more detailed data is not available.
According to the Soil Survey of Jefferson County Area, Washington
I (United States Department of Agriculture, 1975), the subject site is in an
area mapped as Cassolary sandy loam (CfD), and Indianola loamy sand
I
(InC & InD) (Map 8 - Soils on Page 36). The Cassolary soil formed in
glacial drift and/or marine deposits on terraces and is composed of sand,
silty sand and silt/clay with gravel. Runoff is listed as medium and the
I
hazard of water erosion as moderate. The Indianola soil formed on eskers,
kames, or moraines in sandy glacial outwash and is composed of silty
sand with gravel. Runoff is listed as slow to medium and the hazard of
water erosion as slight to moderate.
I
Visual observations of exposures and cuts on the property are consistent
I
with the above descriptions.
3. Conclusions and Recommendations
I
The subject property appears grossly stable and the project seems
I feasible from a geotechnical perspective. Based upon our assessment of
the property, it is our opinion that the hillside does not represent a
landslide hazard. However, the property is subject to erosion due to the
I sloping terrain. Specific sediment and erosion control measures will be
addressed in the engineered drainage, sediment and erosion control plan
being completed for this property by NTI.
IWe recommend that building foundations be placed in undisturbed native
soil and comply with Section 1805.3 (see below) of the International
I
Building Code (IBC) which deals with footings on or adjacent to slopes.
I
I
I
40
I
I 1805.3 Footings on or adjacent to slopes.The placement of buildings and structures on or adjacent to slopes steeper than (2134 nun)from the top of the slope shall be capable of sup-
porting the water in the pool without soil support.
one unit vertical in three units horizontal(33.3-percent slope)
shall conform to Sections 1805.3.1 through 1805.3.5. 1805.3.4 Foundation elevation.On graded sites,the top of
any exterior foundation shall extend above the elevation of
I 1805.3.1 Building clearance from ascending slopes. In the street gutter at point of discharge or the inlet of an
general,buildings below slopes shall be set a sufficient dis- approved drainage device a minimum of 12 inches (305
tance from the slope to provide protection from slope drain- mm)plus 2 percent.Alternate elevations are permitted sub-
age,erosion and shallow failures.Except as provided for in ject to the approval of the building official,provided it can
' Section 1805.3.5 and Figure 1805.3.1,the following criteria will be assumed to provide this protection.Where the exist- be demonstrated that required drainage to the point of dis-
charge and away from the structure is provided at all loca-
ing slope is steeper than one unit vertical in one unit hori- tions on the site.
zontal (100 percent slope), the toe of the slope shall be 1805.3.5 Alternate setback and clearance.Alternate set-
assumed to be at the intersection of a horizontal plane drawn
I from the top of the foundation and a plane drawn tangent to backs and clearances are Bern ildin subject to the approval of
the slope at an angle of 45 degrees(0.79 rad)to the horizon- the building official. The building official is permitted to
tal.Where a retaining wall is constructed at the roe of the require an investigation and recommendation of a registered
slope,the height of the slope shall be measured from the top design professional to demonstrate that the intent of this sec-
of the wall to the top of the slope. tion has been satisfied. Such an investigation shall include
I
consideration of material, height of slope, slope gradient,
1805.3.2 Footing setback from descending slope sur- load intensity and erosion characteristics of slope material.
face. Footings on or adjacent to slope surfaces shall be
founded in firm material with an embedment and set back
I from the slope surface sufficient to provide vertical and lat-
eral support for the footing without detrimental settlement.
Except as provided for in Section 1805.3.5 and Figure
1805.3.1, the following setback is deemed adequate to 1,) 1"(1 v 1[-1'][A7-11g4 ti
meet the criteria.Where the slope is steeper than 1 unit ver- �, :'/
I tical in 1 unit horizontal(100-percent slope),the required
setback shall be measured from an imaginary plane 45
degrees (0.79 rad) to the horizontal, projected upward
•from the toe of the slope. �'`
I 1805.3.3 Pools.The setback between pools regulated by
this code and slopes shall be equal to one-half the building J L 1 i fi iu I�I 1 i N�1 Y „�
footing setback distance required by this section.That por-
tion L 'Y
of the pool wall within a horizontal distance of 7 feet
I FACE OF
4,,./FOOTING
TOP OF
SLOPE
I
V
FACE OF E
/STRUCTURE
il
TOE OF H/3 BUT NEED NOT H
I
w SLOPE EXCEED 40 FT
MAX. 1
H/2 BUT NEED NOT EXCEED 15 FT MAX.
For SI: 1 foot=3(k1.8 rum.
I
FIGURE 1805.3.1
FOUNDATION CLEARANCES FROM SLOPES
2006 INTERNATIONAL BUILDING CODE®
IIn this case, the face of the structure will need to be a minimum of 14.5
feet from the toe of the cut slope unless a retaining wall is utilized, and the
I
face of the footing will need to be a minimum of 8 feet from the edge of the
fill slope.
I The following recommendations should also be considered with regards to
development of the subject property:
I 1. It will be necessary to replant and maintain vegetative ground cover
on the slopes to reduce erosion from surface runoff. Native deep-
rooted vegetation that requires little or no irrigation would be the
I
most beneficial.
I
41
' 2. Heavy irrigation or other activities that would contribute large
quantities of water to the soil should be avoided. One cause of
slope instability is the presence of excessive groundwater (i.e.
' heavy prolonged winter rains, leaving sprinklers running, water line
breaks, draining hot tubs, etc.).
' 3. Surface runoff from hard surfaces such as roofs, driveways,
walkways and patios shall be controlled and routed to a drainage
control system as shown in the Detail Drawings included at the
' beginning of this report.
4. Surface water should not be allowed to flow freely down the face of
the slopes and cause erosion of the slopes. If this occurs, the water
should be directed away from the slopes and/or conveyed to a safe
discharge area.
' 5. Silt fences or other sediment control devices shown in the Detail
Drawings will be needed during construction such that
sedimentation off site does not exceed predevelopment conditions.
' 6. All drainage control devices should be maintained in good working
order and inspected at least once a year.
' For further information please review the three publications published by
the Washington State Department of Ecology (DOE) entitled: "Slope
Stabilization and Erosion Control Using Vegetation", "Vegetation
Management: A Guide for Puget Sound Bluff Property Owners" and
"Surface Water and Groundwater on Coastal Bluffs". These publications
' are now out of print but can be obtained from the DOE website at:
http://www.ecy.wa.gov/biblio/sea.html under the 1993 and 1994 year
heading. The DOE website also contains additional useful information
' regarding slope stability and site development; this reference is highly
recommended.
' 4. Limitations to Geotechnical Report
•
This Geotechnical Report has been prepared for your exclusive use in
conjunction with the above referenced project. The report has not been
prepared for use by others or for other locations. Others may use it only
with the expressed written permission of the Engineer.
Within the limits of scope, schedule and budget, this report was prepared
in general accordance with accepted professional engineering and
geological principles and practices in this or similar localities at the time
the report was prepared. No other warranty, expressed or implied, is made
' as to the conclusions and professional advice included in this report.
The observations, conclusions and recommendations presented in this
' report were based on our visual observations of the subject property at the
time of our site visit; no laboratory tests were performed. Soil and geologic
42
I
Iconditions can vary significantly between test holes and/or surface
outcrops. If there is a substantial lapse of time, conditions at the site have
changed or appear different than those described in this report, NTI
Ishould be contacted and retained to evaluate the changed conditions and
make modifications to this report if necessary.
III. EXISTING CONDITIONS
The following descriptions of the site are its present condition, just before
i
development.
A. Natural Receiving Waters
IThe natural receiving water for this project is East Chimacum Creek, a
tributary to Chimacum Creek, which flows into Port Townsend Bay, a marine
I water connected to the Strait of Juan de Fuca. Flows from this project site are
conveyed to the natural receiving waters by overland flows.
I The entire route of the conveyances from the Calvary Church parcel to the
Chimacum Creek tributary is shown on Map 4 - Neighborhood Drainage
Patterns on Page 11. Because of ongoing agricultural activities on the East
I Chimacum Creek Valley floor, any natural channels from Highway 19 to the
creek have been obliterated. The Soils Map included as Map 8 on Page 36
shows these drainage channels as they existed in the early 1970s.
1 B. Area-Specific Requirements
p q
I Jefferson County has a list of specific requirements which it requests be
included in each drainage plan. This list is included on page 25 near the
beginning of this report.
I
1. Local Plans
I There are no local plans which affect this project beyond the general
requirements relating to stormwater.
I2. Ordinances
There are no special local ordinances which affect this project beyond the
I
general requirements relating to stormwater.
3. Water Cleanup Plans
IThis site is not subject to a cleanup plan.
III. OFF-SITE ANALYSIS
IAn off-site analysis is not required by Jefferson County. Because all new runoff
will be infiltrated, there will be no increase in off site flows.
I
43
I
I
IIV. PERMANENT STORMWATER CONTROL PLAN
This Permanent Stormwater Control Plan governs permanent BMPs relating to
the quality and quantity of stormwater for this project.
A. Methodology
I
Because the only need for hydrological calculations is to determine the peak
I instantaneous flow to verify the capacity of the conveyances and to design
the infiltration/dispersion system, a continuous hydraulics analysis is
unnecessary. This report used the Santa Barbara Urban Hydrograph Method
I
for these purposes.
IB. Existing Site Hydrology
In its present, pre-developed condition flows travel as sheet flows onto,
I across, and away from the building site. The soils appear to be infiltrating
rainfall in all except intense events. The dense ground cover below the
building site (See Photo 9) further detains and delays runoff, allowing
Iadditional time for the sheet flows to be naturally infiltrated.
t. ), j 7" ,s f r x' Z r ui '• SY',Ali'"j
• .1,;"--'. -i.",,T,,---•"1,6,..!. -•1,4 .4,,,,,--,g,,,• ...,,. ,c.-, - ., , -
, /:,- ,.... v„, 4.,,e, .•,,,,. - . .. 1,41-,.'1A--,01,-- :"...., ',-:,,,,, ',-A' . -
I \ - ,1 -2,e, '1/4,-.,dr4- - ::%T.‘, 0... !,,i:,st.,--tok,,...;,-fAie., --t ..4„.. . -r .
Au
,1 i J - V , ? w ..,f 4 tuate .t,,t
--, r am.. g.,... t i iv— .i, 7?A.r--,l S'
Yy ♦ V .ram ; ...may `) ♦per,'
x - kfr
.i r ye' i },".a`a • ''r + 4.'2
till ,
`4 •'` i ».'' t•
I 1 ,, - . ': -,:a .,t om'._.q ,f+ ' 0 1
s
Photo 9 i
What flows do collect and leave the parcel are conveyed westerly, eventually
1 reaching East Chimacum Creek as shown on Map 4 - Neighborhood
I
44
tDrainage Patterns on page 11. This conveyance route is discussed in more
detail in Section II.A. Natural Receiving Waters beginning on Page 43.
1 The drainage basins and directions of flows within the Parcel are well
depicted on Map 6 - Drainage Basins on page 13. Flows in these Basins A, C
& D will remain unchanged by this project. Changes in Basin B are discussed
' in detail in Section I.D.3. Post-Developed Stormwater Runoff, beginning on
Page 33.
' 1. Design Sub Basin
The hydrologic calculations are only performed for those portions of the
ibasins (shown on Map 6 - Drainage Basins on Page 13) within the parcel
bounds. Since flows in Basins A, C & D will be unchanged and essentially
all of Basin B lies within the parcel, this simplification will yield accurate
results. Changes in subbasins of Basin B are discussed in detail in
Section I.D.3. Post-Developed Stormwater Runoff, beginning on Page 33.
2. Soils Hydrologic Group
' The soils in this sub basin are in Hydrologic Groups A and C as discussed
in Section I.J. Surface Soils, beginning on page 35.
3. Time of Concentration
The length of time that it takes a drop of rainfall to travel from the
' uppermost point of a basin to the point of discharge from the basin, or to
the point where flows are to be calculated, is referred to as the time of
concentration (Tc). This is the sum of the time it takes for runoff to flow
across the various types of flow channels as it crosses the basin.
' The following calculations are per Section III-1.4.2, pages III-1-13 through
III-1-16, of the Washington State Department of Ecology's Stormwater
Management Manual For The Puget Sound Basin, The Technical Manual,
' (DOE 1992).
' (i) Pre-development Condition
The time of concentration is first determined for the existing condition
' of the basin.
' (a) Unconcentrated Flow
Immediately after falling to the ground, rainwater initially travels as
unconcentrated sheet flow for a period of time (Tt) calculated by:
45
I
I 0.80
0.42 (NsL)
ITt = = 12.35 min
0.527 0.4
(P2) (SO)
Where:
I Ns = 0.400 = Sheet flowManning's
Manning s n
I
(DOE Table III-1.4)
P2 = 1.5 = 2 yr, 24 hr rainfall (in)
SO = 0.2000 = Slope of flow path (ft/ft)
I
L = 100 = Length (L) of flow path (ft)
I
This is sheet flow through light ground cover brush at the top of the
small ridge immediately above the building site. The view in Photo
10 may reflect pre-contact conditions where over mature old growth
I
trees would have predominated.
I7.re.,e... . ` _
4s. E, to i . 7 l I$yST1 i '
r' ., {-
♦ , - '� ..Ark i IA
a 1 J • \ y; .„
I
1 -+t- ` `3 ;n P.ems - 4•`; ;'4 >` 1:7
Y -r .,0:- 'S0'• 44" .,\ 'N n ' , t, ' -e *. .*-* **,' , .:t% '11' ..
'orik., ,rldlp ..., , ,*.f4_, . ,..J.,: : , ,,i, -, ..:1 4-..sL,. .,..,. -;i,,..,i: A
it
ilk
Photo 10
I (b) Shallow Concentrated Flow
IAs sheet flows run together and become concentrated, they travel
as shallow concentrated flow for a period of time (Tt) calculated by:
I
I
46
I
IL
Tt = = 2.48 min
60 Ks SQRT(S0)
I
I
Where: Ks = 3 = Velocity factor (Ks)
(per DOE Table III-1.4)
SO = 0.2000 = Slope of flow path (ft/ft)
I
L = 200 = Length (L) of flow path (ft)
1 This is flow through light brush down the swales between the small
ridges immediately below the building site through conditions
I
similar to those depicted in Photo 11.
AF
i X. .
•
4
I
t `•
it
I y
I \ ii \ ....--
iri - ""'" •, ,,),,1',,,,r •. .... \ 11„ ,...4:i
Ii v , -. -4*--; L4., 1.'1.4 ..-114- : \ .'' ''''
IN'4 '-‘,-4 . •.; .••; .. ' •.• ' • . .^- i, ,- - - '4"/
:\‘'l — -' ,‘, '-.Pc. il ikerN' ' . ' • .. Y' -' • ' :r• l'il
I L. \ , . \,` 1 :,+ Tad::.
- 41‘i.";.44,;‘io:'It 4'..'' S
' -,, fr i::.! *-7-7 . c. - :' \ -.1:1:
r..;tlh % �r �� .d:.'1'.' ' -2',,i 0
�:: s air . y• 3
1 Photo 11
I (c) Open Channel (Intermittent) Flow
1 Flows next travel through intermittent open channels fora period of
9 p
time (Tt) calculated by:
1
I47
1
1 L
Tt = = 1.05 min
60 Kc SQRT(SO)
Where: Kc = 5 = Velocity factor (Kc)
(DOE Table III-1.4)
1 SO = 0.1000 = Slope of flow path (ft/ft)
L = 100 = Length (L) of flow path (ft)
These are sheet and loosely concentrated flows down the slope
P
near the bottom of the parcel in conditions similar to those shown at
1 the bottom of the far slope in Photo 12.
1
1 1, •
1 . ;7
}ti
1 ri .
"
Photo 12
1 (d) Open Channel (Continuous Stream) Flow
1 Further down the channel, a continuously flowing stream is formed.
Flows follow continuously flowing streams for a period of time (Tt)
calculated by:
1
1 Tt = = 0.28min
60 Kc SQRT(S0)
1 48
Where: Kc = 27 = Velocityfactor
(Kc
)
(per DOE Table III-1.4)
SO = 0.0500 = Slope of flow path (ft/ft)
L = 100 = Length of flow path (ft)
1
While a continuous stream is obviously lacking at this site, this
section of the calculations provides a convenient spot to account for
flow onto and along the highway right of way to the edge of the
parcel.
(ii) Pre-development Time of Concentration
As noted above, the time of concentration (Tc) is the sum of the time it
takes for runoff to flow across the various types of flow channels as it
crosses the basin. For the predevelopment condition:
' Tc = the sum of the various Tt's = 16.17 min
This is rounded to 16 min for use in further calculations.
4. Runoff Curve Nu
mbers
Calculations of the Weighted Runoff Curve Number for the parcel in the
pre-contact condition are included in Table 1 - Pre and Post Development
Land Uses on Page 50.
j
Y's., . _ .
Jttr iMJPJ LUtffiIY HD
I
I
' 49
I
I co
G G O O
O O O O O
O
0
x N • %
Q Q G
I
0 0 0 0 i y O P r
O 0 0 0 0 O O
14 z IO 0 b 0U W z .-1 II
o 0r r r 1-
a
G o
N O O O O 0 0 0 4
o O O O
O O O O COVI `� o 0 0 o c m a r
a 0 0 0 0 0 o o v v o
N 7,V Z coo 0 C4 4) E1(J Q ro O co.
I
ro m m a w m a
a Cu i-'
> a a
H 41 H 4 > > 0 4 >
I Q 4, 0 N 4
04
W0.' a
a E e: a a,
I
0 0m a -
a lc,4 c 4 0
IV a
0. C
E z E z°
a> >
'd
ro
0
E 11 01 En-, 0)
.1-1W
c N 0
c w
44 44 O 0 '
H Y 4,W a
I
m "u "u u a 0000
w w w w >a-laa4.1 00~a :rI
a -,rn Am UO of
m
C C C C a C a
1-0 m m m CO0 m
N
O
cc e Cl 17 cT 0 0 cc T a CV a O In r4
an cn O
CJ l0 10 Ti ,0 CI I .
U N �n c.I i-
U U V
z x o 0
Q to a Q w co
o 0 0 0 o a o 0 0 0 o
I
0 0 0 0 0 ! J !
00000
0
U •
W Z b 10 10 ID m II W A J a
O O O O G0 O 7 G C O O O O O 0 O 0 0 0 00 - H
I
A N 0 10 c O a ) c o co 4 N [ A 1/1
m .i V c` c 0 a ti
•00 .40 m o m .ao
U N N N O O N O N N N N u
a a' n VI V CO 01 0 m O 0' C a 4 n m .�V'I.'I - C a
F GI Q 0000 a j C Q b O N O O O C) yJ H
a.� a I. x.c a n•
I
0 4 II II II I II W 4) 4 . W
.� 0 II II it II II a 0
m w a m a n a roa''' a ro ro m u ro 0 0
'O 1.1 a a cJ N O O 0 41 tll N III II 43 Z
G IIV
Q 4 Q Q Q a O w" Q"Q Q"a" Q" a
O 41 V 4 01 of •I 0 > I 0 4 0 0 •I W 4
0 IX a s a s •j 4 a s a s •a a
0. 0 Z 0 o a 01 0 a 0 0 •N .. 0
,a ,-I a 0 U 0 C , , O 0
I
c � '0) 0 F >•4 .a
4 :U 4 4 W 4 0 4 > F W
an
AL:
p N a W a
a NN d a n, N a G 0 0
Itl N N •N N Z
04
u -a Z 0 0 ,-i a
a 0
0-4 4) a 31 •.OI 0 E N Cl IC
C 0 0 > Q Y•O � 0 4
a in F 0 � S.
O 3n EI U 'd
o ✓ [L H
- ,0 V O w o,
ri, 0 0 0 0 0 ' O a o O ',.a{
0 41 4J 44 w
.a 44 001 01 N '' 44 M 0 0 a rJ
y 0 0 01 0 , VON 0 O
I
_ H H H H U' ✓ H W T H H a >
al0 0 0 0 > > 0 O O > Cl
W W W W Q 0 W W W Q '0
v C m N ~~ 41
H m U q Cl 4 I CA CO CI a 0
4C M .yyl_Nq M OI 00
'0 A-.y4+0p1 ..p4--y4
0N 0 b q F Ia0 ,, III 0 0 0 10 0 .0
a .1 m CO 0 m 3 a CO CO m CO m
' Table 1 - Pre and Post Development Land Uses RI of C ' 71 1 '7 T)
50
I
I5. Rainfall
I The total amount of precipitation falling over a 24 hour period during a
storm having a mean recurrence interval of 2 years, will be 1.5 inches.
This information was taken from a 2 year, 24 hour Isopluvial Map
I published by the U.S. Soil Conservation Service, a portion of which is
reproduced here as Figure 2. The project location is marked on the map.
I
I 40
40 PROJECT
I
u 50
6Q 5 45 LOCATION
35 30 25
0
I
Wt... lorLA
N , A%\
60 55 40 35 30tiji '♦,
40 65 50 1„ 10
vim
I45 5 20 15
50 55 60 6 70 5 6 0
5 25
50 40 35 30
II
4 5 45
0 75
70
2 YEAR, 24 HOUR
40 65 ISOPLUWL LINES
35� \ Fr,,55 n IN 1/10s Of AN INCH
Figure 2 - 2 Year Isopluvials
I
IThe isopluvial lines represent total precipitation in 24 hours, in tenths of
inches. 2 year rainfall data is used to calculate runoff and in the calculation
I
of times of concentration for the site.
The total amount of precipitation falling over a 24 hour period during a
storm having a mean recurrence interval of 25 years, will be 2.8 inches.
IThis information was taken from a 25 year, 24 hour Isopluvial Map
published by the U.S. Soil Conservation Service, a portion of which is
I
reproduced here as Figure 3. The project location is marked on the map.
I
I51
I
I 6065
T� 70
PROJECT
9L
LOCATION
I9 55 40 35 25 2020
45 30 i.
. ,,,4`� �i �` :
I 70
90 85 80 75 7 65 o
100 ma -
I 65 �� , ' l i ,
70 . r,l
Ce
90 � �►} 30
80 785 120 130 11 100 9 85 8 7 70 t[ 40 3I 75 110 13012 6055 5045
70 12 65 1 : . il' , ' n,,
I •
65 110
100 25 YEAR, 24 HOUR
60 ISOPLUVIAL LINES
55- /� a^ 0 77 IN 1/lOs OF AN INCH
I Figure 3 - 25 Year Isopluvials
I The total amount of precipitation falling over a 24 hour period during a
storm having a mean recurrence interval of 100 years, will be 3.3 inches.
This information was taken from a 25 year, 24 hour Isopluvial Map
I published by the U.S. Soil Conservation Service, a portion of which is
reproduced here as Figure 4. The project location is marked on the map.
While calculations for 100 year rainfall events are not included in this
Ireport, summary information is presented for the 100 year event.
70
I � 7580
r 80 PROJECT
V1.3 LOCATION
2_,.. ..._____7.75
9070 65 ,1 5045 25
' 75 1� l \ ` 40 3530'\
I
100
75 120 �� 30
80 �� 35
Is cz7110 130 � �� 40
90
,0� t50
4:t1 60
I
965
8:' 4121 ,
1 8580
' 10 100 YEAR, 24 HOUR
75 100 ISOPLUVIAL LINES
65� , 90 IN 1/10s OF AN INCH
IFigure 4 - 100 Year Isopluvials
I52
The rainfall distribution is assumed to be a Type IA distribution per
standard practice in the area.
6. Pre-Contact Runoff Volumes
Pre-contact stormwater runoff volumes are important
p t because they form
the base flow against which all other flow regimes are compared. Per the
' 2005 DOE Manual these flows are based on conditions assumed to exist
prior to European arrival.
' Because this project will infiltrate 100% of runoff from the proposed
development the Santa Barbara Urban Hydrograph is appropriate for use.
The more cumbersome continuous simulation model is required for
designing of detention facilities to adequately account for water remaining
in the facility when the next storm begins. Since these conditions will not
' exist on the project, the continuous simulation model is unnecessary.
The pre-contact runoff volumes are estimated to be 0.0679, 0.6785, and
' 1.0657 cfs at the 2 year, 25 year, and 100 year level respectively.
Appendix I contains runoff calculations for the entire parcel for both 2-year
' and 25-year storms. While 100 year runoff is tracked in the computerized
calculations, full intermediate calculations are not included. The data in
Appendix I is organized as follows:
Subsection 1 - Summary of various coefficients and operational
values for the site.
' Subsection 2 - Catalog of pre- and post-development land uses.
Subsection 3 - Raw rainfall data for the design storms falling on the
site.
' Subsection 4 - Pre-development runoff calculations for the design
storms.
Subsection 5 - Post-development runoff calculations for the design
storms.
C. Developed Site Hydrology
Calculation of the hydrology of the site in the developed condition is
necessary to determine post-development runoff and to design the infiltration
' system. Areas of the various surfaces are shown in Table 1 - Pre and Post
Development Land Uses on Page 50.
' 1. Design Sub Basin
The Post Development basin is the same as the Pre Development basin.
I
53
' 2. Soils Hydrologic Group
The soils in this sub basin are in Hydrologic Groups A and C as discussed
in Section I.J. Surface Soils, beginning on page 35.
3. Time of Concentration
' The length of time that it takes a drop of rainfall to travel from the
uppermost point of a basin to the point of discharge from the basin, or to
the point where flows are to be calculated, is referred to as the time of
' concentration (Tc). This is the sum of the time it takes for runoff to flow
across the various types of flow channels as it crosses the basin.
The following calculations are per Section III-1.4.2, pages III-1-13 through
III-1-16, of the Washington State Department of Ecology's Stormwater
Management Manual For The Puget Sound Basin, The Technical Manual,
(DOE 1992).
111 (i) Post-development ment Condition
' The time of concentration is next determined for the post-development
condition of the basin.
(a) Unconcentrated Flow
' Immediately after falling to the ground, rainwater initially travels as
unconcentrated sheet flow for a period of time (Tt) calculated by:
0.80
0.42 (NsL)
Tt
= = 10.03min
0.527 0.4
' (P2) (SO)
' Where:
Ns = 0.150 = Sheet flow Manning's n
' (DOE Table III-1.4)
P2 = 1.5 = 2 yr, 24 hr rainfall (in)
SO = 0.0200 = Slope of flow path (ft/ft)
' L = 65 = Length (L) of flow path (ft)
54
This is sheet flow through healthy lawn on the building site following
completion of the project.
(b) Shallow Concentrated Flow
As sheet flows run together and become concentrated, they travel
as shallow concentrated flow for a period of time (Tt) calculated by:
L
' Tt = = 2.48 min
60 Ks SQRT(SO)
Where: Ks = 3 = Velocity factor (Ks)
' (per DOE Table III-1.4)
SO = 0.2000 = Slope of flow path (ft/ft)
L = 200 = Length (L) of flow path (ft)
' This is flow down the slopes below the building site through
conditions similar to those shown in Photo 11 on Page 47.
(c) Open Channel (Intermittent) Flow
' Flows next travel through intermittent open channels for a period of
time (Tt) calculated by:
L
Tt = = 1.05min
60 Kc SQRT(SO)
Where: Kc = 5 = Velocity factor (Kc)
' (DOE Table III-1.4)
SO = 0.1000 = Slope of flow path (ft/ft)
L = 100 = Length (L) of flow path (ft)
' 55
1
' These are sheet and loosely concentrated flows down the slope
near the bottom of the parcel in conditions similar to those shown at
the bottom of the far slope in Photo 12 on Page 48.
(d) Open Channel (Continuous Stream) Flow
Further down the channel, a continuously flowing stream is formed.
Flows follow continuously flowing streams for a period of time (Tt)
calculated by:
1 L
Tt = = 0.28 min
60 Kc SQRT(S0)
Where: Kc = 27 = Velocity factor (Kc)
(per DOE Table III-1.4)
1 SO = 0.0500 = Slope of flow path (ft/ft)
L 100 = Length of flow path (ft)
While a continuous stream is obviously lacking at this site, this
section of the calculations provides a convenient spot to account for
1 flow along the highway right of way to the edge of the parcel.
' (ii) Post-development Time of Concentration
As noted above, the time of concentration (Tc) is the sum of the time it
1 takes for runoff to flow across the various types of flow channels as it
crosses the basin. For the predevelopment condition:
Tc = the sum of the various Tt's = 13.84 min
This is rounded to 14 min for use in further calculations.
1
4. Runoff Curve Numbers
Calculations of the Weighted Runoff Curve Number for the overall site are
included in Table 1 - Pre and Post Development Land Uses on Page 50.
1 56
' 5. Rainfall
Rainfall is taken to remain unchanged since pre-contact times. A
discussion of rainfall and isopluvial maps for the various storm events is
included in Section IV.B.5. Rainfall, beginning on page 51.
6. Post-Development Runoff Volumes
' Post-development stormwater runoff volumes are calculated based on
conditions that will prevail after completion of construction of this facility.
' Because this project will infiltrate 100% of runoff from developed areas the
Santa Barbara Urban Hydrograph is appropriate for use. The more
cumbersome continuous simulation model is required for designing of
' detention facilities to adequately account for water remaining in the facility
when the next storm begins. Since these conditions will not exist on the
project, the continuous simulation model is unnecessary.
' The post-development runoff volumes are estimated to be 0.0631, 0.6702,
and 1.0380 cfs at the 2 year, 25 year, and 100 year level respectively. The
' small decrease in runoff is the result of 100% infiltration of runoff from the
developed portion of the site. This lowered the weighted overall site runoff
curve number sufficiently to account for the bit of additional runoff from the
' previous construction of Spring Hill Road.
' Appendix I contains runoff calculations for the entire parcel for both 2-year
and 25-year storms. While 100 year runoff is tracked in the computerized
calculations, full intermediate calculations are not included. The data in
Appendix I is organized as follows:
' Subsection 1 - Summary of various coefficients and operational
values for the site.
' Subsection 2 - Catalog of pre- and post-development land uses.
Subsection 3 - Raw rainfall data for the design storms falling on the
site.
' Subsection 4 - Pre-development runoff calculations for the design
storms.
Subsection 5 - Post-development runoff calculations for the design
' storms.
' 57
I
ID. Performance Standards and Goals
The various thresholds of the DOE Manual are used to determine the
I required Minimum Requirements for this project. Table 2 is a flow chart taken
from the DOE Manual to determine the minimum requirements for this project.
The path for this project is indicated in red.
IStart Here
Does the site have Yes See Redevelopment
I 35%or more of Minimum
existing impervious Requirements and
coverage? Flow Chart
Does the project convert (Figure 2.3)
INo 3/4 acres or more of native
• vegetation to lawn or
I
Does the project add No landscaped areas, or
5,000 square feet or convert 2.5 acres or more
more of new of native vegetation to
impervious surfaces? pasture?
Yes Yes No
I Does the project have
2,000 square feet or
All Minimum
Requirements apply to more of new,replaced,or new plus replaced I
the new impervious impervious surfaces?
surfaces and converted
pervious surfaces. Yes No
Minimum Does the project have
' ' Requirements#1 f land-disturbing
through#5 apply to activities of 7,000
the new and replaced Yes square feet or more?
impervious surfaces
Iand the land disturbed. No
V
See Minimum I
Requirement#2,
Construction
Stormwater Pollution
IPrevention
Figure 2.2 -Flow Chart for Determining Requirements for New Development
ITable 2 - Threshold Flow Chart
ITable 2 indicates that this project must meet all Minimum Requirements.
I58
1
' 1. Minimum Requirement #1: Stormwater Site Plan
This report is the Stormwater Site Plan for the Calvary Community Church
Multipurpose Building project.
2. Minimum Requirement #2: Construction Stormwater Pollution
' Prevention Plan
A complete Construction Stormwater Pollution Prevention Plan is included
with this report, beginning on page 65.
3. Minimum Requirement #3: Source Control of Pollution
The following source control BMPs are recommended for the
management of lawn and landscaping areas.
' Common sources of pollution from lawns and landscaped areas are
fertilizers, pesticides and other substances used to control weeds, insects,
' mold, bacteria, and other pests.
(i) Landscaping
' Applicable Operational BMPs for Landscaping:
' • Install engineered soil/landscape systems to improve the
infiltration and regulation of stormwater in landscaped areas.
• Do not dispose of collected vegetation into waterways or storm
' drainage systems.
Recommended Additional Operational BMPs for Landscaping:
' • Conduct mulch-mowing whenever possible
• Dispose of grass clippings, leaves, sticks, or other collected
' vegetation, by composting, if feasible.
• Use mulch or other erosion control measures when soils are
exposed for more than one week during the dry season or two
days during the rainy season.
• If oil of other chemicals are handled, store and maintain
' appropriate oil and chemical spill cleanup materials in readily
accessible locations. Ensure that employees are familiar with
proper spill cleanup procedures.
' • Till fertilizers into the soil rather that dumping or broadcasting
onto the surface. Determine the proper fertilizer application for
the types of soil and vegetation encountered.
' • Till a topsoil mix or composted organic material into the soil to
create a well-mixed transition layer that encourages deeper root
systems and drought-resistant plants.
' • Use manual and/or mechanical methods of vegetation removal
rather than applying herbicides, where practical.
' 59
(ii) Vegetation Management
Applicable Operational BMPs for Landscaping: r
• Use at least an eight-inch "topsoil" layer with at least 8 percent
' organic matter to provide a sufficient vegetation-growing
medium. Amending existing landscapes and turf systems by
increasing the percent organic matter and depth of topsoil can
' substantially improve the permeability of the soil, the disease
and drought resistance of the vegetation, and reduce fertilizer
demand. This reduces the demand for fertilizers, herbicides,
' and pesticides. Organic matter is the least water-soluble form of
nutrients that can be added to the soil. Composted organic
matter generally releases only between 2 and 10 percent of its
' total nitrogen annually, and this release corresponds closely to
the plan growth cycle. If natural plant debris and mulch are
returned to the soil, this system can continue recycling nutrients
indefinitely.
• Select the appropriate turf grass mixture for your climate and
' soil type. Certain tall fescues and rye grasses resist insect
attack because the symbiotic entophytic fungi found naturally in
their tissues repel or kill common leaf and stem-eating lawn
' insects. They do not, however, repel root-feeding lawn pests
such as Crane Fly larvae, and are toxic to ruminants such as
cattle and sheep. The fungus causes no known adverse effects
' to the host plants or to humans.
• Use the following seeding and planting BMPs, or equivalent
BMPs to obtain information on grass mixtures, temporary and
permanent seeding procedures, maintenance of a recently
planted area, and fertilizer application rates: Temporary
Seeding, Mulching and Matting, Clear Plastic Covering,
' Permanent Seeding and Planting, and Sodding as described in
Volume II of the DOE Manual.
• Selection of desired plant species can be made by adjusting the
' soil properties of the subject site. For example, a constructed
wetland can be designed to resist the invasion of reed canary
grass by layering specific strata of organic matters (e.g.,
' compost forest product residuals) and creating a mildly acidic
pH and carbon-rich soil medium. Consult a soil restoration
specialist for site-specific conditions.
' • Aerate lawns regularly in areas of heavy use where the soil
tends to become compacted. Aeration should be conducted
while the grasses in the lawn are growing most vigorously.
' Remove layers of thatch greater than 3/4 inch deep.
• Mowing is a stress-creating activity for turf grass. When grass is
mowed too short its productivity is decreased and there is less
' growth of roots and rhizomes. The turf becomes less tolerant of
environmental stresses, more disease prone and more reliant
' 60
' on outside means such as pesticides, fertilizers and irrigation to
remain healthy. Set mowing height at the highest acceptable
level and mow at times and intervals designed to minimize
' stress on the turf. Generally mowing only 1/3 of the grass blade
height will prevent stressing the turf.
' (iii) Irrigation
BMPs for Landscaping:
' • The depth from which a plant normally extracts water depends
on the rooting depth of the plant. Appropriately irrigated lawn
grasses normally root in the top 6 to 12 inches of soil; lawns
' irrigated on a daily basis often root only in the top 1 inch of soil.
improper irrigation can encourage pest problems, leach
nutrients, and make a lawn completely dependent on artificial
' watering. The amount of water applied depends on the normal
rooting depth of the turf grass species used, the available water
' holding capacity of the soil, and the efficiency of the irrigation
system. Consult with the local water utility, Conservation
District, or Cooperative Extension office to help determine
optimum irrigation practices.
(iv)Fertilizer Management
' BMPs for Fertilizing:
' • Turf grass is most responsive to nitrogen fertilizer, followed by
potassium and phosphorus. Fertilization needs vary by site
depending on plant, soil and climatic conditions. Evaluation of
' soil nutrient levels through regular testing ensures the best
possible efficiency and economy of fertilization. For details on
soils testing, contact the local Conservation District or
' Cooperative Extension Service.
• Fertilizers should be applied in amounts appropriate for the
target vegetation and at the time of year that minimizes losses
to surface and ground waters. Do not fertilize during a drought
or when the soil is dry. Alternatively, do not apply fertilizers
within three days prior to predicted rainfall. The longer the
period between fertilizer application and either rainfall or
irrigation, the less fertilizer runoff occurs.
• Use slow release fertilizers such as methylene urea, IDBU, or
' resin coated fertilizers when appropriate, generally in the spring.
Use of slow release fertilizers is especially important in areas
with sandy or gravelly soils.
' • Time the fertilizer application to periods of maximum plant
uptake. Generally fall and spring applications are
recommended, although WSU turf specialists recommend four
' fertilizer applications per year.
' 61
' • Properly trained persons should apply all fertilizers. At
commercial and industrial facilities fertilizers should not be
applied to grass swales, filter strips, or buffer areas that drain to
' sensitive water bodies unless approved by the local jurisdiction.
' 4. Minimum Requirement #4: Preservation of Natural Drainage Systems
and Outfalls
The natural hydrology of this site is discussed in Section IV.B. Existing
' Site Hydrology on page 44. This natural discharge is shown in Map 6 -
Drainage Basins on Page 13.
' Natural flow regimes are preserved by this plan.
' 5. Minimum Requirement#5: On-site Stormwater Management
This project will infiltrate 100% of runoff from the developed portions of the
' site. This will mitigate the increased runoff from the previous construction
of Spring Hill Road.
' The net effect will be that flow regimes are preserved. The design of the
infiltration facility is discussed in Section IV.E Flow Control System
beginning on page 63.
6. Minimum Requirement#6: Runoff Treatment
There are two thresholds that will require that runoff treatment BMPs be
implemented:
' • Projects in which the total of effective, pollution-generating impervious
P 9 9 P
surface (PGIS) is 5,000 square feet or more in a threshold discharge
area of the project, or
• Projects in which the total of pollution-generating pervious surfaces
(PGPS) is three-quarters (3/4) of an acre or more in a threshold
discharge area, and from which there is a surface discharge in a
' natural or man-made conveyance system from the site.
Both conditions apply to this project. New (pollution generating) impervious
' surfaces (roof and driveway) will be 0.1629 acres (7,096 square feet) while
landscaping (pollution generating pervious surfaces) will occupy the 0.3163
acres (13,778 square feet) remainder of the converted area.
' This plan utilizes biofiltration followed by infiltration for treatment of runoff
from the developed portion of the site as shown on the Detail Drawings at the
beginning of this report.
' 62
7. Minimum Requirement#7: Flow Control
' Flow control for this project will be provided by the infiltration facility
discussed in Section IV.E Flow Control System beginning on page 63 and
depicted in the Detail Drawings included at the beginning or this report.
' Because the effect of the infiltration facility is that there will be no
discharge from the developed portion of this project, the remainder of
' Minimum Requirement#7 does not apply.
8. Minimum Requirement#8: Wetlands Protection
There are no wetlands known to exist on or adjacent to this site.
9. Minimum Requirement#9: Basin/Watershed Planning
This project site is not the subject of a Basin/Watershed Plan.
' 10.Minimum Requirement#10: Operation and Maintenance
Due to the limited size and scope of this project, Operation and
' Maintenance issues for permanent water quality control BMPs are
discussed for each BMP as they are introduced in this SSP.
' An operation and maintenance manual for Construction Phase water
quality BMPs is included as Section V.K. Maintenance of BMPs, beginning
' on page 70.
An Operation and Maintenance Manual for the infiltration facility is
' included in Section VIII. Operation and Maintenance Manual, beginning on
page 72.
E. Flow Control System
The flow control system for this project consists of an infiltration facility for all
' runoff from the roof.
Design data for the system are included in Appendix II. Appendix II contains
runoff calculations for the design (25-year) storm for the roof area to be
routed into infiltration facilities. The data in Appendix II is organized as
' follows:
Subsection 1 - Summary of various coefficients and operational values for
the infiltrated portion of the site.
' 63
' Subsection 2 - Catalog of pre- and post-development land uses for the
infiltrated portion of the site.
' Subsection 3 - Raw rainfall data for the design storm falling on the
infiltrated portion of the site.
' Subsection 4 - Post-development runoff calculations for the design storm.
Subsection 5 - Staging table with operational data related to the infiltration
facility.
Subsection 6 - Flood routing data for the infiltration facilities.
Detail drawings for the infiltration facility are included as at the beginning of
' this report.
' F. Water Quality System
While all runoff from the developed portion of the parcel will be infiltrated, the
' threshold areas requires water quality treatment. Water quality treatment
primarily relies on source controls, including biofiltration, to reduce silts from
' entering the infiltration system. See the discussion in Section IV.D.6.
Minimum Requirement #6: Runoff Treatment, beginning on page 62.
Operational BMPs are suggested in Section IV.D.3 Minimum Requirement
#3: Source Control of Pollution, beginning on page 59 for the management of
Landscaping, Vegetation, Irrigation, and Fertilizer.
G. Conveyance System Analysis and Design
' Conveyances from the catch basins to the infiltration system was sized based
on 100 year storm event flows using Mannings equation. See Table 3 for
design calculations for the stormwater pipe.
' 64
I
I
STORM SEWER PIPE- BARREL CAPACITY& INLET CAPACITY
IAssumptions: Hazen/Williams C value = 80
Min barrel slope is based on pipe flowing
I full and is the slope necessary to just overcome
friction losses in the pipe barrel
I Min depth of inlet is based on a square edge
circular inlet (inlet coefficient= 0.62) and is
that head necessary to get the water started
Iflowing down the pipe.
Pipe
IDia. ==> 4 in. 6 in. 8 in.
Min Min Min
Depth Depth Depth
I
to Min to Min to Min
Flow Pipe IE Barrel Pipe IE Barrel Pipe IE Barrel
I (cfs) (ft) Slope (ft) Slope (ft) Slope
0.20 0.38 1.51% 0.29 0.21% 0.35 0.05%
0.21 0.40 1.65% 0.30 0.23% 0.35 0.06%
I0.22 0.42 1.80% 0.30 0.25% 0.35 0.06%
0.23 0.45 1.95% 0.31 0.27% 0.35 0.07%
0.24 0.47 2.11% 0.31 0.29% 0.35 0.07%
I0.25 0.50 2.28% 0.32 0.32% 0.35 0.08%
0.26 0.53 2.45% 0.32 0.34% 0.36 0.08%
I
0.27 0.55 2.63% 0.33 0.37% 0.36 0.09%
0.28 0.58 2.81% 0.33 0.39% 0.36 0.10%
0.29 0.61 3.00% 0.34 0.42% 0.36 0.10%
I
0.30 0.64 3.20% 0.34 0.44% 0.36
0.37 0.11%
0.31 0.68 3.40% 0.35 0.47% 0.12%
0.32 0.71 3.60% 0.36 0.50% 0.37 0.12%
ITable 3 - Stormwater Pipe Design
I
IV. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN
This portion of the plan was prepared with the goal of preventing damage to
I adjoining or downstream properties due to erosion and sediment deposition and
preventing the degradation of the quality of the receiving waters during the
construction phase of this project.
I
I65
I
I This Construction Stormwater Pollution Prevention Plan (SPPP) is to be used in
conjunction with the remainder of the overall Stormwater Site Plan, which
contains much of the descriptive material upon which this Construction SPPP is
Ibased.
To ensure that the provisions of this Erosion and Sediment Control Plan are
I followed during construction, the complete text of this Erosion and Sediment
Control Plan should be included in the construction plans for this project. Where
formal construction plans will not be prepared for all or portions of the work, a
Icopy of this document should be made available to the contractor and
appropriate subcontractors. Subcontractors that will not be receiving copies
should be made aware of the plan's existence and advised where copies can be
Iobtained.
Water quality controls, commonly referred to as Best Management Practices, or
IBMPs, are necessary to prevent three distinct types of impacts. The first
consists of damage done as the result of soils being taken up by running water.
This type of damage typically consists of rilling, rutting and loss of topsoil. The
Isecond type of damage is the degradation of water quality that occurs as the
water transports the smaller soil particles. The third type of damage occurs when
I
the running water reduces its velocity and drops the suspended soils.
The Erosion and Sediment Control features (BMPs) of this plan are designed to
I
address all three types of damage with the emphasis on preventing the initial soil
uptake. Successful prevention of soil uptake will also prevent damage caused by
degradation of water quality and by soil deposition. While the measures
I
described below for preventing soil uptake should theoretically prevent any
removal of soil, common sense advises that additional measures will be
necessary and indeed, the DOE Manual requires additional measures. These
I
additional measures will allow deposition of transported soils under controlled
conditions before flows leave the project site or enter the receiving waters.
I Detail drawings for construction stormwater pollution prevention are included at
the beginning of this report. Specific drawings are referenced as they are
discussed in the narrative below.
IA. Clearing Limits
I Appropriate clearing limits, property lines, easement lines, and similar
boundaries shall be determined prior to starting construction. Clearing,
grubbing, grading and similar operations shall not begin until the appropriate
I limits are staked in the field. Once these stakes are set, care shall be taken
that the stakes are not disturbed.
IB. Construction Access
In addition to the following general requirements, the specific requirement
I regarding construction access contained in the Jefferson County Standard
Stormwater Site Plan Notes on page 25 shall be followed.
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It is expected that minor amounts of soil will be tracked onto paved roads,
especially when unexpected circumstances such as rains and delays occur.
' To prevent this from becoming a nuisance or source of sedimentation, the
roads shall be cleaned thoroughly at the end of each day if there is evidence
of any significant accumulation of soil. Sediment shall be removed from
' roads by shoveling or sweeping and be transported to a controlled sediment
disposal area. Washing of the street shall be allowed only after sediment is
removed in this manner. Wherever construction, delivery, and similar vehicles
' enter paved roads from this project, the following provisions shall be followed
to minimize the transport of soil onto the paved road.
' During periods of dry weather (where the soil is too dry to adhere to the tires
of construction vehicles) construction vehicles may access paved streets
directly from the project site with monitoring and occasional sweeping of the
tpaved street as necessary to prevent accumulations of soil.
During periods of wet weather (where soil readily adheres to the tires of
' vehicles) the vehicles may access graveled roads directly from the project site
as necessary, but shall not access paved roads without first having been
' routed over areas where existing grass or other vegetation remains or routed
down a minimum of 150 feet of graveled road. Access routes over grass or
other vegetation shall be changed occasionally to ensure that wheel ruts are
' not allowed to develop and that the vegetation is not unduly worn down.
C. Flow Rate Controls
Flow controls are not required on this project due to lack of runoff leaving the
' site.
D. Sediment Controls
Sediment controls shall initially be utilized on this site as specified in the
Detail Drawings included at the beginning of this report. Additional controls
shall be installed if conditions dictate that additional protection is necessary.
E. Soil Stabilization
From October 1 through April 30, no soils shall remain exposed and
unworked for more that 2 days. From May 1 to September 30, no soils shall
' remain exposed and unworked for more than 7 days. This condition applies to
all soils on site, whether at final grade or not.
' Soils shall be stabilized at the end of the shift before a holiday or weekend if
needed based on the weather forecast.
' The actual type of soil stabilization used is to be determined by the contractor
based on the requirements of the DOE Manual to match his construction
procedures. Sediment controls as described in the Detail Drawing included at
the beginning of this report are required in addition to the requirement for soil
stabilization.
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F. Slope Protection
Any slopes such as at the ends of retaining walls or the sides of stockpiles
shall be stabilized as required in Section V.E. Soil Stabilization beginning on
page 67.
G. Drain Inlet Protection
' Catch Basin protection is required by the notes in the Detail Drawings
included at the beginning of this report.
H. Channel and Outlet Stabilization
This section is not applicable to this project.
' I. Control of Pollutant
s
' All potential pollutants other than sediments that may occur on the site during
the construction process shall be handled and disposed of in a manner that
does not cause contamination of stormwater.
' 1. Control of Toxic Substances
' No toxic or noxious substances shall be used, stored or disposed of on or
off the project site in conjunction with the project except in full compliance
with all applicable federal, state and local laws and regulations and the
' recommendations of the supplier of the substance. The product label or
instructions for use and the Material Safety Data Sheets (MSDS) for such
products shall be kept on the site until the product has been used up or
' removed from the site and properly disposed of.
While not commonly thought of as a hazardous material, common fertilizer
' can be very damaging if allowed to enter receiving waters. Fertilizers shall
only be used in accordance with the recommendations of the supplier and
any concentrations such as dribbles or leaks shall be cleaned up.
' In the event of a spill or other unusual event involving toxic or hazardous
materials, work in the vicinity shall be immediately stopped and the
following agency notified:
Washington State Department of Ecology, (206) 459-6000 during
normal business hours or (206) 753-2353 after hours.
If the incident presents a threat to life, health, or property, the Fire and
Police Departments shall be notified by dialing 911.
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' 2. Petroleum Spills
The following requirements are included to ensure compliance with Part
' 40 of CFR 112 in cases where SPCC Plans are required. They shall be
followed on all projects.
' Storage of fuel for construction vehicles and fueling of construction
vehicles shall be performed in accordance with the following requirements:
(i) Driver Training
All employees assigned to operate fuel trucks will be properly trained in
' appropriate regulations and safety procedures. Training shall include
proper inspection and use of tanks, hatches, valves, pumps, hoses and
fuel delivery equipment.
' (ii) Fueling of Vehicles
Fuel nozzles shall be locked when not attended and hoses shall be
' rewound or otherwise properly stored when not in use. Unattended
fueling which relies on the proper operation of automatic shutoff
nozzles shall not be permitted.
(iii)Parking of Fuel Tankers
Parking areas for fuel trucks shall be selected such that spills will not
leave the area. Fuel trucks shall not be parked closer than 25 feet to a
conveyance BMP such as a grassy swale or interceptor swale. When
fuel trucks must be taken to other portions of the project to fuel
' equipment, they must be continuously attended or returned to the
staging/storage area. Fuel trucks shall be locked with the wheels
chocked when unattended and not in use.
' (iv)Containment of Spills
Spills shall be immediately diked and every effort made to stop
' spillage. Each fuel truck shall carry a long handled shovel for use in
containing spills. In the event of a spill, the U. S. Environmental
Protection Agency, Seattle, Washington (206) 442-1263, shall be
' notified as soon as possible. If the magnitude of the spill is such that it
presents an immediate threat to life, health, or property, it shall be
promptly reported by dialing 911.
J. Control of De-Watering
' Underground utility construction shall proceed subject to the following criteria:
A major source of potentially contaminated flows is from pumping or
' otherwise dewatering trenches. For this reason, flows discharged from
pumping or other method of trench dewatering shall be closely monitored
and, except where there is no visible turbidity, treated as described below
' in the Section titled "Dewatering Construction Sites."
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Where feasible, no more than 500 feet of trench shall be opened at one
time.
' Where consistent with safety and space considerations, stockpiles of
excavated soils shall be placed on the uphill side of the trench. Any such
stockpiles shall be protected from erosion as provided for in this plan.
' Trenches shall be backfilled and revegetated as soon as reasonably
y
possible following placement of utilities. Wherever trenches run more or
' less straight up and down a slope, either the backfill shall be mounded
over the trench or waterbars or similar BMPs shall be utilized as
necessary to prevent the backfilled trench from becoming a water course.
Simply covering the exposed soil may not prevent the trench from
conveying waters.
Where the upstream end of a pipe is subject to inundation, it shall be
temporarily capped or plugged at the end of each day's work to prevent
' soil from being washed into the pipe.
?T) T(l "IR TrN r r
The underground utility locate service, 1-800-424-5555, shall be called a f 1 I )
minimum of 48 hours (2 working days) prior to beginning any excavation
and arrangements made to have all buried utilities marked.
' K. Maintenance of BMPs
This section constitutes the Operation and Maintenance Manual for the
' erosion and sediment control BMPs used during the construction phase of
this project.
' Most of the various BMPs required to maintain water quality during the
construction phase of this project are of a temporary nature. They are neither
intended nor expected to remain in service for months at a time. The typical
' BMP often has a life expectancy of only 6 - 12 weeks unless time and effort
are expended to bring it back to its original condition.
' Foul weather, rough use, overloading and similar conditions will reduce the
life of these items. It is critical that all of the erosion and sediment control
BMPs be maintained in their intended condition until they have served their
' purpose and are ready to be removed.
The project foreman shall inspect the various parts of the system at least
' once daily during rainy weather. In addition, the foreman shall perform
additional inspections during or immediately after significant rainfall. Any
damaged or non-functioning components of the system shall be repaired
' before noon of the next day.
In addition to verifying that the various BMPs are functioning as intended, the
' foreman shall check for formation of rills, deposits of silt and similar
indications that the system is not functioning properly. If it is found that the
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I
I system is not performing its role in preventing erosion and sedimentation,
additional BMPs shall be provided as necessary.
I Specific maintenance instructions for the various erosion and sediment
control BMPs are contained in the DOE Manual.
IL. Project Management
The following guidelines are not intended to be a substitute for common
I sense and good judgment. They must be tightened when necessary to
accomplish the objective of preventing erosion and siltation. They may be
relaxed after consulting with the local authority when the situation will allow a
Ilesser level of protection.
I 1. Phasing of Construction
The lower portion of the site, including the septic system, interceptor
swales, and catch basins, should be installed first if at all practicable. As
Ithis area is revegetated or is covered with grass, it will act as a filter
medium for minor sheet flows leaving the area of home construction.
I2. Seasonal Work Limitations
From October 1 through April 30, clearing, grading, and other soil
disturbing activities shall only be in consultation with the local authority
and upon a consideration of the following:
I1. Site conditions including existing vegetation coverage, slope, soil
type, and proximity to receiving waters; and
2. Limitations on activities and the extent of disturbed area; and
I3. Proposed erosion and sediment control measures.
I3. Coordination with Utilities and Other Contractors
The contractor shall coordinate his work with other entities to the extent
necessary to avoid the need for additional excavation and soil disturbing
Iactivities.
I4. Inspection and Monitoring
The project foreman shall inspect the various parts of the system at least
once daily during rainy weather. In addition, the foreman shall perform
Iadditional inspections during or immediately after significant rainfall. Any
damaged or non-functioning components of the system shall be repaired
before noon of the next day.
I In addition to verifying that the various BMPs are functioningas intended,
9
I
the foreman shall check for formation of rills, deposits of silt and similar
indications that the system is not functioning properly. If it is found that
I71
I
I the system is not performing its role in preventing erosion and
sedimentation, additional BMPs shall be provided as necessary.
I5. Maintaining an Updated Construction SWPPP
To ensure that the provisions of this Erosion and Sediment Control Plan
I are followed during construction, the complete text of this Erosion and
Sediment Control Plan should be included in the construction plans for this
project. Where formal construction plans will not be prepared for all or
I portions of the work, a copy of this document should be made available to
the contractor and appropriate subcontractors. Subcontractors that will
not be receiving copies should be made aware of the plan's existence and
Iadvised where copies can be obtained.
IVI. SPECIAL REPORTS AND STUDIES
I
There are no special studies applicable to this project.
I VII. OTHER PERMITS
This project will need a building permit and a septic permit.
IVIII. OPERATION AND MAINTENANCE MANUAL
IDue to the limited size and scope of this project, Operation and Maintenance
issues for permanent water quality control BMPs are discussed for each BMP as
Ithey are introduced in this SSP.
An operation and maintenance manual for Construction Phase water quality
IBMPs is included as Section V.K. Maintenance of BMPs, beginning on page 70.
The Operation and Maintenance Manual for the infiltration facility is included
Iimmediately below.
The infiltration system consists of the roof gutters and down drain pipes, the
I catch basins, the buried piping and joints which carry roof flows to the infiltration
facility, and the infiltration facility itself.
I The roof gutters and down drain pipes, including screens, is the most likely point
of where maintenance will be needed. While these are outside of the scope of
this report (they are a part of the building design) they should be inspected once
I a year and clogged screens, loose pipes, loose joints, and damaged components
repaired or replaced as necessary.
I
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1
Catch basins should be monitored monthly during the first wet season following
completion of construction and twice a year during the rainy season thereafter
and any accumulations of silt removed.
' There is no easy way to inspect the buried components of the system. The most
likely point of failure requiring maintenance will be the collection piping and joints.
The infiltration system is designed to operate as a flow dispersion system at the
100 year flood event level of flows so overland sheet flows leaving the facility
' during typical yearly heavy storms will be an indication of problems with the
system.
' The points at the bottoms of the roof drain pipes should be inspected
occasionally to see if any water is backing up during periods of extreme flows.
' The system is designed with capacity to handle a 100 year storm event so any
signs of water backing up should be an indication of a blocked, damaged, or
disconnected pipe. This will require the services of a qualified plumber to find and
' repair the problem.
Feel free to contact this office at: Northwestern Territories, Inc., 717 S Peabody
Street, Port Angeles, WA 9836, 360-452-8491 with any questions regarding the
operation of the system.
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