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SUB18840 HEX Exhibit 9Transmittal Date: March 24, 2014 To: Sean Conrad City of Bainbridge Island From: Kelsey Laughlin, P.E. 0 Browne Wheeler Engineers, Inc. Inml MAR 2 2014 !JE(OE�VI-En POO Re: BGH Sunrise Preliminary Plat Report and Plans PRE18840 Enclosed are 3 copies of BGH Sunrise Preliminary Plat Plans, one 11x17 reduced set of plans and report, all dated 3/24/2014. Please contact us if you have questions. Browne Wheeler Engineers, Inc. 241 Ericksen Avenue NE Bainbridge Island, WA 98110 phone 206.842.0605 fax 206.780.9322 March 24, 2014 Michel Girard BGH Development, LLC Michel@BGHdevelopment.com 206.33531649 Re: Sunrise Subdivision Preliminary Plat Dear Michel: BKOWNE • WHEELER ENGINEERS, INC MAR 2 4 201 g PCV This letter presents our preliminary drainage, utility and road design for the proposed BGH Sunrise Preliminary Plat. The proposed plat includes the subdivision of one 3.41 -acre parcel into 7 single family residential parcels. EXISTING CONDITIONS The site is located south of the road end of Sunrise Drive, and north of Hyla Avenue. Currently the site is undeveloped with grass, brush and trees. The site is served by a gravel access road through a 20 -ft easement from Sunrise Drive. The soil is mapped by the United States Department of Agriculture as Harstine gravelly ashy sandy loam. The site slopes generally to the south gently to steeply across the site. STORM DRAINAGE Existing Stormwater appears to infiltrate into the soils on-site or flows in a dispersed manner with no indications of runoff on-site. Downstream System The site drains south toward Hyla Avenue and two private properties (see Drainage Map). Hyla Avenue is a gravel road that does not have any stormwater management infrastructure installed. Stormwater runoff appears to flow in a dispersed manner south to a closed depression along Hyla Avenue, approximately 200 -ft from the southwest of the subject property. The property owner southwest of the project indicated that water frequently ponds on both sides of Hyla Avenue on private and public property where it eventually infiltrates. The property southeast of the project property also has an apparent closed depression along the south edge but the owners have not indicated any issues related to stormwater runoff. Proposed The proposed project consists of providing storm drainage facilities for two access roads to serve the seven lots. The storm drainage system will infiltrate 100% of the stormwater runoff from the roads on-site through the installation of infiltration trenches along the two access roads. 241 ERICKSEN AVENUE NE, BAINBRIDGE ISLAND, WA 98110 206.842.0605 info@Brow eWheeleccom OUNDARY FOR CL D DEPRESSION \� ;Lu _ l f i uii ` 1 \ 1 Z /— DU CAN LN (J /IN \✓ } CLOSED EPRESSION, ( — — LOCATION FREQUENT PONDING. ER 1 1 NO KNOWN ISSUES TH WATER �W -BEACH CREST DR — l ` -� .i w / / Lu co r N _ si�P Y J PUG�� sQ�N 0 75 150 300 600 900 TOPOGRAPHIC INFORMATION BASED UPON KITSAP COUNTY LIDAR AERIAL SURVEY, 2 -FT SCALE: 1" = 300' CONTOURS. ELEVATION DATUM: NAVD88. DRAINAGE MAP BROWNE • WHEELER BGH- SUNRISE ENGINEERS, INC 241 ERICKSEN AVENUE NE BAINBRIDGE ISLAND, WA 98110 P 206.842.0605 INFO®Browne Wheeler.COM Threshold Determination Runoff from approximately 10,800 -square feet (so, of new impervious road area, will be infiltrated resulting in zero effective impervious area; therefore Minimum Requirements No.'s 1-5 apply to the project as outlined by DOE in the Stormwater Management Manual for Western Washington (SWMMWW), 2005 edition (Figure 2.2). Table 1 describes how each of Minimum Requirements No.'s 1-5 will be met. All new gravel access roads will drain through a grass shoulder to an infiltration trench along the road to allow stormwater runoff from the road area to infiltrate. Check dams will be installed along the infiltration trenches as required to disperse infiltration and prevent accumulation of water in one spot. The new rooftop areas on the seven lots will vary between 1,100-sf and 2,400-sf and the new driveways on each lot will vary between 400-sf and 1,250-sf. All stormwater runoff generated from each lot will be kept on-site to the maximum extent practicable through the installation of rain gardens or other methods to infiltrate all stormwater from new impervious areas. Disturbed landscaping areas will have the soil amended in accordance with BMP T5.13 Post -Construction Soil Quality and Depth. Drainage plans for individual lots will be developed during their respective building permit applications. ON-SITE UTILITIES WATER Existing There is no water utility connection currently to the property. Kitsap PUD's water system is in the vicinity of the project. Proposed A new 8 -inch water main will be connected to the water system in Sunrise Drive. The new water main will be extended south through the access easement and west and south to provide water service to all seven lots. Two fire hydrants will be installed, one along the North access road and one along the South access road and will be served by this new water main. Water service for the proposed seven lots will be provided through seven new 5/8" water meters, connected to the water main extension. SANITARY SEWER Existing There are no sewer services currently serving the property. BGH- Sunrise Preliminary Plat, Bainbridge Island Browne Wheeler Engineers, Inc. �� H - Swri5cJ Start Here Does the site have Yes See Redevelopment 35% or more of 0 Minimum existing impervious Requirements and coverage? Flow Chart Does the project convert (Figure 2.3) Noo. 3/4 acres or more of native vegetation to lawn or 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 All Minimum Requirements apply to the new impervious surfaces and converted pervious surfaces. Yes ,N`4, Does the project have 2,000 square feet or more of new, replaced, or new plus replaced impervious surfaces? Yeg No Minimum Requirements #1 through #5 apply to the new and replaced impervious surfaces and the land disturbed. Does the project have land -disturbing activities of 7,000 Yes square feet or more? No See Minimum Requirement #2, Construction Stormwater Pollution Prevention Figure 2.2 — Flow Chart for Determining Requirements for New Development February 2005 Volume 1— Minimum Technical -jYDvvne- WVweLu' 2-9 Proposed Each of the seven lots will have a private septic system on-site. The systems have not been designed yet but space is allocated for drainfields to maintain required separations from stormwater facilities. Power, telephone, and television cable will be designed by others. SITE ACCESS Existing The site currently has a gravel driveway located in an easement which provides access to the site from Sunrise drive to the north. Proposed The existing access driveway to the north will be widened and extended to serve the upper 4 lots. The road will be widened to 12 -ft with 2 and 3 -ft gravel shoulders as required by the City. The length of road with 2 -ft shoulders rather than 3 -ft is 200 -ft in length, from Sunrise Drive through the 20 -ft wide access easement to provide space for a 2 -ft wide infiltration trench paralleling the road. A new access is proposed off of Hyla Avenue to the southwest in which an easement through private property exists. The new access approach will be at a 90 -degree turn in Hyla Avenue. Because both access roads are gravel surfacing, the road approaches are proposed to be gravel. FRONTAGEIMPROVEMENTS Existing There are no current frontage improvements since the property does not front any right of way. Proposed The property does not front any rights of ways and no frontage improvements are proposed. EROSION CONTROL The Contractor will be responsible for maintaining erosion control facilities on the site during construction and for ensuring that sediment does not leave the site. The general principles of construction pollution prevention are: • Retain native vegetation • Prevent erosion rather than treat sediment laden water • Employ site specific best management practices (BMPs) • Divert upslope runoff around disturbed area • Phase construction operations to reduce total amount of disturbance at one time • Amend soils before seeding • Minimize the slope length and steepness of disturbed areas • Reduce runoff velocities BGH- Sunrise Preliminary Plat, Bainbridge Island Browne Wheeler Engineers, Inc. • Prevent the tracking of sediment off site • Employ BMPs that address not only erosion but also other potential pollutants. A detailed erosion and sediment control plan will be developed during final design. Very truly yours, BROWNE WHEELER ENGINEERS, INC. 3/24/2014 �r f165914 � 4V s`4IONAL �rU � 48830 GISTV °��SSIONAL' 3/24/2014 BGH- Sunrise Preliminary Plat, Bainbridge Island Browne Wheeler Engineers, Inc. Table 1 Summary of Stormwater Minimum Requirements BGH- Sunrise Preliminary Plat, Bainbridge Island Browne Wheeler Engineers, Inc. Minimum Requirement Comment 1. Stormwater site plan A stormwater site plan will be presented. 2. pollution Construction stormwater prevention A detailed construction stormwater pollution prevention plan will be developed during final design. 3. Source control of pollutants Not applicable. 4. Preservation of natural drainage systems and outfalls All stormwater will continue to discharge in the same location. 5. On-site stormwater management Stormwater will be kept on-site to the maximum extent practicable through infiltration and the amendment of all landscaping areas. 6. Runoff treatment Not applicable. 7. Flow control Not applicable. 8. Wetlands protection Not applicable. 9. Basin and watershed planning Not applicable. 10. Operation and maintenance Not applicable. BGH- Sunrise Preliminary Plat, Bainbridge Island Browne Wheeler Engineers, Inc.