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Home My WebLink AboutFloodplain Review & Grading Plans 07.31.2017FLOOD PLAIN REVIEW AND GRADING PLANS LOTS 23 and 28, RAPIDS VIEW LANE NEW CASTLE, COLORADO Prepared For: Chronos Builders Grand Junction, Colorado Prepared By: CAPSTONE ENTERPRISES WEST LLC GEOTECHNICAL AND MINING ENGINEERING TESTING AND INSPECTION SERVICES 618 PARTEE DRIVE GRAND JUNCTION, CO 81504 PHONE (970) 250-3331 capstonewest@juno.com July 31, 2017 Job No. 4100-3 CAPSTONE ENTERPRISES WEST, LLC GEOTECHNICAL AND MINING ENGINEERING TESTING AND INSPECTION SERVICES 618 PARTEE DRIVE GRAND JUNCTION, CO 81504 PHONE (970) 250-3331 FAX (970) 241-9721 July 31, 2017 JOB # 4100-3 Attn: Chronos Builders 637 25 Road Grand Junction, CO 81505 Subject: Flood Plain Review and Grading Plans Lots 23 and 28, Rapids View Lane New Castle, CO At your request, Capstone Enterprises West, LLC (Capstone) reviewed the flood plain mapping for the Rapids of Colorado subdivision, with particular interest in Tots 23 and 28, which Capstone performed site specific geotechnical investigations on earlier. The following maps show the location of the parcels and the flood plain. The first map is taken from the Garfield County GIS website. The second is form the National Flood Insurance Program (NFIP) Flood Insurance Rate Map (FIRM). The third map compares the two flood plains to the 1962 USGS contours. CAPSTONE ENTERPRISES WEST, LLC 2 JOB NUMBER 4100-3 ri Flo .....% I aM.1. o e 1111 WM►.....1. A..• .�. 1 Y'lY lir .>ru 1e•• Garfield County GIS website Flood Hazard Map .r✓ •C+•-�.•.�4••. ..-...11..E .i.it.4r.....br 1KY, • r•na '4'••■ . - •• . r ZINE • • 1•. ■ • • • ■ • • a ■ 1�l 1 it • • r• a1-1- • • • ■ • i• • • •■•. tau •■ ■ •a ■ • • • it • ■ a ••• r aV r• n. • • • • r 4. ■ ■ w r, r • • ■ r • • • ■ ■ a ■ r 4v• 4 • • .'. •■ . a • • r, a • 1, • r 11 • ■ ■ • � . ■ • • w II II a �, ••••■R•••■ lo -1 , r a■*••■•••ri••••■a■ 1 +� ' • • • • 1i U • .:f ••,a • e••h■' • is r •''■ 1 9 a ■ • ■ >i ■ 9 1 • 91 • • • ■ ■ • ■ ■ • r, a •••f• ■ •• •* •4 •r • • NFIP Flood Insurance Rate Map (October2011) CAPSTONE ENTERPRISES WEST, LLC 3 JOB NUMBER 4100-3 • FLOOD PLAIN LIMIT NFIP - FIRM fS USGS Topography Map with Flood Plain Limits FLOOD PLAIN LIMIT GARFIELD COUNTY GIS 1' \y F,'•4i . • •1 While the Garfield County flood plain appears to mimic the 1962 USGS contours, there was no roadway at that time. The NFIP FIRM map was prepared after the subdivision was constructed and the flood plain limit seems to mimic the grading north of the roadway. Base on the recommendations of the Garfield County Flood Plain Administrator, Capstone surveyed the lots as well as the top of foundations (TOF) of the two houses across the street from lot 28. No USGS benchmarks were within a reasonable proximity to tie into; therefore, the elevations were relative to the assigned elevation 100.00 for the northeast property corner nail for lot 28. The following Google Earth images shows the spot elevations surveyed at the site in July of 2017. CAPSTONE ENTERPRISES WEST, LLC 4 JOB NUMBER 4100-3 Based on the surveying performed and the comparison of the flood plain maps, Capstone believes that the actual flood plain is a combination of the two maps. While the site grading for the roadway may act as a dam, preventing water from flowing to the south, the flood waters would be able to back up through the drainage culverts and inundate lot 28 to the extents shown on the Garfield County map. To prevent flooding of the residence on lot 28, Capstone recommends that the TOF be 103.0, this should be over 1 foot above the projected flood plain. The residence on lot 23 should have TOF of 105.4. CAPSTONE ENTERPRISES WEST, LLC 5 JOB NUMBER 4100-3 SITE GRADING Lot 23 is bounded on the east with a 10 -foot -wide drainage easement that will be utilized to prevent surface drainage from running on to the lot. The same is true of the west boundary. The foundation backfill will direct away from the house in all directions. Where the backfill meets the existing ground, a swale will result that will capture the natural runoff and the house runoff and that captured flow will be directed to the drainage easements on the east and west side of the lot. The following drawing shows the general arrangement. NORTH 10" CULVERT UNDER DRIVEWAY SCALE (FEET) Elev. 100.0 = NE Property Pin Lot 2 r NATURAL FLAN LINED POND LOT 23 Rapids View Lane NATURAL ROW Lot 28 is bounded on the north and west property lines with drainage ditches. The foundation backfill will direct runoff away from the house in every direction. Where the foundation backfill meets the existing ground the resulting swale will be used to direct the runoff into the existing drainage ditches the bound the north and west property limits. The following drawing shows the general arrangement. The site grading plans are attached. CAPSTONE ENTERPRISES WEST, LLC 6 JOB NUMBER 4100-3 * NAIL 100.0 NORTH I0 25 50 75 IGOr �% ✓ 10" CULVERT ..4n ��..�..., � f GRADING FLOW N N NNGTIRAI FIf1W N LINED POND LOT 28 Rapids View Lane ,o 6(6 LIMITATIONS The analysis and recommendations submitted in this report are based in part upon the data obtained from the existing maps, field observations and surveying. This report, does not constitute a warranty either expressed or implied, as no one can predict the extents of a major flood. If you have any questions, or if we may be of further assistance, please do not hesitate to contact us. Respectfully Submitted: CAPSTONE ENTERPRISES WEST, LLC Martin W. Chenoweth, PE Registered Professional Engineer MWC CAPSTONE ENTERPRISES WEST, LLC 7 JOB NUMBER 4100-3 NORTH 0 25 50 75 100 SCALE (FEET) Elev. 100.0 = NE Property Pin Lot 2 NATURAL FLOW \REV. DATE DESCRIPTION BY CK 10" CULVERT UNDER DRIVEWAY N GRADING FLOW r >>DITCH>> l GRADING FLOW G�'3�03M-c) NATURAL FLOW LOT 23 Rapids View Lane CAPSTONE 1 ENTERPRISES WEST, LLC 618 PARTEE DRIVE GRAND JUNCTION, CO 81504 PHONE (970) 250-3331 capstonewest@juno.com NATURAL FLOW GRADING PLAN LOT 23 RAPIDS VIEW LANE NEW CASTLE, COLORADO BY M W CHENOWETH DATE 7/31/17 SCALE 1"=50' PROJECT NO. 4100-3 (SHEET NO. 10F2 NORTH 0 25 50 75 SCALE (FEET) 100 NAIL 100.0 UR -ROW Q � ` �AT'��o 10" CULVERT D VEWAY '<o� / ��- GRADING FLOW i \� N / R, // X / cq ,4\N) OF OF 103. r VERT _ 97.1 /// ` O, GRADING Flaw / N //N N �r /N NATURAL FLOW q)n J} / N LINED POND LOT 28 Rapids View Lane \REV. DATE DESCRIPTION BY CK CAPSTONE \\ ENTERPRISES WEST, LLC 618 PARTEE DRIVE GRAND JUNCTION, CO 81504 PHONE (970) 250-3331 capstonewest@juno.com GRADING PLAN LOT 28 RAPIDS VIEW LANE NEW CASTLE, COLORADO BY MW CHENOWETH DATE 7/31/17 SCALE 1"=50' PROJECT NO. 4100-3 SHEET NO.2U`'2