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Home My WebLink AboutSDP2013-00051 - SHORELINE RECON P r k.- NORTHWESTERN TERRITORIES, INC. ti......---,-- 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362 I 1 914 WASHINGTON STREET SUITE 6,PORT TOWNSEND,WA 98368 111! ti Engineers•Land Surveyors•Geologists �' Construction Inspection•Materials Testing y Port Angeles(360)452-8491 I /VTI E-Mail: info(ointi4u.com I ( , December 9, 2013 I i/t)tt 5ggedj&iri444,ped Kathleen and Reimer Douglas I 2021 N. 78th Street Seattle, Washington 98103-4907 ISubject: SHORELINE PROCESS ANALYSIS OF WAMPUM POINT-A PORTION OF THE IJEFFERSON COUNTY, WASHINGTON-SHORELINE. Dear Mr. and Mrs. Douglas, IIn November and December of 2013, Northwestern Territories Engineering and Land Surveying completed a reconnaissance study of the shoreline processes occurring at Wampum Point along the I eastern shore of Quilcene Bay within Section 19,Township 27, Range 1 West,WWM. At the time of the study a proposed action to mitigate a problem affecting the shoreline zone was under consideration by Jefferson County Department of Community Development. In particular, Kathleen and Reimer Douglas I seek a permit to refill a ditch and restore the backshore and tidelands in the shoreline zone near Wampum Point at Quilcene Bay, in Jefferson County. I The remedial action being considered involves the refilling of a ditch crossing the Quilcene Bay tidelands that was constructed under an emergency permit late in 2008.The original action, which re-routed a local stream, had both beneficial and detrimental effects that are outlined in this report.The proposed Iremedial actions seek to correct some of the detrimental affects while maintaining the benefits of the original stream dredging and ditching work. IRecent Geologic History of the Site I The Wampum Point Road area is alluvial fan/delta deposit whose gravel and sand soil arrived at the site from a small unnamed creek on the east that runs parallel to Lindsey Hill Road. The flashy creek drains a mile-long watershed and, due to the steepness of the creek's bed,the creek carries a large I amount of sand and gravel from glacial outwash deposits in the upland area. Before the Wampum Point area was settled,the creek meandered freely over the fan depositing gravel and sand along the shoreline and slowly building the low-lying Wampum Point. A significant oyster and clam fishery I developed on the clean and porous sand and gravel of the adjoining tidal areas. I I 1 Shoreline Rehabilitation with Jefferson County 2 Older USGS mapping and 1970 aerial photos show that in the 1960s Wampum Point Road crossed the shoreline on a gravel fill leading to a pile-supported pier that has since been removed. The shoal that ' remained after the road and pier were removed, creating a groin-like barrier to the longshore drift of sand and gravel coming from the south along the beach. As a result, a large deposit of sand and gravel has from time to time embanked along the southern and central part of the Wampum Point shoreline forming a point bar and slender sand spit. (Please see the photograph on the following page.) The constructional fan/delta deposit is now divided into several low-bank waterfront home sites.The modern backshore north of the old pier has been armored with rock to prevent its erosion. The un- named creek that transported much of the sandy soil to the area was channelized by the developer who constructed low dikes in a narrow zone between two of the waterfront parcels. ' Mechanics of Sediment Transport at the Site and the Shoreline Sand and gravel transported from the south by longshore drift has in the past banked against and over the shoal at Wampum Point creating a sandy point bar and narrow sand spit projecting to the west well into Quilcene Bay.The sand and gravel arriving at Wampum Point has at least two sources: ' • Sand and gravel arriving at the shoreline from the un-named creek • Longshore drift of sand from the shoreline and beaches on the south. ' During most of the recent past since the pier was constructed,the creek has most often emptied into Quilcene Bay on the south side of Wampum Point.The capture of some drifting sand and gravel sand by a groin about a thousand feet south of Wampum Point suggests that much of the sand reaching ' Wampum Point was washed down to the site by the creek. The aerial photograph below shows the conditions at the Wampum Point shoreline in 2008. A triangular ' point and sandy spit that were deposited over the shoal beyond the creek's mouth. Most of the sand arriving at the beach was transported to the north by shoreline drift processes. Some of the sand nourishing the beach and Wampum Point bar spilled over to the north side of the bar and spit during periods of storm-driven wind and waves.The shape of the deposits suggests that some of the drifting sand was sculpted by occasional reverse shore drift resulting in the sandy foreshores on both the north ' and south side of the point bar and spit. The photograph below shows Wampum Point before the creek was re-routed across the sandy point bar. Note the position of the creek's mouth at the right edge of the photograph. ' 2 Shoreline Rehabilitation with Jefferson County I I I — - la* , '.4:i. :A, 4i, , ,' ** .k . u "., -,..F ,#NN,I - - H ry2 *� h 4 " �� Zd e', �" u I IWAPUM POINT SAND BAR AND SPIT IN 2008.THE CREEK MOUTH IS ON THE RIGHT (SOUTH) In recent times,the flood-born sediment flowing down the creek had begun to fill the dikes that were I constructed to contain the creek.As in many places within the Puget Sound Lowland,the slow buildup of sediments in the creek bed may have led to the overflow of the dikes, local flooding and problems with underground wastewater treatment on the adjoining properties. Late in 2008,the waterfront Iproperty owners whose homes adjoin the creek undertook emergency dredging of the creek bed and the shoreline area where the creek passes into Quilcene Bay. IDue to land ownership issues and possibly misjudging the position of property lines,the dredging work turned the creek north parallel to the shoreline as it crossed the backshore. At the conclusion of the I work,the creek's mouth ended up on the north side of the point bar and spit.The spoils dredged from the tideland ditch were placed on the seaward side of the excavation where they remain in unsightly piles to this date. ICreek Realignment and Dredging Modifies Shoreline I Although the dredging of the creek bed gave relief from local flooding,the realignment of the lower part of the creek changed the nature of the shoreline in the Wampum Point area. I 3 1 Shoreline Rehabilitation with Jefferson County ggg ,.=1 I Sand and fine soil that originated within the creek's watershed were now being discharged north of the ' drift cell that formed the point bar and sand spit at Wampum Point. Some of the gravel and sand that formerly reached the beach was now being trapped in the dredged streambed and in the backshore ' area. The finer suspended particles of silt and clay size are now being discharged onto the beach north of the former bar and spit. The sum of these effects appear to have altered the balance between degradation and aggradation that existed at Wampum Point leading to the gradual disappearance of the ' sandy point bar and sand spit as shown in the photographs below. d Wit; #„ ."',+, 71. a 7„.., •s4 .- — s x."- Via.. 414 , y "Y55 1 1 WAMPUM POINT AFTER THE SHORELINE CREEK DREDGING - NORTH IS LEFT IN THIS VIEW 1 1 1 4 1 I Shoreline Rehabilitation with Jefferson County 20 I 1 a .. 7 x ' I ~ � 4 t YJ "`� '✓'q�, Ji b: Y iT'' # 4,.2) 1 . < y r � ,.n I I YY#� #�y+ 'W" �N iii. " ? �i r.. { Yf. A VIEW OF WAMPUM POINT IN 2011 AFTER THE CREEK DREDGING-NORTH IS UP AND TO THE RIGHT I After the creek was dredged across the backshore,the larger and heavier gravel and some of the sand I that formerly nourished the spit was deposited within the broad low area behind the beach. Fine grain silt and clay particles that remain suspended in the creek's water emerged on the tidelands in new I location on the north of Wampum Point as can be seen in the photographs above. These finer sediments settled from the creek's flood discharges in the tidal area lying north of the former spit resulting in the muddy foreshore shown in the photograph below. I I I I I S Shoreline Rehabilitation with Jefferson County i I I - ' ' a . � � �. � a , � �-,q„ �` f� .... .v^ w� -",:t.'---`� . fin' �'• k `� ..r' '' ; ' ,-4:. ; :; �%�t � �" ',..1;''.�� ,per "t` .. ""�.+.��at.' ar b .414 � ,y+ 4 ,.` -''.7..,-t,..`z" a �. l ""' m�""F *�. *°,� u.:ra�z s � y . - 4' -ii�i.,r 1-1.t,016.„,,' .Y'4,...�.f 4" ' •+�-'` I 1k' ,, at w'.. - +.* ...F..» ' ..,.I '-� 2« - . ,y,_ , , — " ' "''''' ',..-1' '--b" . ,,...E � � , ' r '"�^a' awe.. > , ,.„. I ii �*�'xaw. .n; i. .,. .`[ - s �'' i, �''. :"S'*m .at ,� CONDITIONS NORTH OF WAMPUM POINT SHOWING THE DEPOSITION OF FINE—GRAINED SEDIMENT IThe Proposal to Fill the Dredged Creek Bed Along the Shoreline It has been proposed to remedy the disturbance to the shoreline by refilling the dredged ditch with the spoils of the original excavation that are still lying in the shoreline area on the seaward side of the ditch. An alternative alignment has been proposed that would again place the creek's mouth on the south side of Wampum Point and the shoals there.This action may reverse the loss of sand that occurred after the realignment by re-establishing one of the most important sources of the sediments within the original drift cell. Fine-grain sediments that led to the deposition of silt and mud along the foreshore on the Inorth would be routed to the west to deeper water beyond Wampum Point as was the case in most of the recent past. IIn our opinion,the re-filling of the dredged ditch across the tidelands is consistent with the goals of the Shoreline Master Program that is about to be implemented in Jefferson County. Although the I shoreline and backshore have been much modified, it is our opinion the proposed action may help restore the historic shoreline conditions including the sand beach and spit conditions that have important values within the Shoreline Master Program. I I 6 IShoreline Rehabilitation with Jefferson County I IFilling and Straightening of the Dredged Stream Channel - Recommendations The dredging of the stream channel through the backshore area probably helped relieve the flooding by I providing a low-elevation receiving area for the sediment transported by the creek.The natural beach berm of gravel and sand that tends to block the creek's flow was temporarily eliminated by the dredging activity. This allows higher stream flow velocity and better sediment scouring in the upstream diked Iportion of the creek. Over time, however, it is clear that the continuing longshore drift of the beach sand and gravel will block the re-routed stream channel. IIt is also clear that provision needs to be made to provide a receiving area for sediment washed down the creek so that future sediment deposits at the backshore do not obstruct the creek's flow.This I condition could impair the flood protection that the streambed and tideland dredging was originally intended to provide. I A balance between the benefits of the former dredging and the unfortunate impacts to the shoreline Imight be obtained by following remedial actions which are described in the current permit application: • Refill the ditch as it crosses the Wampum Point area using the dredging spoils that were Ioriginally removed. Filling may be economically performed by a tracked excavator. • Grade and reshape the beach and foreshore at the abandoned mouth of the creek north of the Iformer point bar and spit.A light bulldozer would have the least impact to the tidelands. I • Complete a new broad channel for the creek over the backshore that allows the creek to follow its historic direct route to the tidelands on the west. I • Excavate enough sand and gravel from the new channel to provide an open floodway to and through the tideland so that there that there is no net loss of the sediment receiving area that was created by the 2008 dredging. ILimitations of This Study and These Recommendations I The reconnaissance study of shoreline processes provided here was completed in a necessarily short period in 2013. The study was completed without the benefit of long-term observations, shoreline sediment migration studies, and it was completed without detailed studies of the shape and grades of Ithe shoreline. Users who require a high degree of reliance on the conclusions and recommendations of this reconnaissance study may wish to obtain more detailed studies of the situation. I I 7 IShoreline Rehabilitation with Jefferson County 1 4 t-) IThis reconnaissance study was conscientiously completed in accordance with the professional practice of geotechnical engineering and in accordance with the principles of geologic science. No other warranty Iis provided herewith. Please call on the undersigned Engineers if you have questions on this study or its conclusions. ISincerely yours, INTI Engineering and Land Surveying '4'J f- ,f,e- 1. 091\y4 ,o, 0, g LG ;t ,r'2--- ''� t. ;, '> GIST ISteve S. Luxton MSc. PE Justin Wilson, PE Senior Geotechnical Engineer Principal Engineer and Project Manager I I I I I I I I I I 8 it . '�►'R`�' NORTHWESTERN TERRITORIES, INC. �� 717 SOUTH PEABODY STREET,PORT ANGELES,WA 98362 ' 914 WASHINGTON STREET SUITE 6,PORT TOWNSEND,WA 98368 ti Engineers•Land Surveyors•Geologists Construction Inspection•Materials Testing Port Angeles(360)452-8491 NT/ E-Mail: info(a�nti4u.com December 9, 2013 JJ�ll 1 WQ4"5 / Kathleen and Reimer Douglas ' 2021 N. 78th Street Seattle, Washington 98103-4907 Subject: SHORELINE PROCESS ANALYSIS OF WAMPUM POINT- A PORTION OF THE ' JEFFERSON COUNTY, WASHINGTON-SHORELINE. Dear Mr. and Mrs. Douglas, In November and December of 2013, Northwestern Territories Engineering and Land Surveying completed a reconnaissance study of the shoreline processes occurring at Wampum Point along the t eastern shore of Quilcene Bay within Section 19,Township 27, Range 1 West,WWM. At the time of the study a proposed action to mitigate a problem affecting the shoreline zone was under consideration by Jefferson County Department of Community Development. In particular, Kathleen and Reimer Douglas ' seek a permit to refill a ditch and restore the backshore and tidelands in the shoreline zone near Wampum Point at Quilcene Bay, in Jefferson County. ' The remedial action being considered involves the refilling of a ditch crossing the Quilcene Bay tidelands that was constructed under an emergency permit late in 2008.The original action, which re-routed a local stream, had both beneficial and detrimental effects that are outlined in this report.The proposed ' remedial actions seek to correct some of the detrimental affects while maintaining the benefits of the original stream dredging and ditching work. tRecent Geologic History of the Site ' The Wampum Point Road area is alluvial fan/delta deposit whose gravel and sand soil arrived at the site from a small unnamed creek on the east that runs parallel to Lindsey Hill Road. The flashy creek drains a mile-long watershed and, due to the steepness of the creek's bed,the creek carries a large amount of sand and gravel from glacial outwash deposits in the upland area. Before the Wampum Point area was settled,the creek meandered freely over the fan depositing gravel and sand along the shoreline and slowly building the low-lying Wampum Point.A significant oyster and clam fishery ' developed on the clean and porous sand and gravel of the adjoining tidal areas. 1 IShoreline Rehabilitation with Jefferson County ¢ , ,, IOlder USGS mapping and 1970 aerial photos show that in the 1960s Wampum Point Road crossed the shoreline on a gravel fill leading to a pile-supported pier that has since been removed. The shoal that I remained after the road and pier were removed, creating a groin-like barrier to the longshore drift of sand and gravel coming from the south along the beach. As a result, a large deposit of sand and gravel has from time to time embanked along the southern and central part of the Wampum Point shoreline Iforming a point bar and slender sand spit. (Please see the photograph on the following page.) The constructional fan/delta deposit is now divided into several low-bank waterfront home sites.The Imodern backshore north of the old pier has been armored with rock to prevent its erosion.The un- named creek that transported much of the sandy soil to the area was channelized by the developer who constructed low dikes in a narrow zone between two of the waterfront parcels. IMechanics of Sediment Transport at the Site and the Shoreline Sand and gravel transported from the south by longshore drift has in the past banked against and over Ithe shoal at Wampum Point creating a sandy point bar and narrow sand spit projecting to the west well into Quilcene Bay. The sand and gravel arriving at Wampum Point has at least two sources: I • Sand and gravel arriving at the shoreline from the un-named creek • Longshore drift of sand from the shoreline and beaches on the south. I I During most of the recent past since the pier was constructed,the creek has most often emptied into Quilcene Bay on the south side of Wampum Point.The capture of some drifting sand and gravel sand by a groin about a thousand feet south of Wampum Point suggests that much of the sand reaching IWampum Point was washed down to the site by the creek. The aerial photograph below shows the conditions at the Wampum Point shoreline in 2008. A triangular I point and sandy spit that were deposited over the shoal beyond the creek's mouth. Most of the sand arriving at the beach was transported to the north by shoreline drift processes. Some of the sand nourishing the beach and Wampum Point bar spilled over to the north side of the bar and spit during Iperiods of storm-driven wind and waves.The shape of the deposits suggests that some of the drifting sand was sculpted by occasional reverse shore drift resulting in the sandy foreshores on both the north I and south side of the point bar and spit. The photograph below shows Wampum Point before the creek was re-routed across the sandy point bar. Note the position of the creek's mouth at the right edge of the photograph. I I I I 2 MEW I Shoreline Rehabilitation with Jefferson County I +im*"I 1 • e p:_ / "1 f` I Rn .. _ 1 IWAPUM POINT SAND BAR AND SPIT IN 2008.THE CREEK MOUTH IS ON THE RIGHT(SOUTH) In recent times,the flood-born sediment flowing down the creek had begun to fill the dikes that were I constructed to contain the creek. As in many places within the Puget Sound Lowland, the slow buildup of sediments in the creek bed may have led to the overflow of the dikes, local flooding and problems with underground wastewater treatment on the adjoining properties. Late in 2008,the waterfront Iproperty owners whose homes adjoin the creek undertook emergency dredging of the creek bed and the shoreline area where the creek passes into Quilcene Bay. I Due to land ownership issues and possibly misjudging the position of property lines,the dredging work turned the creek north parallel to the shoreline as it crossed the backshore. At the conclusion of the work,the creek's mouth ended up on the north side of the point bar and spit.The spoils dredged from Ithe tideland ditch were placed on the seaward side of the excavation where they remain in unsightly piles to this date. ICreek Realignment and Dredging Modifies Shoreline I Although the dredging of the creek bed gave relief from local flooding, the realignment of the lower part of the creek changed the nature of the shoreline in the Wampum Point area. I 1 3 1 Shoreline Rehabilitation with Jefferson County v I Sand and fine soil that originated within the creek's watershed were now being discharged north of the Idrift cell that formed the point bar and sand spit at Wampum Point. Some of the gravel and sand that formerly reached the beach was now being trapped in the dredged streambed and in the backshore I area. The finer suspended particles of silt and clay size are now being discharged onto the beach north of the former bar and spit. The sum of these effects appear to have altered the balance between degradation and aggradation that existed at Wampum Point leading to the gradual disappearance of the Isandy point bar and sand spit as shown in the photographs below. ryG A v � I I I WAMPUM POINT AFTER THE SHORELINE CREEK DREDGING - NORTH IS LEFT IN THIS VIEW I I I I I 4 I Shoreline Rehabilitation with Jefferson County Y I rrC I p„iw � ,' ; . . ,'.'il,,.'",- ' s� ,fie x. -, fit%„:' �' I ,t ''4.. I F ti's .5 f .,-"' ,. ..- • '''.**-40.'„,,,':,-,',. s* . '( aJ„+ a ,' , ' .�;,, `, "f{ + *. IL'� �4'.....,, ... '�r Sn.;'k ';d.;%, .. C e° ,.a�' ' fit�� . .. v A VIEW OF WAMPUM POINT IN 2011 AFTER THE CREEK DREDGING-NORTH IS UP AND TO THE RIGHT I After the creek was dredged across the backshore,the larger and heavier gravel and some of the sand Ithat formerly nourished the spit was deposited within the broad low area behind the beach. Fine grain silt and clay particles that remain suspended in the creek's water emerged on the tidelands in new I location on the north of Wampum Point as can be seen in the photographs above. These finer sediments settled from the creek's flood discharges in the tidal area lying north of the former spit resulting in the muddy foreshore shown in the photograph below. I I I I 5 I Shoreline Rehabilitation with Jefferson County 2013 I in I x I t f.w^ 'fix•:I' '" . „. } ,: • . '4'.,''''.-: _., gat, ` *�^u.+p`'z '.�'� - ---,:.:',"':;1- " +cp x .r-' .r' rte .,,w cr' df .t:',' I gym '�,. � �' ws. . w. tP x q-mar-> n ' , "\ car efi' z., -. *k �,.. t!? Jam_ __ " . '4" - ` :' : ;r -`zq .-****4 *'�` *` tea. . CONDITIONS NORTH OF WAMPUM POINT SHOWING THE DEPOSITION OF FINE-GRAINED SEDIMENT IThe Proposal to Fill the Dredged Creek Bed Along the Shoreline It has been proposed to remedy the disturbance to the shoreline by refilling the dredged ditch with the Ispoils of the original excavation that are still lying in the shoreline area on the seaward side of the ditch. An alternative alignment has been proposed that would again place the creek's mouth on the south side I I of Wampum Point and the shoals there.This action may reverse the loss of sand that occurred after the realignment by re establishing one of the most important sources of the sediments within the original drift cell. Fine grain sediments that led to the deposition of silt and mud along the foreshore on the north would be routed to the west to deeper water beyond Wampum Point as was the case in most of I the recent past. IIn our opinion,the re-filling of the dredged ditch across the tidelands is consistent with the goals of the Shoreline Master Program that is about to be implemented in Jefferson co unty. Although the I shoreline and backshore have been much modified, it is our opinion the proposed action may help restore the historic shoreline conditions including the sand beach and spit conditions that have important values within the Shoreline Master Program. I I 6 Shoreline Rehabilitation with Jefferson County 4 g I ' Filling and Straightening of the Dredged Stream Channel - Recommendations The dredging of the stream channel through the backshore area probably helped relieve the flooding by providing a low-elevation receiving area for the sediment transported by the creek.The natural beach berm of gravel and sand that tends to block the creek's flow was temporarily eliminated by the dredging activity.This allows higher stream flow velocity and better sediment scouring in the upstream diked ' portion of the creek. Over time, however, it is clear that the continuing longshore drift of the beach sand and gravel will block the re-routed stream channel. It is also clear that provision needs to be made to provide a receiving area for sediment washed down the creek so that future sediment deposits at the backshore do not obstruct the creek's flow. This ' condition could impair the flood protection that the streambed and tideland dredging was originally intended to provide. 1 A balance between the benefits of the former dredging and the unfortunate impacts to the shoreline might be obtained by following remedial actions which are described in the current permit application: • Refill the ditch as it crosses the Wampum Point area using the dredging spoils that were ' originally removed. Filling may be economically performed by a tracked excavator. • Grade and reshape the beach and foreshore at the abandoned mouth of the creek north of the ' former point bar and spit.A light bulldozer would have the least impact to the tidelands. • Complete a new broad channel for the creek over the backshore that allows the creek to follow its historic direct route to the tidelands on the west. ' • Excavate enough sand and gravel from the new channel to provide an open floodway to and through the tideland so that there that there is no net loss of the sediment receiving area that was created by the 2008 dredging. ' Limitations of This Study and These Recommendations ' The reconnaissance study of shoreline processes provided here was completed in a necessarily short period in 2013. The study was completed without the benefit of long-term observations, shoreline sediment migration studies, and it was completed without detailed studies of the shape and grades of ' the shoreline. Users who require a high degree of reliance on the conclusions and recommendations of this reconnaissance study may wish to obtain more detailed studies of the situation. 7 I Shoreline Rehabilitation with Jefferson County I This reconnaissance study was conscientiously completed in accordance with the professional practice of geotechnical engineering and in accordance with the principles of geologic science. No other warranty Iis provided herewith. Please call on the undersigned Engineers if you have questions on this study or its conclusions. ISincerely yours, NTI Engineering and Land Surveying I S. LOs, . ` 4i, rwAS A, ` \ W ' SO co - y i J/s P 0 S' t. � .�6��.1�7 /� ' 0/3-- ��i q� 45910� 1 ' Steve S. Luxton MSc. PE Justin Wilson, PE Senior Geotechnical Engineer Principal Engineer and Project Manager I I I I I I I I I 8